Functional significance of two cytolytic pathways of cytotoxic T lymphocytes

Cytotoxic lymphocytes are equipped with several effector molecules mediating cytotoxicity. Two pathways have been molecularly defined and functionally characterized through the analysis of deficiency states. It is evident from these results that lysis by granule exocytosis serves primarily to eliminate exogenous and endogenous hazards such as virally infected and transformed cells. In contrast, lysis by induced suicide in the fas pathway is used to maintain homeostasis of rapidly expanding and contracting cell populations including T cells.