Murine splenocyte migration inhibition assay I. Detection of differential responses to murine leukemia P388 and its adriamycin-resistant subline P388/ADR.

A direct splenocyte migration inhibition assay system was used to evaluate cellular sensitization in BDF1 mice carrying intraperitoneal transplants of the lymphocytic leukemia, P388, and its adriamycin-resistant subline, P388/ADR. The individual splenocyte populations, PS and PAD (from the mice bearing P388 tumor and its subline, respectively), were tested against the 3 M KCl extracts, S-Ag and R-Ag (of P388 and P388/ADR tumor cells, respectively). The results indicated a gradual development of cellular sensitization against P388 tumors but not P388/ADR tumors. The migration of only PS cells was inhibited by extracts of both the syngeneic tumors in a dose-dependent manner. An extract of an allogeneic tumor, S-180, did not alter the migration of PS cells. The nonresponsive PAD cells, when mixed with the responsive PS cells at a ratio of 1:9, abrogated the latters' response to both the antigens. Such suppression was tumor-related and detected in the spleen 2 days after P388/ADR transplantation. Addition of normal murine splenocytes or P388/ADR tumor cells did not prevent PS cells from responding to the tumor extracts. These results indicated the presence of suppressor cells in the spleens of mice with P388/ADR tumors.