The Induction of Apoptosis in Macrophages with Activated Human Cytolytic T 4 Cell Clones
Buckmaster, Tarek R.
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Macrophages, activated through cytolytic T cell recognition of their presented antigens, undergo cell death in the maintenance of homeostatic control over cell numbers. We examined the interaction of activated human T4 cell clones with macrophages to determine if helper T-Iymphocytes could be induced into initiating the cytolysis of macrophages. We sought to compare cytolytic capabilities of different T-Iymphocyte cell lines through their ability to express a cytoplasmic trypsin-like granular enzyme, serine esterase. The cloned T4 cells and the cytolytic T8 cells contained similar levels of serine esterase activity, while freshly isolated T4 cells showed negligible activity. Thus, cloned T4 cells become activated during culture. A previous report indicated that murine T cells became activated between the seventh and ninth days of culture, although the means is not yet known.(Lancki et al. 1991) We attempted to determine if the length of activation for cultured human T4 cells was equivalent to the murine cells, but the esterase activity levels did not reach significant amounts during the nine days of the test culture. When cultured T4 cells were combined with antigen-presenting macrophages and stimulated by the tetanus toxoid antigen, isolated DNA showed signs of fragmentation through gel electrophoresis. These fragmented segments of nuclear DNA, approximately 200 base pairs in length, displayed that apoptosis was occurring within the macrophages.(Wyllie 1980) Thus, cultured human T4 cells express cytolytic serine esterase and can initiate the apoptotic mechanism within antigen-presenting macrophages.