Antibodies are proteins that play an integral role in the complex system of specific immunity.
They bind to and inactivate foreign proteins called antigens.
Each type of antibody binds to one kind of antigen molecule.
B cells are one of the two types of white blood cells that make antibodies.
When a bacterial cell enters the bloodstream, proteins on its surface act as antigens and trigger response by the immune system.
These antigens will bind to the unique B cells that have the corresponding antibodies on their surfaces.
These B cells now divide.
Some continue to divide, producing many plasma cells.
Plasma cells secrete large quantities of antibodies into the bloodstream.
This division of only the appropriate B cells is called clonal selection.