In Search of the Elusive Membranous Nephropathy Antigen

I favor is that antibodies may wax and wane with disease activity during the clinical course, and the presence of proteinuria in MN does not necessarily imply immunological activity. Another interesting finding is that most of the reactivity to the MN antigen resides in the IgG4 subclass. This is significant because most of the immunoglobulin that is deposited in the glomeruli of patients with MN is IgG4. However, the serum of several patients also has lesser amounts of IgG1 reactivity to the antigen. This is noteworthy because we believe that the podocyte injury that occurs in MN is complement-mediated [8, 9] , and IgG4 does not fix complement; however, IgG1 does. We have also obtained repeat samples from a few patients with MN and found that the presence of the antibodies corresponds to disease activity in that they disappear during drug-induced or spontaneous remission and reappear with relapse. These findings have clear implications for the diagnosis of idiopathic MN and for monitoring the response to treatment.