Effector and enhancing lymphoid cells in plasmacytoma-bearing mice. I. Methodological studies on the Winn assay.

Some parameters of the Winn assay for the detection of tumor-suppressing ("effector") and tumor-enhancing lymphoid cells were studied in BALB/c mice. Spleen cells of mice that were preimmunized with mitomycin-C-treated MOPC-104E plasmacytoma cells were inhibitory in this test system for both the MOPC-104E and the HOPC-I plasmacytomas, thus indicating cross-reactivity. Spleen cells taken from mice 6 days after the surgical removal of 15-day-old MOPC-104E tumors inhibited the growth of lethal doses of MOPC-104E cells in normal recipients, but no inhibition was observed 2 days after the removal of 18-day-old tumors. Spleen cells from mice bearing MOPC-104E for 13 days enhanced tumor growth. This enhancement was not influenced significantly by the wide dose range (from 10(5) to 3 x 10(7)) of MOPC-104E cells used to initiate tumors in the lymphoid cell donors, although tendency for stronger enhancing potential occurred after low tumor doses. When spleen cells from donors bearing MOPC-104E for 10 days were injected at the constant tumor-lymphocyte ratio of 1:30 with increasing numbers of tumor cells (from 5 x 10(5) to 2 x 10(6)), tumor inhibition occurred at the lowest dose only, while no significant effect was observed at higher tumor cell doses. When a constant dose (5 x 10(5)) of tumor cells was injected with spleen cells from 10-day tumor-bearers at tumor/lymphocyte ratios of 1:10, u:40 and 1:160, a significant tumor inhibition occurred only at the ratio of 1:40. The relevance of the Winn test to the study of immune mechanisms in tumor-bearing hosts is discussed.