antigens and antibodies

Antigens are complex molecules such as proteins, glycoproteins, and glycolipids that are

genetically unique to each individual (except identical twins). They are located on the

surfaces of all cells and allow the body to distinguish its own cells from foreign matter.

When the body detects an antigen of a foreign body, it activates an immune response.

This response consists in the production of antibodies.

Antibodies bind to antigens and mark them, or the cells bearing them, for destruction.

One method of antibody action is agglutination, in which each antibody molecule binds

to two or more antigen molecules and sticks them together. Repetition of this process

produces large antigen–antibody complexes that immobilize the antigens until certain

immune cells can break them down.

Based on the presence or absence of various antigens on the surface of the erythrocytes,

blood is categorized into different blood types. Here we discuss two major blood

groups—ABO and Rh.