Immunopathogenesis of inflammatory bowel disease

Figure 3 Th1 Polarization Pathway. Polarization of naïve T-cells towards Th1 cell subtype is initially induced by IL-12, a heterodimer of the p40 and p35 subunits. Activation of signal transducer and activator of transcription-1 (STAT1) and its stimulation of transcription factor T-bet, a TH1 “master switch” that upregulates and stabilizes the expression of IL-12. IL-12 can then amplify TH1 response by upregulating IL-18 on T-cells. IL-18 then stimulates NF-κB and AP1, and in synergy with STAT4 (activated by IL-12), transactivates IFN-γ expression.