Herpes simplex virus and atopy in Finnish and Russian Karelian children.

Although the focus in the context of the hygiene hypothesis in explaining raised atopy prevalences has largely shifted from pathogens to commensals and saprophytes, the role of pathogens cannot be wholly ignored. Many pathogens are able to establish persistent or chronic infections, and have evolved strategies for immune evasion. A common immune subversion strategy used by such pathogens involves the increased production of the regulatory cytokines interleukin (IL)-10 and/or transforming growth factor-b by innate immune cells or via the generation of regulatory T (T-reg)-cells [1]. These cytokines, by inhibiting/downregulating the function of antigen-presenting cells and effector T-cells, appear, in turn, to be crucial for the development of tolerance against allergens.