Combination Of Anti-phospholipase A2 Receptor Antibodies And IgG4 In Diagnosis Of Idiopathic Membranous Nephropathy

BackgroundMembranous nephropathy(MN)is one of the most common pathological types related to adult nephrotic syndrome,including idiopathic membranous nephropathy(IMN)and secondary membranous nephropathy(SMN).Its typical pathological characteristics are that immune complexes deposit under epithelium and glomerular basement membrane thickens.SMN is usually secondary to SLE,malignant tumor,viral infection,some certain medicine or poisons and its treatment and prognosis is also associated with primary diseases.Without secondary reasons,idiopathic membranous nephropathy accounted for 80% of membranous nephropathy.Although KDIGO Guildline recommands glucocorticoids accompanied with immunosuppressive agents as the first-line therapy,but the results and prognosis are different.About 1/3 of IMN patients get to remission,about 1/3 are effective to the therapies,and about 1/3 progress to ESRD.Although IMN is similar to SMN in pathology and clinical manifestation,its treatments are different from SMN,and it is always hot to distinguish them.It's still unclear about the pathogenesis of the IMN,but we gradually realize the importance of its autobodies,especially M-PLA2 R antibodies.M-PLA2 R is the type I transmembrane protein on the podocytes,and it belongs to the mannitol receptor families,which extracellular glycosylation region consists of CysR?FnII?CTLD1-10 from the N-terminal to the C-terminal.Beck et al.has found the sensitivity of PLA2 R antibodies in the IMN patients is about 70%~80%,while it's very low in other primary glomerular diseases and secondary SMN.Then it means PLA2 R can be a particular biological marker for the diagnosis of IMN,and it is mainly composed of IgG4.More and more researches show its titer is related to the activity of the disease and the level of urine protein.So it can be used not only to guide when to use immunosuppresssants and whether the immunosuppressants are effective,but also to forecast the prognosis of IMN patients and monitor the relapse of IMN disease.In 2014,Tomas has found the thrombospondin type-1 domain containing 7A(THSD7A),which is seen as the secondary autoantigen of IMN.Its antibodies don't exist in the IMN patients with the PLA2 R antibodies at the same time.Though one of them positive can explain the pathogenesis of most IMN patients,there are still 15%~25% patients whose autoantibodies are serologically negative.Researchers speculate(1)on the sensitivity of the current detection methods aren't high enough;(2)on the compositional complexity of the PLA2 R antigenic epitope;(3)that it has getting well before collecting blood from the patients;(4)that it may exists other autoantibodies like SOD2?AR antibodies;(5)and that may exists some unknown secondary factors,which shoule be classified as SMN.In total,we propose PLA2 R antibodies in serum combined with PLA2 R antigens in renal tissue,or IgG4 in renal tissue combined with PLA2 R antibodies in serum or renal tissue to diagnose IMN,aimed at increasing the sensitivity of IMN patients and decreasing the missing rate of serologically conversion because of remission.Aims1.To evaluate the value of serum PLA2 R antibodies and glomerular PLA2 R deposits detection in diagnosis and differential diagnosis of IMN.2.To evaluate the value of serum and glomerular IgG4 detection in diagnosis and differential diagnosis of IMN.Methods1.A total of 177 patients who have received renal biopsy and serum detection were collected in this study as experimental group,including 123 patients with IMN,72 males and 51 females,mean age47.00(31.00,60.00)years old;54 patients with non-IMN,29 males and 25 females,mean age40.5(29.00,54.75)years old,such as IgA nephropathy,MCD and HBV-related nephritis.2.Records general information and clinical data of the patient,including