Characterization of the recognition of target cells sensitive or resistant to cytolysis by activated rat peritoneal macrophages.

The interaction between tumoricidal rat peritoneal exudate macrophages and normal or neoplastic target cells has been examined both with respect to the sensitivity of the target cells to macrophage-mediated cytolysis and the ability of such targets to compete with one another for the lytic activity of macrophages. The results demonstrate that, in confirmation of earlier work from other laboratories, target cells are either sensitive or largely resistant to lysis, and such sensitivity correlates well with the neoplastic phenotype of the target cell. However, in target cell competition experiments all cultured cells as well as Con A-stimulated splenocytes and freshly isolated thymocytes exhibit the capacity to block cytolysis of sensitive indicator targets. In contrast, freshly prepared non-mitogen-stimulated splenic or lymph node lymphocytes are completely devoid of competitive activity. These results show that macrophages can recognize and interact with both normal and tumorigenic cells and that such target recognition can be distinguished from target cytolysis. Furthermore, the evidence suggests that at least 1 target cell feature that correlates with recognition is cell cycle traverse.