CHROMOSOMAL LOCALIZATION OF THE GENE FOR HUMAN B-CELL ANTIGEN-CD40

CD40 is a surface glycoprotein expressed on all human B lymphocytes an d plays an important role in B-cell development, growth, and different iation. Anti-CD40 monoclonal antibodies cause isotype switching in B c ells treated with IL-4. CD40 is a member of a family of proteins that include low-affinity nerve growth factor receptor, TNF receptor, and t he antigen Fas. The ligand for CD40 had been recently identified and h as been assigned to the X chromosome. Using a panel of human-rodent so matic cell hybrids, we now show that CD40 maps to human chromosome 20.