[Immunobiological studies of interferon-alpha A/D in comparison with a streptococcal preparation, OK-432].

In order to clarify the characteristics of interferon-alpha A/D (IFN-alpha) as a biological response modifier (BRM), several immunobiological activities were compared with OK-432. 1) Both IFN-alpha and OK-432 inhibited the multiplication of Meth-A cells in vitro. 2) IFN-alpha (2 X 10(5) IU, ip) augmented the NK activity of peritoneal exudate cells (PEC) and spleen cells, and the peak of NK activity was observed 1 day after injection. OK-432 (1 KE, ip) augmented the NK activity of PEC, but not of spleen cells, and the peak was 3 days after. 3) Macrophage activating activity was more potent with OK-432 (1 KE) than IFN-alpha (2 X 10(5) IU). 4) Induction of CTL against alloantigens was augmented by IFN-alpha and OK-432. 5) By the combination of IFN-alpha with OK-432, a synergistic antitumor effect was obtained against Meth-A ascites tumor. Immunobiological effects of IFN-alpha seemed to be somewhat different from those of OK-432. Therefore, the combination of the two agents might cause a synergistic antitumor effect.