Monocyte infiltration and cross-linked fibrin deposition in IgA nephritis and Henoch-Schoenlein purpura nephritis.

To clarify the role of immune cell infiltration and fibrin deposition in glomerular injury, renal biopsy specimens taken from patients with primary IgA nephritis and Henoch-Schönlein purpura nephritis (HSPN) were evaluated using monoclonal antibodies specific to mononuclear cell surfaces and cross-linked fibrin (XFb). Monocytes/macrophages were the predominant cell type infiltrating glomeruli in IgA nephritis and HSPN. The intraglomerular monocyte population in both diseases was significantly higher than that in normals, mesangial proliferative (non-IgA) glomerulonephritis or minimal change nephrotic syndrome. In IgA nephritis, there was a clear correlation between glomerular monocyte accumulation and the degree of proteinuria. Although the monocyte influx tended to decline with time in HSPN, it remained unchanged in IgA nephritis. XFb deposition was found in the glomeruli of 27 out of 48 patients with IgA nephritis, and in 15 out of 20 with HSPN. The degree of XFb deposition in IgA nephritis correlated significantly with the degree of mesangial proliferation. These findings indicate a close relationship of monocyte/macrophage infiltration and XFb deposition with glomerular injury in IgA nephritis.