blood types

well.. antigen & antibody is the differentiating factors between the blood of different ppl.All humans & many other primates can be typed for the ABO blood group. There r four principal types: A, B, AB, & O. There r two antigens & two antibodies that r mostly responsible for the ABO types. The specific combination of these four components determines an individual is type in most cases. The table below shows the possible permutations of antigens & antibodies with the corresponding ABO type (''yes'' indicates the presence of a component & ''no'' indicates its absence in the blood of an individual).

ABO Blood Type Antigen A Antigen B Antibody anti-A antibody Anti-B antibody

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A yes no no yes
B no yes yes no
O no no yes yes
AB yes yes no no

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For example, people with type A blood will have the A antigen on the surface of their red cells. As a result, anti-A antibodies will not be produced by them because they would cause the destruction of their own blood. However, if B type blood is injected into their systems, anti-B antibodies in their plasma will recognize it as alien & burst or agglutinate the introduced red cells in order to cleanse the blood of alien protein.
and antigen a stands for alpha & b for beta.i must confess i really do not know the meaning of the anti bodies.

Blood is a fluid connective tissue common to all human beings whereas blood types are variants due to the variety of only 2 antigens as A and B with their corresponding antibodies as alpha and beta, respectively!