The dynamic TCRdelta: TCRdelta chains in the amphibian Xenopus tropicalis utilize antibody-like V genes.

摘要

The content and organization of the Xenopus tropicalis TCRalpha/delta locus was determined. This locus is highly conserved among tetrapods, with the genes encoding the TCRdelta chains embedded with those encoding TCRalpha. However, the frog TCRalpha/delta is unusual in that it contains V genes that appear indistinguishable from those in the IgH locus (VH). These V genes, termed VHdelta, make up 70% of the V genes at the TCRdelta locus and are expressed exclusively in TCRdelta chains. Finding TCRdelta chains that use antibody-like V domains in frogs is similar to the situation in shark TCRdelta variants and TCRmu in marsupials. These results suggest that such unconventional TCR may be more widespread across vertebrate lineages than originally thought and raise the possibility of previously unrealized subsets of T cells. We also revealed close linkage of TCRalpha/delta, IgH, and Iglambda in Xenopus which, in combination with linkage analyses in other species, is consistent with the previous models for the emergence of these antigen receptor loci.