ObjectiveTo observe the expression of nephrin in hepatitis B virus-associated membranous nephropathy (HBV-MN),and investigate the impairment and significance of podocyte in HBV-MN.MethodsThe protein expression of nephrin in renal biopsy specimens in 35 patients,who were diagnosed as HBV-MN by renal biopsy,was determined by immunohistochemistry and tested by semiquantitative method.The relationship between the expression of nephrin and clinicopathological data was analyzed.Results Among the 35 cases with HBV-MN,6 were in MN phase Ⅰ,20 in MN phase Ⅱ and 9 in MN phase Ⅲ.A strong intensity expression of nephrin in normal glomerulus was found along capillary loop of glomerulus,while its expression in HBV-MN patients decreased obviously.There was no significantly difference in the expression of nephrin among the different stages of HBV-MN ( P ＞ 0.05 ).The expression of nephrin in different clinical types was significantly different ( P ＜ 0.05 ).The expression of nephrin in patients with nephrotic syndrome was significantly lower than that in patients without nephrotic syndrome (P ＜0.01 ).The expression of nephrin in different grades of 24-hour urinary protein excretion quantity was significantly different( P ＜ 0.05 ).There was negative correlation between the expression of nephrin and 24-hour urinary protein excretion quantity(r = -0.378,P ＜ 0.05).In the patients with HBV-MN phase Ⅱ,the expression of nephrin in patients with nephrotic syndrome was also significantly lower than that in patients without nephrotic syndrome( P ＜ 0.01 ).Conclusions The damage of podocytes emerge in the early stage of HBV-MN and the expression of nephrin in HBV-MN patients,especially in patients with nephrotic syndrome,are significantly down regulated.The descended expression of nephrin in HBV-MN patients may promote the production of proteinuria.