[Interleukin 6 in the physiopathology of rheumatoid arthritis]

Interleukin (IL) 6 was identified in 1986 as a factor produced by T lymphocytes, that mediates growth and immunoglobulin synthesis on B lymphocytes. IL-6 is a member of a large cytokine family sharing a gp130 membrane receptor. This receptor mediates specific Jak/STAT3 activation, which induces widespread expression of pro-inflammatory and immunoregulatory genes. IL-6 mediates potent systemic responses, in organs distant from its local inflammatory sources, in a prominent fashion compared to other cytokines. Most specific effects involve hematopoiesis and hepatic acute phase reactants synthesis. IL-6 became a rheumatoid arthritis (RA) target due to its pro-inflammatory and joint destructive potential, as well as its participation in T and B immunoregulation. The therapeutic success of tocilizumab has confirmed IL-6 as an RA target. Although additional studies on the participation of IL-6 in RA physiopathology are needed, a number of indirect data point to a relevant position in this setting.