Phenotypes of immunocompetent cells and Ia antigen expression in oral mucosa and skin of autoimmune mouse strains

The phenotypic characteristics of resident and infiltrating cells in skin and oral mucosa of MRL/Mp-lpr/lpr (MRL-lpr), MRL/Mp+/+ (MRL-(+)), NZB x NZW F1 (NZB/W) and Balb/c mice have been studied using monoclonal antibodies (Mabs) and immunoperoxidase staining with the Avidin-Biotin Complex method. Macroscopically evident skin lesions appeared spontaneously exclusively in aging MRL-lpr mice. Infiltration of lymphocytes was detected within the mucosa and the skin of MRL-lpr-mice. These lymphocytes expressed predominantly L3T4 and to a lesser extent Lyt-2 phenotype (T helper/inducer and T suppressor/cytotoxic subset, respectively). Class II major histocompatibility complex antigen (Ia) expression was detected on macrophages, dendritic cells and few lymphoid cells in normal oral mucosa and skin of all strains examined. However, in the oral mucosa and skin lesions of the 4 months old MRL-lpr mouse also keratinocytes expressed Ia antigens. Keratinocytic Ia expression was also detected in oral mucosa of 8 months old MRL-(+) mice. The described immunopathological findings in skin and oral mucosa of old MRL-lpr mice show a number of important similarities to human SLE disease.