MS4A3 and immunoglobulin G4-related sclerosing disease: Although MS4A3 was thought to be associated with elevated serum IgE and allergic rhinitis, we found that its level of expression was significantly lower in PBMCs from IgG4-RD patients prior to steroid treatment than from healthy controls (Fig 1), and that its level of expression in IgG4-RD patients increased after steroid treatment (Fig 2).