How does the body develop antibodies?
Antigen-can be anything, a virus, bacteria, any molecule, etc.
Antibody- they are secreted from b cells.
We have a problem: we need
• To recognize a trillion of possible antigens, individually and specifically
• Each lymphocyte has a specific antibody that is expresses for its lifetimes.
• In order to mount an effective response we need to have sufficient cells specific for the
antigen in question (at least million cells)
• It is not possible having 1 million x 1 trillion (10 ) cells in the body just for specific
o Our body consist of 10 cells.
Clonal Selection of Lymphocytes
Solution: Clonal Selection
• The immune system has an extremely low frequency of cells specific for each of trillion
of specificities. (5-10 / cell)
• When a cell encounters its specific Ag, it replicates extensively, turning ~5-10 cells into
millions of progeny
• Rare antigen-specific cells can increase in number so that they get the ability to