Function of T cells; most effective against intracellular microorganisms: viruses, fungi, intracellular bacteria, parasitesCytotoxic T cells function in two ways:Lyse virus-infected cells, tumor cells, and tissue transplants. Major lysin is perforin, which forms a hole in the plasma membrane of the target cell.Produce cytokines, which promote phagocytosis and inflammationAs in antibody mediated immunity, memory cells are produced.Delayed hypersensitivity T cells. Involved in allergic reactions; e.g., poison ivy. Hapten that binds to proteins in the skin, then antigen processed by Langerhans cells (APCs) of the skin and presented to delayed hypersensitivity T cells.