Full-length transcriptome sequencing of lymphocytes respond to IFN-γ reveals a Th1-skewed immune response in flounder (Paralichthys olivaceus).

Interferon gamma (IFN-γ), the member of type II interferons, is a major driver and effector cytokine for Th1 cells and plays broad roles in regulating the function of immune cells. Teleost fish represents the oldest living bony vertebrates containing T-lymphocyte subsets. However, whether or how the regulatory mechanisms of IFN-γ on Th1 cells occur in teleost fish remain unknown. In this study, full-length transcriptome sequencing was performed to analyze the differentially expressed genes (DEGs) and signaling pathways in the IFN-γ stimulated lymphocytes of flounder (Paralichthys olivaceus), the data showed 811 genes were upregulated and 1107 genes were downregulated, Th1 and Th2 cell differentiation pathway was remarkably enriched from DEGs, and the genes in the Th1 cell differentiation pathway were upregulated and verified. Accordingly, variations on Th1 cell differentiation marker genes and CD4+ cells were investigated after IFN-γ stimulation, the results confirmed that CD4+ T lymphocytes proliferated significantly after IFN-γ stimulation, accompanied by eight genes significant upregulation and increased T-bet expression in lymphocytes. In conclusion, the results revealed an induction of IFN-γ on Th1-type immune response, providing novel perspectives into the differentiation of CD4+ T lymphocytes in teleost.