Changes in IgE- and Antigen-dependent histamine-release in peripheral blood of Schistosoma mansoni-infected Ugandan fishermen after treatment with praziquantel

There was a significant increase in the total cellular histamine in blood samples at 1-day post-treatment, followed by a very significant further increase by 21-days post-treatment. In vitro histamine-release induced by S. mansoni egg (SEA) or worm (SWA) Ags or anti-IgE antibody, was significantly reduced 1-day post-treatment. The degree of this reduction correlated with pre-treatment infection intensity. Twenty-1-days post-treatment, SEA-induced histamine-release was still significantly lower than at pretreatment. Histamine-release was not correlated to plasma concentrations of total or parasite-specific IgE, nor to specific IgG4 plasma concentrations.The biology of human blood basophils is modulated by S. mansoni infection and praziquantel treatment. Infection intensity-dependent suppression of basophil histamine-release, histamine-dependent resistance to infection, and similarities with allergen desensitisation are discussed as possible explanations of these observations.High levels of circulating IgE are characteristic of both parasitic helminth infections and hypersensitivity conditions such as asthma and allergy. IgE and other Th2 mediated responses have been shown to be important in immunity to helminth infections. In human populations living in schistosomiasis endemic areas, high levels of IL-4, IL-5 [1,2], eosinophilia [3] and parasite-specific IgE are associated with resistance to reinfection after chemotherapy [4-6]. In previous studies in Kenya, levels of IgE specific for the adult Schistosoma mansoni worm, when measured after PZQ treatment but before re-infection, negatively correlated with subsequent reinfection intensities [7]. Specific IgE responses against Ags present in the outer tegument of the adult worm were also significantly associated with resistance to reinfection after treatment [8]. Human IgE and eosinophils have been shown to combine in antibody-dependent, cellular cytotoxicity mechanisms (ADCC) to kill early schistosome larvae in vitro[9