Objective    To investigate the expression of indoleamine 2，3-dioxygenase (IDO) in renal tissues of crescent nephritis and its correlation with cell proliferation and pathologic tubulointerstitial lesion.     Methods    Immunohistochemistry was used to detect IDO expression in renal tissues of crescent nephritis and normal renal tissues. The correlation between IDO expression and the number of proliferating cell nuclear antigen (PCNA) positive cells or pathologic tubulointerstitial lesion were analyzed.     Results    IDO expression was found in the renal tubular epithelial cells of crescent nephritis

while that in the normal renal tissues was negative by immunohistochemical staining. The expression of IDO protein in tubular epithelial cells showed a significantly negative correlation with the number of PCNA positive cells or tubulointerstitial lesion of crescent nephritis.     Conclusion    IDO may participate in the pathogenesis of crescent nephritis by inhibiting the cell proliferation.