IgA nephropathy--human disease and animal model.

IgA nephropathy is one of the most common chronic glomerulonephritides worldwide. Since the first publication on IgA nephropathy, a number of clinical and pathological investigations have revealed that the clinical course of patients with IgA nephropathy is extremely diverse, with approximately 10-20% of the patients developing end-stage chronic renal failure. Glomerular changes similar to IgA nephropathy have also been observed in patients with Schoenlein-Henoch purpura, and with other diseases such as liver cirrhosis and chronic inflammatory diseases of the lung. The broad spectrum of clinical and pathological features of IgA nephropathy encompasses a syndrome which includes both primary and secondary IgA nephropathy. The common etiology and pathogenesis of primary and secondary IgA nephropathy appear to be closely related to immunological abnormalities in the production of IgA induced by antigenic stimulation of the common mucosal immune system. IgA is one of the most important humoral factors of the mucosal immune defense system and functions as an antibody against various extrinsic and intrinsic substances. This review describes the Arthus type of IgA immune complex deposition in the glomeruli which can result from persistent or repeated increases in circulating IgA immune complexes. The latter occurs as a consequence of overproduction of IgA antibodies and/or impairment in clearance of IgA immune complexes by the mononuclear phagocytic system. The present review also focuses on the biology of the IgA-mediated immune system and on the etiology, pathogenesis, and animal models of IgA nephropathy.