Interleukin-6 (IL-6) is an endogenous chemical with multiple forms and functions. It acts as both a pro and an anti-inflammatory cytokine (1). In the early phase of infectious inflammation, IL-6 is produced by monocytes and macrophages immediately after the stimulation of Toll-like receptors (TLRs) with distinct pathogen-associated molecular patterns (PAMPs). In non-infectious inflammation, such as a burn or traumatic injury, damage-associated molecular patterns (DAMPs) from damaged or dying cells stimulate TLRs to produce IL-6 (2).
IL-6 helps T-cells to differentiate in their development. It is required for progenitor cell development or helps B-cells differentiate and proliferate, and promotes the formation of plasma cells from B-cells. IL-6 also plays a vital role in the development of blood cells, whether white cells, red cells or platelets. Besides, IL-6 leads to the activation of osteoclasts and osteoporosis. It also induces the secretion of vascular endothelium growth factor (VEGF), which leads to the increased growth of blood vessels and vascular permeability in inflammation (3).
Genetic variations of IL6 are associated with rheumatoid arthritis systemic juvenile (RASJ), and its promoter polymorphism can be an indicator for Kaposi sarcoma development in HIV-infected men (4-5).