IL6 encodes interleukin-6, a multifunctional cytokine that serves as a central mediator of inflammation, immune responses, and metabolic homeostasis. The protein functions as both a pro-inflammatory and anti-inflammatory signal depending on context, activating the JAK-STAT signaling pathway through its receptor complex. IL6 plays essential roles in bone homeostasis and angiogenesis by inducing VEGF production, though IL6-stimulated blood vessels show defective pericyte coverage compared to VEGF-induced vessels 1. The cytokine acts as a myokine released after muscle contraction to regulate lipolysis and insulin sensitivity, and controls iron metabolism through hepcidin regulation. In disease contexts, IL6 promotes tumor progression and metastasis, particularly in non-small cell lung cancer where it suppresses T-cell and NK-cell function in tyrosine kinase inhibitor-resistant tumors 2. IL6 facilitates brain metastasis through activation of anti-inflammatory microglia via the JAK2/STAT3 pathway 3. Genetic variants in the IL6 promoter region, particularly rs1800795, are associated with metabolic syndrome risk and anterior cruciate ligament rupture susceptibility in certain populations 4 5. The clinical significance of IL6 is underscored by multiple approved therapeutic antibodies including clazakizumab, siltuximab, and ziltivekimab. Genetic evidence suggests IL6 inhibition reduces cardiovascular disease risk, supporting the therapeutic rationale for anti-IL6 interventions 6.