Development of reagents to study the turkey's immune response: Identification and molecular cloning of turkey CD4, CD8α and CD28

The cDNAs of three turkey CD markers, CD4, CD8α and CD28, were identified by screening a turkey cDNA library. The coding regions of the chicken and turkey genes are highly conserved, with 91.3–96.1% nucleotide (nt) and 84.2–95.5% amino acid (aa) identity. Identity was less conserved between avian CD markers and their mammalian homologues, ranging from 44.7 to 59.8% and 22.4 to 50.4% at the nt and aa levels, respectively. Anti-chicken CD8α and CD28 monoclonal antibodies were demonstrated to specifically cross-react with turkey CD8α and CD28, respectively.