Memory cells insure that subsequent infections by the pathogen receive a more rapid response. Plasma cells secrete large amounts of the antigen-specific antibody. T helper cells, part of the cellular system, are usually required for the clonal selection of B cells. Antibody secreted by plasma cells forms complexes with free pathogens and their toxic products. The complexes can inactivate pathogens and stimulate other innate systems including phagocytic cells and complement to eliminate the danger from our extracellular fluids.
Some pathogens can escape antibody detection by infecting cells.
Cells containing pathogen display antigen fragments on their cell surfaces. Helper T cells regulate other cells of the immune system through secretion of molecules called cytokines. All rights reserved.