View source for Blood type

{{Short description|Classification based on antibodies and antigens on RBC surfaces}}
{{About|blood type in humans}}
{{Distinguish|Human blood group systems}}
[[Image: ABO blood type.svg|thumb|right|435px|Blood type (or blood group) is determined, in part, by the ABO blood group antigens present on red blood cells.]]

A '''blood type''' (also known as a '''blood group''') is a classification of [[blood]] based on the presence and absence of [[antibody|antibodies]] and [[Heredity|inherited]] [[antigen]]ic substances on the surface of [[red blood cell]]s (RBCs). These antigens may be [[protein]]s, [[carbohydrate]]s, [[glycoprotein]]s, or [[glycolipid]]s, depending on the blood group system. Some of these antigens are also present on the surface of other types of [[Cell (biology)#Eukaryotic cells|cell]]s of various [[Tissue (biology)|tissues]]. Several of these red blood cell surface antigens can stem from one [[allele]] (or an alternative version of a gene) and collectively form a blood group system.<ref>{{cite book  | last = Maton  | first = Anthea  | author2 = Jean Hopkins  | author3 = Charles William McLaughlin  | author4 = Susan Johnson  | author5 = Maryanna Quon Warner  | author6 = David LaHart  | author7 = Jill D. Wright  | title = Human Biology and Health  | publisher = Prentice Hall  | year = 1998
  | location = Englewood Cliffs NJ  | isbn = 0-13-981176-1  | url-access = registration  | url = https://archive.org/details/humanbiologyheal00scho  }}</ref>

Blood types are inherited and represent contributions from both parents of an individual. As of June 2025, a total of 48 [[human blood group systems]] are recognized by the [[International Society of Blood Transfusion]] (ISBT).<ref name=":1">{{Cite web  |title='Gwada negative': French scientists find new blood type in woman |url=https://www.lemonde.fr/en/science/article/2025/06/21/gwada-negative-french-scientists-find-new-blood-type-in-woman_6742577_10.html |access-date=2025-06-21 |website=www.lemonde.fr |language=en}}</ref> The two most important blood group systems are [[ABO blood group system|ABO]] and [[Rh blood group system|Rh]]; they determine someone's blood type (A, B, AB, and O, with + or − denoting [[RhD antigen|RhD]] status) for suitability in [[blood transfusion]].

==Blood group systems==
{{main|Human blood group systems}}

A complete blood type would describe each of the 48 blood groups, and an individual's blood type is one of many possible combinations of blood-group antigens.<ref name=":2" /> Almost always, an individual has the same blood group for life, but very rarely an individual's blood type changes through addition or suppression of an antigen in [[infection]], [[malignancy]], or [[autoimmune disease]].<ref name=":2">{{harvnb|Dean|2005|loc=[https://www.ncbi.nlm.nih.gov/books/NBK2267/ The ABO blood group] "... A number of illnesses may alter a person's ABO phenotype ..."}}</ref><ref>{{cite journal |vauthors=Stayboldt C, Rearden A, Lane TA |title=B antigen acquired by normal A1 red cells exposed to a patient's serum |journal=Transfusion |volume=27 |issue=1 |pages=41–4 |year=1987 |pmid=3810822 |doi=10.1046/j.1537-2995.1987.27187121471.x }}</ref><ref>{{cite journal |vauthors=Matsushita S, Imamura T, Mizuta T, Hanada M |title=Acquired B antigen and polyagglutination in a patient with gastric cancer |journal=The Japanese Journal of Surgery |volume=13 |issue=6 |pages=540–2 |date=November 1983 |pmid=6672386 |doi=10.1007/BF02469500 }}</ref><ref>{{cite journal |last1=Kremer Hovinga |first1=Idske CL |last2=Koopmans |first2=Marije |last3=de Heer |first3=Emile |last4=Bruijn |first4=Jan A |last5=Bajema |first5=Ingeborg M |title=Change in blood group in systemic lupus erythematosus |journal=The Lancet |date=January 2007 |volume=369 |issue=9557 |pages=186–187 |doi=10.1016/S0140-6736(07)60099-3 |pmid=17240276 |doi-access=free }}</ref> Another more common cause of blood type change is a [[bone marrow transplant]]. Bone-marrow transplants are performed for many [[leukemias]] and [[lymphomas]], among other diseases. If a person receives bone marrow from someone of a different ABO type (e.g., a type O patient receives a type A bone marrow), the patient's blood type should eventually become the donor's type, as the patient's [[hematopoietic stem cell]]s (HSCs) are destroyed, either by ablation of the bone marrow or by the donor's T-cells. Once all the patient's original red blood cells have died, they will have been fully replaced by new cells derived from the donor HSCs. Provided the donor had a different ABO type, the new cells' surface antigens will be different from those on the surface of the patient's original red blood cells.<ref name="pmid27022317">{{cite journal |vauthors=Worel N |title=ABO-Mismatched Allogeneic Hematopoietic Stem Cell Transplantation |journal=Transfus Med Hemother |volume=43 |issue=1 |pages=3–12 |date=January 2016 |pmid=27022317 |doi=10.1159/000441507 |pmc=4797460 |url=}}</ref>

Some blood types are associated with the inheritance of other diseases; for example, the [[Kell blood group system|Kell antigen]] is sometimes associated with [[McLeod syndrome]].<ref><!--
 -->{{cite journal |author1=Chown B. |author2=Lewis M. |author3=Kaita K. |title=A new Kell blood-group phenotype |journal=Nature |volume=180 |issue=4588 |page=711 |date=October 1957 |pmid=13477267 |doi=10.1038/180711a0|bibcode=1957Natur.180..711C |doi-access=free }}</ref> Certain blood types may affect susceptibility to infections, such as the resistance to specific [[malaria]] species seen in individuals lacking the [[Duffy antigen]].<ref><!--
 -->{{cite journal |doi=10.1056/NEJM197608052950602 |vauthors=Miller LH, Mason SJ, Clyde DF, McGinniss MH |title=The resistance factor to Plasmodium vivax in blacks. The Duffy-blood-group genotype, FyFy |journal=The New England Journal of Medicine |volume=295 |issue=6 |pages=302–4 |date=August 1976 |pmid=778616}}</ref><!--
 --> The Duffy antigen, presumably as a result of [[natural selection]], is less common in population groups from areas having a high incidence of malaria.<ref>{{cite journal |author=Kwiatkowski DP |title=How Malaria Has Affected the Human Genome and What Human Genetics Can Teach Us about Malaria |journal=American Journal of Human Genetics |volume=77 |issue=2 |pages=171–92 |date=August 2005 |pmid=16001361 |pmc=1224522 |doi=10.1086/432519 |quote=The different geographic distributions of α thalassemia, G6PD deficiency, ovalocytosis, and the Duffy-negative blood group are further examples of the general principle that different populations have evolved different genetic variants to protect against malaria}}</ref>  

===ABO blood group system===
[[Image:ABO blood group diagram.svg|right|thumb|350px|''ABO blood group system'': diagram showing the carbohydrate chains that determine the ABO blood group]]
[[Image:Punnett_square_blood_types.svg|right|thumb|350px|Simplified [[Punnett square]] of the possible genotypes and phenotypes of children given genotypes and phenotypes of their mother (rows) and father (columns) shaded by phenotype]]
{{Main|ABO blood group system}}

