We examined specific immunoglobulin G1 (IgG1) and IgG3 responses to Plasmodium falciparum schizont and Schistosoma mansoni egg and worm antigens in individuals from Kenya, Uganda, and the Sudan who had been exposed to malaria and schistosomiasis. A strong correlation between malaria- and schistosome-specific IgG3 responses was observed. This association appears to result from the presence of cross-reactive components of the 2 parasites that bind IgG3 antibodies, rather than to be mediated by immunological cross-regulation or specific regulatory mechanisms induced by either parasite. Cross-reactivity of IgG3 antibodies was confirmed in a Brazilian cohort of individuals living in an area where schistosomiasis is endemic but no malaria occurs and in a Pakistani cohort from an area where malaria is endemic but no schistosomiasis occurs. An IgG3 interaction with antigens from both parasites was observed in individuals from both cohorts, but not in uninfected European control subjects. The immunological and biological implications of this observation require further exploration.

SUMMARYThe present work was a longitudinal study on Schistosoma mansoni infection in occupationally hyperexposed canal cleaners in the Sudan and the influence of therapy on the parasitological and humoral immune parameters. Chronically infected canal cleaners (n 28) were more resistant to reinfection (Fisher's exact test, P<0 . 05) than newly recruited canal cleaners

Background: Parasite-specific IgE levels correlate with human resistance to reinfection with Schistosoma spp. after chemotherapy. Although the role of eosinophils in schistosomiasis has been the focus of a great deal of important research, the involvement of other Fcε receptor-bearing cells, such as mast cells and basophils, has not been investigated in relation to human immunity to schistosomes. Chemotherapy with praziquantel (PZQ) kills schistosomes living in an in vivo blood environment rich in IgE, eosinophils and basophils. This releases parasite Ags that have the potential to cross-link cell-bound IgE. However, systemic hypersensitivity reactions are not induced by treatment. Here, we describe the effects of schistosomiasis, and its treatment, on human basophil function by following changes in total cellular histamine and in vitro histamine-release induced by schistosome Ags or anti-IgE, in blood samples from infected Ugandan fishermen, who are continuously exposed to S. mansoni infection, before and 1-day and 21-days after PZQ treatment.