JAK1 is a non-receptor tyrosine kinase that mediates cytokine and interferon signaling through the JAK-STAT pathway 1. JAK1 serves as a kinase partner for type I interferon receptor IFNAR2, where interferon binding triggers JAK1 phosphorylation of IFNAR2 to create docking sites for STAT proteins 2. JAK1 directly phosphorylates STAT proteins and transactivates other JAK kinases associated with signaling receptors 1. Additionally, JAK1 functions with IL-2 and IL-10 receptors to mediate interleukin signaling 34. Dysregulated JAK1 signaling associates with multiple pathologies. Gain-of-function JAK1 variants cause severe atopy with enhanced myelopoiesis, Th cell skewing, and marked eosinophilia; JAK1/2 inhibitor ruxolitinib treatment of affected children improved growth and allergic inflammation 5. In inflammatory skin diseases, elevated keratin 6A promotes JAK1-STAT3 activation in keratinocytes by reducing JAK1 ubiquitination, exacerbating rosacea and psoriasis-like inflammation 6. JAK1 polymorphism rs310241 associates with allergic rhinitis susceptibility 7. Clinically, selective JAK1 inhibitors (upadacitinib, abrocitinib) effectively treat moderate-to-severe atopic dermatitis and rheumatoid arthritis 89. Ruxolitinib inhibits basophil and mast cell mediator release, providing therapeutic potential for inflammatory disorders 10. JAK1 also integrates STING and type I interferon signaling in endothelium to promote tumor vasculature normalization and CD8+ T cell infiltration 11.