The JAK-STAT signaling pathway is central to cytokine-mediated gene expression, particularly in response to interferons (IFNs) and other cytokines. This review summarizes the JAK-STAT signaling paradigm, focusing on STAT-dependent transcription. The JAK family includes Jak1, Jak2, Jak3, and Tyk2, which are tyrosine kinases involved in cytokine signaling. Jak1 is essential for signaling through IFN-α/β, IL-2, and IL-6 receptors, while Jak2 is critical for signaling through single-chain cytokine receptors and the IFN-γ receptor. Jak3 is specific to leukocytes and is involved in IL-2 signaling. Tyk2 is important for signaling through IFN-I, IL-6, IL-10, and IL-12/23, and its deficiency leads to immune defects. The STAT family consists of seven members (STAT1-6), which are involved in transcriptional regulation. STAT1 is crucial for IFN-γ signaling and is involved in innate immunity. STAT2 is important for type I IFN signaling and is involved in the autocrine loop. STAT3 is involved in IL-6 and IL-10 signaling and is associated with cancer. STAT4 is critical for IL-12 and IL-23 signaling, promoting Th1 and Th17 responses. STAT5 is involved in IL-3, IL-5, and IL-21 signaling and is important for erythropoiesis and lymphopoiesis. STAT6 is involved in IL-4 and IL-13 signaling and is important for Th2 responses and mast cell activation. The JAK-STAT pathway is regulated by various mechanisms, including dephosphorylation, nuclear export, and SOCS feedback inhibition. STATs undergo covalent modifications such as serine phosphorylation, acetylation, and O-glycosylation, which influence their activity and transcriptional function. STATs also interact with coactivators and chromatin-modifying enzymes to regulate gene expression. The regulation of STAT activity is crucial for proper immune responses and disease pathogenesis.The JAK-STAT signaling pathway is central to cytokine-mediated gene expression, particularly in response to interferons (IFNs) and other cytokines. This review summarizes the JAK-STAT signaling paradigm, focusing on STAT-dependent transcription. The JAK family includes Jak1, Jak2, Jak3, and Tyk2, which are tyrosine kinases involved in cytokine signaling. Jak1 is essential for signaling through IFN-α/β, IL-2, and IL-6 receptors, while Jak2 is critical for signaling through single-chain cytokine receptors and the IFN-γ receptor. Jak3 is specific to leukocytes and is involved in IL-2 signaling. Tyk2 is important for signaling through IFN-I, IL-6, IL-10, and IL-12/23, and its deficiency leads to immune defects. The STAT family consists of seven members (STAT1-6), which are involved in transcriptional regulation. STAT1 is crucial for IFN-γ signaling and is involved in innate immunity. STAT2 is important for type I IFN signaling and is involved in the autocrine loop. STAT3 is involved in IL-6 and IL-10 signaling and is associated with cancer. STAT4 is critical for IL-12 and IL-23 signaling, promoting Th1 and Th17 responses. STAT5 is involved in IL-3, IL-5, and IL-21 signaling and is important for erythropoiesis and lymphopoiesis. STAT6 is involved in IL-4 and IL-13 signaling and is important for Th2 responses and mast cell activation. The JAK-STAT pathway is regulated by various mechanisms, including dephosphorylation, nuclear export, and SOCS feedback inhibition. STATs undergo covalent modifications such as serine phosphorylation, acetylation, and O-glycosylation, which influence their activity and transcriptional function. STATs also interact with coactivators and chromatin-modifying enzymes to regulate gene expression. The regulation of STAT activity is crucial for proper immune responses and disease pathogenesis.