type iv sensitivity
Type IV Hypersensitivity. Type IV hypersensitivity â cell-mediated reactions: This is a common response to many intracellular pathogens and to large or complex infectious agents. Type IV cell-mediated hypersensitivity is initiated by T lymphocytes specifically sensitized to locally deposited antigen. The two effector mechanisms (1) delayed-type and (2) direct cytotoxicity are mediated by 2 different sub-populations of T cells.