Activation and augmentation of guinea pig macrophages with streptococcal preparation OK-432 and stimulated spleen cell products.

A mechanism of macrophage activation by a streptococcal preparation (OK-432) was studied. Peritoneal exudate macrophages from normal guinea pigs treated in vitro with OK-432 were activated, manifesting increased glucose consumption, increased spreading, and morphological alterations under scanning electron microscopy. Macrophages showed extensive spreading within 1 hr after OK-432 treatment; they then became rounded with characteristic ruffles in their surfaces after 6 hr of treatment. Highly purified macrophages were activated as effectively as a crude macrophage preparation, suggesting that the macrophage activation resulted from a direct interaction between macrophages and OK-432. However, when spleen cells were treated with OK-432, a factor(s) capable of activating macrophages was produced in the culture supernatant. Spleen macrophage-rich preparation was found to release the factor(s) upon stimulation with OK-432, but this did not occur with the lymphocyte-or granulocyte-rich preparations. These results indicate that OK-432 not only activates macrophages by direct interaction without lymphokine participation, but also augments the activation by affecting spleen cells, probably macrophages, in such a way as to produce monokines.