Induction of Cytocidal Macrophages after in Vitro Interactions between Listeria-Immune T Cells and Macrophages—Role of H-2

Abstract

Twenty-four-hour cultures of macrophages from non-immune mice with T cells from mice immune to Listeria resulted in the acquisition of cytocidal activity by the macrophages. The macrophages killed P815 tumor cells in a chromium-release assay. Macrophages from non-immune mice given peptone or thioglycollate injections were much better effector cells than resident macrophages. Experiments established the conditions for generation of cytolytic macrophages: the specificity of T cells to Listeria and the need for macrophages to specifically interact with heat-killed Listeria organisms. Cells from the immune T cell inoculum did not participate in the killing process by the activated macrophages. The interactions leading to the generation of cytocidal macrophages required homology at the I region between macrophages and T cells, as well as the presence of macrophages bearing Ia molecules. Cultures of T cells and macrophages with heat-killed Listeria contained a factor that, when added to peptone macrophages, resulted in their activation for cytolytic activity. The factor could activate syngeneic or allogeneic macrophages, or macrophages lacking detectable Ia molecules. The immunogenic moiety associated with Listeria was short-lived.