Complement Fragment C4d In Two Renal Lesions In The Clinical And Pathological Significance

Background and ObjectiveDiffuse peritubular capillary C4d(PTC-C4d) deposition in renal allograft has been recognized as a marker of antibody mediated rejection(AMR), and a prognostic indicator for graft loss as well, the clinical implications of focal PTC C4d deposition is yet under debate. The meaning of glomerular capillaries (GC) C4d deposition is still controversial. Few literature deals with the effect of total C4d deposition in renal allograft. This study is designed to further investigate the clinical meanings of C4d deposition with different Banff scores, GC-C4d deposition and total C4d (a combination of PTC C4d and GC-C4d).MethodsClinical and pathological features of46renal transplantation patients who had undergone a renal graft indication biopsy between year2000and2009were reviewed. C4d was detected by immunoperoxidase method on formalin-fixed, paraffin-embedded allograft tissues. Patients were divided into different groups separately according to PTC C4d Banff score(Group A,B,C and D), PTC C4d positivity(>10%), GC-C4d positivity and T-C4d score(Group Ⅲ,Ⅱ,Ⅰ, with T-C4d≥2, T-C4d=1, T-C4d=0,respectively).Clinical features of patients were compared among groups and allograft survival was analysed with Kaplan-Meier survival analysis.Results46patients were enrolled.Mean age at transplantation was37.5±9.75years old.Time from transplantation to biopsy was593[33,1430] days.Cyclosporine/tacrolimus, mycophenolate mofetil/azathioprine and steroids were the main baseline immunosupressive therapy. Serum creatinine (Scr) at biopsy was233.8[151.57,443.0] umol/L.There were30cases with acute rejection (AR),21with chronic allograft nephropathy (CAN), and4with transplant glomerulopathy (TGP).24(52.2%) cases were identified with PTC C4d Banff score0,10(21.7%) with1score, and for2and3scores each6(13%)cases, as well as14(30.4%) with GC-C4d deposits.Mean graft survival time among different Banff score groups(A,B,C and D) were:2315(95%CI:1693-2937)days,1042(95%CI:623-1461)days,481(95%CI:144-817)days and672(95%CI:0-1441)days, respectively.Significant difference was observed between Group D and A(P=0.043).Focal PTC C4d deposition was not identified with significant difference in graft survival from Group A, C and D.There was little difference in age, gender, time from transplantation to biopsy, acute rejection episode, immunosuppressive therapy and baseline Scr levels, among different groups.Patients with PTC C4d positivity were discovered with shorter graft survival time (658[95%CI:171-1145] vs2075[95%CI:1532-2618] days for negative group, P=0.024) and more urine protein excretion (2.3[0.85,9.53] vs0.7[0.38,0.81] g/day, P=0.027), compared with negative ones.Baseline therapy and Scr levels did not differ significantly between groups.There was an association between GC-C4d deposition and PTC C4d Banff score (Cramer's V=0.469, P=0.018).More patients with GC C4d deposits were diagnosed as CAN (10/14vs11/32, P=0.020), compared with negative ones. Scr4weeks after biopsy was significantly higher in patients with GC C4d deposits (203.3[161.00,565.76] vs159.1[125.50,240.01]μmol/L, P=0.034).Mean graft survival time between the two groups were not significantly different (379days for C4d positive vs1980days for C4d negative, P=0.056).Graft survival time among groups with different T-C4d score were555(95%CI:140-969) days for Group Ⅲ,1184(95%CI:805-1563) days for Group Ⅱ and2288(95%CI:1754-3023) days for Group I.Graft survival time was significantly shorter in Group Ⅲ either than Group Ⅱ (P=0.043) or Group I (P=0.020).ConclusionsEither diffuse PTC C4d deposition, PTC C4d≥10%, or T-C4d≥2were a prognostic marker for graft loss. Background and ObjectivesPrimary Sjogren's syndrome (pSS) is a systemic autoimmune disease with salivary and/or lachrymal glandular