Macrophage killing capacity. Aspects of mechanism.

Immune macrophages have the capacity to kill in mixed macrophage cultures (MMC) allogeneic macrophages bearing the alloantigens used for immunization. The killing is expressed by a lytic mechanism as neither phagocytosis nor fusion between effector and target cells could be detected by E.M. T but not B lymphocytes isolated from immune spleen cells, are able to "arm" syngeneic nonimmune macrophages and render them cytotoxic. It is suggested that mediator(s) and/or membranal components are released from T cells and attach to macrophages. Such an "arming" factor enables the macrophage to recognize and kill target cells.