Fig 2. Factors controlling CD4⁺ T-cell differentiation in vivo and in silico.

Upon activation, an unpolarised CD4⁺ T cell (red) can differentiate into a Th1 or a Th17 cell dependent on the cytokine milleu. Th17 cells can subsequently transition through a double-positive (DP) cell to an ex-Th17 cell. Labels on each arrow indicate cytokines involved in this process in vivo (A) and the model species that correspond to these cytokines in silico (B). In both cartoons yellow cells secrete IL-17 and IL-21, blue cells secrete IFN-γ, and green cells secrete a combination of IL-17, IL-21 and IFN-γ.