RESUMEN
BACKGROUND: Tubulointerstitial nephritis (TIN) is an inflammatory disease of unknown pathogenesis. To evaluate a possible role of regulatory T cells (Tregs) in the pathophysiology of TIN with (TINU) and without uveitis, we investigated the presence and quantity of FOXP3+ T regulatory lymphocytes in diagnostic kidney biopsies from pediatric patients. METHODS: A total of 33 patients (14 TIN and 19 TINU) were enrolled. The quantity of CD4+, FOXP3+ and double-positive T cells in formalin-fixed kidney biopsies was determined using double label immunohistochemistry with anti-human CD4 and FOXP3 antibodies. RESULTS: FOXP3 staining was successful in all 33 patients. In patients with chronic uveitis, the density of FOXP3+ cells was significantly lower (p = 0.046) than in TIN patients without uveitis or with uveitis lasting <3 months. CD4+ staining was successful in 23 patients. The density of all lymphocytes (CD4+, CD4+FOXP3+ and FOXP3+ cells) was significantly lower (p = 0.023) in patients with chronic uveitis than in other patients. CONCLUSIONS: FOXP3+ T cells are present in kidney biopsy samples from TIN and TINU patients. In patients with chronic uveitis, the density of FOXP3+ T cells is significantly lower than in other patients, suggesting a different pathomechanism for these clinical conditions.