Resistance to Schistosoma mansoni in humans: influence of the IgE/IgG4 balance and IgG2 in immunity to reinfection after chemotherapy.

The hypothesis of an association between human resistance to reinfection by the parasite Schistosoma mansoni and anti-larval immunoglobulin isotypes was tested by logistic regression in the presence of the explicative variables water contact, age, and sex. Of the seven isotypes tested (IgM, IgG1, IgG2, IgG3, IgG4, IgA, and IgE), only IgE, IgG4, and IgG2 showed an association (positive for IgE and negative for IgG2 and IgG4) with resistance to reinfection after chemotherapy. The opposite effects of IgE and IgG4 were undissociable in the analysis, indicating that these isotypes probably antagonize each other in protection. The negative association of IgG2 with resistance is consistent with the view that anti-carbohydrate antibodies may facilitate reinfection. Finally, epidemiologic and immunologic studies support the view that there is a progressive but slow development of acquired immunity in children and adolescents.