The term human blood group systems is defined by International Society of Blood Transfusion as systems in the human species where cell-surface antigens--in particular, those on blood cells--are "controlled at a single gene locus or by two or more very closely linked homologous genes with little or no observable recombination between them", and include the common ABO and Rh- (Rhesus) antigen systems, as well as many others; thirty-five major human systems are identified as of November 2014.
In addition to the ABO and Rh systems, the antigens expressed on blood cell membrane surfaces include 346 red blood cell antigens and 33 platelet antigens, as defined serologically. The genetic basis for most of these antigens lie in 45 red blood cell and 6 platelet genes. An individual, for example, can be AB RhD positive, and at the same time M and N positive in the MNS system, K positive in the Kell system, and Lea or Leb positive in the Lewis system, where these and many of the systems are named for patients in whom the corresponding antibodies were first detected.
Video Human blood group systems
Blood grouping postulates
Cells
Blood is composed of cells suspended in a liquid called plasma. Suspended in the plasma are three types of cells:
- Red blood cells carry oxygen
- White blood cells fight infection
- Platelets stop bleeding in injuries
Antigens
The most common type of grouping is the ABO blood group system. The varieties of glycoprotein coating on red blood cells divides blood into four groups:
- A (A oligosaccharide is present)
- B (B oligosaccharide is present)
- AB (A and B oligosaccharides are present)
- O (neither A nor B, only their precursor H oligosaccharide present)
Another protein, the Rh factor, plays an important part in the grouping of blood. If this is present, the particular blood type is called Rh-positive. If it is absent, it is called Rh-negative.
Maps Human blood group systems
Rare blood types
In addition to the ABO and Rh blood group systems, there are more than two hundred minor blood groups that can complicate blood transfusions. These are known as rare blood types. Whereas common blood types are expressed in a letter or two, which may be a plus or a minus, a smaller number of people express their blood type in an extensive series of letters in addition to their AB± type designation.
For example, the h/h blood group, also known as Oh or the Bombay blood group, is a rare blood type.
Blood group systems
References
Further reading
- Dean, Laura (2005). Blood Groups and Red Cell Antigens. Bethesda, MD, USA: National Center for Biotechnology Information (NCBI), National Library of Medicine, National Institutes of Health. Retrieved 19 February 2016.
- SIB-EBI-PIR (2016). "Blood group Antigen Proteins: List of Entries, 17 February version". Swiss-Prot Protein Knowledgebase. Geneva, CHE: Swiss Institute of Bioinformatic (SIB), in cooperation with the European Bioinformatics Institute (EBI, Hinxton, ENG), and the Protein Information Resource (PIR, Washington DC, USA). Retrieved 19 February 2016.
- ISBT Table of blood group antigens within systems, updated August 2008.
- BGMUT Blood Group Antigen Gene Mutation Database at NCBI, NIH.
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