The Clinical Significance Of Serum IgG、urine IgG And The Ratio Of Urine IgG/Serum IgG In Idiopathic Membranous Nephropathy

Background:Idiopathic membranous nephropathy is an autoimmune disease with unclear etiology and pathogenesis.In recent years,the incidence of idiopathic membranous nephropathy has gradually increased and tended to be younger.Its clinical severity is closely related to prognosis and has been the focus of domestic and foreign scholars.The long-term prognosis of IMN patients is nice,but the manifestations of IMN can evolve into three different clinical conditions:spontaneous remission without any immunosuppressive treatment.Persistent nephrotic syndrome with massive proteinuria with deterioration of renal function or retention of renal function.The pathological features are subepithelial immune deposition,which mainly composed of immunoglobulin G and complement.Immunoglobulin G play an important role in Idiopathic membranous nephropathy pathogenicity.IMN is thought to be due to the production of autoimmmunity IgG antibodies that recognize target antigens of glomerular podocytes and form in situ immune complexes,leading to increased basement membrane permeability,causing proteinuria,hypoproteinemia and a series of clinical symptoms.As glomerular filtration membrane permeability increases,The glomerular mechanical barrier was destroyed,IgG in the blood leak out,Urine IgG level increased.This paper retrospectively analyzed the clinical data of 502 IMN patients hospitalized in the Department of Nephrology of the first Hospital of Jilin University from January 2016 to April 2020.The purpose of this study was to explore whether the expression level of serum IgG、urine IgG and the ratio of urine IgG/blood IgG can be used as clinical indicators to reflect the severity of IMN and the relationship with clinical risk classification of IMN patients.Objective:To investigate the relationship between serum IgG,urine IgG and the ratio of urine IgG/serum IgG in patients with idiopathic membranous nephropathy.Methods:A retrospective analysis of the clinical data of 502 IMN patients admitted to the Department of Nephrology of the first Hospital of Jilin University from January 2016 to April 2020,IMN patients were divided into three groups according to 24-hour urine protein quantification:<3.5 g/d（group A n=109）,3.5-8 g/d（group B n=224）and≥8 g/d（group C n=169）,age,sex,urine IgG,serum IgG,serum Ig M,complement C3,complement C4,24hour urine protein quantification,urine microalbumin,urineα₁microglobulin,urineβ₂microglobulin,serum albumin,serum creatinine,total cholesterol,triglycerides,high density lipoprotein cholesterol,low density lipoprotein cholesterol,erythrocyte sedimentation rate,C-reactive protein,serum PLA2R antibodies,and pathological results of renal biopsy were recorded in the three groups.Urine IgG/serum IgG and estimated glomerular filtration rate calculated,In addition,According to KDIGO 2020 guidelines for glomerulonephritis,Referring to the clinical index of progressive deterioration of renal function in membranous nephropathy,502 cases of IMN were divided into three groups according to serum PLA2R antibody:<50RU/m L（group D）,n=168),50-150RU/m L（group E）,n=178),>150RU/m L（group F）,n=156),The test indexes of each group were compared.Compare the correlation between serum and urine IgG levels and other test indicators.SPSS 25.0 statistical software is used to analyze the above statistical data.Results:（1）A total of 502 patients with idiopathic membranous nephropathy were included in this study,324 males,178 females,With an average 50.52±11.94 years old.All patients were confirmed by renal biopsy as idiopathic membranous nephropathy.Most IMN patients（98%）had elevated urinary IgG levels,Serum IgG levels decreased in 90%of IMN patients.