Pathogen induced regulatory cell populations preventing allergy through the Th1/Th2 paradigm point of view.

Epidemiological studies have demonstrated an inverse correlation between prevalence of helminth infections and allergic diseases both associated to Th2 immune responses. On the other hand, such an inverse correlation has also been evidenced between allergies and bacterial infections, associated to Th1 responses. In this review, we will examine and compare the various mechanisms by which Th1- or Th2-inducing infectious agents regulate the development of atopic diseases. We will emphasize the key role of various regulatory cell populations associated to the immune responses toward pathogen.