age,sex,serum albumin,serum urea nitrogen,serum creatinine,serum uric acid,serum total cholesterol and triglyceride,serum immunoglobulins and 24-hour total urine protein quantitation.3.PLA2 R antibodies(PLA2R-Abs)in serum were measured by ELSA,regarded<8.95RU/ml as a negative result and ?8.95RU/ml as a positive result.According to serum PLA2R-Abs levels,IMN patients were divided into positive and negative groups.PLA2 R,Ig subclasses with their subtypes and C3,C4,C1 q deposits in glomeruli were detected by immunohistochemical staining.Afterward,the correlation among serum PLA2R-Abs,glomerular deposits and clinical data were analyzed.4.Applicate SPSS19.0 software for statistical analysis.Taken ?=0.05 as a test level,P<0.05 represents the difference is statistically significant.Then,we calculate AUC and 95%CI by making ROC curve and rank the difference between sensitivity and(1-specificity),the maximum of which is what we want.And the value in the first column before it is the Cut-off value.Results1.The serum PLA2R-Abs titer 34.80(11.20,109.70)RU/ml in the IMN group is apparently higher than that 2.75(2.30,4.23)RU/ml in non-IMN group;P<0.05.In the IMN group,the sensitivity of serum PLA2 R antibodies is 78.9%,the specificity is 92.6% and the AUC of its ROC curve is 0.871,with 95% CI(0.810-0.932)and Cut-off value 8.95.2.The serum IgG4 titer 0.22(0.13,0.44)RU/ml in the IMN group is similar to that 0.22(0.10,0.46)RU/ml in non-IMN group;P > 0.05.In the IMN group,the sensitivity of serum PLA2 R antibodies is 65.9%,the specificity is 55.6% and the AUC of its ROC curve is 0.526,with 95% CI(0.431-0.621)and Cut-off value 0.17.3.The glomerular PLA2 R antigens expression(0.56)in the IMN group is apparently higher than that(0.08)in non-IMN group;P<0.05.In the IMN group,the sensitivity of serum PLA2 R antibodies is 73.7%,the specificity is 88.0% and the AUC of its ROC curve is 0.814,with 95% CI(0.746-0.883)and Cut-off value 0.25.4.The glomerular IgG4 expression(2.05)in the IMN group is apparently higher than that(0.11)in non-IMN group;P<0.05.In the IMN group,the sensitivity of serum PLA2 R antibodies is 95.0%,the specificity is 94.0% and the AUC of its ROC curve is 0.949,with 95% CI(0.906-0.992)and Cut-off value 0.25.5.Combination detection of serum PLA2R-Abs and glomerular IgG4 deposits to diagnose IMN can increase specificity and keep the sensitivity and the AUC of its ROC curve is 0.949,with 95% CI(0.901-0.996).Combination detection of glomerular PLA2 R and IgG4 deposits to diagnose IMN can increase the sensitivity and keep the specificity and the AUC of its ROC curve is 0.951,with 95% CI(0.906-0.997).6.Combination detection of serum PLA2 R antibodies and glomerular PLA2 R deposits can increase the sensitivity of diagnosis,but decrease the specificity and the AUC of its ROC curve is 0.894,with 95% CI(0.836-0.952).7.Pearson correlation analysis showed that serum PLA2R-Abs levels were not correlated with serum albumin,serum total cholesterol and urine protein degree.Spearman rank correlation analysis showed that glomerular PLA2 R deposits were not correlated with serum albumin,serum total cholesterol and urine protein degree.Conclusion1.serum PLA2 R antibodies,glomerular PLA2 R and IgG4 deposits are particular biological markers for diagnosis of IMN.Moreover,the sensitivity of glomerular IgG4 deposits,serum PLA2 R antibodies and glomerular PLA2 R deposits rank from high to low,which is the same to their efficiency of diagnosis.Whereas,serum Ig G4 isn't.2.Combination detection of glomerular IgG4 and PLA2 R deposits and serum PLA2 R antibodies can increase the sensitivity or specificity of the diagnosis,and its ability to predict IMN is close to pathology.3.Combination detection of serum PLA2 R antibodies and glomerular PLA2 R deposits can increase the sensitivity of diagnosis,but decrease the specificity and its efficiency of diagnosis has some improved.