Correlation between antigenemia of Paracoccidioides brasiliensis and inhibiting effects of plasma in patients with paracoccidioidomycosis

Metabolites produced by pathogenic fungi may be involved in the pathogenesi s of fungal infections consequently altering the defence mechanisms of the host. In this study the levels of Paracoccidioides brasiliensis antigens de tected in the plasma of patients with paracoccidioidomycosis correlated wit h the suppression index detected by the low mitogenic response of periphera l blood mononuclear cells (PBMC) to phytohaemaglutinin (PHA). This inhibito ry effect on lymphoproliferation was observed in the plasma of 58% of the p atients, suggesting the presence of inhibitory factors. Plasma samples from paracoccidioidomycosis patients having or not having inhibitory factors sh owed no significant effect on chromosomes of lymphocytes from healthy indiv iduals, However, these plasmas had a suppressive activity on the blastogeni c response of these lymphocytes stimulated with PHA, that was independent o f a cytotoxic effect. P. brasiliensis antigens added to the proliferative r esponse of PBMC from healthy individuals stimulated or not stimulated with PHA showed a dose-dependent suppressor effect, reproducing the inhibitory e ffect of patients' plasma. We suggest that the antigens of P, brasiliensis present in the plasma of patients, even at low concentrations, can play an important role in the reduction of the cellular immune response and in the genesis of the immuneregulatory disturbances observed in paracoccidioidomyc osis.