The Th1 chemokine MIG in Graves’ ophthalmopathy
Chemokine (C-X-C motif) ligand (CXCL)9/monokine induced by interferon (IFN)-γ (MIG) and its receptor, chemokine (C-X-C motif) receptor (CXCR)3, are involved in the pathogenesis of Graves’ ophthalmopathy (GO). In tissues, recruited Type 1 helper (Th1) lymphocytes could cause an increased production of IFN-γ and tumor necrosis factor (TNF)-α, which in turn stimulate MIG secretion from these cells; all this creates an amplification feedback loop, and perpetuates the autoimmune process. In particular, MIG is secreted by fibroblasts and preadipocytes under the influence of IFN-γ. The IFN-γ induced MIG secretion in vitro, in GO fibroblasts and preadipocytes can be modulate by peroxisome proliferator-activated receptors (PPAR)-γ and PPAR-α activators.
High levels of MIG in peripheral liquids could be considered as a marker of an especially Th1 orientated immune response. The presence of circulating MIG is associated with the active phase of GO. An increased concentrations of MIG in patients with GO reflect, at least in part, the orbital inflammation activity.
Since MIG concentrations are significantly reduced during corticosteroids and/or radiotherapy treatments, with respect to control group and basal values of patients with GO, MIG has been proposed as a marker in the therapy choice for patients with GO.
More studies are needed to investigate interactions between chemokines and cytokines in the GO pathogenesis and to evaluate whether MIG is a novel therapeutic target in these autoimmune disorders