Channel catfish CD8α and CD8β co-receptors: Characterization, expression and polymorphism

In this study we report the identification and characterization of channel catfish, Ictalurus punctatus CD8 alpha and CD8 beta genes. Both genes encode predicted proteins containing a leader, a immunoglobulin superfamily V domain, a stalk/hinge region, a transmembrane region and a positively charged cytoplasmic tail (CYT) containing the conserved teleost C-X-H motif. Catfish CD8 alpha and CD8 beta are encoded as single copy genes and as in other vertebrates exhibit a conserved head to tail synteny: the CD8 beta gene is found 14.1 kb upstream of the CD8 alpha gene. Both CD8 alpha and CD8 beta transcripts showed a low degree of polymorphism. Finally, as determined by q-PCR both CD8 alpha and CD8 beta are expressed in various catfish lymphoid tissues with the highest expression observed in thymus from 2 month old catfish-fry. In the future these results will provide the basis for evaluating the role of CD8(+) CTL. and other CD8-bearing cells in response to immunization or infection in the catfish. Published by Elsevier Ltd.