Increased C4 and decreased C3 levels are associated with a poor prognosis in patients with immunoglobulin A nephropathy: a retrospective study

The ratio of high aspartate aminotransferase to alanine aminotransferase: an independent risk factor associated with poor prognosis in IgA nephropathy

OBJECTIVE

To investigate the relationship between the aspartate aminotransferase to alanine aminotransferase ratio (AAR) and the prognosis of IgA nephropathy (IgAN).

METHODS

Clinical, pathological and follow-up data of 271 patients with IgAN from January 1, 2013, to July 31, 2023, were collected. A 50% decrease in estimated glomerular filtration rate (eGFR) or end-stage renal disease (ESRD) was used as renal composite end point events. A receiver operating characteristic (ROC) curve was plotted to predict the composite end point events by AAR. The optimal cutoff value of 1.24 was determined, and patients were allocated to high AAR and low AAR groups. Kaplan‒Meier (K‒M) curves and Cox proportional hazard models were used to evaluate the predictive effect of AAR on renal composite end point events.

RESULTS

After a mean follow-up of 29 months, 39 patients achieved renal composite end point events. Among them, 9 and 30 patients in the low and high AAR groups achieved renal composite end point events, respectively, with a significant difference (P < 0.001). After adjustment for confounding factors, AAR was found to be an independent prognostic factor for renal composite end point events (HR = 3.283, 95% CI: 1.489-7.238, P = 0.003). Kaplan‒Meier analysis showed that high AAR was associated with achieving renal composite end point events in patients with IgAN. Moreover, the clinical features in the high AAR group were more severe. Further subgroup analysis showed that high AAR had a better predictive effect in patients with more severe clinicopathological manifestations.

CONCLUSION

AAR is an independent prognostic factor in patients with IgAN.

The prognostic role of activation of the complement pathways in the progression of advanced IgA nephropathy to end-stage renal disease

INTRODUCTION

The role of complement system in late stage of IgA nephropathy (IgAN) remains unknown. We therefore investigated the effects of complement system on worsening kidney function in advanced (stage 4 CKD) IgAN.

METHODS

Renal specimens of 69 IgAN patients who underwent renal biopsy during stage 4 CKD between 2010 and 2021, were stained using immunofluorescence (IF) and immunohistochemistry (IHC) for glomerular complement components. The primary outcome was progression to end-stage renal disease (ESRD). Associations of complement components with baseline clinicopathological characteristics and outcomes were assessed using multivariable Cox regression and Spearman analyses.

RESULTS

During a median follow-up of 18.0 months, 26 (37.7%) patients progressed to ESRD and none died. C1q and C3 deposition were detected in 12 and 66 patients, respectively. Higher eGFR [hazards ratio (HR), 0.852, 95% confidence interval (CI), 0.756-0.959; P = 0.008], higher C3 intensity (HR, 2.955, 95%CI, 1.063-8.220; P = 0.038) and T1-2 score (HR, 2.576, 95%CI, 1.205-5.576, P = 0.015) were predictive of time to ESRD in CKD 4 stage IgAN. Significant expressions of C1q (P = 0.005), C4d (P < 0.001), factor B (P < 0.001), C3 (P = 0.042) and C5b-9 (P = 0.004) were identified in ESRD group than in non-ESRD group by IHC, while MBL expression was low. Although they were not associated with baseline 24 h-UP, higher factor B and C1q expressions were both correlated with a lower baseline eGFR (P < 0.001 and = 0.04, respectively) and the deterioration of kidney function during follow-up (P = 0.046 and 0.015, respectively).

CONCLUSION

Complement deposition in IgAN patients with stage 4 CKD portends a faster deterioration of kidney function. Activation of classical and alternative complement pathways plays a major role in this stage.

Elevated concentration of beta2-microglobulin among patients with carpal tunnel syndrome in the course of primary Sjögren syndrome - a prospective observational study on 50 patients

INTRODUCTION

Sjögren's syndrome (SS) is a chronic autoimmune disease characterized by lymphocytic infiltrates in the exocrine glands. Carpal tunnel syndrome (CTS) is suggested to be more frequent among SS patients than in the general population. The aim of this study was to seek associations between the CTS and the laboratory and clinical findings of SS patients.

