Molecular cloning and sequencing of canine T-cell costimulatory molecule (CD28)

T-cells express CD28 and CTLA-4, and through binding to their shared ligand s (CD80/CD86) on antigen presenting cells, provide a potent co-stimulatory signal for T-cell activation and proliferation. To investigate the role of CD28 in canine immune system, we hereby report the molecular cloning and se quencing of the full-length complementary DNA (cDNA) coding for canine CD28 , from pokeweed mitogen stimulated canine peripheral blood lymphocytes. The cloned cDNA contains an open reading frame of 663 nucleotides, encoding fo r a polypeptide of 221 amino acids. The amino acid sequence of the canine C D28 showed 91.9, 80, and 79.6% similarities with those of the cat, cattle, and human counterparts, respectively. Five sequence motifs of TATT or ATTTA involved in the regulation of gene expression by influencing mRNA stabilit y are found in the 3' untranslated region. The hexapeptide motif (MYPPPY), five cysteine residues, a potential N-glycosylation site and a cytoplasmic phosphatidylinositol 3-kinase binding site in canine CD28 molecule are comp letely conserved in canine CTLA-4. The availability of full length canine C D28 will provide a useful molecule for studying its role in dog immune syst em. (C) 2001 Elsevier Science B.V. All rights reserved.