A dominant role of TGFβ in regulating T-cell size and physiology

During an immune response, cells are simultaneously exposed to multiple cytokine signals that collectively determine their phenotype. Transforming growth factor β (TGFβ) is a pleiotropic cytokine acting as a key regulator of T-cell differentiation with activating and suppressive effects on their immune function. Here, we systematically analyze the cellular responses of CD4 + T cells to TGFβ across diverse cytokine environments in the presence or absence of TGFβ. We found that TGFβ had a profound dominant effect independent of the presence of other cytokines, modulating the expression of more than 4,000 genes. In the presence of TGFβ, cells exhibit lower expression of translation-related and apoptosis-related genes, accompanied by increased survival of activated T cells. Notably, cells cultured in the presence of TGFβ were smaller in size while preserving their proliferative ability. Accordingly, we identified a dense network of transcription factors that were modulated by TGFβ, suggesting a core gene set connecting TGFβ signaling to the regulation of T-cell size. We found N-Myc to be at the center of this network, and we directly show that TGFβ regulates its gene expression level, protein level, and nuclear localization. Our work provides a system to study cell size control and demonstrate the profound effect of TGFβ in the modulation and regulation of T-cell properties, expanding its role beyond guiding their phenotype. Significance Statement TGFβ is a key determinant of CD4 + T-cell differentiation; however, understanding its effect on additional aspects of T-cell state is lacking. Here, we systematically studied the role of TGFβ in regulating T-cell physiology. Exposing cells to diverse combinations of cytokines enabled us to distill the core effect of TGFβ. We found TGFβ to have a profound effect on multiple cellular processes critical to T-cell function. Significantly, TGFβ induced smaller T-cells both in vitro and in vivo, suggesting that TGFβ could skew the population towards tissue infiltration and residency. Furthermore, TGFβ can be used to fine-tune T-cell size, providing a system for studying cell size control. Overall, our findings demonstrate the profound effect of TGFβ in the regulation of T-cell physiology.