A monoclonal Ro‐antibody and the serum of a Ro‐positive patient with subacute cutaneous lupus erythematosus (SCLE) react with basal layers of human epidermis

Skin lesions, especially at areas exposed to sunlight, prove to be a major form of manifestation of diseases related to Ro-antibodies and neonatal-, 'ANA-negative-', and cutaneous types of lupus erythe- matosus. A monoclonal Ro-antibody established by our group reacts with a 60 kD polypeptide in extracts from human spleen, whereas in extracts from human epidermis the monoclonal Ro-antibody and a purified Ro-antibody from a monospecific serum of a patient with subacute cutaneous lupus erythematosus reacted with a 60 kD and a 48 kD protein. Performing immunofluorescence microscopy on HEp2-cells both antibodies showed a nuclear speckled staining pattern and a reaction with cytokeratin filaments. On skin biopsies obtained from the patient, predominantly the basal layers of the proliferative stratum germinativum demonstrated a high rate of immunofluorescence; antigen-expression seems to depend on sunlight expo- sure. From these data we assume that, especially in subacute cutaneous lupus erythematosus, cross-reac- tion of the Ro-antibody with one of the lower molecu- lar keratins happens in that area of human epidermis which histologically shows cellular destruction.