Secretory mechanisms in cell-mediated cytotoxicity.

Cytotoxic T lymphocytes (CTLs) play a critical role in the immune system; they are able to recognize and destroy virally infected and tumorigenic cells. Specific recognition of MHC class I-peptide complexes by the T cell receptor (TcR) results in precise delivery of lytic granules to the target cell, sparing neighboring cells and the CTL itself. Over the past 10 years various studies have eludicated the mechanisms that lead to the rapid polarization of the secretory apparatus in CTLs. These studies highlight similarities and differences between polarity and secretory mechanisms seen in other cell types and developmental systems. This review focuses on recent advances in our understanding of the molecular basis of polarized secretion from CTLs and the novel mechanism used by these cells to deliver their lethal hit.