Abstract: The present invention relates to the cloning, sequencing and characterization of a unique human epidermal surface antigen, ESA, and to methods for preparing and using the ESA gene and protein. The ESA gene is mapped to the region 17q11-12, on the long arm of chromosome 17, in the same area as the NF1 locus (the gene for von Recklinghausen neurofibromatosis). The mouse ESA has been located to chromosome 11. ESA mRNA is expressed in cultured keratinocytes and melanocytes, as well as in several carcinoma cell lines. Methods employing the antigen and/or DNA segments in diagnostic and therapeutic methods, including gene therapy, for the treatment of a variety of diseases, including cancer and autoimmunity, are disclosed. Methods for targeting molecules to the suprabasal epidermal cell layer are also presented.