Current understanding of the role of tyrosine kinase 2 signaling in immune responses

Figure 1 Schematic representation of the tyrosine kinase 2-related cytokine receptors. The IL-6 receptor, which comprises IL6RA (gp80) and IL6RB (gp130) subunits, activates signal transducer and activator of transcription (STAT)1 and STAT3 through interactions with Tyrosine kinase 2 (Tyk2), Janus family of protein tyrosine kinases 1 (Jak1), and Jak2. The IL-10 receptor, which comprises IL-10R1 and IL10-R2 subunits, activates STAT1, STAT3, and STAT5 through interactions with Tyk2 and Jak1. IL-12 is a heterodimeric cytokine comprising the IL-12p35 and IL-12p40 subunits. The IL-12 receptor, which comprises IL-12Rβ1 and IL-12Rβ2, mainly activates STAT4 through interactions with Tyk2 and Jak2. The IL-12p40 component of IL-23 can dimerize with IL-23p19 to form IL-23. The IL-23 receptor, which comprises IL-12Rβ1 and IL-23R subunits, activates STAT1, STAT3, and STAT4 through interactions with Tyk2 and Jak2. The type I IFN receptor, which comprises IFNAR1 and IFNAR2 subunits, activates STAT1 and STAT2 through interactions with Tyk2 and Jak1. STAT: Signal transducer and activator of transcription; Tyk2: Tyrosine kinase 2; Jak1: Janus family of protein tyrosine kinases 1.