The ABO blood group system involves two antigens and two antibodies found in human blood. The two antigens are antigen A and antigen B. The two antibodies are A and B. The antigens are present on the red blood cells, and the antibodies in the [[serum (blood)|serum]]. Regarding the antigen property of the blood, all human beings can be classified into four groups: those with antigen A (group A), those with antigen B (group B), those with both antigen A and B (group AB), and those with neither antigen (group O). The antibodies present together with the antigens are found as follows:{{citation needed|date=November 2021}}
# Antigen A with antibody B
# Antigen B with antibody A
# Antigen AB with neither antibody A nor B
# Antigen null (group O) with both antibodies A and B

There is an [[Agglutination (biology)|agglutination]] reaction between similar antigen and antibody (for example, antigen A agglutinates the antibody A, and antigen B agglutinates the antibody B). Thus, transfusion can be considered safe as long as the serum of the recipient does not contain antibodies for the blood cell antigens of the donor.{{citation needed|date=November 2021}}

The ABO system is the most important blood-group system in human-blood transfusion. The associated anti-A and anti-B antibodies are usually [[immunoglobulin M]], abbreviated [[IgM]], antibodies. It has been hypothesized that ABO IgM [[antibodies]] are produced in the first years of life by sensitization to environmental substances such as food, [[bacteria]], and [[virus]]es.<ref>{{cite web|title=Position statement: Red blood cell transfusion in newborn infants |url=https://www.cps.ca/en/documents/position/red-blood-cell-transfusion-newborn-infants |publisher=Canadian Pediatric Society |archive-url=https://web.archive.org/web/20180519120449/https://www.cps.ca/en/documents/position/red-blood-cell-transfusion-newborn-infants |archive-date=19 May 2018 |date=April 14, 2014}}</ref> The original terminology used by [[Karl Landsteiner]] in 1901 for the classification was A/B/C; in later publications "C" became "O".<ref name=Oor0>{{cite journal |last1=Schmidt |first1=P. |last2=Okroi |first2=M. |title=Also sprach Landsteiner – Blood Group 'O' or Blood Group 'NULL' |journal=Transfusion Medicine and Hemotherapy |date=2001 |volume=28 |issue=4 |pages=206–208 |doi=10.1159/000050239 }}</ref> Type O is often called ''0'' (''zero'', or ''null'') in other languages.<ref name="Oor0"/><ref>{{cite web |url=https://www.bloddonor.dk/fileadmin/Fil_Arkiv/PDF_filer/Andre/Your_Blood__June_2006.pdf |title=Your blood&nbsp;– a textbook about blood and blood donation |access-date=2008-07-15 |page=63 |archive-url = https://web.archive.org/web/20080626184746/https://www.bloddonor.dk/fileadmin/Fil_Arkiv/PDF_filer/Andre/Your_Blood__June_2006.pdf |archive-date = June 26, 2008}}</ref>
{| class="wikitable plainrowheaders" style="text-align:center;"
|+Phenotype and genotype of blood types
|-
! scope="col"|[[Phenotype]]
! scope="col"|[[Allele|Alleles]]
|-
!scope="row"| A
| ABO*A1.01
|-
!scope="row"| B
| ABO*B1.01
|-
!scope="row"| AB
| ABO*A1.01, ABO*B1.01
|-
!scope="row"| O
| Two nonfunctional ABO genes
|}

===Rh blood group system===
{{Main|Rh blood group system}}
The Rh system (Rh meaning ''[[Rh blood group system|Rhesus]]'') is the second most significant blood-group system in human blood transfusion, with currently 50 antigens. The most significant Rh antigen is the D antigen, because it is the most likely to provoke an immune system response of the five main Rh antigens. It is common for D-negative individuals not to have any anti-D IgG or IgM antibodies, because anti-D antibodies are not usually produced by sensitization against environmental substances. However, D-negative individuals can produce [[Immunoglobulin G|IgG]] anti-D antibodies following a sensitizing event: possibly a fetomaternal transfusion of blood from a fetus in pregnancy or occasionally a blood transfusion with D-positive [[Red blood cell|RBC]]s.<ref name="Talaro, Kathleen P. 2005 510–1">{{cite book|author=Talaro, Kathleen P.|title=Foundations in microbiology|url=https://archive.org/details/foundationsinmic00kath|url-access=registration|publisher=McGraw-Hill|location=New York|year=2005|pages=[https://archive.org/details/foundationsinmic00kath/page/510 510–1]|isbn=0-07-111203-0 |edition=5th}}</ref><ref>{{cite journal |last1=Moise |first1=Kenneth J. |title=Management of Rhesus Alloimmunization in Pregnancy |journal=Obstetrics & Gynecology |date=July 2008 |volume=112 |issue=1 |pages=164–176 |doi=10.1097/AOG.0b013e31817d453c |pmid=18591322 }}</ref> Rh negative blood types are much less common in Asian populations (0.3%) than they are in European populations (15%).<ref name="Rh group and its origin">{{cite web|url=https://hospital.kingnet.com.tw/activity/blood/html/a.html|title=Rh血型的由來|publisher=Hospital.kingnet.com.tw|access-date=2010-08-01|archive-date=2009-12-11|archive-url=https://web.archive.org/web/20091211201528/http://hospital.kingnet.com.tw/activity/blood/html/a.html|url-status=live}}</ref>

The presence or absence of the Rh(D) antigen is signified by the + or − sign, so that, for example, the A− group is ABO type A and does not have the Rh (D) antigen.<ref>{{cite book |doi=10.1016/B978-075067572-7.50033-3 |chapter=Bleeding, Hemostasis, and Transfusion Medicine |title=Cardiothoracic Critical Care |date=2007 |last1=Levy |first1=Jerrold H. |last2=McKee |first2=Andrew |pages=437–460 |isbn=978-0-7506-7572-7 }}</ref>

===ABO and Rh distribution by country===
{{main|Blood type distribution by country}}

As with many other genetic traits, the distribution of ABO and Rh blood groups varies significantly between populations.{{citation needed|date=November 2021}}<ref>{{Cite journal |last1=Mohamud |first1=Mohamed Hayir Tahill |last2=Aweis |first2=Abdullah Dahir H |last3=Adam |first3=Abdiwahab Sheikh Elmi |last4=Mohamed |first4=Farhia Abdullahi |last5=Fidow |first5=Safia Qasim |last6=Mohamed |first6=Lul Mohamud |date=30 January 2022 |title=Distribution and Frequency of ABO and Rhesus (D) Blood Groups in Somalia: A Retrospective Study on Students of Jazeera University, Mogadishu-Somalia |journal=BioMed Research International |volume=2022 |issue=7981325|pages=1–5 |doi=10.1155/2022/7981325 |pmid=35136827 |pmc=8818412 |doi-access=free }}</ref> While theories are still debated in the scientific community as to why blood types vary geographically and why they emerged in the first place, evidence suggests that the evolution of blood types may be driven by genetic selection for those types whose antigens confer resistance to particular diseases in certain regions – such as the prevalence of blood type O in malaria-endemic countries where individuals of blood type O exhibit the highest rates of survival.<ref>{{Cite journal |last1=Cserti |first1=Christine M. |last2=Dzik |first2=Walter H. |date=1 October 2007 |title=The ABO blood group system and Plasmodium falciparum malaria |journal=American Society of Hematology |volume=110 |issue=7|pages=2250–2258 |doi=10.1182/blood-2007-03-077602 |pmid=17502454 |doi-access=free }}</ref>

