Cell-Mediated Immunity

• Provides resistance in the intracellular phase of bacteria and viral infections.
• Pathogens invade and replicate inside their host's own cells.
• There are thousands of T-cells, and each type responds to one particular antigen.
• Antigen-presenting cells present the antigen to a particular type of T-cell which then becomes sensitised.
• Sensitised T-cells enlarge and divide, becoming clones.
• Some cloned T-cells become memory cells, which can recognise antigens providing a quicker response.
• Killer T-cells migrate to the site of infection and attach to the invading cells and secrete a chemical.
• The chemical released by killer T-cells destroy antigens.
• Helper T-cells bind to the antigen on antigen-presenting cells stimulating the secretion of cytokines.
• Cytokines secreted by Helper T-cells attract lymphocytes which intensifies the response.
• Cytokines released by Helper T-cells attract macrophages which destroy antigens by phagocytosis.