Role of IgE in Human Helminth Infections

Because of the marked differences in the immune responses observed during acute and chronic helminth infections, the potential protective role of IgE during the two stages of infection will be addressed separately. 

The vast majority of individuals exposed to low infective doses of helminth parasites remain asymptomatic, although parasitological evidence of parasite patency may be evident (e.g., presence of eggs of Schistosoma spp. or geohelminth parasites). Generally, clinically apparent infections follow relatively high infective doses (21), although the presence of detectable IgE at the time of presentation is not invariable. 

Experimental human inoculations with low doses of hookworm (e.g., 50 infective larvae) have been shown to result in marked eosinophilia but only small increases in total and parasite-specific IgE (2). In another human experiment, IgE levels increased only after subsequent infections, becoming detectable only after the third or fourth infection (1). Observations in acute schistosomiasis noted that the magnitude of IgG and IgE responses was related closely to the intensity of infection (21). 

Many allergic syndromes have been reported in individuals in the acute stages of helminth infection. Typical examples are  

Wheezing or urticaria during the early migratory phase of infections with Ascaris spp., hookworm spp., Strongyloides stercoralis, and Schistosoma spp. (14). 

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