[Demonstration of antigen-specific suppressor cells in Toxoplasma infection of man].

Detection of antigenspecific suppressor cells in Toxoplasma infection of man. Investigations adapted to demonstrate the action of antigen-specific suppressor cells were carried out in subjects with acute toxoplasmosis (n = 5) and latent infections (n = 16) and compared to non-infected controls (n = 11). The investigations were carried out in vitro in the form of autologous one-way lymphocyte mixed culture. Suppressor cells were activated by toxoplasma lysate antigen (325 micrograms/ml) and, for comparison, by concanavalin A (10 micrograms/ml). Responder cells were stimulated by toxoplasma lysate antigen (200 micrograms/ml). In the acute cases, antigen-specific suppressor cells were identified which caused the lymphocyte transformation to be suppressed (tritium thymidine incorporation) to the same extent as did the mitogen-activated cells. The subjects with latent infections revealed a statistically significant difference (p less than 0.01) between the means of the percentage suppression of suppressor cells activated by toxoplasma lysate antigen or concanavalin A, suggesting a diminishing suppressive action of antigen-specific cells at this stage of infection. In addition to the effect on phagosome formation in macrophages, the activation of suppressor cells too should be considered as a factor of virulence for Toxoplasma gondii.