Immune response in chronic Schistosomiasis haematobium and mansoni. Reversibility of alterations after anti-parasitic treatment with praziquantel.

Peripheral blood mononuclear cells from Sudanese children heavily infected with Schistosoma haematobium and S. mansoni were examined for lymphocyte subpopulations, for mitogen and antigen responsiveness, and for natural killer (NK) cell activity before and 5 months after treatment with praziquantel. The humoral immune response was simultaneously investigated by determination of parasite-specific IgG and IgE antibodies, IgE-containing circulating immune complexes, and circulating schistosome antigen. A single dose treatment with praziquantel (40 mg/kg) resulted in a normalization of numerical imbalances in lymphocyte subpopulations, a significant increase in the blastogenic response upon stimulation with adult worm antigen, phytohaemagglutinin (PHA), and concanavalin A (Con A), and restoration of natural killer (NK) cell-mediated lysis of K562 targets. These findings were paralleled by a remarkable decrease in parasite-specific IgE antibodies, IgE-containing circulating immune complexes, and circulating schistosome antigen. The results indicate that the modulation of immune responses in chronic schistosomiasis is associated with active infection and is reversible after successful chemotherapy.