The blood groups derive their names from particular structures called oligosaccharides (simply a kind of sugar) on the surface of the red blood cells (RBC). There are 2 types of sugar, sugar A and sugar B, whose combination determines part of the names. read more
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. read more