MOLECULES

Full name: Interleukin-6

Aliases: Hepatocyte-stimulating factor, B-cell stimulatory factor 2, cytotoxic T-cell–differentiation factor, B-cell–differentiation factor, hybridoma/plasmacytoma growth factor, monocyte–granulocyte inducer type 2, and thrombopoietin¹

Size: 19–26 kDa^1,2

Family: Main member of the IL-6 cytokine family that also includes leukemia inhibitor factor, ciliary neurotrophic factor, oncostatin M, IL-11, and cardiotrophin-1^1,2

Receptors: IL-6 receptor (membrane bound IL-6R and soluble sIL-6R) gp130^1,2

Major cellular sources: T cells, B cells, macrophages, monocytes, fibroblasts, chondrocytes, osteoblasts, mast cells, keratinocytes, and endothelial cells^1,2

Major cellular targets: T cells, B cells, hepatocytes, leukocytes, and hematopoietic cells²

Disease states associated with: Immune diseases, inflammation, and autoimmune diseases^1,2

Major physiologic functions:

• IL-6 is involved in B-cell differentiation and survival, T-cell proliferation, development of osteoclasts in bone resorption, synovial fibroblast proliferation, and cartilage degradation.²
• IL-6 is responsible for acute phase proteins synthesis and neutrophil production in the bone marrow.^2,3
• IL-6 induces direct stimulation of CRP from hepatocytes and plays a significant role in rheumatoid arthritis pathogenesis.¹
• Allergen-induced IL-6 promotes type 2 and type 17 airway inflammation.²
• Chronic psoriatic lesions may produce large amounts of IL-6 and other pro-inflammatory cytokines, which release free fatty acids, cholesterol, and triglycerides from the adipose tissue. Consequently, patients with psoriasis have increased serum concentrations of triglycerides, total cholesterol, LDL-C, and VLDL-C.⁴

CRP: C-reactive protein; gp130: glycoprotein 130 subunits; IL: interleukin; LDL-C: low-density lipoprotein cholesterol; sIL-6R: soluble IL-6 receptor; VLDL-C: very low–density lipoprotein cholesterol.