Structural analysis of TRG1@ and TRG2@ loci of the ovine immune system

Abstract

The cellular immune system visualizes the world of pathogens largely through its T cell immune receptors (TCRs), a dimer which may be αβ or γδ. The proportion of T cell expressing the γδ TCR, among total T lymphocytes, is known to vary greatly between species. In human and mouse, γδ T cells account for less than 3% of the peripheral T cell pool (“γδ low” species), whereas in artiodactyls (Binns, 1992; Hein and MacKay, 1991) and chicken (Cooper, 1991), γδ T cell account for close to half of the peripheral T-cell pool (“γδ high” species). T cell receptor monomers are encoded by four distinct gene families: α, β, γ and δ contained within three chromosomal loci: α/δ, β and γ. The genes encoding the receptor chains are generated, during T cell development, by somatic rearrangement, of Variable (V), Diversity (D; in the β and δ loci only) and Joining (J) segments. After transcription, the V(D)J sequence is spliced to a Constant region, C. The genomic organization and chromosomal localization of TRG@ locus has been first determined in human (IMGT Database, 2002).........