Studies on the properties of a streptococcal preparation OK-432 (NSC-B116209) as an immunopotentiator. I. Activation of serum complement components and peritoneal exudate cells by group A streptococcus.

The inhibition of transplanted tumors in animals, which were previously injected with a streptococcal preparation, OK-432, has been suggestible to be induced by direct or host mediated effects. In this paper, it was examined of immunopotentiating ability of Group A streptococcus (Su-strain), which is a active component of OK-432, with respects to reticuloendotherial system and serum complement components. Human fresh serum incubated with the heated streptococcus (HSu-coccus) was analyzed by means of immunoelectrophoresis. Activated component of C3 proactivator was observed in gamma region as immunoprecipitin line developed by rabbit anti human C3 proactivator serum, and conversion of C3 component (beta1C) to beta1A was observed in alpha region by rabbit anti human beta1C/beta1A serum. The activation of serum complement components might be occurred via alternate pathway, because EDTA inhibited the activation but EGTA did not. Meanwhile, the peritoneal exudate cells from mice injected intraperitoneally with HSu-coccus were examined with respects to cell population and their antitumor effect. On the 7th day after injection of HSu-coccus, about 90% of the peritoneal cells was lymphocytes, and 70% of these lymphocytes was susceptible to rabbit anti mouse thymus cell serum or to AKR anti thetaC3H serum. When L1210 leukemia cells preincubated with these peritoneal cells were inoculated intraperitoneally into BALB/c mice, the leukemic cells could not allowed the growth, resulting in prolongation of life-span of the experimental animals. These results suggested that nonspecific effector activity of T-derived lymphocyte induced by HSu-coccus could be one of the factors participating in antitumor activity of OK-432. Additionally, the results obtained with OK-432 were most the same as those with HSu-coccus in these respects. Further, the relation between the stimulation of leucocytes and activation of complement components was discussed.