===Other blood group systems===
{{Main|Human blood group systems}}
As of June 2025, 48 blood-group systems have been identified and are recognized by the International Society for Blood Transfusion.<ref name=":1" /> Thus, in addition to the ABO antigens and Rh antigens, many other antigens are expressed on the RBC surface membrane. For example, an individual can be AB, D positive, and at the same time M and N positive ([[MNS antigen system|MNS system]]), K positive ([[Kell antigen system|Kell system]]), Le<sup>a</sup> or Le<sup>b</sup> negative ([[Lewis antigen system|Lewis system]]). Many of the blood group systems were named after the patients in whom the corresponding antibodies were initially encountered. Blood group systems other than ABO and Rh pose a potential, yet relatively low, risk of complications upon mixing of blood from different people.<ref name="GoodellUhl2010">{{cite journal |last1=Goodell |first1=Pamela P. |last2=Uhl |first2=Lynne |last3=Mohammed |first3=Monique |last4=Powers |first4=Amy A. |title=Risk of Hemolytic Transfusion Reactions Following Emergency-Release RBC Transfusion |journal=American Journal of Clinical Pathology |date=August 2010 |volume=134 |issue=2 |pages=202–206 |doi=10.1309/AJCP9OFJN7FLTXDB |pmid=20660321 |doi-access=free }}</ref>
[[File:Antigen component for ABO and Rh factor presence.svg|thumb|The image illustrates the presence of the Rh factor across different blood types, examines the antigens associated with each ABO blood group, and shows which traits are dominant and recessive.]]

Following is a comparison of clinically relevant characteristics of antibodies against the main human blood group systems:<ref name="Mais 2014">{{cite book | last=Mais | first=Daniel | title=Quick compendium of clinical pathology | publisher=American Society for Clinical Pathology Press | publication-place=United States | year=2014 | isbn=978-0-89189-615-9 | oclc=895712380 | page=}}{{pn|date=November 2024}}</ref>
{|class="wikitable"
!  !! [[ABO blood group system|ABO]] !! [[Rh blood group system|Rh]] !! [[Kell antigen system|Kell]] !! [[Duffy antigen system|Duffy]] !! [[Kidd antigen system|Kidd]]
|-
! Naturally occurring
| Yes || No || No || No || No
|-
! Most common in immediate hemolytic transfusion reactions
|  A|| ||  Yes||  Fy<sup>a</sup>||  Jk<sup>a</sup>
|-
! Most common in delayed hemolytic transfusion reactions
| ||  E, D, C|| || ||  Jk<sup>a</sup>
|-
! Most common in [[hemolytic disease of the newborn]]
|  Yes||  D, C||  Yes|| ||
|-
! Commonly produce intravascular hemolysis
|  Yes|| || || ||  Yes
|}

==Clinical significance==

===Blood transfusion===
{{Main|Blood transfusion}}
Transfusion medicine is a specialized branch of [[hematology]] that is concerned with the study of blood groups, along with the work of a [[blood bank]] that provides a [[Blood transfusion|transfusion]] service with blood and other blood products. Across the world, blood products must be prescribed by a medical doctor (licensed [[physician]] or [[surgeon]]) in a similar way as medicines.{{citation needed|date=November 2021}}

[[File:Main symptoms of acute hemolytic reaction.png|thumb|right|220px|Main symptoms of [[acute hemolytic reaction]] due to blood type mismatch.<ref>[https://www.cancer.org/docroot/ETO/content/ETO_1_4x_Possible_Risks_of_Blood_Product_Transfusions.asp Possible Risks of Blood Product Transfusions] {{Webarchive|url=https://web.archive.org/web/20091105182210/http://www.cancer.org/docroot/ETO/content/ETO_1_4x_Possible_Risks_of_Blood_Product_Transfusions.asp |date=2009-11-05 }} from American Cancer Society. Last Medical Review: 03/08/2008. Last Revised: 01/13/2009</ref><ref>[https://www.pathology.med.umich.edu/bloodbank/manual/bbch_7/index.html 7 adverse reactions to transfusion] {{Webarchive|url=https://web.archive.org/web/20151107032014/https://www.pathology.med.umich.edu/bloodbank/manual/bbch_7/index.html |date=2015-11-07 }} Pathology Department at University of Michigan. Version July 2004, Revised 11/5/08</ref>]]

Much of the routine work of a [[blood bank]] involves testing blood from both donors and recipients to ensure that every individual recipient is given blood that is compatible and as safe as possible. If a unit of incompatible blood is [[Blood transfusion|transfused]] between a [[Blood donation|donor]] and recipient, a severe [[acute hemolytic reaction]] with [[hemolysis]] (RBC destruction), [[kidney failure]] and [[shock (circulatory)|shock]] is likely to occur, and death is a possibility.<ref>{{cite book |last1=Rout |first1=Preeti |last2=Harewood |first2=Janine |last3=Ramsey |first3=Adam |last4=Master |first4=Samip R. |title=StatPearls |date=2024 |publisher=StatPearls Publishing |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK448158/ |chapter=Hemolytic Transfusion Reaction |pmid=28846280 }}</ref> Antibodies can be highly active and can attack RBCs and bind components of the [[complement system]] to cause massive hemolysis of the transfused blood.<ref>{{cite journal |vauthors= Fujii Y |title=Prevention of ABO-incompatible transfusion |journal=Masui |volume=60 |issue=1 |pages=47–54 |year=2011 |pmid=21348250 }}</ref>

Patients should ideally receive their own blood or type-specific blood products to minimize the chance of a [[transfusion reaction]]. It is also possible to use the patient's own blood for transfusion. This is called [[autotransfusion|autologous blood transfusion]], which is always compatible with the patient. The procedure of washing a patient's own red blood cells goes as follows: The patient's lost blood is collected and washed with a saline solution. The washing procedure yields concentrated washed red blood cells. The last step is reinfusing the packed red blood cells into the patient. There are multiple ways to wash red blood cells. The two main ways are centrifugation and filtration methods. This procedure can be performed with microfiltration devices. Risks can be further reduced by [[cross-matching]] blood, but this may be skipped when blood is required for an emergency. The oldest form of cross-matching involves mixing a sample of the recipient's serum with a sample of the donor's red blood cells and checking if the mixture ''agglutinates'' or forms clumps. If agglutination is not obvious by direct vision, a blood bank technologist may check for [[Agglutination (biology)|agglutination]] with a [[microscope]]. If agglutination occurs, that donor's blood cannot be transfused to that particular recipient. In a bank transfusion service, all blood specimens must be correctly identified, so labelling has been standardized using a [[barcode]] system known as [[ISBT 128]].

The blood group may be included on [[Dog tag (identifier)|identification tags]] or historically on [[tattoo]]s worn by military personnel, in case they should need an emergency blood transfusion. Frontline German [[SS blood group tattoo|Waffen-SS had blood group tattoos]] during [[World War II]].

