| Objective:(1) Cross sectional study:To evaluate the value of anti-phospholipase A2 receptor (PLA2R) antibody in the diagnosis of idiopathic membranous nephropathy (IMN). To explore the methodology differences between enzyme-linked immunosorbent assay (ELISA) and Immunofluorescence(IF) in the IMN diagnosis and PLA2R antibody detection. (2) Prospective study:To reveal the change characteristics of PLA2R antibody during IMN treatment process. To assess the relationship between PLA2R antibody changes and therapy reactions in IMN. (3) Complement mechanism research:To investigate the complement damage mechanisms in PLA2R associated IMN.Methods:(1) Cross sectional study:A total of 233 patients with IMN proven by kidney biopsy at Peking Union Medical College Hospital from January 1,2012 to March 31,2014 were enrolled in this study. Another 46 patients with non-IMN kidney diseases at the same period were selected as control group. Serum titer of PLA2R antibody was measured by quantitative enzyme-linked immunosorbent assay (ELISA) at the time of renal biopsy. Clinical data were reviewed and retrospectively analyzed. The diagnostic accuracy of PLA2R antibody in IMN was estimated by ROC curve. The PLA2R antibody was detected by ELISA and IF respectively in 60 IMN patients who were selected randomly from 233 IMN and 46 control patients in order to compare the ROC curve differences of IMN diagnosis between two methods. Additionally, the difference and consistence comparisons between the two methods in the antibody detection rate were conducted. (2) Prospective study:A total of 102 patients with IMN proven by kidney biopsy at Peking Union Medical College Hospital from January 1,2014 to December 31,2015 were enrolled in this study. A prospective follow-up was conducted monthly to monitor the changes in PLA2R antibody titer and treatment reaction in IMN. The end point was the clinical complete remission or the follow-up deadline. (3) Complement mechanism research:A total of 27 patients with IMN proven by kidney biopsy and with positive PLA2R antibody at Peking Union Medical College Hospital from December 1,2014 to June 1,2015 were enrolled in this study.13 IMN patients without detectable PLA2R antibody were selected as the antibody negative control group. The complement components Clq, MBL, C3c and C4d were detected by immunofluorescence staining. The IgG and IgG subtypes (including IgG1, IgG2, IgG3, and IgG4), which may be related to the complement activation pathway, were also measured.Results:(1) cross sectional study:The total sensitivity of PLA2R autoantibody was 60.0% in IMN. However, the sensitivity increased to 71.3% in patients who did not receive immuno-suppression therapies before antibody detection. The specificity of PLA2R autoantibody was 100.0%. The antibody were not detectable in 25 patients with lupus nephritis in control group. The area under ROC curve of PLA2R autoantibody for IMN diagnosis was 0.800. The prevalence of PLA2R autoantibody positive rate in nephrotic range proteinuria group and non-nephrotic range proteinuria group were 68.3% and 41.7%(P<0.05), respectively. The positive rates in patients with serum albumin level less than 30g/L and more than 30g/L were 67.3% and 44.6% (P<0.05), respectively. Hypoalbuminemia became worse (P<0.05) and the proportion of nephrotic arrange proteinuria rose significantly (P<0.05) in accord with the elevation of antibody level. There was no difference in IMN diagnostic accuracy between ELISA and IF. No significant difference was observed in the detection rate of PLA2R autoantibody between ELISA and IF. The two methods showed good consistency in antibody detection rate. (2) Prospective study:The overall average time of PLA2R autoantibody turning negative in the whole IMN group was 3.11±2.97months. In subgroups, the average time of autoantibody turning negative in the CR group and PR group were 3.17±3.23months and 3.13±3.05 months, respectively. If the baseline of autoantibody titers higher than 150RU/ml, the PR time and CR time became longer. When the time of autoantibody titers decreasing 50% was more than 3 months, the PR time and CR time became slower. If the time of autoantibody turning negative was more than 5 months, the PR time and CR got longer. The CR rate and PR rate in the antibody turning negative group were higher than that of antibody not turning negative group. Compared with the conservative therapy group, the antibody titers decreasing 80% and 50% were faster, and the CR rate was higher in the immunosuppressive therapy group. But the differences were not existed in immunosuppressive therapy groups. There was 1.91±2.51 months earlier for autoantibody turning negative than proteinuria reaching clinical PR. There was 6.91±3.33 months earlier for antibody to turn negative than proteinuria to achieve clinical CR. There was 3.09±4.66 months earlier for antibody turning positive again than proteinuria recurrence. The antibody changing trends were consistent with the clinical reactivity changes. (3) Complement mechanism research:The C3 detection rate in positive autoantibody group and negative group were 54.5% and 18.2%, respectively. The C4d detection rate in positive autoantibody group and negative group were 100% and 63.6%, respectively. The C1q detection rate in positive autoantibody group and negative group were 13.6% and 18.2%, respectively. The MBL detection rate in positive autoantibody group and negative group were 13.6% and 18.2%, respectively. The detection rate of IgG4 and IgGl in positive antibody group were 90.9% and 81.8%, respectively. The detection rate of IgG4 and IgGl in negative antibody group were 54.5% and 63.6%, respectively.Conclusions:(1) Cross sectional study:PLA2R antibody has high sensitivity and notable specificity for the diagnosis of IMN, with a good diagnostic accuracy. The antibody positive rate is affected by immunosuppression therapies, disease activity status and other clinical factors. The higher the antibody titers, the more serious the disease activity. The role of antibody in MN complicated with tumors and other special diseases is still unknown. There is no differences in IMN diagnosis accuracy, PLA2R antibody detection difference and detection consistency. ELISA can be used as a method for the PLA2R antibody detection clinically. (2) Prospective study:The higher the antibody baseline titers, the faster the antibody decreasing speeds and the shorter the antibody turning negative time, the better the clinical remission results. The antibody descending speed is faster at the early stage and the clinical remission rate is better in immunosuppressive therapy group than conservative therapy group. However, this phenomenon is not existed between Pred+CTX and Pred CNIs groups. PLA2R antibody could predict IMN clinical remission and recurrence in advance. (3) Complement mechanism research:The C3 and C4 detection rate were high in positive antibody group in IMN, which indicate classic and MBL complement pathway may involve in tissue injury. The C1q and MBL were detectable but the detection rate were low in positive antibody group, which imply classic and MBL complement pathway may involve in tissue injury. But the C1q and MBL detection rates was not consistent with the C3 and C4 detection rates. IgG1 detection rate in positive antibody group was high, which could activate the classic and alternative complement pathway. Thus, three complement pathway all may involve in IMN tissue injury. |
PDF Full Text Request