Blood type represent contributions from both parents. A total of 36 human blood group systems and 346 antigens are now recognized by the International Society of Blood Transfusion (ISBT). The two most important ones are ABO and the Rh blood group systems; they determine someone's blood type (A, B, AB and O, with +, − or null denoting RhD status) for suitability in blood transfusion. A complete blood type would describe a full set of 30 substances on the surface of red blood cells, and an individual's blood type is one of many possible combinations of blood-group antigens. Across the 36 blood
Blood type donor's type. Some blood types are associated with inheritance of other diseases; for example, the Kell antigen is sometimes associated with McLeod syndrome. Certain blood types may affect susceptibility to infections, an example being the resistance to specific malaria species seen in individuals lacking the Duffy antigen. The Duffy antigen, presumably as a result of natural selection, is less common in racial groups from areas with a high incidence of malaria. 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 antibody