Purpose of review: The morphological features of membranous nephropathy have been recognized for over five decades, but the pathogenetic mechanisms underlying this lesion in humans have only recently been elucidated. This review analyzes the recent developments in understanding the pathogenesis of the primary and secondary forms of membranous nephropathy.
Recent findings: Seminal studies have identified several autologous antigens that are targets of an autoantibody response in primary membranous nephropathy. The leading candidate autoantigen is M-type phospholipase A2 receptor (PLA2R) protein. Autoantibodies to PLA2R, usually of IgG4 subclass, are found in 70-80% of patients with primary membranous nephropathy, bind to conformational epitopes on PLA2R expressed in the glomerular podocyte, form immune complexes in situ and induce proteinuria, mostly likely via local activation of complement. The autoimmune response is governed by genes at the HLA-DQA1 locus. The level of autoantibody to PLA2R correlates with the severity of the clinical disease and predicts recurrences in renal allografts (at least in some patients). Most forms of secondary membranous nephropathy appear to be due to distinctly different pathogenetic mechanisms.
Summary: The identification of target antigens provides new tools for diagnosis, prognosis and monitoring of therapy in human membranous nephropathy.