IgA Related Diseases

IgA Related Diseases

IgA and IgA receptors occupy key roles in mucosal and systemic immunity. Defects in IgA receptors profoundly affect immunohemostasis and can result in pathologies as diverse as allergy, gut autoimmunity, vasculitis, and IgA nephropathy. IgA-associated renal diseases likely arise due to glomerular deposition of IgA-containing circulating immune complexes that escape normal clearance. This process may ensue in patients with immunoglobulin type A nephropathy (IgAN) or Henoch-Schönlein purpura nephritis (HSPN) because the large size of the complexes precludes access to the hepatic asialoglycoprotein receptor, while wider endothelial fenestrae in the glomeruli permit the complexes to enter renal mesangium. Patients with other disorders may also develop immune-complex glomerulonephritis in which IgA plays a pivotal role. Mesangial deposits of IgA arise in patients with cirrhosis because the hepatic receptor for IgA is dysfunctional. Patients infected with the hepatitis C virus (HCV) show augmented production of IgA, perhaps due to virus-induced transformation of B cells. IgA-associated nephritis frequently afflicts patients with end-stage cirrhosis due to chronic HCV infection.