Rare blood types can cause supply problems for [[blood bank]]s and hospitals. For example, [[Duffy antigen|Duffy]]-negative blood occurs much more frequently in people of African origin,<ref>{{cite journal |author=Nickel RG |title=Determination of Duffy genotypes in three populations of African descent using PCR and sequence-specific oligonucleotides |journal=Human Immunology |volume=60 |issue=8 |pages=738–42 |date=August 1999 |pmid=10439320 |doi=10.1016/S0198-8859(99)00039-7 |author2=Willadsen SA |author3=Freidhoff LR |display-authors=3 |last4=Huang |first4=Shau-Ku |last5=Caraballo |first5=Luis |last6=Naidu |first6=Raana P |last7=Levett |first7=Paul |last8=Blumenthal |first8=Malcolm |last9=Banks-Schlegel |first9=Susan|doi-access=free }}</ref> and the rarity of this blood type in the rest of the population can result in a shortage of Duffy-negative blood for these patients.  Similarly, for RhD negative people there is a risk associated with travelling to parts of the world where supplies of RhD-negative blood are rare, particularly [[East Asia]], where blood services may endeavour to encourage Westerners to donate blood.<ref>{{cite web|url=https://www.bloodcare.org.uk/html/resources_chairman_2001.htm |title=BCF&nbsp;– Members&nbsp;– Chairman's Annual Report |access-date=2008-07-15 |last=Bruce |first=MG |date=May 2002 |publisher=The Blood Care Foundation |quote=As Rhesus Negative blood is rare amongst local nationals, this Agreement will be of particular value to Rhesus Negative expatriates and travellers |url-status=dead |archive-url=https://web.archive.org/web/20080410111425/https://www.bloodcare.org.uk/html/resources_chairman_2001.htm |archive-date=April 10, 2008 }}</ref>

===Hemolytic disease of the newborn (HDN)===
{{Main|Hemolytic disease of the newborn}}
A [[Pregnancy|pregnant]] woman may carry a [[fetus]] with a blood type that is different from her own. Typically, this is an issue if a RhD negative mother has a child with a RhD positive father, and the fetus ends up being Rh positive.<ref>{{cite web |last1=Freeborn |first1=Donna |title=Hemolytic Disease of the Newborn (HDN) |url=https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02368 |website=University of Rochester Medical Center |access-date=30 November 2020 |archive-date=19 September 2016 |archive-url=https://web.archive.org/web/20160919082228/https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02368 |url-status=live }}</ref> In those cases, the mother can make [[Immunoglobulin G|IgG]] blood group antibodies. This can happen if some of the fetus' blood cells pass into the mother's blood circulation (e.g., a small fetomaternal [[bleeding|hemorrhage]] at the time of childbirth or obstetric intervention), or sometimes after a therapeutic [[blood transfusion]].  This can cause [[hemolytic disease of the newborn]] (HDN) in the current pregnancy and/or subsequent pregnancies.  Sometimes this is lethal for the fetus; in these cases it is called [[hydrops fetalis]].<ref name =Letsky2000>{{cite book |title =Antenatal & neonatal screening |edition = 2nd |chapter = Chapter 12: Rhesus and other haemolytic diseases |author = E.A. Letsky |author2=I. Leck|author3=J.M. Bowman |year = 2000 |publisher = Oxford University Press|isbn=978-0-19-262826-8}}</ref> If a pregnant woman is known to have anti-D antibodies, the RhD blood type of a [[fetus]] can be tested by analysis of fetal DNA in maternal plasma to assess the risk to the fetus of Rh disease.<ref>{{cite journal |vauthors=Daniels G, Finning K, Martin P, Summers J |title=Fetal blood group genotyping: present and future |journal=Annals of the New York Academy of Sciences |volume=1075 |pages=88–95 |date=September 2006 |issue=1 |pmid=17108196 |doi=10.1196/annals.1368.011 |bibcode=2006NYASA1075...88D }}</ref> Cell-free DNA testing can determine the fetal ''RHD'' genotype in a sample of material plasma after 10 weeks of gestation. One of the major advances of twentieth-century medicine was to prevent this disease by stopping the formation of anti-D antibodies by D-negative mothers with an injectable medication called [[Rho(D) immune globulin]].<ref>{{cite web|url=https://www.rcog.org.uk/index.asp?PageID=1972 |title=Use of Anti-D Immunoglobulin for Rh Prophylaxis |publisher=[[Royal College of Obstetricians and Gynaecologists]] |date=May 2002 |url-status=dead |archive-url=https://web.archive.org/web/20081230200349/https://www.rcog.org.uk/index.asp?PageID=1972 |archive-date=December 30, 2008 }}</ref><ref>{{cite web |url = https://www.nice.org.uk/guidance/TA41/?c=91520 |title = Pregnancy&nbsp;– routine anti-D prophylaxis for D-negative women |publisher = [[National Institute for Health and Clinical Excellence|NICE]] |date = May 2002 |access-date = 2022-02-11 |archive-date = 2022-02-05 |archive-url = https://web.archive.org/web/20220205182251/https://www.nice.org.uk/guidance/TA41/?c=91520 |url-status = live }}</ref> Antibodies associated with some blood groups can cause severe HDN, others can only cause mild HDN and others are not known to cause HDN.<ref name="Letsky2000"/>

=== Blood products ===
To provide maximum benefit from each blood donation and to extend shelf-life, [[blood bank]]s [[blood fractionation|fractionate]] some whole blood into several products. The most common of these products are RBCs, [[Blood plasma|plasma]], [[platelet]]s, [[cryoprecipitate]], and [[Blood plasma#Fresh frozen plasma|fresh frozen plasma]] (FFP).  FFP is quick-frozen to retain the labile [[clotting factor]]s [[Factor V|V]] and [[Factor VIII|VIII]], which are usually administered to patients who have a potentially fatal clotting problem caused by a condition such as advanced [[liver]] disease, overdose of [[anticoagulant]], or [[disseminated intravascular coagulation]] (DIC).{{citation needed|date=November 2021}}

Units of packed red cells are made by removing as much of the plasma as possible from whole blood units.

[[Clotting factors]] synthesized by modern [[Recombinant DNA|recombinant]] methods are now in routine clinical use for [[hemophilia]], as the risks of infection transmission that occur with pooled blood products are avoided.

===Red blood cell compatibility===
{{Redirect|O negative||O Negative (disambiguation)}}
{{Further|Blood compatibility testing}}
* '''Blood group AB''' individuals have both A and B antigens on the surface of their RBCs, and their [[blood plasma]] does not contain any antibodies against either A or B antigen. Therefore, an individual with type AB blood can receive blood from any group (with AB being preferable), but cannot donate blood to any group other than AB.  They are known as universal recipients.
* '''Blood group A'''  individuals have the A antigen on the surface of their RBCs, and blood serum containing [[IgM]] antibodies against the B antigen. Therefore, a group A individual can receive blood only from individuals of groups A or O (with A being preferable), and can donate blood to individuals with type A or AB.
* '''Blood group B'''  individuals have the B antigen on the surface of their RBCs, and blood serum containing IgM antibodies against the A antigen. Therefore, a group B individual can receive blood only from individuals of groups B or O (with B being preferable), and can donate blood to individuals with type B or AB.
* '''Blood group O''' individuals have no A or B antigens on the surface of their RBCs, and their blood serum contains IgM anti-A and anti-B antibodies. Therefore, a group O individual can receive blood only from a group O individual, but can donate blood to individuals of any ABO blood group (i.e., A, B, O or AB). If a patient needs an urgent blood transfusion, and if the time taken to process the recipient's blood would cause a detrimental delay, O-negative blood can be used. Because it is compatible with anyone, there are some concerns that O-negative blood is often overused and consequently is always in short supply.<ref name="AABBfive">{{Citation |author1 = American Association of Blood Banks |author1-link = American Association of Blood Banks |date = 24 April 2014 |title = Five Things Physicians and Patients Should Question |publisher = American Association of Blood Banks |work = [[Choosing Wisely]]: an initiative of the [[ABIM Foundation]] |url = https://www.choosingwisely.org/doctor-patient-lists/american-association-of-blood-banks/ |access-date = 25 July 2014 |archive-url = https://web.archive.org/web/20140924075027/https://www.choosingwisely.org/doctor-patient-lists/american-association-of-blood-banks/ |archive-date = 24 September 2014 |url-status = dead }}, which cites
* {{cite web|author1=The Chief Medical Officer's National Blood Transfusion Committee|title=The appropriate use of group O RhD negative red cells|url=https://hospital.blood.co.uk/library/pdf/nbtc_bbt_o_neg_red_cells_recs_09_04.pdf|archive-url=https://web.archive.org/web/20140809134013/https://hospital.blood.co.uk/library/pdf/nbtc_bbt_o_neg_red_cells_recs_09_04.pdf|archive-date=9 August 2014|publisher=[[National Health Service]]|access-date=25 July 2014|year=c. 2008}}</ref> According to the Association for the Advancement of Blood and Biotherapies ([[AABB]]) and the British Chief Medical Officer's National Blood Transfusion Committee, the use of group O RhD negative red cells should be restricted to persons with O negative blood, women who might be pregnant, and emergency cases in which blood-group testing is genuinely impracticable.<ref name="AABBfive"/>

