Induction of interleukin 1 secretion and of tumoricidal activity in macrophages are not closely related phenomena.

Rat bone marrow-derived mononuclear phagocytes (BMM phi), induced to differentiate in vitro and homogeneous with respect to the cell lineage, were interacted with various macrophage-activating agents. The effect of these agents on the secretion of interleukin 1 (IL 1) activity and on the development of tumoricidal capacity was comparatively assessed. The findings show that IL 1 secretion is considerably enhanced by macrophage-activating factor and by recombinant interferon-gamma but remained unaffected or was even suppressed by heat-killed C. parvum or Listeria monocytogenes. In contrast, lymphokines as well as C. parvum and Listeria were similarly potent in inducing in BMM phi a tumoricidal state. The findings indicate that induction of IL 1 secretion and of tumoricidal activity are not necessarily closely linked phenomena.