In vivo antitumor effect of lymphokine-activated rodent polymorphonuclear leukocytes.

In vivo tumor inhibitory activity of polymorphonuclear leukocytes (PMN) treated in vitro with lymphokine(s) (LK) was investigated with Winn's assay. Culture supernatants of BALB/c mouse spleen cells incubated with a streptococcal preparation, OK-432, were used as an LK source. With the use of a [3H]uridine release assay, RL male-1 tumor cells were lysed to some extent by peritoneal BALB/c mouse PMN treated with this LK preparation. With Winn's assay, LK-treated PMN from BALB/c mice completely inhibited the growth of the admixed syngeneic tumor at a high effector to target ratio, when normal mice were used as recipients. When X-irradiated mice or nude mice were used as recipients, the tumor growth was partially inhibited by admixed LK-treated PMN, but the tumor began to grow gradually and finally killed the recipient mice, even when a high effector target ratio was used. When nude mice which had been given i.v. transfers of nylon wool column effluent spleen cells were used as recipients, the tumor inhibitory activity of LK-treated PMN was recovered to the same level as when normal mice were used as recipients. On the other hand, tumor inhibition by admixed LK-treated PMN in nude mice was not recovered by the transfer of X-irradiated nylon column effluent T-cells. As a mechanism of tumor inhibition by LK-treated PMN, a possible role of LK-treated PMN in reduction of tumor load is discussed.