Immunohistology of genital warts in different stages of regression after therapy with interferon gamma.

Twenty patients with papillomavirus-induced genital warts received pulsatory treatment with interferon gamma by subcutaneous injections in the abdominal skin. The condylomata regressed completely in 11 of the 20 patients analyzed. Sequential biopsies taken from genital warts and nonlesional skin were investigated by immunohistological techniques with the use of monoclonal antibodies against differentiation and HLA antigens to evaluate immunological effector mechanisms of condylomata regression. In all responders regression was shown to be associated with increasing dermal and epidermal infiltrates of activated CD4 and CD8 T lymphocytes, as well as with aberrant expression of HLA-DR and/or DY antigens on keratinocytes. Thus alteration of HLA class II antigen expression on keratinocytes in the presence of T lymphocytes is an important criterium for regression of genital warts.