特異性：Chicken CD28, a monomeric molecule of Mr 40-44 kDa with 50% amino acid sequence identity with mammalian CD28 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 Ag presenting cells. Peripheral gamma delta + T cells are CD28-negative.1 Monoclonal antibodies against CD28 have a costimulatory effect on T cells stimulated by phorbol myristate acetate (PMA), concanavalin A or MAbs against the avian T cell receptor (TCR). Both V beta 1- and V beta 2-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 signalling pathway at least partly distinct from that triggered by TCR/CD3.2 MAb AV7 also reacts with turkey CD28 as demonstrated by flow cytometry and immunoprecipitation/Western blotting.3