[[Image:Blood Compatibility.svg|right|230px|thumb|'''Red blood cell compatibility chart'''<br />In addition to donating to the same blood group, type O blood donors can give to A, B, and AB; blood donors of types A and B can give to AB.]]
{| class="wikitable" style="text-align:center;"
|+ Red blood cell compatibility table<!--
 --><ref name=rbccomp>{{cite web |url=https://chapters.redcross.org/br/northernohio/INFO/bloodtype.html |title=RBC compatibility table |access-date=2008-07-15 |date=December 2006 |publisher=American National Red Cross |url-status=dead |archive-url=https://web.archive.org/web/20080913165654/https://chapters.redcross.org/br/northernohio/info/bloodtype.html |archive-date=2008-09-13 }}</ref><ref name=bloodbook>[https://www.bloodbook.com/compat.html Blood types and compatibility] {{Webarchive|url=https://web.archive.org/web/20100419103919/https://www.bloodbook.com/compat.html |date=2010-04-19 }} bloodbook.com</ref><!--
 -->
|-
! {{diagonal split header|<br />Recipient|Donor<sup>[1]</sup>}}
! O−
! O+
! A−
! A+
! B−
! B+
! AB−
! AB+
|-
! O−
| style="width:3em" | {{Y}}
| style="width:3em" | {{N}}
| style="width:3em" | {{N}}
| style="width:3em" | {{N}}
| style="width:3em" | {{N}}
| style="width:3em" | {{N}}
| style="width:3em" | {{N}}
| style="width:3em" | {{N}}
|-
! O+
| {{Y}}
| {{Y}}
| {{N}}
| {{N}}
| {{N}}
| {{N}}
| {{N}}
| {{N}}
|-
! A−
| {{Y}}
| {{N}}
| {{Y}}
| {{N}}
| {{N}}
| {{N}}
| {{N}}
| {{N}}
|-
! A+
| {{Y}}
| {{Y}}
| {{Y}}
| {{Y}}
| {{N}}
| {{N}}
| {{N}}
| {{N}}
|-
! B−
| {{Y}}
| {{N}}
| {{N}}
| {{N}}
| {{Y}}
| {{N}}
| {{N}}
| {{N}}
|-
! B+
| {{Y}}
| {{Y}}
| {{N}}
| {{N}}
| {{Y}}
| {{Y}}
| {{N}}
| {{N}}
|-
! AB−
| {{Y}}
| {{N}}
| {{Y}}
| {{N}}
| {{Y}}
| {{N}}
| {{Y}}
| {{N}}
|-
! AB+
| {{Y}}
| {{Y}}
| {{Y}}
| {{Y}}
| {{Y}}
| {{Y}}
| {{Y}}
| {{Y}}
|}
<small>
Table note<br />
1. Assumes absence of atypical antibodies that would cause an incompatibility between donor and recipient blood, as is usual for blood selected by cross matching.
</small>

An Rh D-negative patient who does not have any anti-D antibodies (never been previously sensitized to D-positive RBCs) can receive a transfusion of D-positive blood, but this may cause sensitization to the D antigen, and a female patient could become at risk for [[hemolytic disease of the newborn]].  If a D-negative patient has developed anti-D antibodies, a subsequent exposure to D-positive blood could lead to a potentially dangerous transfusion reaction. Rh D-positive blood should never be given to D-negative women of childbearing age or to patients with D antibodies, so blood banks must conserve Rh-negative blood for these patients. In extreme circumstances, such as for a major bleed when stocks of D-negative blood units are very low at the blood bank, D-positive blood might be given to D-negative females above childbearing age or to Rh-negative males, provided that they did not have anti-D antibodies, to conserve D-negative inventory in the blood bank. The converse is not true; Rh D-positive patients do not react to D-negative blood.

This same matching is done for other antigens of the Rh system as C, c, E, and e, and for other blood group systems with a known risk for alloimmunization, such as the Kell system, particularly for chronically transfused patients.

===Plasma compatibility===
[[File:Plasma donation compatibility path.svg|right|190px|thumb|'''Plasma compatibility chart'''<br />In addition to donating to the same blood group, plasma from type AB can be given to A, B, and O; plasma from types A, B, and AB can be given to O.]]
[[Blood plasma]] compatibility is the inverse of red blood cell compatibility.<ref>{{cite web|title=Blood Component ABO Compatibility Chart Red Blood Cells and Plasma|url=https://www.pathology.med.umich.edu/blood-bank/blood-component-and-compatibility|archive-url=https://web.archive.org/web/20190616012246/https://www.pathology.med.umich.edu/blood-bank/blood-component-and-compatibility|archive-date=16 June 2019|website=Blood Bank Labsite|publisher=University of Michigan|access-date=16 December 2014}}</ref> Type AB plasma carries neither anti-A nor anti-B antibodies and can be transfused to individuals of any blood group; but type AB patients can only receive type AB plasma. Type O carries both antibodies, so individuals of blood group O can receive plasma from any blood group, but type O plasma can be used only by type O recipients.
<!--Please don't switch donor and recipient here without being absolutely sure they're wrong. Check the cited source; any change must match it. It seems a lot of people switch this without actually understanding it, because it's often edited from the correct (AB can donate plasma to all blood groups) to the wrong.-->

{| class="wikitable" style="text-align:center;"
|+ Plasma compatibility table<ref>{{cite web|title=Plasma Compatibility|url=https://mytransfusion.com.au/about-blood/matching-blood-groups|archive-url=https://web.archive.org/web/20200507180725/https://mytransfusion.com.au/about-blood/matching-blood-groups|archive-date=7 May 2020|website=Matching Blood Groups|publisher=Australian Red Cross|access-date=19 June 2020}}</ref>
|-
! {{diagonal split header|Recipient|Donor}}
! style="width:3em" | O
! style="width:3em" | A
! style="width:3em" | B
! style="width:3em" | AB
|-
! O
| {{Y}}
| {{Y}}
| {{Y}}
| {{Y}}
|-
! A
| {{N}}
| {{Y}}
| {{N}}
| {{Y}}
|-
! B
| {{N}}
| {{N}}
| {{Y}}
| {{Y}}
|-
! AB
| {{N}}
| {{N}}
| {{N}}
| {{Y}}
|}

<small>
Table note<br />
1. Assuming the absence of strong atypical antibodies in donor plasma
</small>

===Universal donors and universal recipients===
[[File:US Navy 060105-N-8154G-010 A hospital corpsman with the Blood Donor Team from Portsmouth Naval Hospital takes samples of blood from a donor for testing.jpg|thumb|right|220px|A hospital worker takes samples of blood from a donor for testing]]

