[Pathogenesis of IgA nephropathy: role of outer membranes of Haemophilus parainfluenzae antigens].

IgA nephropathy is characterized by IgA deposits, predominantly in the glomerular mesangium and mesangial proliferative glomerulonephritis. Concerning its pathogenesis, several investigators suggest that the deposited IgA is an antibody to viral, bacterial, or dietary antigens. Such reports strengthen the possibility of a relationship between mucosal immunity and the pathogenesis of IgA nephropathy. We previously observed that Haemophilus parainfluenzae (HP) is more commonly isolated from the pharynx of patients with IgA nephropathy than from those with other diseases. We have also identified the glomerular deposition of the outer membranes of HP antigens (OMHP) and an increased serum concentration of IgA antibodies against OMHP in patients with IgA nephropathy. These findings suggest that HP has a role in the etiology of IgA nephropathy.