Monoclonal anti thymic cell antibodies detecting epidermal cells

Two monoclonal antibodies were obtained from a fusion following immunization with human thymic cells. BL6 reacted with an antigen present on 80% of thymocytes found in the cortex, but absent from all other circulating or non circulating T or B lymphocytes. It immunoprecipitated an antigen of 49 Kd heavy chain with a small 12 Kd subunit. BL6 also reacted with dendritic cells of the epidermis identified as Langerhans cells carrying histocompatibility class II antigens and possessing Birbeck granules. The second antibody, BL7, did not stain thymocytes, but reacted with a cytoplasmic antigen of certain thymic epithelial cells. In skin sections, BL7 detected a cytoplasmic antigen of the keratinocytes of the basal cell layer. These cross reactivities between skin and thymic cells are discussed in view of a possible functional similarity between the two tissues.