dysfunction.Tubular interstitial nephritis(TIN) and glomerulonephritis(GN) are two major renal lesions in pSS, with different renal clinical and pathological features.The difference in serum immunology and pathogenesis between the two needs to be investigated.In pSS, adaptive immune malfunction may have contributed to its pathogenesis, still the role of complement is under debate and lacks direct histological evidence.C4d is a segment of C4in classical/lectin complement pathway.It is a marker of humoral immue reaction and an evidence of complement activation through the two pathways mentioned above.The aim of our study is to delineate and demarcate between TIN and GN by analyzing the clinical and pathological features of pSS patients with renal involvement, as well as to investigate the role of complement in pSS renal lesions by detecting C4d in kidney biopsy tissues.Methods41patients who fulfilled the2002American-European criteria for primary Sjogren's syndrome, were admitted into Peking Union Medical College Hospital between1996and2009, and underwent a renal biopsy.A retrospective analysis was made by comparing clinical and pathological features between cases with TIN and those with GN. C4d was detected in renal biopsy tissues with immunoperoxidase method, and patients were divided according to C4d positivity either in glomeruli or in interstitium, clinical symptoms, laboratory results were compared between groups.Kaplan-Meier analysis was used to compare time from kidney biopsy to1/Scr lowering by0.25.Results1. Clinical and pathological features of renal lesions in pSSMean age of patients at biopsy was43±15years old.The duration of SS syndrome was5years and of renal involvement was1year.20cases were pathologically diagnosed as GN, with7cases featuring mesangial proliferative glomerulonephritis(MePGN),8membranous nephropathy(MN),3minimal change disease(MCD),1proliferative sclerosing glomerulonephritis and1chronic sclerosing glomerulonephritis.21cases diagnosed as TIN, with2presenting acute interstitial nephritis.Immune complex(IC) deposits were detected in9cases in glomeruli and4in interstitium by immunofluorescence(IF), mainly with IgG, IgA, IgM, Clq and C3, C4was negative.Patients with pathological features of GN were older than those with TIN at kidney biopsy(Group G49.5±14.05vs Group T36.7±12.51years old, P=0.003), and longer duration of SS(Group G10.5[2.0,17.75] vs Group T3[1.75,7.50] years, P=0.018).Onset of renal lesions was earlier in cases with TIN than those with GN(32.1±12.68years old vs46.5±14.57years old, respectively, P=0.002).Longer duration of renal lesions was observed in cases with TIN(Group G3[1,5.5]vs Group T0.58[0.05,1.75]years, P=0.009).92.7%patients had xerostomia, and73.2%xerophthalmia.Symptoms other than renal involvement were identified:24cases with fatigue,20with hematological abnormalities,18with pulmonary involvement,18with skin rash,17with thyroid lesions, each16with arthragia and gastro-intestinal symtoms,14with lymphomegaly,12with myalgias,11with fever,6with neurological involvement,5with Raynaud's phenomenon, and1with autoimmune pancreatitis. Significant differences were observed in fatigue (Group T17/21vs Group G7/20cases, P=0.003) and myalgia (Group T11/21vs Group G1/20cases, P=0.001), between different groups.Lab tests revealed92.7%of cases with antinuclear antibodies(ANA),87.8%with anti-SSA antibodies, and13cases with anti-SSB antibodies.Other autoantibodies such as anti-Ul-small nuclear ribonucleoprotein antibodies(RNP), anti-cardiolipin antibodies (ACL), anti-mitochondrial antibodies(AMA), anti-neutrophil cytoplasmic antibodies (ANCA) and lupus anticoagulant(LA) were also observed.Rheumatoid factor(RF) were detected in81.5%of patients, hypergammaglobulinemia in11/37(29.7%)cases, elevated serum IgG in26/40(65.0%) cases, elevated serum IgA in15/40(37.5%) cases and IgM in4(10.0%) cases.3/40cases