Trypanosoma cruzi suppresses the expression of the p75 chain of interleukin-2 receptors on the surface of activated helper and cytotoxic human lymphocytes.

When Trypanosoma cruzi is co-cultured with activated human lymphocytes the latter manifest a marked level of suppression in their capacity to express high-affinity interleukin-2 receptors (IL-2R). In this study we asked whether this effect could result from reduced expression of the p75 component of the IL-2R, a condition which would limit the number of heterodimeric receptors that could be assembled by activated T cells. The results of two-colour flow cytometric analyses revealed that both the percentage and surface density of p75 molecules on phytohaemagglutinin-stimulated CD3+, CD4+ or CD8+ lymphocytes were significantly reduced in the presence of T. cruzi, whether or not the parasites were separated from the lymphocytes by a cell-impermeable filter. These results suggested that reduced expression of p75 chains would limit the number of IL-2R assembled by activated T lymphocytes, contributing in this manner to the immunosuppression that occurs during acute T. cruzi infection.