Abstract
BACKGROUND: The hygiene hypothesis states that children exposed to higher loads of microbes such as farmers' children suffer less from allergies later in life. Several immunological mechanisms underpinning the hygiene hypothesis have been proposed such as a shift in T helper cell balance, T regulatory cell activity, or immune regulatory mechanisms induced by the innate immunity. OBJECTIVE: To investigate whether the proposed immunological mechanisms for the hygiene hypotheses are found in farmers' children. METHODS: We assessed gene expression levels of 64 essential markers of the innate and adaptive immunity by quantitative real-time PCR in white blood cells in 316 Swiss children of the PARSIFAL study to compare farmers' to non-farmers' expressions and to associate them to the prevalence of asthma and rhinoconjunctivitis, total and allergen-specific IgE in serum, and expression of Cε germ-line transcripts. RESULTS: We found enhanced expression of genes of the innate immunity such as IRAK-4 and RIPK1 and enhanced expression of regulatory molecules such as IL-10, TGF-β, SOCS4, and IRAK-2 in farmers' children. Furthermore, farmers' children expressed less of the TH1 associated cytokine IFN-γ while TH2 associated transcription factor GATA3 was enhanced. No significant associations between the assessed immunological markers and allergic diseases or sensitization to allergens were observed. CONCLUSION: Farmers' children express multiple increased innate immune response and immune regulatory molecules, which may contribute to the mechanisms of action of the hygiene hypothesis.