（2）24-hour urine protein was used to investigate serum and urine IgG levels,IMN patients were divided into three groups according to 24-hour urine protein quantification:<3.5g/d（Group A,n=109）,3.5-8g/d（Group B,n=224）and≥8g/d（Group C,n=169）,The urine IgG、the ratio urine IgG/serum IgG of IMN patients in group C was significantly higher than that in group A、B,There were also significant differences in urine IgG、the ratio urine IgG/serum IgG between B and A（P<0.001）.The serum IgG level of IMN patients in the group C was significantly lower than that in the group A or the group B,There was also a statistically significant difference in serum IgG between group B and A（P<0.001）.There were statistically significant differences in sex,urine microalbumin,urineα1 microglobulin,urineβ2 microglobulin,erythrocyte sedimentation rate,serum albumin,e GFR,serum PLA2R antibody,triglyceride,total cholesterol,low density lipoprotein cholesterol among the three groups（P<0.01）,There was no significant difference in age,serum Ig A、serum IgG、complement C3、complement C4,serum creatinine,high density lipoprotein cholesterol,CRP and other laboratory indexes between each two groups（P>0.05）.（3）IMN patients were divided into three groups according to serum PLA2R antibodies:<50 RU/m L（group D,n=168）,50-150 RU/m L（group E,n=178）,≥150 RU/m L（group F,n=156）,The urine IgG、the ratio urine IgG/serum IgG of IMN patients in F group was significantly higher than that in D、E group,There was significant difference in urine IgG between D and E groups（P<0.001）.The serum IgG level of IMN patients in the F group was significantly lower than that in the D group or the E group,There was also a statistically significant difference in serum IgG between E and D groups（P<0.01）.There were significant differences in laboratory indexes of urine protein,urine microalbumin,urineα₁microalbumin,urineβ₂microalbumin,serum albumin and e GFR、creatinine between D and F groups（P<0.01）.There was significant difference in ESR level between D group and F group、E group and F group（P<0.001）.There was no significant difference between E group and F group in laboratory indexes such as urine protein,urine microalbumin,urineα₁microglobulin,urineβ₂microglobulin,e GFR,serum creatinine,eserum albumin（P>0.05）.There was no significant difference in serum Ig A、serum Ig M,complement C3,complement C4,triglyceride,total cholesterol,low density lipoprotein cholesterol,high density lipoprotein cholesterol,CRP and other laboratory indexes（P>0.05）.（4）The correlation between the comparative variables showed that IMN urine IgG level was positively correlated with 24 hour urine protein,urine microalbumin,urineα₁microglobulin,urineβ₂microglobulin,erythrocyte sedimentation rate,serum PLA2R antibody,and urine IgG level was negatively correlated with serum albumin and e GFR level.IMN serum IgG levels were negatively correlated with 24-hour urine protein,urine microalbumin,urineα₁microglobulin,urineβ₂microglobulin,serum PLA2R antibody,and serum IgG levels were positively correlated with serum albumin and e GFR levels.urine IgG/serum IgG were positively correlated with 24-hour urine protein,urine microalbumin,urineα₁microglobulin,urineβ₂microglobulin,erythrocyte sedimentation rate,serum PLA2R antibody,and negatively correlated with serum albumin and e GFR levels.Conclusion:（1）Most IMN patients had elevated urine IgG levels（98%in this study）,decreased serum IgG levels（90%in this study）.（2）Lower serum IgG and higher urine IgG、the ratio of urine IgG/serum IgG are associated with increased clinical risk grading in idiopathic membranous nephropathy.（3）Urine IgG levels of IMN were positively correlated with 24-hour urine protein,urine microalbumin,urineα₁microglobulin,urineβ₂microglobulin,erythrocyte sedimentation rate,serum PLA2R antibody,negatively correlated with serum albumin and e GFR.（4）Serum IgG levels of IMN were negatively correlated with 24-hour urine protein,urine microalbumin,urineα₁microglobulin,urineβ₂microglobulin,serum PLA2R antibody,positively correlated with serum albumin and e GFR.（5）The ratio of urine IgG/serum IgG of imn patients were positively correlated with24-hour urine protein,urine microalbumin,urineα₁microglobulin,urineβ₂microglobulin,erythrocyte sedimentation rate,serum PLA2R antibody,negatively correlated with serum albumin and e GFR.（6）Serum albumin is significantly associated with serum IgG levels,Urinaryα₁microglobulin,urinaryβ₂microglobulin were significantly associated with urine IgG levels,Urineα₁microglobulin,serum albumin were significantly correlated with the ratio of urine IgG/serum IgG.