Correlation between the presence of intracellular OK-432 and antitumor activity of peritoneal macrophages

Abstract

The mechanism of the generation of tumoricidal macrophages by intraperitoneal administration of OK-432 was investigated. An association between the presence of intracellular FITC-conjugated OK-432 and the increase of macrophage cytostatic activity was observed after i.p. administration of OK-432. When peritoneal exudate cells were fractionated on the basis of cell size by velocity sedimentation, a higher proportion of macrophages and a strong cytostatic activity were shown in the large cell fractions. Furthermore, in these fractions, increased numbers of macrophages with intracellular FITC conjugated and 3H-acetate labelled OK-432 were observed. Thus, the more cytocidal macrophages can be identified by the presence of intracellular microorganisms. A role for OK-432 in the direct activation of macrophages is suggested.