Interleukin-6 (IL-6) is a multifunctional cytokine that plays a crucial role in the coordination of both the innate and acquired immune responses, acting as a key mediator in inflammation and immune regulation. IL-6 is primarily produced at sites of inflammation and is secreted into the serum, where it triggers a transcriptional inflammatory response through the interleukin-6 receptor, alpha. This cytokine is involved in the maturation of B cells, the production of acute phase proteins, and the regulation of T cell responses, including the promotion of Th2 and Th17 cell differentiation. IL-6 also has effects on hepatocytes, inducing the production of C-reactive protein and other acute phase reactants, and it plays a role in the regulation of iron and zinc metabolism during inflammation. Additionally, IL-6 has been implicated in the pathogenesis of various diseases, including autoimmune disorders and cancer, where it can promote cell proliferation, differentiation, and apoptosis. The cytokine's signaling is mediated through the IL-6 receptor complex, which includes the IL-6R and the signaling subunit gp130, initiating intracellular signaling pathways such as JAK/STAT and ras/MAP kinase. IL-6's pleiotropic effects make it a significant target for therapeutic interventions in immunoinflammatory diseases.