Human immunodeficiency virus (HIV)-associated nephropathies are characterized by renal immune cell interstitial infiltration in patients with peripheral T-cell depletion. Since interstitial inflammation may mediate cytokine-induced fibrosis, we evaluated the immune cell population in the interstitium and glomeruli in renal biopsy tissue from 10 HIV-infected patients with focal segmental glomerulosclerosis (HIVFGS), staining renal biopsy specimens for UCHL-1 (a T-cell marker), OPD4 (predominantly a T helper-cell marker), PG-M1 (a macrophage marker), and L26 (a B-cell marker), and comparing them with renal tissue specimens from patients with HIV-associated immune complex glomerulonephritis (ICD) and from uninfected patients with FGS. Five fields comprising 0.2 mm2 were examined at a magnification of x400, a total area of 1 mm2. Total immune cells were estimated as the sum of UCHL-1, L-26, and PG-M1 cells. The T helper to suppressor (H/S) ratio was estimated as OPD4/(UCHL-1 - OPD4) lymphocytes. Tubular interstitial infiltrate was variable but dense in the majority of the infected biopsies, and was mild to moderate in all uninfected cases. The proportion of interstitial macrophages was greater in biopsy specimens from patients with HIVFGS than in those with HIVICD. In contrast, there was a greater percentage of B cells in the infiltrate in HIVICD compared with HIVFGS. Although there were fewer immune cells in whole glomeruli compared with 1 mm2 interstitium, macrophages were the predominant cells in glomeruli. B lymphocytes were generally absent in glomeruli in infected tissue, a pattern similar to uninfected tissue. The blood H/S ratio in HIV-infected patients was 0.2 +/- 0.03.(ABSTRACT TRUNCATED AT 250 WORDS)