Th17 cells drive autoimmune disease but also control commensal microbes. A common link among antigens from self-proteins or commensal microbiota is relatively low activation of T cell receptor (TCR) and costimulation signaling. Indeed, strong TCR/CD28 stimulation suppressed Th17 cell differentiation from human naive T cells, but not effector/memory cells. CD28 suppressed the classical Th17 transcriptional program, while inducing known Th17 regulators, and acted through an Akt-dependent mechanism. Th17 cells differentiated without CD28 were not anergic: they showed robust proliferation and maintained Th17 cytokine production following restimulation. Interleukin (IL)-23 and IL-1β promoted glucose uptake and increased glycolysis. Although modestly increased compared to CD28 costimulation, glycolysis was necessary to support Th17 differentiation, indicating that cytokine-mediated metabolic shifts were sufficient to obviate the classical requirement for CD28 in Th17 differentiation. Together, these data propose that, in humans, strength of TCR/CD28/Akt activation serves as a rheostat tuning the magnitude of Th17 development driven by IL-23 and IL-1β. CD28 costimulation is considered the requisite “signal 2” for T cell activation, driving aerobic glycolysis and preventing anergy. Revu et al. find that, for human Th17 cells, IL-23 and IL-1β provide sufficient signals for metabolic increases and avoidance of anergy, whereas CD28 costimulation suppresses induction of the Th17 transcriptional program.
Revu, S., Wu, J., Henkel, M., Rittenhouse, N., Menk, A., Delgoffe, G. M., … McGeachy, M. J. (2018). IL-23 and IL-1β Drive Human Th17 Cell Differentiation and Metabolic Reprogramming in Absence of CD28 Costimulation. Cell Reports, 22(10), 2642–2653. https://doi.org/10.1016/j.celrep.2018.02.044