In situ production of TNF-α, IL-1β and IL-2R in ANCA-positive glomerulonephritis

In situ production of TNF-α, IL-1β and IL-2 receptors in ANCA-positive glomerulonephritis. Humoral and cellular immune mechanisms are thought to be involved in various forms of vasculitis and glomerulonephritis. Recent clinical and experimental results point to a role of cytokines in ANCA-positive vasculitides. We analyzed tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-2 receptors (IL-2R) in renal biopsies and in plasma from 22 patients with Wegener's granulomatosis and microscopic polyangiitis. Kidney biopsies were examined by immunocytochemistry, polymerase chain reaction and in situ hybridization. Immunoreactive TNF-α, IL-1β and/or IL-2R positive infiltrating cells were observed in 21 of 22 biopsies. TNF-α, IL-1β and IL-2R staining was evident in the interstitium and at periglomerular and perivascular sites. The number of positive cells was markedly increased in biopsies with active lesions. Positive cells were also present in cellular and fibrocellular crescents, surrounding tuft necrosis and in the walls of arteries and arterioles with acute vasculitic lesion. Some tubular epithelial cells stained for TNF-α and IL-1β. TNF-α, IL-1β and IL-2R positive infiltrating cells correlated with the presence of histologically active renal lesions. The evaluation of TNF-α and IL-1β expression at the mRNA level assessed by the polymerase chain reaction demonstrated specific transcripts for TNF-α and IL-1β in all six cases analyzed. In situ hybridization studies showed an increased expression of mRNA for TNF-α and IL-1β in infiltrating mononuclear cells, in epithelial cells of Bowman's capsule and in some tubules, predominantly of patients with active renal lesions. The results at the mRNA level correlated with the immunocytochemical findings. Compared to healthy individuals higher TNF-α plasma levels were observed in patients with vasculitis (34.4 ± 16.6 pg/ml (sem) VS. 1.9 ± 0.7 pg/ml in controls; P < 0.01). All patients presented a marked increase in SIL-2R plasma levels (3512 ± 485 U/ml vs. 397 ± 21 U/ml in healthy controls; P < 0.001). IL-1β was not detected in most plasma samples. Elevated TNF-α and sIL-2R plasma levels were related to active renal lesions. Our study clearly demonstrates that in ANCA-positive vasculitis TNF-α and IL-1β are produced in situ by activated infiltrating mononuclear cells and resident renal cells. Intrarenal localization of cytokine producing cells and the correlation between cytokine production and histological signs of activity suggest that TNF-α and IL-1β are important locally acting mediators in the vasculitic/glomerulonephritic process.