Th2 polarization of the inflammatory reaction in allergic reactions in children: mechanisms and implications for the development of new treatments

The Th1/Th2 lymphocyte polarization has been recently described during infl ammatory response. This new concept provides a better understanding of the inflammatory response observed in diseases such as allergy. First described in mice, this distinction of two subsets of T lymphocytes named Th1 and Th 2 is based upon the type of secreted cytokines. The secretion of IL2, TNF a lpha and IFN gamma characterizes the Th1 polarization which is mainly invol ved in cellular reactions. On the other side, IL-4, IL-5, IL-6, IL-10 are p art of the Th2 response which is observed during the humoral res ponse. In mice the distinction seems clear. The situation In human seems less obvious . In fact, it would be more appropriate to speak about a global polarizatio n of the Immune response instead of a final T lymphocyte differentiation. A Th2 polarization characterizes the allergic manifestations as asthma, hay fever or eczema. Numerous; factors drive the inflammatory response towards a Th2 phenotype: at birth, newborns display a Th2 type immune response whic h will evolve towards a Th2 or a Th1 type depending on the genetic and envi ronmental forces. The possible switch from a Th2 to a Th1 phenotype may rep resent a new target to some new therapeutic strategies in allergy by interf ering with the main ors of the Th2 response.