Experimental murine Trypanosoma congolense infections. II. Role of splenic adherent CD3+Thy1.2+ TCR-alpha beta- gamma delta- CD4+8- and CD3+Thy1.2+ TCR-alpha beta- gamma delta- CD4-8- cells in the production of IL-4, IL-10, and IFN-gamma and in trypanosome-elicited immunosuppression.

Trypanosome-induced suppression of T and B cell responses to parasite-related and -unrelated Ags is considered a major mechanism of evasion of the host's immune defenses by the parasite. Reduced T and B cell responses have been attributed to suppressor T cells, suppressor macrophages, or both. We have previously shown that endogenously produced IL-10 and IFN-gamma mediate the suppression of T cell responses in Trypanosoma congolense-infected mice. Here, we show for the first time that splenic CD3+ Thy1.2+ alphabeta- gammadelta- CD4+ 8- and CD3+ Thy1.2+ alphabeta- gammadetla- CD4- 8- cells that copurify with plastic-, nylon wool-, or Sephadex G-10-adherent cell populations, in synergy with adherent Thy1.2- cells, are the major producers of IL-4, IL-10, and IFN-gamma in T. congolense-infected mice. We further demonstrate the involvement of these cells in the suppression of T cell proliferative responses to mitogen and in B cell responses to a parasite-unrelated Ag.