Genomic sequence encoding diversity segments of the pig TCR delta chain gene demonstrates productivity of highly diversified repertoire

To better understand the function and diversity of gamma delta T cells, we determined the genomic sequence encoding diversity (D) segments of the porcine TCR delta chain and its upstream regions, because pigs and other artiodactyls have relatively high proportions of gamma delta T cells. The revealed sequence contained 28 variable (V) alpha/delta segments, including 4 TRDV1 and at least 6 D delta segments, a much higher number than in humans and mice. All 6 of the D delta segments that had canonical recombination signal sequences were functionally utilized in expressed TCR delta chain genes. The multiplicity of D delta segments enabled the use of more than 3 D delta segments in a single functional TCR delta chain. The increased number of TCR delta segments was acquired by the duplication of the germline sequence, which occurred after the divergence of artioclactyls from primates and rodents. These data demonstrate that the pig is able to generate a highly diversified repertoire of TCR delta chain molecules. (C) 2008 Elsevier Ltd. All rights reserved.