Antigen specific lymphocyte transformation induced by secreted antigens from Toxoplasma gondii.

Secreted (TSA) and water lysed (WLA) antigens derived from cell culture of the RH strain of Toxoplasma gondii have been used to induce antigen specific mitogenesis of lymphocytes from patients with symptomatic and asymptomatic toxoplasmosis. Lymphocyte responsiveness to WLA was similar to previous reports, with about 50% of patients showing a false negative reaction. Responses to TSA however were highly specific, with no false negative reactions. This increased specificity was not due to an increased response against TSA by patients' lymphocytes (P less than 0.001), but a lower TSA response by uninfected subjects' lymphocytes (P greater than 0.1) compared with WLA in both cases. In a minority of both infected and uninfected subjects, there was a low but detectable response to antigens secreted by the host cell line (HCA), and this was directly compared to their responses against TSA. There was at least a 10-fold increase in the patients' responses to TSA when compared with HCA (P less than 0.001), whereas there was no significant difference between the uninfected subjects' responses to these antigens (P greater than 0.1). Preliminary observations have suggested that TSA is distinct from other defined secreted antigens as both heat treatment and solid phase immunosorption did not have any noticeable effect on TSA-induced mitogenesis.