TYK2 and COVID-19: More importantly, a genetic polymorphism study of COVID-19 patients showed the polymorphism locus near the Janus kinase (JAK) TYK2, the key for IFN, interleukin (IL)-12, and IL-23 signaling, and T helper (Th) 1/Th17 cell mediated antiviral immune responses, suggesting the critical role of the JAK-STAT signaling pathway in the development of cytokine storm in COVID-19 [28].