Abstract:
The human immune response to allergens involves 2 IL-4 dependent antibodies: the well-known IgE and the less well-known IgG4. IgG4 has several unusual features, both at the protein level (IgG4 in plasma behaves as a monovalent antibody, due to its tendency to exchange halfmolecules with other IgG4) and at the B cell level (acting as a regulatory cell analogous to the Treg). The latter feature is possibly a factor contributing to a syndrome called IRD = IgG4-related disease. IRD is characterized by excessive production of IgG4 by tumor-like masses of plasma cells in non-lymphoidal tissues such as the pancreas.