blood groups

• Surface of red blood cells are coated with sugar and protein molecules which are able to stimulate the immune system, these molecules are called antigens
• the protein produced by the immune system is called antibodies
• antigens and antibodies combine to form a complex and cause a reaction
• there are two sugar antigens involved in the classification of ABO blood groups : antigen A and antigen B
• on the surface of red blood cells, either, both or neither antigen is present
• antigen A -> group A

  antigen B -> group B

  both -> group AB

  neither -> group O
• the body's ability to make antigens, and so their ABO blood group, is determined by DNA, therefore it is inherited
• the immune system recognises own antigens and will not produce antibodies for them, but will produce antibodies for antigens that are non-self
• group A -> produces anti-B

  group B -> produces anti-A

  group AB -> produces neither

  group O -> produces both
• Rh antigens are proteins on the surface of red blood cells
• a person with Rh antigen is Rh positive and cannot produce the antibody anti-Rh
• a person without Rh antigen is Rh negative and produces anti-Rh which reacts against Rh antigens