AN ANTIMICROBIAL ACTIVITY OF CYTOLYTIC T-CELLS MEDIATED BY GRANULYSIN

Cytolytic T Lymphocytes (CTLs) kill intracellular pathogens by a granu le-dependent mechanism. Granulysin, a protein found in granules of CTL s, reduced the viability of a broad spectrum of pathogenic bacteria, f ungi, and parasites in vitro. Granulysin directly killed extracellular Mycobacterium tuberculosis, altering the membrane integrity of the ba cillus, and, in combination with perforin, decreased the viability of intracellular M. tuberculosis. The ability of CTLs to kill intracellul ar M, tuberculosis was dependent on the presence of granulysin in cyto toxic granules, defining a mechanism by which T cells directly contrib ute to immunity against intracellular pathogens.