CD28 Antibody [AV7]

Chicken CD28 antigen is a type I transmembrane monomeric glycoprotein which does not contain the cysteine residues that form disulfide-linked covalent homodimers found in the mammalian counterpart. This may reduce the avidity of binding to individual ligand molecules expected to be present on antigen presenting cells. Peripheral gammadelta+ T cells are CD28 negative. Monoclonal antibodies against CD28 have a costimulatory effect on T cells stimulated by phorbol myristate acetate (PMA), concanavalin A, or monoclonal antibodies against the avian T cell receptor (TCR) . Both Vbeta1- and Vbeta2-expressing cells respond equally well to stimulation with anti-CD28 in combination with PMA. These responses are resistant to cyclosporin A but inhibited by herbimycin A suggesting that CD28 employs a signaling pathway at least partly distinct from that triggered by TCR/CD3. The monoclonal antibody AV7 also reacts with turkey CD28 as demonstrated by flow cytometry.