Con-A-induced suppressor activity of lymphocytes distinguished by the presence or absence of the Fc receptor

Concanavalin A induces suppressor cell activity in both T gamma and T non-gamma cells: most of the suppressor cells do not carry HLA-DR antigens

Concanavalin A (Con A) stimulation of T lymphocytes for 48 h induced a dose-dependent increase in the percentage of T gamma cells, and proliferation of these cells was dependent on pre-existing T gamma cells. Con A stimulation also induced a dose-dependent increase in suppressor cell activity as measured in a Con A/mixed lymphocyte culture assay. Removal of T gamma cells before stimulation with Con A did not influence suppressor cell activity, whereas depletion of T gamma cells after Con A stimulation significantly reduced the suppression. Treatment of T lymphocytes with monoclonal anti-HLA-DR antibodies and complement significantly increased the percentage of T gamma cells and also increased the suppressor cell activity, both when the cells were treated before and when they were treated after Con A stimulation. Similarly, increased suppressor cell activity was also seen when T mu cells were removed. The results indicate that Con-A-induced suppressor cells are recruited from both T gamma and T non-gamma cells and also suggest that most of the Con-A-induced suppressor cell activity is exerted by HLA-DR-negative cells.

Concanavalin A-induced alteration of surface marker expression on murine T cells

The activation of suppressor T cells by Concanavalin A (Con A) was characterized by changes in expression of T cell surface markers. Treatment of normal mouse spleen cells with monoclonal antibody to Ly-1 prior to activation with Con A consistently reduced the resulting suppressor cell activity as assayed by mixed culture with primed spleen cells responding to sheep erythrocytes. Addition of indomethacin to anti-Ly-1 depleted spleen cells together with Con A had no effect on the resulting suppressor cell activity, whereas its addition to normal spleen cells together with Con A significantly abrogated suppressor T cell induction. In contrast, treatment of normal spleen cells with anti-Ly-1 following 24h culture with Con A had no effect on resulting suppressor cell activity. Treatment of spleen cells either prior to or following culture with Con A with monoclonal antibody to Ly-2 completely abrogated suppressor T cell activity. Suppressor T cells activated by Con A were depleted significantly by fractionation on columns containing insolubilized histamine. In contrast, fractionation of normal spleen cells on histamine columns followed by culture with Con A had no effect on subsequent suppressor T cell induction. Furthermore, direct addition of histamine (5 x 10(-4) M - 5 x 10(-8) M) to Con A preculture had no effect on resultant suppressor T cell generation, suggesting that possible immunodulatory actions of histamine may be expressed at the effector rather than during induction stages of Con A-induced suppressor T cell activation.