ABO blood group system alleles in white individuals of the ABO gene that produce one's blood type: The same study also identified 18 rare alleles, which generally have a weaker glycosylation activity. People with weak alleles of A can sometimes express anti-A antibodies, though these are usually not clinically significant as they do not stably interact with the antigen at body temperature. Cis AB is another rare variant, in which A and B genes are transmitted together from a single parent. The distribution of the blood groups A, B, O and AB varies across the world according to the population. There are also variations
Blood type (non-human) blood. Two categories of blood groups, human-type and simian-type, have been found in apes and monkeys, and can be tested by methods established for grouping human blood. The rhesus system is named after the rhesus monkey, following experiments by Karl Landsteiner and Alexander S. Wiener, which showed that rabbits, when immunised with rhesus monkey red cells, produce an antibody that also agglutinates the red blood cells of many humans. Data on blood groups of chimpanzees, baboons, and macaques. Two complex chimpanzee blood group systems, V-A-B-D and R-C-E-F systems, proved to be counterparts of the human MNS and Rh-Hr blood group