There is some experimental evidence supporting this contention. Earlier studies described that antigens of A. suum potentiate ‘reaginic’ response to ovalbumin (95,96). Also, Ascaris pseudocoelomic body fluid and the purified allergen ABA-1 prolonged the response to ovalbumin as third-party allergen, but they did not enhance the IgE

levels to this allergen (97). In another investigation, co-administration of hen egg lysozyme with the excretory/secretory products of N. brasiliensis results in the generation of egg-lysozyme-specific lymphocyte proliferation, IL-4 release and IgG1 antibody responses, supporting the role of some nematode products as adjuvants for third-party antigens (98). Furthermore, it has been shown that unidentified components in the body fluid

of Ascaris promote a Th2 response and are adjuvants for specific Quizartinib IgE synthesis to some parasitic allergens like ABA-1 (57). Because, in addition to this allergen, A. lumbricoides extract has at least 11 human-IgE-binding components, the BAY 73-4506 research buy adjuvant effect may be more generalized (24), and because of co-exposure, this could happen for cross-reactive and non-cross-reactive mite allergens, a process that may have roots in the co-evolutionary relationship between worms and vertebrates (99). Based on their findings from early epidemiological studies, Lynch et al. (100,101) suggested that the prevalence of allergies may be lower in individuals with high parasite burdens of geohelminths compared with those with low burdens. This idea is now widely accepted and has been related to the acute and chronic clinical phenotypes observed in helminth-infected humans (102). In addition, intermittent mass de-worming programmes in preschool and school-aged 4��8C children (103) reduce parasite burdens and boost the immune response to the parasites, because reinfections may elicit immune responses different in nature from the original primary infections (102). Therefore, it is theoretically possible that, in the presence of

intermittent infections with low worm burdens, exposure to A. lumbricoides promotes allergic sensitization and asthmatic symptoms by increasing the synthesis of parasite-specific, mite-specific and mite–parasite cross-reacting IgE antibodies. The clinical impact may be particularly important in urban zones of underdeveloped countries, because in rural areas, the infections are usually more intense and associated with higher degrees of immunosuppression. Also, differences in mite fauna and levels of mite allergen exposure may influence the type of sensitization and, in consequence, the relevance of cross-reactivity. Cross-reactivity is a frequent feature of the adaptive immune response, involving antibodies or T lymphocyte receptors directed to diverse molecules (antigens or allergens) and resulting in diverse biological or clinical effects.