Somatic Cell Genetics, Vol. 8, No. 2, 1982,pp. 197-206 Expression of Human Transferrin Receptor Is Controlled by a Gene on Chromosome 3: Assignment Using Species Specificity of a Monoclonal Antibody P.N. Goodfellow, 1 G. Banting, 1 R. Sutherland, 1 M. Greaves, 1 E. Solomon, 1 and S. Povey 2 ~Imperial Cancer Research Fund, Lincoln's Inn Fields, London, WC2A 3PX; and 2M.R.C. Blochemical Genetics Unit, Wolfson House, 4 Stephenson Way, London, NW1 2HE, U.K. Received 5 August 1981--Final 20 October 1981 Abstract-- The monoclonal antibody OKT-9 has been shown to recognize the human transferrin receptor. We have exploited the species specificity of OKT-9 to map a gene controlling human transferrin receptor expression to chromosome 3, using human-mouse somatic cell hybrids. The gene for the human transferrin receptor and the gene controlling transferrin expression may be linked in humans. INTRODUCTION The presence of transferrin is a requirement for in vitro growth of cells in the absence of serum (1, 2). This growth-promoting effect of transferrin is probably due to its iron-transporting properties. Transferrin is bound specifi- cally to cells by a surface-membrane receptor (3), which is thought to be a protein of approximately 180,000-dalton molecular weight composed of two 90,000-dalton disulfide-linked subunits (3-5). Recently, it has been demon- strated that the monoclonal antibody OKT-9 recognizes a determinant carried by the human transferrin receptor. OKT-9 was raised against human thymocytes and T acute lymphoblastic leukemia cells (T-ALL) and was described as recognizing an antigen associated with immature thymocytes and their corresponding leukemias (6). Subsequent work, however, indicated that the OKT-9 antigen, like the transferrin receptor, was found on a wide variety of normal and transformed cells of both hematopoietic and nonhema- topoietic origin (7). Expression of the OKT-9 antigen (7,8) and the transfer- 197 0098~)366/82/03004)197503.00/0 9 1982Plenum Publishing Corporation