Expression of perforin in murine natural killer cells and cytotoxic T lymphocytes in vivo

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Abstract
We have previously detected perforin expression in a subpopulation of asialo GM1+ natural killer (NK) cells and CD8+ T lymphocytes in murine spleen cells by immunocytochemical staining with an anti‐perforin monoclonal antibody. In the present study, more datailed analyses of perforin expression in murine cytotoxic lymphocyte subpopulations were performed. The expression of perforin in asialo GM1+ spleen cells was predominantly confined to the NK1.1+ subset, where all NK activity also resided. Perforin expression was also studied on alloreactive cytotoxic T lymphocyte (CTL) induced in vivo. The cells expressing perforin in peritoneal exudate lymphocytes predominantly resided in the CD8+ T cell subpopulation co‐expressing asialo GM1 where an allospecific CTL activity also resided. Furthermore, the percentage of perforin‐positive cells in this population was greatly reduced after stimulation with anti‐CD3 or anti‐T cell receptors antibodies, which induce serine esterase release from the cytoplasmic granules. These findings highly suggest that perforin is involved in in vivo NK cell and CTL‐mediated cytolysis.