In a previous paper we demonstrated with the Winn test that rat spleen cells sensitized to an allogeneic tumor (AH-66 from Donryu strain) nonspecifically inhibited in vivo growth of a syngeneic tumor (KMT-17 from WKA strain) only when the spleen cells were stimulated with inactivated AH-66 cells used for immunization. These results were obtained with spleen cells harvested 2 weeks after immunization.

In the present study with the Winn test, when tumor inhibitory activity of AH-66-sensitized spleen cells was serially examined after immunization, the early spleen cells (1 week after immunization) inhibited growth of KMT-17 without further addition of inactivated AH-66 cells, but the late spleen cells (2 weeks after immunization) did not. AH-66-sensitized spleen cells 60 days after immunization did not inhibit growth of KMT-17 even with further addition of inactivated AH-66 cells, whereas these spleen cells inhibited in vivo growth of homologous AH-66. On the other hand, the early spleen cells alone did not inhibit growth of admixed KMT-17 when the mixtures were in vivo cultured in diffusion chambers where no inflammatory cells existed. However, further addition of polymorphonuclear leukocytes (PMN) to the early spleen cells reduced the number of viable KMT-17 cells even in diffusion chambers. The late spleen cells did not inhibit KMT-17 growth in diffusion chambers even when PMN were further added. Normal thymocytes, spleen cells or peritoneal macrophages did not cooperate with the early spleen cells in inhibiting the growth of KMT-17.

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This work was partially supported by a Grant in Aid for Immunological Research from the Ministry of Education Science and Culture, Japan.

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