IgG4

Immunoglobulin G4 (IgG4) is a member of the IgG family. Unlike other subtypes, IgG4 can selectively bind to low-affinity receptors and transmit immunosuppressive signals, reducing the intensity of immune response and inducing the occurrence of immune tolerance. IgG4 related disease (IgG4-RD) is an autoimmune disease that can affect organs such as the lung, liver, stomach, thymus, pancreas, and salivary gland, but the pathogenesis is still unclear. The main pathological features of the disease are massive infiltration of IgG4+ plasma cells, layered fibrosis, and obstructive phlebitis, so IgG4 has become an essential diagnostic indicator for IgG4-RD. Meanwhile, IgG4 deposition is found in idiopathic membranous nephropathy (IMN), which may be associated with the occurrence of IMN. In addition, colorectal cancer can promote the differentiation of B cells into IgG4+ plasma cells, which can synergize with regulatory T cells by secreting IL-35, affect antigen presentation function by down-regulating IL-21, and hinder the proliferation and activity of cytotoxic T cells by inhibiting IL-2 and IFN-γ.