Effects of the removal of adherent and phagocytic cells on the spleen cell lymphoproliferative response of tumor-bearing mice

Enhanced tumor growth in brain dopamine-depleted mice following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment

Brain dopamine influences immune functions and the role of immune functions in tumor growth is well established. Therefore, a study has been carried out to evaluate the correlation, if any, between brain dopamine and tumor growth. MPTP selectively destroys dopaminergic neurons in the brain. In the present study, Ehrlich carcinoma growth was evaluated in MPTP-treated mice. Results showed a correlation between depletion of striatal dopamine and enhanced tumor growth. Since in the present study striatal dopamine depletion in mice was associated with significantly decreased immune responses, the suggested correlation between brain dopamine and tumor growth was possibly mediated by the immune system.

Synergistic action of gamma interferon and catalase to reverse the suppressive effect of peritoneal macrophages on concanavalin A-induced lymphocyte proliferation

The suppressive effect of normal rat peritoneal exudate cells (PEC) on concanavalin A (Con-A)-induced lymphocyte proliferation was studied. Partial suppression of proliferation was obtained by adding 3% PEC and complete suppression was observed with 6% PEC. The suppressive effect was mediated by W3/25+ plastic-adherent macrophages, which constitute about 60% of normal PEC. Addition of PEC prior to, simultaneously with, or 24 h after, but not 48 h after, the stimulation of lymphocytes with Con A resulted in suppression. Suppressed cultures produced normal or slightly increased amounts of interleukin 2 (IL-2), but the expression of the IL-2 receptor on lymphocytes was decreased. Pre-exposure of PEC to gamma interferon (IFN-gamma) resulted in decreased suppression, whereas IFN-gamma added simultaneously with the lymphocytes had no effect. Catalase reversed PEC-induced suppression and significant synergistic effects were recorded when combined with IFN-gamma. Even completely suppressed cultures were effectively protected from suppression. Indomethacin and combinations of indomethacin with catalase or IFN-gamma did not result in additional protection from PEC-mediated suppression.