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.[better source needed] 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.
O (neither A nor B, only their precursor H oligosaccharide present)
There are subtypes under this grouping (listed as A1, A2, A1B or A2B…) some of which are quite rare. Apart from this there is a protein which plays an important part in the grouping of blood. This is called the Rh factor. If this is present, the particular blood type is called positive. If it is absent, it is called negative. Thus we have the following broad categories:[dubious– discuss][better source needed]
In the "ABO" system, (and Rhesus D system) all blood belongs to one of four major groups: A+/−, B+/−, AB+/−, or O+/−. The presence (+) or absence (−) of the RhD (Rhesus D) antigen is indicated by the plus or minus following the ABO type. But 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. The h/h blood group, also known as Oh or the Bombay blood group, is a rare blood type.
^This blood phenotype was first discovered in Bombay, now known as Mumbai, in India, by Dr. Y. M. Bhende in 1952.
^ abHelias, V.; Saison, C.; Ballif, B.A.; Peyrard, T.; Takahashi, J.; Takahashi, H.; Tanaka, M.; Deybach, J.C.; Puy, H.; Le Gall, M.; Sureau, C.; Pham, B.N.; Le Pennec, P.Y.; Tani, Y.; Cartron, J.P. & Arnaud, L. (2012). "ABCB6 is Dispensable for Erythropoiesis and Specifies the New Blood Group System Langereis"(PDF). Nature Genetics. 44 (2, January 15): 170–173. PMC3664204. PMID22246506. doi:10.1038/ng.1069. [Quoting Abstract: The human ATP-binding cassette (ABC) transporter ABCB6 has been described as a mitochondrial porphyrin transporter essential for heme biosynthesis, but it is also suspected to contribute to anticancer drug resistance, as do other ABC transporters located at the plasma membrane. We identified ABCB6 as the genetic basis of the Lan blood group antigen expressed on red blood cells but also at the plasma membrane of hepatocellular carcinoma (HCC) cells, and we established that ABCB6 encodes a new blood group system (Langereis, Lan). Targeted sequencing of ABCB6 in 12 unrelated individuals of the Lan(-) blood type identified 10 different ABCB6 null mutations. This is the first report of deficient alleles of this human ABC transporter gene. Of note, Lan(-) (ABCB6(-/-)) individuals do not suffer any clinical consequences, although their deficiency in ABCB6 may place them at risk when determining drug dosage.]CS1 maint: Uses authors parameter (link)
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.