Autocytotoxic T-cell clones in lichen planus

We examined the in vitro cytotoxic activity of cutaneous T-cell lines and c lones from lichen planus (LP) patients against autologous epidermal keratin ocytes. T cells were cultured from LP lesions and adjacent clinically norma l skin and cloned by limiting dilution. Keratinocytes were cultured from LP lesions and adjacent clinically normal skin and immortalized by transfecti on with the E6 and E7 genes from human papillomavirus 16 (HPV16), The lesio nal T-cell line from one LP patient contained 27% gamma delta+ T cells and was significantly more cytotoxic against autologous lesional keratinocytes than the T-cell line from clinically normal skin. Clones isolated from the lesional T-cell line were significantly more cytotoxic against autologous l esional keratinocytes than clones isolated from the non-lesional T-cell lin e. Most cytotoxic clones from LF lesions were CD8+ and most noncytotoxic cl ones from LP lesions were CD4+. One cytotoxic clone was CD4- and CD8- and e xpressed the gamma delta T-cell receptor. Two CD8+ LP lesional T-cell clone s showed dose-dependent killing of HPV16 E6/E7-immortalized autologous lesi onal and normal keratinocytes, but no cytotoxic activity against Epstein-Ba rr virus-transformed autologous B-cell blasts, The cytotoxic activity of CD 8+ lesional T-cell clones against autologous lesional keratinocytes was par tially blocked with anti-major histocompatibility complex (MHC) class I mon oclonal antibodies. These data support the hypothesis that CD8+ lesional T cells recognize an antigen associated with MHC class I on lesional keratino cytes and that CD8+ cytotoxic T cells lyse keratinocytes in LP lesions.