The role of interstitial infiltrates in IgA nephropathy: a study with monoclonal antibodies.

The leucocyte subpopulations in the interstitium and the glomeruli in renal biopsies from 34 patients with IgA nephropathy were analysed using monoclonal antibodies and immunoperoxidase techniques. Monocyte/macrophages and T-cells constituted the predominant infiltrating cell type in the interstitium (278 +/- 24 and 269 +/- 37 cells/mm2 respectively). Few intraglomerular leucocytes were seen, the majority of them belonging to the monocyte/macrophage phenotype (1.1 +/- 0.1 cells/glomerular cross-section). CD4+ lymphocytes predominated among the interstitial and glomerular T-cell populations and the CD4:CD8 ratio was 2.1 +/- 1.1 and 2.4 +/- 1.5 respectively. Only small numbers of NK cells and B cells were found in the interstitium, and almost none in the glomeruli. In contrast, significantly increased numbers of DR-expressing interstitial cells were seen (487 +/- 29/mm2), whereas DR expression by the tubular cells was minimal (37 +/- 6/mm2). Numbers of total leukocytes and T-cells were well correlated with the degree of tubulointerstitial damage and there was a significant correlation between renal functional impairment at the time of biopsy and the numbers of interstitial T cells (P less than 0.05) and CD4+ T cells (P less than 0.01). In contrast, interstitial mononuclear cells did not correlate with subsequent progression of the disease over 2-3 years. However, a more rapid decline of renal function was associated with increased numbers of interstitial B cells. No association was found between intraglomerular cells and degree of renal impairment either at the time of biopsy or in the long term.(ABSTRACT TRUNCATED AT 250 WORDS)