[Effective mechanisms of BRM, with special reference to induction of autologous tumor cell-killing (ATK) activity by OK-432].

OK-432, a streptococcal preparation, is known to have strong BRM functions and is expected to produce clinical improvement and prolongation of survival in treated cancer patients. In order to clarify the immunopharmacological mechanisms involved with its clinical effectiveness, intrapleural injection of OK-432 was attempted in patients with malignant pleural effusion due to metastasis from lung cancer. About 70-80% of patients thus treated showed clinical improvements with reduction or disappearance of effusion and effusion tumor cells within a week after the therapy. The clinical response was accompanied by an abrogation or reduction of suppressor macrophages and a stimulatory increase of effective cytotoxic cells resulting in an increase of NK and ATK activity. These in vivo effects observed in the OK-432-treated patients were reproducible in vitro by incubating normal or effusion lymphocytes with tumor-associated macrophages. OK-432 was also shown to reduce the locomotor inhibitory activity of macrophages toward LGL, and to augment the production of various sorts of cytokines, such as IL-1 and MCF by macrophages and IL-2 and NKCF by lymphocytes, all of them being exerted upon activation of the anti-tumor immunological mechanism.