Leukocyte infiltration and intercellular adhesion molecule-1-mediated cell interactions in immunoglobulin A nephropathy.

Abstract

Mononuclear leukocytes have a role in immunoglobulin (Ig) A nephropathy. Renal leukocyte recruitment is mediated by adhesive interactions between leukocytes and their ligands on renal cells. We assessed interstitial and glomerular leukocytes using an avidin-biotin-peroxidase method with monoclonal antibodies (MAbs) against leukocytes (CD45), beta2-integrin (CD18), macrophages (CD14), T cells (CD3) and T-cell subsets (CD4, CD8), intercellular adhesion molecule-1 (ICAM-1) (CD54), and HLA class II antigens. We analyzed their relation with the abnormal expression of ICAM-1 on proximal tubular epithelium in sequential renal sections from 57 patients with IgA nephropathy stratified by degrees of interstitial cellular infiltration as seen by light microscopy. In IgA nephropathy without infiltration (n = 15) and with interstitial cellular infiltration of 1+ by light microscopy (n = 11), ICAM-1 expression on vascular endothelium was unchanged with respect to that observed in the normal kidney; the proximal tubular epithelium was negative for this stain. Moreover, in IgA nephropathy with interstitial cellular infiltration greater than or equal to 2+ by light microscopy (n = 31), ICAM-1+ stain was seen on proximal tubular epithelium. The value of ICAM-1+ tubule staining was significantly (P = .0004) higher in the biopsies with a higher degree of interstitial cellular infiltration seen by light microscopy. The tubular ICAM-1+ stain was significantly associated with the number of interstitial leukocytes identified by the MAbs tested and correlated (P < .05) with CD45+ (r = 0.59), CD14+ (r = 0.54), and CD3+ (r = 0.51) interstitial leukocytes in IgA nephropathy with interstitial cellular infiltration by light microscopy. Interstitial ICAM-1+ cells and interstitial CD18+ leukocytes were correlated (r = 0.85, P < .001). Correlation was found between the value of ICAM-1+ tubule staining and the number of CD45+ (r = 0.87, P < .01), CD14+ (0.58, P < .05), and CD8+ (r = 0.68, P < .05) glomerular leukocytes. Our results suggest that tubular and interstitial ICAM-1+ cells may participate in adhesive interactions with interstitial leukocytes. Epithelial tubular cells expressing ICAM-1 may be a marker of tubulointerstitial disturbance upregulated by interstitial and glomerular infiltration of macrophages and T cells in IgA nephropathy.