In transfusions of red blood cells, individuals with type O Rh D-negative blood are often called universal donors. Those with type AB Rh D-positive blood are called universal recipients. However, these terms are only generally true with respect to possible reactions of the recipient's anti-A and anti-B antibodies to transfused red blood cells, and also possible sensitization to Rh D antigens. One exception is individuals with [[hh antigen system]] (also known as the Bombay phenotype) who can only receive blood safely from other hh donors, because they form antibodies against the H antigen present on all red blood cells.<ref>{{cite book |title=Harrison's Principals of Internal Medicine |last=Fauci |first=Anthony S. |author2=Eugene Braunwald |author3=Kurt J. Isselbacher |author4=Jean D. Wilson |author5=Joseph B. Martin |author6=Dennis L. Kasper |author7=Stephen L. Hauser |author8=Dan L. Longo |year=1998 |publisher=McGraw-Hill |isbn=0-07-020291-5 |page=[https://archive.org/details/harrisonsprincie14harr/page/719 719] |url-access=registration |url=https://archive.org/details/harrisonsprincie14harr }}</ref><ref>{{cite web |url=https://www.webmd.com/a-to-z-guides/blood-type-test |title=Universal acceptor and donor groups |publisher=Webmd.com |date=2008-06-12 |access-date=2010-08-01 |archive-date=2010-07-22 |archive-url=https://web.archive.org/web/20100722071429/http://www.webmd.com/a-to-z-guides/blood-type-test |url-status=live }}</ref>

Blood donors with exceptionally strong anti-A, anti-B, or any atypical blood group antibody may be excluded from blood donation of high plasma volume blood products. In general, while the plasma fraction of a blood transfusion may carry donor antibodies not found in the recipient, a significant reaction is unlikely because of dilution.

Additionally, red blood cell surface antigens other than A, B and Rh D might cause adverse reactions and sensitization, if they can bind to the corresponding antibodies to generate an immune response.  Transfusions are further complicated because [[platelet]]s and [[white blood cell]]s (WBCs) have their own systems of surface antigens, and sensitization to platelet or WBC antigens can occur as a result of transfusion.

For transfusions of [[Plasma (blood)|plasma]], this situation is reversed.  Type O plasma, containing both anti-A and anti-B antibodies, can only be given to O recipients.  The antibodies will attack the antigens of any other blood type.  Conversely, AB plasma can be given to patients of any ABO blood group, because it does not contain any anti-A or anti-B antibodies.

==Blood typing==
{{main|Blood typing}}
Typically, blood type tests are performed by adding a blood sample to a solution containing antibodies corresponding to each antigen. The presence of an antigen on the surface of the blood cells is indicated by [[Hemagglutination|agglutination]].

===Blood group genotyping===
In addition to the current practice of serologic testing of blood types, the progress in molecular diagnostics allows the increasing use of blood group genotyping,<ref>{{cite journal | author=Flegel | author2=Wagner | author3=Müller | author4=Gassner | title=Rh phenotype prediction by DNA typing and its application to practice | journal=Transfusion Medicine | volume=8 | issue=4 | date=1998 | issn=0958-7578 | doi=10.1046/j.1365-3148.1998.00173.x | pages=281–302 | url=https://onlinelibrary.wiley.com/doi/10.1046/j.1365-3148.1998.00173.x | access-date=2025-07-20| url-access=subscription }}</ref> commonly known as [[red cell genotyping]].<ref>{{cite journal |author=Avent ND |title=Molecular genetic methods: principles and feasibility in transfusion medicine |journal=Vox Sang |volume=74|year= 1998|doi= 10.1111/j.1423-0410.1998.tb05432.x|pmid=9704457| pages=275–84}}</ref><ref>{{cite journal |author=Anstee DJ |title=Red cell genotyping and the future of pretransfusion testing |journal=Blood |volume=114|issue=2|year= 2009|doi= 10.1182/blood-2008-11-146860|pmid=19411635| pages=248–56|doi-access=free}}</ref><ref>{{cite journal | last=Flegel | first=Willy A | last2=Gottschall | first2=Jerome L | last3=Denomme | first3=Gregory A | title=Integration of red cell genotyping into the blood supply chain: a population-based study | journal=The Lancet Haematology | volume=2 | issue=7 | date=2015 | doi=10.1016/S2352-3026(15)00090-3 | doi-access=free |pmid=26207259| pages=e282–e288 | url=https://europepmc.org/articles/pmc4508019?pdf=render | access-date=2025-07-20| pmc=4508019 }}</ref> In contrast to serologic tests reporting a direct blood type phenotype, genotyping allows the prediction of a phenotype based on the knowledge of the molecular basis of the currently known antigens. This allows a more detailed determination of the blood type and therefore a better match for transfusion, which can be crucial in particular for patients with needs for many transfusions to prevent alloimmunization.<ref>{{cite journal |author=Avent ND |title=Large-scale blood group genotyping: clinical implications |journal=Br J Haematol |volume=144|issue=1|year= 2009|doi= 10.1111/j.1365-2141.2008.07285.x|pmid=19016734| pages=3–13|doi-access=free}}</ref>

==History==
Blood types were first discovered by an Austrian physician, [[Karl Landsteiner]], working at the Pathological-Anatomical Institute of the University of Vienna (now [[Medical University of Vienna]]). In 1900, he found that blood sera from different persons would clump together (agglutinate) when mixed in test tubes, and not only that, some human blood also agglutinated with animal blood.<ref>{{cite journal |author=Landsteiner K |title=Zur Kenntnis der antifermentativen, lytischen und agglutinierenden Wirkungen des Blutserums und der Lymphe |journal=Zentralblatt für Bakteriologie, Parasitenkunde und Infektionskrankheiten|volume=27 |pages=357–362 |year=1900}}</ref> He wrote a two-sentence footnote:

{{Blockquote|The serum of healthy human beings not only agglutinates animal red cells, but also often those of human origin, from other individuals. It remains to be seen whether this appearance is related to inborn differences between individuals or is the result of some damage of a bacterial kind.<ref name=kantha>{{cite journal |last1=Kantha |first1=S.S. |title=The blood revolution initiated by the famous footnote of Karl Landsteiner's 1900 paper |journal=The Ceylon Medical Journal |date=1995 |volume=40 |issue=3 |pages=123–125 |pmid=8536328 }}</ref>}}

This was the first evidence that blood variation exists in humans. The next year, in 1901, he made a definitive observation that the blood serum of an individual would agglutinate with only those of certain individuals. Based on this, he classified human blood into three groups, namely group A, group B, and group C. He defined that group A blood agglutinates with group B, but never with its own type. Similarly, group B blood agglutinates with group A. Group C blood is different in that it agglutinates with both A and B.<ref>{{Cite journal |last=Kantha |first=S. S. |date=September 1995 |title=The blood revolution initiated by the famous footnote of Karl Landsteiner's 1900 paper |journal=The Ceylon Medical Journal |volume=40 |issue=3 |pages=123–125 |issn=0009-0875 |pmid=8536328}}</ref> This was the discovery of blood groups for which Landsteiner was awarded the Nobel Prize in Physiology or Medicine in 1930. (C was later renamed to O after the German ''Ohne'', meaning without, or zero, or null.<ref>{{Cite journal |last=Landsteiner |first=Karl |date=1961-01-02 |title=On Agglutination of Normal Human Blood |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1537-2995.1961.tb00005.x |journal=Transfusion |language=en |volume=1 |issue=1 |pages=5–8 |doi=10.1111/j.1537-2995.1961.tb00005.x |pmid=13758692 |issn=0041-1132|url-access=subscription }}</ref>) Another group (later named AB) was discovered a year later by Landsteiner's students Adriano Sturli and Alfred von Decastello without designating the name (simply referring it to as "no particular type").<ref>{{Cite journal |last1=Farhud |first1=Dariush D. |last2=Zarif Yeganeh |first2=Marjan |date=2013 |title=A brief history of human blood groups |journal=Iranian Journal of Public Health |volume=42 |issue=1 |pages=1–6 |issn=2251-6085 |pmc=3595629 |pmid=23514954}}</ref><ref>{{cite journal |last1=Von Decastello |first1=A. |last2=Sturli |first2=A. |title=Concerning isoagglutinins in serum of healthy and sick humans |journal=Munchener Medizinische Wochenschrift |date=1902 |volume=26 |pages=1090–1095}}</ref><ref name="Farr1979">{{cite journal |author=Farr AD |title=Blood group serology—the first four decades (1900–1939) |journal=Medical History |volume=23 |issue=2 |pages=215–26 |date=April 1979 |pmid=381816 |pmc=1082436 |doi=10.1017/s0025727300051383}}</ref> Thus, after Landsteiner, three blood types were initially recognised, namely A, B, and C.<ref name="Farr1979" />

