Although the pathogenesis of
immunoglobulin A (
IgA) nephropathy and Henoch-Schönlein
nephritis (HSN) remains uncertain, there is substantial evidence that they are
immune complex-mediated diseases. Recently, Haemophilus parainfluenzae
antigens were shown in the glomerular mesangium of adult patients with
IgA nephropathy, and greater levels of
IgA antibody against H parainfluenzae were also shown in the sera of adult patients with
IgA nephropathy. The present study was performed to detect H parainfluenzae
antigens and antibody against H parainfluenzae in children with
IgA nephropathy and HSN. H parainfluenzae
antigens in the mesangium were examined by indirect immunofluorescence, and antibody against H parainfluenzae was examined by
enzyme-linked
immunosorbent assay. Diffuse global staining of the mesangium with rabbit
antisera against H parainfluenzae was shown in 10 of the 32 patients (31%) with
IgA nephropathy and 12 of the 34 patients (35%) with HSN. Conversely, only 2 of the 47 patients (4%) with other renal diseases showed staining of glomeruli with rabbit
antisera against H parainfluenzae (
IgA nephropathy versus other renal diseases, P = 0.003; HSN versus other renal diseases, P = 0.0006). Patients with
IgA nephropathy and those with HSN showed significantly greater levels of plasma
IgA1 antibody against H parainfluenzae than patients with other renal diseases (
IgA nephropathy versus other renal diseases, P = 0.008; HSN versus other renal diseases, P = 0.025). These findings suggest that H parainfluenzae has a role in the cause of these two conditions in a subset of patients.