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Journal Review 1

1. High-dose exposure to cat is associated with clinical tolerance - a modified Th2
    immune response?
    (Clin Exp Allergy 2003;33:1681-5)
2. The relevance of maternal immune reponses to inhalant allergens maternal
    symptoms, passive transfer to the infant, and development of antibodies in the first
    2 years of life (J Allergy Clin Immunol 2003;111:123-30)

  Exposure to allergens plays an important role in the allergic disease. For dust-mite allergens, dose-response link between exposure and both sensitization and asthma. By contrast, recent population-based studies suggest that having a cat in the house from early childhood decrease the risk of sensitization and asthma. It is not exactly known what mechanisms could lie behind this development of immune tolerance, although Platts-Mills et al. recently suggested the modification of Th2 immune response as an possible explanation. They showed that high-dose exposure to cat allergen can produce IgG and IgG4 antibody responses with decreased production of IgE antibodies, and that the response could be regarded as a modified Th2 response. Recent studies have shown that expression of the gene for IgG4 can be induced by the Th2 cytokine, interleukin-4. Hesselmar et al., the authors of the former article, intended to test the hypothesis of modified Th2 response on differing populations. The investigators also found that significant portion of children had an immune response with only IgG4, and no IgE antibodies to cat, and this group of children had the highest frequency of cat-keeping, but was not associated with an increased risk of asthma or allergy. And, as the previous studies shown, there was a dose-response relationship between low and moderate exposure to cat and sensitization to cat, whereas a negative association for high-dose exposure. But the dose-response relationship for mite exposure and sensitization was linear. The authors suggest that the modified Th2 response associated with high-dose allergen exposure is probably due to less IgE production and not due to any protective effect of IgG4 itself.

  The latter article investigated the influence of maternal immune responses to cat and mite allergens on the development of immune responses in the infant and allergic disease during the first 3 years of life. It showed the same results that were revealed in the former article, demonstrating the different immune responses to cat and dust-mite. This article revealed that maternal IgG antibody was transferred to the infant and might influence IgG antibody production in the child. The authors say that these results may indicate the importance of understanding the mechanisms of tolerance to cats and raise questions about the independent role of the mother in the inheritance of allergy.

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