Lymphoblast transformation as a measure of immune competence during experimental Chagas' disease.

Spleen cells from normal mice and mice infected with Trypanosoma cruzi undergo mitogen-induced lymphoblast transformation in different ways. Some of these differences may be interpreted as suppression of the blastogenic response, whereas others cannot. Close examination of the culture conditions has enabled us to discriminate between in vivo-induced suppression and in vitro-determined (artifactual) suppression. Regardless of the type of suppression observed, it was shown to be dependent on duration of culture, length of labeling period, dose of mitogen, density of spleen cells, and method of expressing lymphoblast transformation data. The titration of mitomycin C-treated spleen cells from infected mice into cultures of normal spleen cells revealed two, separate, regulatory activities of spleen cells from infected mice as follow: (1) an enhancing effect which appeared late in infection and was obtained with low input of cells, and (2) a suppressive effect which appeared early in infection and was obtained with high input of cells. The enhancing effect was mediated by cells with properties characteristic of T-lymphocytes, whereas macrophages were found to be responsible for the suppressive effects.