were identified with low serum CH50levels,6/39with low serum C3, and6/36with low serum C4.There were3cases with C-reactive protein (CRP) elevation, and1case with cryoglobulinemia.More cases with TIN were identified with serum IgG elevation(Group T17/20vs Group G9/20cases,P=0.008), and higher blood platelet(Group T240.9±71.43vs Group G165.8±90.58×109/L, P=0.005).22(53.7%) cases clinically presented renal tubular acidosis (RTA),18cases with type I RTA, and4with type Ⅱ.There were3cases with Fanconi syndrome.15cases featured obvious glomerulonephritis, including8cases of nephrotic syndrome.There were10cases with chronic renal insufficiency and2acute renal failure.There were more cases with RTA in Group T than in Group G (20/21vs2/20cases, respectively, P<0.001), and more with urinary tract stones(10/21vs2/20cases, respectively, P=0.008) More patients with microhematuria were identified in Group G(13/20vs5/21cases in Group T, P=0.008).Median serum creatinine(Scr) at kidney biopsy was95umol/L for all patients,which did not differ between groups(Group T106[78.66,149.40] vs Group G92[71.16,116.25] umol/L,P>0.05).Those with GN were found with higher urinary protein excretion(G:1.85[0.55,6.08] vs T:0.69[0.41,1.27]g/d, P=0.025), lower serum albumin(G:30[20,36.8] vs T:41[38,43.8]g/L, P<0.001), lower serum calcium(G:2.05[1.925,2.210] vs T:2.22[2.173,2.305]mmol/L, P=0.004) compared with TIN patients.Serum potassium(T:3.39±0.50vs G:3.79±0.53mmol/L,P=0.017), uric acid(T:232.49±117.025vs G:310.45±116.597mmol/L,P=0.047), PH(T:7.34±0.06vs G:7.41±0.06,P=0.002) and HCO3-(T:19.84±3.708vs G:25.22±3.818mmol/L,P<0.002) were all identified lower in patients with TIN than with GN.2. C4d deposition in kidney biopsy tissues in pSS patients with renal lesionsGlomerular C4d (G-C4d) deposition was associated with IF positivity in glomeruli (cp=0.431, P=0.006), and so did C4d deposition in interstitium positively associated with interstitial IF positivity ((p=0.385, P=0.015).More cases of G-C4d deposition were identified with more IgG deposition in local renal tissue (Cramer's V=0.629, P<0.001). More cases with C4d deposition and IF positivity were found in GN group.Cases of G-C4d deposits were with lower serum y globulin levels (24.80±6.28vs29.60±7.73(%) in G-C4d negative group, P=0.046), lower blood platelet (173.6±82.22vs252.13±78.91×109/L in G-C4d negative group, P=0.004), and more cases with hypertension (41.7%vs6.9%in G-C4d negative group, P=0.016).10/41cases were identified with interstitial C4d deposition, who were with longer renal injury duration (P=0.034), more cases with anemia (60%vs I-C4d negative Group22.6%, P=0.049), lymphomegaly (80%vs I-C4d negative Group19.4%, P=0.001), and elevated serum CRP levels (3/8vs I-C4d negative Group0/26, P=0.009).Time from biopsy to lowering of1/Scr by0.25were found significantly shorter in G-C4d positive group than negative ones (Median time:1381vs2451days, respectively, P=0.002).Conclusions1. Tubular interstitial nephritis was identified as main type of renal involvement in pSS, but unlike previous studies, cases with GN were not rare.2. Patients with TIN were identified with earlier renal onset than those with GN, even before onset of sicca symptoms.3. The sicca syndrome, extraglandular symptoms other than kidney, and serum immunologic characteristics of primary Sjogren's syndrome did not differ greatly between patients with TIN or GN.4. TIN and GN were two different type of kidney injury secondary to pSS in different phase of disease duration.5. Patients with C4d glomerular deposition were identified with glomerular lesions in accordance with glomerular C4d, which might have attributed to lesions in GN.6. Interstitial C4d deposition was likely to be associated with inflammatory status in pSS.7. G-C4d was a likely indicator of renal function deterioration in pSS patients with renal involvement.