CUTTING EDGE - THE CHICKEN TCR ZETA-CHAIN RESTORES THE FUNCTION OF A MOUSE T-CELL HYBRIDOMA

The TCR/CD3 complex has been intensively studied in mammals, but it ha s been difficult to isolate homologues in other vertebrates, Here, we characterize the chicken zeta-chain, the first nomnammalian homologue identified. The comparison of mammalian and chicken zeta proteins reve aled high identity of the transmembrane and the C-terminal cytoplasmic domains. Transfection of a mouse zeta-deficient cell Line, with the c hicken zeta gene, restored surface expression of the murine TCR/CD3 co mplex, The chicken zeta-chain was stably associated with the mouse TCR /CD3 components and fully restored its signaling capacity upon stimula tion with Ab, superantigen, and peptide Ag. This is the first report o f a nonmammalian TCR component that is capable of fully restoring a ma mmalian TCR in every aspect analyzed, thus demonstrating the enormous selective pressure to maintain the zeta-chain as a structural and sign aling component over a period of 300 million years.