Early exposure to unhygienic conditions and infections is associated with expression of different Toll-like receptors.

BACKGROUND We have previously shown a lower prevalence of atopy in children living in foster homes than in children living with their parents. OBJECTIVES In this study, we explored the associations between atopy and expression of Toll-like receptors (TLRs) 2, 4, 7 and 9 in the same groups of children. MATERIAL AND METHODS We enrolled all the atopic children living in foster homes in Lodz, Poland and carefully selected, on the basis of age, sex, sensitization profile, clinical manifestation of allergy, and treatment, a similar number of nonatopic children living in foster homes, and a similar number of both atopic and nonatopic children living with their parents. Expression of TLRs 2, 4, 7 and 9 was analyzed in all children. RESULTS Expression of TLR2 in foster care children was significantly higher in nonatopic children than atopic children (P = .047), while that of TLR7 and TLR9 was significantly higher in atopic children than in nonatopic children. Additionally, expression of TLR9 in nonatopic children in foster care was significantly lower than in nonatopic children living with their parents (P = .003).We also found that both groups of nonatopic children had a greater number of features characteristic of foster home children (poor living conditions in the first year of life) than atopic children. CONCLUSION Our results may suggest that alternative mechanisms might underlie the in vivo regulation of the expression of different TLRs involved in the development of atopy.