Prediction of the clinical and histological severity of IgA nephropathy by flow cytometry of urinary mononuclear cells

Background. Urinary mononuclear cells (UMCs) were studied in IgA nephropathy (IgAN) in relation to clinical and histopathological parameters. Methods. A two-color flow-cytometry analysis was used to phenotype and quantitate UMCs in patients with IgAN (n = 37) and those with other kidney diseases (n = 27). Results. The IgAN patients had higher numbers of UMCs than the patients with other kidney diseases. Macrophages (CD14+; P < 0.0001) and T lymphocytes (CD3+; P = 0.0001; CD4+, P < 0.0001) were predominantly found. In the IgAN patients, the quantities of urinary CD3+, CD14+ cells correlated with impaired renal function; namely, serum creatinine, creatinine clearance, and urinary protein excretion. The UMCs were associated with histopathological changes such as glomerular segmental lesions (r = 0.511; P < 0.01 for CD3+; r = 0.623, P < 0.0001 for CD4+, and r = 0.552; P < 0.001 for CD14+) and the index of glomerular hypercellularity (r = 0.405; P = 0.01 for CD3+ T cells and r = 0.392, P = 0.01 for CD14+ macrophages). Moreover, the UMCs reflected the severity of pathology, as estimated by the glomerular score (r = 0.424; P < 0.01 for CD3+; r = 0.458; P < 0.01 for CD4+; r = 0.500, P = 0.001 for CD14+ cells). UMCs were weakly correlated with tubulointerstitial changes. Conclusion. UMCs were associated with the clinical stage of IgAN and mirrored the extent of histopathology in the kidney. Flow-cytometry analysis of UMCs may help to predict the course of the disease.