Antibody-mediated immunity involves the activation of B cells and secretion of antibodies when in contact with a pathogen.
When exposed to the chemicals released by activated helper T cells, a sensitized B cell divides, producing daughter cells that differentiate into memory B cells and plasma cells.
Plasma cells manufacture large quantities of antibody molecules. These antibodies are specific, and will only recognize and attack the antigen that sensitized the original B cell. Antibodies can inactivate or destroy the antigen through a variety of mechanisms. For example, antibodies can bind to their antigenic targets and form antigen-antibody complexes. They can also agglutinate invading cells, forming clusters of antibodies and toxins that are relatively easy for phagocytes to find and engulf. Another potential effect of antibody binding is the activation of nonspecific defenses, such as the complement system or the inflammatory response.
Memory B cells, produced by the division of activated B cells, can patrol the body for years. Like other memory cells, memory B cells defend the body against future infections by the same pathogen.