FOXP3.sup.+ T cells are present in kidney biopsy samples in children with tubulointerstitial nephritis and uveitis syndrome

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.sup.+ 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.sup.+, FOXP3.sup.+ 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.sup.+ cells was significantly lower (p = 0.046) than in TIN patients without uveitis or with uveitis lasting