Granule serine proteases are normal nuclear constituents of natural killer cells

Abstract

One mechanism by which cytotoxic T lymphocytes and natural killer cells inflict target cell death depends upon secreting the contents of their specialized cytoplasmic granules, containing a pore-forming protein, perforin, and a family of homologous serine proteases ('granzymes') with various enzyme activities. We used a granzyme B-specific mouse anti-human monoclonal antibody 2C5 and Western blotting to demonstrate that nuclear extracts of human interleukin-2-stimulated peripheral blood mononuclear cells, the human NK leukemia cell line YT, and the rat NK leukemia cell line RNK-16 contain abundant granzyme B. In interleukin-2-activated peripheral blood mononuclear cells, more than 50% of the..