Urinary macrophages as activity markers of renal injury.

The presence of macrophages (Mφ) in the urine of patients with glomerulonephritis (GN) reflects the pathological events in the kidney, and we have discovered the following correlations between the Mφ phenotype and the pattern of renal injury. (1) Urinary macrophage (Mφ) counts increase in patients with proliferative GN, especially in the presence of active glomerular lesions (glomerular tuft necrosis, crescent, and endocapillary proliferation). In patients with hematuria, a combination of urinary Mφ and T-lymphocyte counts can be used to differentiate proliferative GN from non-proliferative renal disease (hereditary nephropathy and idiopathic renal hematuria). (2) The urinary Mφ of patients with active proliferative GN express FcgammaRIII (CD16) regardless of the type of GN. (3) There are two types of urinary CD68(+) cells, CD68(+)25F9(-) cells (infiltrating Mφ) and CD68(+)25F9(+) cells (mature Mφ). The CD68(+)25F9(-) cell counts in the urine correlate well with the activity of proliferative GN, and the CD68(+)25F9(+) cell counts in the urine correlate with the magnitude of non-selective proteinuria and with the subsequent decline of renal function. The CD68(+)25F9(+) cell count increases in the urine of patients with focal segmental glomerular sclerosis, but their numbers are negligible in minimal change nephrotic syndrome. These findings indicate that the analysis of the urinary Mφ phenotype is a useful strategy for evaluating renal injury as a 'risk-free renal biopsy'.