Effects of OK-432 on the proliferation and cytotoxicity of lymphokine-activated killer (LAK) cells.

We studied the effect of a streptococcal preparation, OK-432, on the cytotoxicity and the proliferation of lymphokine-activated killer (LAK) cells for use in adoptive immunotherapy. Peripheral blood mononuclear cells (PBMC) were derived from healthy donors and patients with malignant brain tumors. We divided PBMC into two groups; these cells then were stimulated with interleukin-2 in the presence or absence of OK-432. OK-432 was added only in the initial 3 days during the 3-week midterm culture period. Then, we compared OK-432-stimulated LAK (OK-LAK) cells with standard LAK (sLAK) cells in terms of their rate of proliferation and cytotoxicity. OK-LAK cells proliferated more rapidly than sLAK cells. The cytotoxicity of OK-LAK cells increased, whereas that of sLAK cells decreased. We also investigated the phenotypic differences between these two types of LAK cells and found that, on day 21, the OK-LAK cells consisted mostly of CD3-CD56+ NK cells, whereas the sLAK cells consisted mostly of CD3+CD56- T cells. The difference in their level of cytotoxic potential might be explained by the difference of predominant phenotype.