Czech serologist [[Jan Janský]] was the first to recognise and designate four blood types in 1907 that he published in a local journal,<ref name="Janský_1907">{{cite journal |author=Janský J. |year=1907 |title=Haematologické studie u psychotiků |journal=Sborník Klinický |language=cs |volume=8 |pages=85–139}}</ref> using the Roman numerical I, II, III, and IV (corresponding to modern O, A, B, and AB respectively).<ref>{{cite journal |last1=Garratty |first1=G. |last2=Dzik |first2=W. |last3=Issitt |first3=P.D. |last4=Lublin |first4=D.M. |last5=Reid |first5=M.E. |last6=Zelinski |first6=T. |title=Terminology for blood group antigens and genes—historical origins and guidelines in the new millennium |journal=Transfusion |date=April 2000 |volume=40 |issue=4 |pages=477–489 |doi=10.1046/j.1537-2995.2000.40040477.x |pmid=10773062 }}</ref> Unknown to Janský, American physician [[William Lorenzo Moss|William L. Moss]] introduced an almost identical classification in 1910,<ref name="Moss_1910">{{cite journal|author=Moss W.L.|year=1910|title=Studies on isoagglutinins and isohemolysins|journal=Bulletin of the Johns Hopkins Hospital|volume=21|pages=63–70}}</ref> but with Moss's I and IV corresponding to Janský's IV and I.<ref name="Farr19793">{{cite journal |last1=Farr |first1=A. D. |title=Blood group serology—the first four decades (1900–1939) |journal=Medical History |date=April 1979 |volume=23 |issue=2 |pages=215–226 |doi=10.1017/S0025727300051383 |pmc=1082436 |pmid=381816 }}</ref> Thus the existence of two systems immediately created confusion and potential danger in medical practice. Moss's system was adopted in Britain, France, and the US, while Janský's was preferred in most other European countries and some parts of the US. It was reported that "The practically universal use of the Moss classification at that time was completely and purposely cast aside. Therefore, in place of bringing order out of chaos, chaos was increased in the larger cities."<ref>{{cite journal |last1=Kennedy |first1=James A. |title=BLOOD GROUP CLASSIFICATIONS USED IN HOSPITALS IN THE UNITED STATES AND CANADA: FINAL REPORT |journal=Journal of the American Medical Association |date=23 February 1929 |volume=92 |issue=8 |pages=610 |doi=10.1001/jama.1929.02700340010005 }}</ref> To resolve the confusion, the [[American Association of Immunologists]], the [[American Society for Microbiology|Society of American Bacteriologists]], and the Association of Pathologists and Bacteriologists made a joint recommendation in 1921 that the Jansky classification be adopted based on priority.<ref>{{cite journal |last1=Garratty |first1=G. |last2=Dzik |first2=W. |last3=Issitt |first3=P.D. |last4=Lublin |first4=D.M. |last5=Reid |first5=M.E. |last6=Zelinski |first6=T. |title=Terminology for blood group antigens and genes—historical origins and guidelines in the new millennium |journal=Transfusion |date=April 2000 |volume=40 |issue=4 |pages=477–489 |doi=10.1046/j.1537-2995.2000.40040477.x |pmid=10773062 }}</ref> But it was not followed particularly where Moss's system had been used.<ref name="Doan1927">{{cite journal |last1=Doan |first1=Charles A. |title=The Transfusion Problem |journal=Physiological Reviews |date=1927 |volume=7 |issue=1 |pages=1–84 |doi=10.1152/physrev.1927.7.1.1 }}</ref>

In 1927, Landsteiner, who had moved to the [[Rockefeller University|Rockefeller Institute for Medical Research]] in New York, and as a member of a committee of the [[National Research Council (United States)|National Research Council]] concerned with blood grouping suggested to substitute Janský's and Moss's systems with the letters O, A, B, and AB. There was another confusion on the use of O, which was introduced by Polish physician [[Ludwik Hirszfeld]] and German physician [[Emil von Dungern]] in 1910.<ref name=":0">{{cite journal |last1=Okroi |first1=Mathias |last2=McCarthy |first2=Leo J. |title=The Original Blood Group Pioneers: The Hirszfelds |journal=Transfusion Medicine Reviews |date=July 2010 |volume=24 |issue=3 |pages=244–246 |doi=10.1016/j.tmrv.2010.03.006 |pmid=20656191 }}</ref> It was never clear whether it was meant for the figure 0, German ''null'' for zero or the upper case letter O for ''ohne'', meaning without; Landsteiner chose the letter.<ref name="SchmidtOkroi2001">{{cite journal |last1=Schmidt |first1=P. |last2=Okroi |first2=M. |title=Also sprach Landsteiner – Blood Group 'O' or Blood Group 'NULL' |journal=Transfusion Medicine and Hemotherapy |date=2001 |volume=28 |issue=4 |pages=206–208 |doi=10.1159/000050239 }}</ref>

In 1928 the Permanent Commission on Biological Standardization adopted Landsteiner's proposal and stated:{{blockquote|The Commission learns with satisfaction that, on the initiative of the Health Organization of the League of Nations, the nomenclature proposed by von Dungern and Hirszfeld for the classification of blood groups has been generally accepted, and recommends that this nomenclature shall be adopted for international use as follows: 0 A B AB. To facilitate the change from the nomenclature hitherto employed, the following is suggested:
* Jansky ....O(I) A(II) B(III) AB(IV)
* Moss ... O(IV) A(II) B(III) AB(I)<ref>{{Cite journal|last=Goodman|first=Neville M.|date=1940|title=Nomenclature of Blood Groups|journal=British Medical Journal|volume=1|issue=4123|pages=73|doi=10.1136/bmj.1.4123.73-a|pmc=2176232}}</ref>
}}This classification became widely accepted and after the early 1950s it was universally followed.<ref>{{Cite journal |last=Goodman |first=N. M. |date=1940-01-13 |title=Nomenclature of Blood Groups |url=https://www.bmj.com/lookup/doi/10.1136/bmj.1.4123.73-a |journal=BMJ |language=en |volume=1 |issue=4123 |pages=73 |doi=10.1136/bmj.1.4123.73-a |issn=0959-8138|url-access=subscription }}</ref><ref>{{cite journal |last1=Garratty |first1=G. |last2=Dzik |first2=W. |last3=Issitt |first3=P.D. |last4=Lublin |first4=D.M. |last5=Reid |first5=M.E. |last6=Zelinski |first6=T. |title=Terminology for blood group antigens and genes—historical origins and guidelines in the new millennium |journal=Transfusion |date=April 2000 |volume=40 |issue=4 |pages=477–489 |doi=10.1046/j.1537-2995.2000.40040477.x |pmid=10773062 }}</ref>

