Suppressed antibody responses to sheep erythrocytes in mice with chronic Trypanosoma cruzi infections are restored with interleukin 2.

Plaque-forming cell (PFC) responses to sheep erythrocytes (SRBC) in cultures of spleen cells from mice with chronic Trypanosoma cruzi infections were found to be suppressed. Responses were restored with purified interleukin 2 (IL 2) and with supernatants that contained IL 2. Interleukin 1 (IL 1) prepared from the P338D1 hybridoma had no effect on in vitro responses when added alone, nor did it augment the effects of IL 2-rich supernatant. Interleukin X (IL X) generated from the FS7-20.6.18 T cell hybridoma was not effective alone or in combination with IL 1, nor were significant additive effects seen when IL X was combined with IL 2. The restorative effect of the IL 2-containing FS6-14.13 hybridoma supernatant (FS6-SN) was concentration dependent and was not seen when supernatant was added after day 1 of the culture period. Thus IL 2 alone, but not IL 1 or IL X, was able to reconstitute spleen cell responses of infected mice. In vivo anti-SRBC responses were also restored when mice were treated with IL 2-rich supernatant after immunization with SRBC. The immunologic defect in the production of PFC to heterologous erythrocytes by mice with chronic T. cruzi infections has been identified as a lack of functional help normally provided by the T cell product IL 2.