Antibodies are proteins that protect against foreign invaders, either foreign molecules, viruses, or cells. They are capable of recognizing specific particles due to their shape. Their ability to recognize foreign shapes makes them useful in defending against foreign invaders.
Antigens are molecules that antibodies are capable of recognizing. They are usually a protein or carbohydrate chain. The body can recognize bacteria and viruses as being foreign because they have antigens on their surface which are different than the bodies "self" antigens.
Antibodies are produced by B lymphocytes.
Antibodies are Y-shaped molecules.
The basic unit of an antibody, or immunoglobulin, is a tetramer of four polypeptides: two identical light chains and two identical heavy chains, each consisting of a constant and a variable region.
Antibodies fit together with and bind with antigens like a lock and key.
The body does not produce antibodies that bind to its own (self) antigens. Therefore all particles that are bound to antibodies are foreign.
Cells, particles, or molecules that are marked with antibodies,
1. may be phagocytized (engulfed) by neutrophils or macrophages.
2. may agglutinate (clump together) because each antibody is capable of binding to two antigens. Antigens attached to cells will cause the cells to clump together. The clumps are then destroyed by phagocytes.