B lymphocytes and humoral immunity

• Pathogens enter the bloodstream and phagocytosis occurs
• Pathogen antigens circulate in the bloodstream
• Specific B lymphocytes engulf pathogenic antigens
• Foreign antigens are presented on the surface of B lymphocytes
• Activated T helper cells bind to the presented antigens
• Activated T helpers "activate" one type of B lymphocyte to divide by mitosis
• The clones differentiate to form plasma and memory B lymphocytes
• Plasma B cells produce thousands of antibodies
• Antibodies are released into the bloodstream and bind to the antigens of the invading pathogen forming antigen-antibody complexes
• Memory B cells remain and are used for subsequent invasions
• In secondary response, the memory cells divide rapidly to form plasma cells
• Secondary response is more rapid and of greater intensity