The expression of Toll‐like receptors 2, 4 and 9 in kidneys of patients with anti‐neutrophil cytoplasmic antibody ( ANCA )‐associated vasculitis

Summary Increasing evidence suggested that Toll‐like receptors ( TLR s) were critically involved in immune responses of anti‐neutrophil cytoplasmic antibody ( ANCA )‐associated vasculitis ( AAV ). The current study aimed to investigate the expression of TLR‐ 2, TLR‐ 4 and TLR‐ 9 in kidneys of patients with ANCA ‐associated vasculitis. Renal biopsy specimens were collected from 24 patients with AAV . The expression of TLR‐ 2, TLR‐ 4 and TLR‐ 9 in kidneys was detected by immunohistochemistry. Double immunofluorescence staining was performed to detect the expression of TLRs on various kinds of cells. In renal specimens, immunohistochemical examination revealed that expression of TLR‐ 2 and TLR‐ 4 could be detected in the glomeruli of AAV patients, while TLR‐ 2 and TLR‐ 4 were scarcely detected in the glomeruli of normal controls. Double immunofluorescence staining of TLR‐ 2, TLR‐ 4 and CD 31 indicated that TLR‐ 4 and TLR‐ 2 were expressed on endothelial cells in the glomeruli. In the tubulointerstitial compartment, expression of TLR‐ 2, TLR‐ 4 and TLR‐ 9 could be detected in both AAV patients and normal controls. The mean optical density of TLR‐ 2 and TLR‐ 4 in the tubulointerstitial compartment in AAV patients were significantly higher than that in normal controls. Among AAV patients, correlation analysis showed that the mean optical density of TLR‐ 4 in the glomeruli correlated inversely with the initial serum creatinine, the proportion of total crescents and the proportion of cellular crescents in renal specimens ( r  = −0·419, P  = 0·041; r  = −0·506, P  = 0·012; r  = −0·505, P  = 0·012, respectively). The expression of TLR‐ 2 and TLR‐ 4 was dysregulated in kidneys of AAV patients. The expression of TLR‐ 4 in glomeruli was associated with the severity of renal injury.