Hirszfeld and Dungern discovered the inheritance of blood types as [[Mendelian genetics]] in 1910 and the existence of sub-types of A in 1911.<ref name=":0" /><ref>{{cite journal |last1=Dungern |first1=E. |last2=Hirschfeld |first2=L. |title=Über Vererbung gruppenspezifischer Strukturen des Blutes |journal=Zeitschrift für Induktive Abstammungs- und Vererbungslehre |date=December 1911 |volume=5 |issue=1 |pages=196–197 |doi=10.1007/BF01798027 }}</ref> In 1927, Landsteiner, with [[Philip Levine (physician)|Philip Levine]], discovered the [[MN blood group|MN blood group system]],<ref>{{cite journal |last1=Landsteiner |first1=K. |last2=Levine |first2=P. |title=A New Agglutinable Factor Differentiating Individual Human Bloods. |journal=Experimental Biology and Medicine |date=1927 |volume=24 |issue=6 |pages=600–602 |doi=10.3181/00379727-24-3483 }}</ref> and the [[P antigen system|P system]].<ref>{{cite journal |last1=Landsteiner |first1=K. |last2=Levine |first2=P. |title=Further Observations on Individual Differences of Human Blood. |journal=Experimental Biology and Medicine |date=1927 |volume=24 |issue=9 |pages=941–942 |doi=10.3181/00379727-24-3649 }}</ref> Development of the [[Coombs test]] in 1945,<ref>{{cite journal |vauthors=Coombs RR, Mourant AE, Race RR |title=A new test for the detection of weak and incomplete Rh agglutinins |journal=Br J Exp Pathol |volume=26 |pages=255–66 |year=1945 |issue=4 |pmid=21006651 |pmc=2065689 }}</ref> the advent of [[transfusion medicine]], and the understanding of [[ABO hemolytic disease of the newborn]] led to discovery of more blood groups. {{as of|2025|June}}, the International Society of Blood Transfusion (ISBT) recognizes 48 blood groups.<ref name=":1" />

==Society and culture==
{{Main|Blood type personality theory}}
A popular [[pseudoscientific]] belief in Eastern Asian countries (especially in [[Japan]] and [[South Korea]]<ref name=AP>{{cite news|url=https://www.medbroadcast.com/channel_health_news_details.asp?news_id=17166&channel_id=1000 |title=Despite scientific debunking, in Japan you are what your blood type is |agency=Associated Press |publisher=MediResource Inc. |access-date=2011-08-13 |date=2009-02-01 |url-status=dead |archive-url=https://web.archive.org/web/20110928021954/https://www.medbroadcast.com/channel_health_news_details.asp?news_id=17166&channel_id=1000 |archive-date=September 28, 2011 }}</ref>) is that a person's ABO blood type is predictive of their [[Personality psychology|personality]], [[moral character|character]], and [[Interpersonal compatibility|compatibility with others]].<ref name=Nuwer>{{cite magazine|last=Nuwer|first=Rachel|author-link=Rachel Nuwer |title=You are what you bleed: In Japan and other east Asian countries some believe blood type dictates personality|url=https://blogs.scientificamerican.com/guest-blog/2011/02/15/you-are-what-you-bleed-in-japan-and-other-east-asian-countries-some-believe-blood-type-dictates-personality/|magazine=Scientific American|access-date=16 Feb 2011|archive-date=10 January 2012|archive-url=https://web.archive.org/web/20120110205136/http://blogs.scientificamerican.com/guest-blog/2011/02/15/you-are-what-you-bleed-in-japan-and-other-east-asian-countries-some-believe-blood-type-dictates-personality/|url-status=live}}</ref> Researchers have established no scientific basis exists for blood type personality categorization, and studies have found no "significant relationship between personality and blood type, rendering the theory 'obsolete' and concluding that no basis exists to assume that personality is anything more than randomly associated with blood type."<ref name=AP/>

==See also==
* [[Blood type (non-human)]]
* [[Human leukocyte antigen]]
* [[hh blood group]]
* [[Relationship between blood group and COVID-19]]

==References==
{{reflist}}

==Further reading==
* {{cite book |title = Blood Groups and Red Cell Antigens, a guide to the differences in our blood types that complicate blood transfusions and pregnancy |last = Dean |first = Laura |publisher = [[National Center for Biotechnology Information]] |location=Bethesda MD |year=2005 |id=NBK2261 |url=https://www.ncbi.nlm.nih.gov/books/NBK2261/ |isbn=1-932811-05-2}}
* {{cite book |vauthors=Mollison PL, Engelfriet CP, Contreras M |title=Blood Transfusion in Clinical Medicine |publisher=Blackwell Science |location=Oxford UK |year=1997 |isbn=0-86542-881-6 |edition=10th }}

==External links==
{{Commons category|Blood types}}{{Wikifunctions|Z14469|blood compatibility}}
* [https://web.archive.org/web/20090110011046/http://www.ncbi.nlm.nih.gov/gv/mhc/xslcgi.cgi?cmd=bgmut/home BGMUT] Blood Group Antigen Gene Mutation Database at [[National Center for Biotechnology Information|NCBI]], [[NIH]] has details of genes and proteins, and variations thereof, that are responsible for blood types
* {{OMIM|110300|ABO Glycosyltransferase; ABO}}
* {{OMIM|111680|Rhesus Blood Group, D Antigen; RHD}}
* {{cite web |url= https://www.gene-tests.org/blood-group-test |title= Blood group test |access-date= 2017-03-23 |publisher= Gentest.ch GmbH |archive-url= https://web.archive.org/web/20170324083743/https://www.gene-tests.org/blood-group-test |archive-date= 2017-03-24 |url-status= dead }}
* {{cite web | url = https://www.lifeshare.org/facts/raretraits.htm | title = Blood Facts&nbsp;– Rare Traits | access-date = September 15, 2006 | publisher = LifeShare Blood Centers | url-status=dead | archive-url = https://web.archive.org/web/20060926110321/https://www.lifeshare.org/facts/raretraits.htm | archive-date = September 26, 2006 }}
* {{cite web | url = https://anthro.palomar.edu/vary/vary_3.htm | title = Modern Human Variation: Distribution of Blood Types | access-date = November 23, 2006 | date = 2001-06-06 | publisher = Dr. Dennis O'Neil, Behavioral Sciences Department, Palomar College, San Marcos, California | archive-url = https://web.archive.org/web/20010606114236/https://anthro.palomar.edu/vary/vary_3.htm | archive-date = 2001-06-06 | url-status=dead }}
* {{cite web | url = https://www.bloodbook.com/world-abo.html | title = Racial and Ethnic Distribution of ABO Blood Types&nbsp;– BloodBook.com, Blood Information for Life | access-date = September 15, 2006 | publisher = bloodbook.com | archive-url = https://web.archive.org/web/20100304222457/https://www.bloodbook.com/world-abo.html | archive-date = 2010-03-04 | url-status=dead }}
* {{cite web | url = https://abobloodgroup.googlepages.com/home | title = Molecular Genetic Basis of ABO | access-date = July 31, 2008 | archive-date = December 7, 2008 | archive-url = https://web.archive.org/web/20081207212956/http://abobloodgroup.googlepages.com/home | url-status = dead }}

{{Transfusion medicine}}
{{Authority control}}

{{DEFAULTSORT:Blood Type}}
[[Category:Blood|Type]]
[[Category:Genetics]]
[[Category:Hematology]]
[[Category:Transfusion medicine]]
[[Category:Antigens]]