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Anthelminthic treatment of chronically infected children results in increased atopic reactivity, which indicates that helminths directly suppress allergic reactions.

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Cytokines are key players in numerous inflammatory processes. Demonstration of a heritable component in the variation of cytokine production would indicate that simultaneous occurrence of conditions might be caused by a heritable inflammatory characteristic. We applied an extended twin study approach to assess heritability estimates of interleukin (IL)-1b, IL-1ra, IL-10, IL-6, and TNF-a production capacity after ex vivo stimulation with lipopolysaccharide. Cytokine production capacity was assessed in 42 monozygotic pairs, 52 dizygotic pairs, one trizygotic triplet, 33 single twins, and 83 additional siblings. Heritability estimates were derived from variance decomposition models using maximum likelihood estimation. For all cytokines, over 50% of the variance was genetically determined. IL-1ra and TNF-a had the lowest heritability estimate of 53%.Estimates for IL-6 and IL-10 were 57 and 62%, respectively. IL-1b had the highest estimate of 86%. We conclude that the production of cytokines is under tight genetic control.

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Background: Allergic diseases seem less prevalent in communities in less developed parts of the world, where parasite infections are highly prevalent. Altogether not much is known about the association between chronic infections with tissue and blood-dwelling parasites and atopy. Methods: In an area in Gabon endemic for blood and tissue parasites, 520 schoolchildren were parasitologically examined and skin prick-tested for a set of common environmental aeroallergens. Levels of allergen-specific IgE and polyclonal IgE were measured. Results: In schoolchildren schistosome and filarial infections increased with age, whereas malaria was more prevalent in younger children. In contrast to allergen sensitization that increased with age, skin test reactivity tended to decline. The number of children with mite-specific IgE antibodies (47%) by far exceeded the number responding to skin prick testing (11%). Mite sensitization was found to be the highest in children infected with schistosomes and/or filariae whereas skin test reactivity was lowest. The multiple logistic regression showed that the risk of a positive skin test was 8-fold higher with increasing levels of mite-specific IgE but was reduced by 72% when infected with blood stage helminths. Conclusions: Chronic blood and tissue parasite infections that are often capable of modulating immune responses in the host are negatively associated with skin test reactivity in a sensitized population.