Skin-induced tolerance and its reversal by Toll-like receptor ligands

In 1970, Gershon was the first to propose that T cells, in addition to their helper activity, can also play a role as regulatory cells capable of suppressing immune responses. However, the initial strong interest in T cell-mediated suppression was followed by a period of doubt and skepticism. Since the late 1990 s the "S" word started to be used in immunology again and interest in T suppressor cells has grown, ushering in a new renaissance for the field. In this article the author presents the current knowledge about a new subject called "skin-induced tolerance". Suppression is induced via epicutaneous immunization and is described in both Th1- and Tc1-mediated contact sensitivity reactions. The subject of skin-induced tolerance is also considered in the regulation of experimental models of autoimmune diseases such as allergic autoimmune encephalomyelitis and collagen-induced arthritis and finally in an animal model of graft rejection. The last part of this presentation will introduce the very fresh subject of "contrasuppression", or the reversal of skin-induced suppression.