OK-432 develops CTL and LAK activity in mononuclear cells from regional lymph nodes of lung cancer patients

We examined the effect of OK-432 on induction of cytotoxic T lymphocytes (CTL) directed against autologous tumor cells (ATC) and lymphokine-activated killer (LAK) cells from mononuclear cells separated from regional lymph node cells (RLMNCs) of 49 lung cancer patients. We also examined the phenotypic changes of RLMNCs during incubation with or without OK-432. Significant CTL activity and LAK activity against ATC developed from RLMNCs after stimulation with OK-432 or IL-2. Sequential treatment with OK-432 plus IL-2 or IL-2 plus OK-432 also developed significant CTL activity and LAK activity from RLMNCs. The CTL activity produced by OK-432 alone was as high as the CTL activity developed by IL-2 alone, OK-432 plus IL-2, or IL-2 plus OK-432. There was no significant difference in the CTL activities achieved by these four treatments. The proportion of CD25+ cells in RLMNCs after incubation with OK-432 was twice that before incubation. Although OK-432 increased IL-2 receptor expression on RLMNCs, it showed no synergistic effect with IL-2 in developing CTL and LAK activity. After incubation with OK-432, the proportion of HLA-DR + cells was also increased significantly. Moreover, the proportions of HLA-ABC+ and HLA-DR+ (class I and class II major histocompatibility complex antigens) cells in ATC were significantly larger than in Daudi cells. OK-432 alone could develop CTL activity against ATC from the RLMNCs of lung cancer patients that was as high as that developed by IL-2 alone or by sequential treatment with OK-432 plus IL-2 or IL-2 plus OK-432. The CTL developed from the RLMNCs of lung cancer patients may recognize class I and/or II antigens on the surface of ATC. These results indicated that treatment with OK-432 might be therapeutically useful for lung cancer patients as a CTL inducer rather than a LAK inducer.