Synergistic Action of Gamma Interferon and Catalase to Reverse the Suppressive Effect of Peritoneal Macrophages on Concanavalin A‐Induced Lymphocyte Proliferation

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Abstract
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.