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 a 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.