THE CONCURRENT ADMINISTRATION OF OK432 AUGMENTS THE ANTITUMOR VACCINATION EFFECT WITH TUMOR-CELLS BY SUSTAINING LOCALLY INFILTRATING NATURAL-KILLER-CELLS

The effect of a local injection with a streptococcal preparation OK432 on the antitumor vaccination with tumor cells was investigated. Natur al killer (NK) cells, which were detected by anti-NK1.1 monoclonal ant ibody (mAb), increased in the peritoneal exudate cells after an intrap eritoneal (i.p.) injection with syngeneic B16 melanoma cells. Furtherm ore, a concurrent i.p. injection with OK432 efficiently sustained the locally infiltrating NK cells. The OK432 treatment also sustained the augmented NK and lymphokine-activated killer activities in the periton eal exudate cells. This treatment also increased the ability of the lo cally infiltrating NK cells to produce interferon gamma in response to the tumor cells. In addition, the concurrent i.p. injection with OK43 2 in combination with the tumor cells enhanced the capacity of the spl een cells to turn into anti-(B16 melanoma) cytotoxic T lymphocytes aft er in vitro restimulation. This augmenting effect of OK432 was depende nt on NK cells. Moreover, the concurrent injection with OK432 at the t ime of antitumor vaccination significantly enhanced the protective imm unity against B16 melanoma at the rechallenge. Taken together, these f indings indicate that a concurrent local injection with OK432 in combi nation with tumor cells efficiently augments the antitumor vaccination effect, in part, by sustaining the locally infiltrating activated NK cells.