The Clinicopathological Characteristics And Pathogenic Mechanism Of IgG4-related Urinary System Damage

BackgroundIgG4-related disease(IgG4-RD)is a systemic autoimmune disease with multi-organ involvement,which is featured by diffuse organ enlargement,serum IgG4 elevation as well as diffuse infiltration of lymphoplasma cells in lesioned organs.Urinary system involvement,including kidney,ureter and bladder involvement,accounts for a large percentage of disease spectrum in IgG4-RD.Both renal parenchymal lesion and postrenal lesion in IgG4-RD could lead to renal function impairment,even result in end stage renal disease(ESRD)without proper treatment.Both the risk factors and pathogenesis of IgG4-RD remains unclear.Although most patients response well to glucocorticoid treatment,relapses are frequently observed during glucocorticoid reduction period.It is reported that CD4+SLAMF7+ cytotoxic lymphocytes(CTL)play a direct role in tissue damage of Mikulicz disease,by secreting granzyme A,perforin and interferon-?,while till now no research conducted to investigate its potential pathogenic role in IgG4-related urinary disease.Objectives1.To evaluate the clinical and pathological characteristics and prognosis of IgG4-related urinary disease,and investigate the potential risk factors for IgG4-related urinary disease.2.To assess the expression of CD4+CTL in peripheral circulation as well as renal tissue of IgG4-related kidney lesion,and its correlation of clinical characteristics as well as renal prognosis.3.To preliminarily investigate the potential mechanism and noninvasive marker of IgG4-related urinary disease.MethodsForty nine inpatients of IgG4-related urinary disease were enrolled in Peking Union Medical College Hospital from 2009.1 to 2018.6.Clinical data and renal biopsy images were collected for the analysis of disease characteristics and prognosis,as well as potential risk factors.For the assessment of treatment response,primary end point was defined by improvement of renal function or urine protein,secondary end point was defined by improvement of serum IgG4.Flow cytometry was conducted to assess CD4+CTL expression in peripheral blood mononuclear cells of IgG4-related urinary disease patients and healthy controls.Dual-immunoflourescence staining of CD4 and SLAMF7,CD4 and granzyme A were performed in renal tissue of IgG4-related kidney lesion to observe CD4+CTL tissue infiltration and its correlation with peripheral expression.Dual-fluroscence Western blot was conducted to assess the expression of mTOR,PI3K,Akt,NF-KB-p65,Fas and caspase 3 in urinary exosomes of IgG4-related urinary disease patients(including IgG4-TIN,retroperitoneal fibrosis and IgG4-related ureter lesion),compared with IgG4-RD patients without urinary system involvement,lithiasis patients and healthy controls,to investigate the possible mechanism and noninvasive markers of IgG4-related urinary disease.Results1.The clinical pathological characteristics and risk factors of IgG4-related urinary diseaseForty-nine inpatients of IgG4-related urinary disease showed male predominance(male:female=30:19),with average diagnosis age of 62.5 ± 11.9.40.8%patients had allergy history.The average involved organ number is 3(1-4),the most frequent accompanied organs were submandibular glands(34.7%),pancreas(26.5%)and parotid glands(26.5%).Hypereosinophilia was observed in 32.7%patients.Renal parenchymal involvement and retroperitoneal fibrosis were the two most common form of urinary disease lesion.Tubulointerstitial nephritis(TIN)was the predominant form in parenchymal lesion,patients of IgG4-TIN always came to clinics with small amount of urine protein 1.12(0.67-1.34)g/24h and renal function of CKD stage 4 to 5.Urinary injury markers such as ?2 microglobulin and NAG were remarkably elevated in TIN patients,while no one presented with Fanconi syndrome.IgG4-related membranous nephropathy(MN)patients always came to clinic with nephrotic syndrome.Retroperitoneal fibrosis patients frequently came with acute kidney injury(AKI),accompanied by small amount of urine protein 0.76(0.38-1.05)g/24h and SCr 279.0(134.0-559.0)?mol/L.Serum IgG4 showed significant difference among three groups(15500 vs 17800 vs 4030mg/L,P<0.05).All IgG4-related urinary disease patients were in active inflammatory status,with elevated serum ESR 70.0(34.0-90.5)mm/h and hsCRP 5.57(1.25-20.89)mg/L.As renal parenchymal lesion and retroperitoneal fibrosis could have co-concurrence(16.3%),it is important to assess urinary tubule injury markers for accurate diagnosis.IgG4-RKD could present with multiple patch-like hypointense signal on T2-weighted images.Renal biopsies of IgG4-RKD always presented with diffuse interstitial inflammation(3.0),tubular atrophy(2.2)and interstitial fibrosis(2.2).Two patients with remarkable chronicity showed no remission under immunosuppressant treatment.For treatment response,patients with prednisone treatment alone were retroperitoneal fibrosis predominant(80%)with remission in 3 months;for those presented with nephrotic syndrome and multi-lesion types,combination of prednisone and immunosuppressant had satisfactory renal outcome(median remission time 32 months).2.The possible role of CD4+SLAMF7+CTL in IgG4-related urinary diseaseThe expression of CD4+SLAMF7+CTL were elevated in peripheral blood of IgG4-related urinary disease patients compared with other controls(1.05%vs 0.35%,P=0.054),but with large intra-group differences.Peripheral CD4+CTL might have positive correlation with disease duration and urine protein level,and negatively correlated with eGFR.No infiltration of CD4+CTL were observed in renal tissue of IgG4-RKD and pseudotumor.3.The preliminary investigation of mechanism and noninvasive diagnosis marker in IgG4-related urinary diseaseThe expression of PI3K(0.733 vs 0.080 vs 0.071 vs 0.024),Akt(5.623 vs 0.106 vs 0.721 vs 0.103),NF-KB-p65(5.588 vs 0.144 vs 1.093 vs 0.083)were elevated in urinary exosomes of IgG4-related urinary disease patients compared with other groups,while mTOR showed no differences(0.301 vs vs 0.143 vs 0.212 vs 0.039).Fas(1.521 vs 0.129 vs 0.535 vs 0.011)and caspase 3(0.588 vs-0.014 vs 0.012 vs 0.017)might also be involved in the pathogenesis of IgG4-urinary disease.Conclusion1.All IgG4-related urinary disease patients presented with active inflammatory status.Urine protein level and tubule injury markers were valuable for judging injury types of IgG4-related urinary disease.The chronicity of renal biopsy detennined the renal prognosis under immunosuppressant treatment.For patients with nephrotic syndrome and multi-lesion types,prednisone combined with immunosuppressant therapy should be the initial treatment.2.The expression of CD4+SLAMF7+CTL in peripheral blood was elevated in IgG4-related urinary disease patients,no infiltration of CD4+CTL were observed in renal tissue.The pathogenic role of CD4+CTL in IgG4-related urinary disease needs further validation.3.PI3K-Akt-NF-KB pathway might be the potential mechanism in IgG4-related urinary disease.