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Abstract: Geohelminth infections are highly prevalent infections with a worldwide distribution. Epidemiological studies have shown an inverse relationship between geohelminth infection and allergy leading to the suggestion that geohelminths protect against allergy. A causal association is supported by the findings of intervention studies in humans and experimental animal models. Geohelminths cause chronic infections during which an intimate host–parasite interaction develops permitting the parasite to survive but protecting the host from damaging inflammation. Geohelminth parasites modulate allergic inflammation directed against parasite antigens and the same mechanisms may affect responses to inhalant aeroallergens. The mechanisms proposed to explain the allergy-modulatory effect of geohelminths include the induction of regulatory T cells and the creation of an immunosuppressive environment in relevant tissues. New treatments being considered for the treatment of asthma include live infections with hookworms. Insights provided by how geohelminths modulate inflammatory responses may allow the development of new treatments that mimic these effects. [Copyright &y& Elsevier]

The ‘hygiene hypothesis’, or lack of microbial and parasite exposure during early life, is postulated as an explanation for the recent increase in autoimmune and allergic diseases in developed countries. The favored mechanism is that microbial and parasite-derived products interact directly with pathogen recognition receptors to subvert proinflammatory signaling via T regulatory cells, thereby inducing anti-inflammatory effects and control of autoimmune disease. Parasites, such as helminths, are considered to have a major role in the induction of immune regulatory mechanisms among children living in developing countries. Invoking Occam''s razor, we believe we can select an alternative mechanism to explain the hygiene hypothesis, based on antibody-mediated inhibition of immune responses that may more simply explain the available evidence. [ABSTRACT FROM AUTHOR]