MOLECULAR CHARACTERIZATION OF THE EARLY ACTIVATION ANTIGEN CD69 - A TYPE-II MEMBRANE GLYCOPROTEIN RELATED TO A FAMILY OF NATURAL-KILLER-CELL ACTIVATION ANTIGENS

CD69 is a disulfide-linked homo-dimer expressed on the surface of acti vated T cells, B cells, natural killer cells, neutrophils and platelet s. Antibody cross-linking of CD69 in the presence of phorbol ester res ults in cellular activation events including proliferation and the ind uction of specific genes. Using an expression cloning strategy we have isolated cDNA encoding human CD69 from a CD4+ T cell clone. Transfect ion of the cDNA clone in CV-1/EBNA cells results in the expression of a covalently linked homodimer. The cDNA insert hybridizes to a 1.7-kb mRNA in phorbol 12-myristate 13-acetate- or phytohemoagglutinin-stimul ated human T cells. Using the human clone we have isolated cDNA encodi ng mouse CD69, which, when expressed in human T cells allowed those ce lls to respond to anti-mouse CD69 antibodies by secreting interleukin- 2 and interferon-gamma. Sequence analysis showed that both mouse and h uman CD69 are type II membrane glycoproteins related to the NKR-P1 and Ly-49 families of natural killer cell activation molecules.