-- determined by the presence or absence of antigens A and B      -- type A blood has only antigen A      -- type B blood has only antigen B      -- type AB blood has antigens A and B      -- type O blood has neither antigen

-- blood contains antibodies against the antigens the red blood cells don’t have      -- type A blood has B antibodies      -- type B blood has A antibodies      -- type AB blood has no antibodies      -- type O blood has both A and B antibodies

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