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In this issue, Shiokawa et al1 recapitulated the approach, previously established in pemphigus vulgaris,2 of passive transfer of IgG1 and IgG4 purified from patients with autoimmune pancreatitis (AIP) type 1 into neonatal Balb/c mice. These patients suffered from IgG4-related disease (IgG4-RD).
IgG4-RD is a novel clinical entity that includes a growing number of medical conditions that have the following features in common: diffuse organ swelling or focal mass formation, sclerosing storiforme (whirl-like) fibrosis with a lymphoplasmacytic infiltrate rich in IgG4-bearing plasma cells and elevated levels of serum IgG4. The disease usually responds well to steroid treatment and is predominantly diagnosed in elderly men.3 ,4 IgG4-RD is poorly understood but is currently classified as an autoimmune disease because of its association with autoantibody formation. However, so far there has been no evidence that the autoantibodies reported in IgG4-RD contribute directly to the pathogenesis.5 In many autoimmune disorders, which are unequivocally T-cell-driven, autoantibodies such as antinuclear antibodies and rheumatoid factor are detected, but such antibodies are not necessarily responsible for the tissue damage resulting in autoimmune disease, which is rather primarily induced by T cells. While T cells are likely also important for IgG4-RD (although it is still debated whether Th1 or Th2 cytokines ultimately drive the disease process6 ,7), the present study provides solid evidence that in IgG4-RD-associated AIP IgG4 is more than just a biomarker, or an epiphenomenon, but a driver and also a modulator of the disease.
Total IgG from patients with IgG4-RD resulted in injury to the pancreas and salivary glands of the mice. …