The occurrence of three D-J-C clusters within the dromedary TRB locus highlights a shared evolution in Tylopoda, Ruminantia and Suina.

The αβ T cells are important components of the adaptive immune system and can recognize a vast array of peptides presented by MHC molecules. The ability of these T cells to recognize the complex depends on the diversity of the αβ TR, which is generated by a recombination of specific Variable, Diversity and Joining genes for the β chain, and Variable and Joining genes for the α chain. In this study, we analysed the genomic structure and the gene content of the TRB locus in Camelus dromedarius, which is a species belonging to the Tylopoda suborder. The most noteworthy result is the presence of three in tandem TRBD-J-C clusters in the dromedary TRB locus, which is similar to clusters found in sheep, cattle and pigs and suggests a common duplication event occurred prior to the Tylopoda/Ruminantia/Suina divergence. Conversely, a significant contraction of the dromedary TRBV genes, which was previously found in the TRG and TRD loci, was observed with respect to the other artiodactyl species.