T_H2 and T_reg candidate genes in elephant shark

Abstract

Arising from B. Venkatesh et al. Nature 505, 174–179 10.1038/nature12826 (2014)

Recently in this journal, Venkatesh and co-workers published their analysis of the elephant shark (Callorhinchus milii, a chimaera) genome sequence¹. Their analyses suggested that at the evolutionary level of cartilaginous fish, only a primordial T-helper-cell (T_H-cell) system was established, geared towards a T_H1-type response, because they could not find several important candidate genes, or gene features, necessary for other types of T_H cells. However, in contrast to Venkatesh and co-workers, I am able to find elephant shark candidate genes for interleukin-2 (IL-2), IL-4, IL-5 and IL-13, which have important roles in mammalian T_H2 and T-regulatory-cell (T_reg-cell) systems; furthermore, I feel that claims by the authors of absent CD4 and FOXP3 functions in cartilaginous fish are insufficiently substantiated. Therefore, I believe that major conclusions by the authors regarding proposed unique features of the T-cell system in the elephant shark are based on false arguments, or, as in the case of their CD4 model, are premature. There is a Reply to this Brief Communication Arising by Venkatesh, B. et al. Nature 511,http://dx.doi.org/10.1038/nature13447(2014).