Welcome to Current TV The Mystery of Human Blood Types The ABO
blood group was discovered in the first decade of the 1900s by
Austrian physician Karl Landsteiner. Through a series of
experiments, Landsteiner classified blood into the four well-
known types. The “type” actually refers to the presence of a
particular type of antigen sticking up from the surface of a red
blood cell. An antigen is anything that elicits a response from
an immune cell called an antibody. Antibodies latch onto foreign
substances that enter the body, such as bacteria and viruses,
and clump them together for removal by other parts of the immune
system. The human body naturally makes antibodies that will
attack certain types of red-blood-cell antigens. For example,
people with type A blood have A antigens on their red blood
cells and make antibodies that attack B antigens; people with
type B blood have B antigens on their red blood cells and make
antibodies that attack A antigens. So, type A people can’t
donate their blood to type B peo