Figure 1.

T-cell differentiation, subsets, and main functions. Naive CD4 T-cells can undergo differentiation into distinct effector subsets (e.g., Th1, Th2, Th9, Th17, and Th22 cells), follicular helper T (Tfh) cells, and regulatory phenotypes (Treg), each producing a characteristic set of cytokines (unfilled boxes next to cells). This differentiation process is mediated in part by the local cytokine microenvironment (arrows), which activates specific transcription factors and signaling molecules (text inside cells). Color-filled boxes next to cells list functions in homeostasis and in IBD (bold text). IBD is associated with changes in T-cell populations.