LAUSR

Abstract Mammalian T cell subset differentiation is strictly controlled by cytokines and transcription factors. T-bet, GATA-3, BCL-6 and Foxp3 are considered the key transcription factors of Th1, Th2, Tfh and Treg cells. Here, we identified the genes and predicted the protein structure of these Th cell transcription factors in the orange-spotted grouper (Epinephelus coioides). The functional domains and 3D-models of grouper T-bet, GATA-3, BCL-6 and Foxp3 all had a degree of identity with that of mammals. Tissue distribution analysis in healthy groupers demonstrated that T-bet, BCL-6 and Foxp3 were highly expressed in central lymphoid organs, whereas GATA-3 was primarily expressed in mucosal organs. After infection with the parasite Cryptocaryon irritans, in both head kidney and gills, grouper T-bet expression increased from 12 h to 1 day, and GATA-3 expression was up-regulated from day 2, suggesting that the response of grouper Th1 cells was earlier than that of Th2 cells. Furthermore, Treg cells were involved in immunotolerance from day 7 in the head kidney after parasite infection owing to the up-regulated expression of Foxp3. In brief, our study described the response characteristics of T cell transcription factors in groupers and provided a theoretical basis for subsequent immunological control.