The
ABO blood group system is the most important
blood type system (or blood group system) in human
blood transfusion. Found on
platelets,
epithelium, and cells other than
erythrocytes, AB
antigens (as with other
serotypes) can also cause an adverse immune response to
organ transplantation. The associated anti-A and anti-B
antibodies are usually
IgM antibodies, which are produced in the first years of life by sensitization to environmental substances, such as food, bacteria, and viruses. ABO blood types are also present in some other
animals, for example
rodents and
apes, such as
chimpanzees,
bonobos, and
gorillas.