Effect of streptococcal lyzate OK-432 on peripheral blood mononuclear cells in gastric cancer patients

OK-432, a killed preparation of Streptococcus pyogenes, as well as Bacillus Calmette-Guerin (BCG) and Corynebacterium parvum are all known biological response modifiers. To examine the immunomodulatory effects of OK-432, natural killer cell activity and cytokine production by peripheral blood mononuclear cells (PBMCs) were assessed in 32 patients with gastric cancer. Skin tests for Streptococcus pyogenes A-3Su (Su-PS) and BCG were performed in all patients. Other nutritional and immunological parameters were also determined. OK-432-treated PBMCs showed a significant increase of cytotoxicity against K562 cells (p < 0.01). Increased levels of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and interleukin-2 (IL-2) were found in the supernatants of cultures treated with OK-432 in 29 (90.6%), 20 (62.5%), and 8 (25.0%) out of 32 patients, respectively. Natural killer cell activity, IFN-gamma production, and the Su-PS skin test were positively correlated (p < 0.01). In contrast, the BCG test and other markers were not correlated with natural killer cell activity and IFN-gamma production. These results suggest that the Su-PS skin test could predict OK-432-induced natural killer cell activity and IFN-gamma production in patients with gastric cancer, and was therefore useful to determine whether patients were responders to OK-432.