The nature of immunity against Trypanosoma crtczi in mice recovered from acute infection

SUMMARY Protective immunity against a lethal, Y strain, T. cruzi infection could be transferred to normal mice by either serum or spleen cells from mice which had recovered from the acute phase of infection. The ability of spleen cells to transfer immunity was abolished by B lymphocyte removal (anti‐Ig column fractiona‐tion), but was relatively insensitive to T lymphocyte depletion (anti‐Thy 1.2 plus complement) or macrophage removal (Sephadex G‐10 fractionation). Immune spleen cells gave an anamnestic antibody response when injected together with T. cruzi antigen into lethally irradiated recipients and these antibodies conferred protection in a passive transfer system. T cell depletion reduced, but did not abolish, this antibody response. These data imply that the protective immunity of T. cruzi ‐convalescent mice is predominantly B cell‐mediated with T cell involvement being restricted to a helper role.