Abstract

The suppression of immune responses to an antigen encountered within a short period after exposure to ultraviolet radiation (UVR) was first described by Margaret Kripke and her colleagues almost 40 years ago. They revealed that when highly antigenic tumor cells were implanted into mice that had been previously irradiated, the cells were not rejected, as might be expected, but grew into tumors. The suppression was shown subsequently to be immunologically mediated, antigen-specific, and long-lasting (Kripke 1981). These results stimulated new ideas and discoveries of great interest and relevance to skin biologists and immunologists. Despite considerable advances, the exact mechanism whereby UVR can lead to changes in immune responses is not entirely clear at present, and no unifying scenario has been proposed.