METHODS

Fifty patients diagnosed with primary SS (pSS) were examined. Clinical evaluation by a rheumatologist and electrophysiological studies were conducted. Data on laboratory tests results was collected. Control group consisted of 50 sex and age-matched individuals with osteoarthritis (OA).

RESULTS

Out of 50 patients in the study group 27 (54%) were diagnosed with CTS. The prevalence of CTS among 50 individuals in the control group was 8%. Among pSS patients with CTS the joint involvement was not more common than in those from the non-CTS group [15 vs. 13 (p = 0.945)]. There was an expected difference in sleep disorders [18 vs. 9 (p = 0.012)] and paresthesia [23 vs. 13 (p = 0.024)]. The major finding was a significant difference in elevated beta2-microglobulin (B2MG) [23 vs. 13 (p = 0.024)]. Other studied factors, suggested in the literature as significant in the pSS-related neuropathy, were not statistically different between the groups.

CONCLUSION

Our study confirms that CTS is more prevalent among pSS patients than in the general population and suggests that a new approach is required towards the pathogenesis of this phenomenon. We hypothesize that CTS is more associated with an overall disease activity than joint involvement as such.

Role of serum complement C3 and C4 on kidney outcomes in IgA nephropathy

IgA Nephropathy (IgAN) is the most prevalent glomerular disease worldwide. Complement system activation is crucial in its pathogenesis. Few studies correlated serum C3 and C4 with disease activity and prognosis. This retrospective study investigated the prognostic value of serum complement at the time of diagnosis in patients with IgAN. Specifically we evaluated whether adding serum C3 and C4 levels to established predictive models-one based on variables related to chronic kidney disease (CKD) progression and another incorporating variables from the International IgA Prediction Tool (IntIgAPT)-enhances the accuracy of outcome prediction. A composite renal outcome was defined as 50% decline in eGFR or onset of kidney failure. 101 patients were stratified according to baseline C3 levels in three groups (Low, Medium and High). During a median follow-up of 54 months, the Low group exhibited higher incidence of primary outcome (16.3 events vs 2.9 and 1.7 events × 100 pts/year, p = 0.0026). Model-1 (M1), consisting of CKD progression variables, and Model-3 (M3), comprising IntIgANPT variables, were implemented with baseline C3 and C4 to create Model-2 (M2) and Model-4 (M4), respectively. M2 demonstrated better predictive performance over M1, showing higher discrimination (lower AIC and BIC, higher C-index and NR2). Similarly, M4 outperformed M3, showing enhanced outcome prediction when C3 and C4 levels were added. Implementation of serum C3 and C4 can enhance prediction accuracy of already-validated prognostic models in IgAN. Lower C3 and higher C4 levels were associated with poorer prognosis, highlighting a more 'Complement-Pathic' subset of patients.

Identification of novel therapeutic targets for chronic kidney disease and kidney function by integrating multi-omics proteome with transcriptome

BACKGROUND

Chronic kidney disease (CKD) is a progressive disease for which there is no effective cure. We aimed to identify potential drug targets for CKD and kidney function by integrating plasma proteome and transcriptome.

METHODS

We designed a comprehensive analysis pipeline involving two-sample Mendelian randomization (MR) (for proteins), summary-based MR (SMR) (for mRNA), and colocalization (for coding genes) to identify potential multi-omics biomarkers for CKD and combined the protein-protein interaction, Gene Ontology (GO), and single-cell annotation to explore the potential biological roles. The outcomes included CKD, extensive kidney function phenotypes, and different CKD clinical types (IgA nephropathy, chronic glomerulonephritis, chronic tubulointerstitial nephritis, membranous nephropathy, nephrotic syndrome, and diabetic nephropathy).

RESULTS

Leveraging pQTLs of 3032 proteins from 3 large-scale GWASs and corresponding blood- and tissue-specific eQTLs, we identified 32 proteins associated with CKD, which were validated across diverse CKD datasets, kidney function indicators, and clinical types. Notably, 12 proteins with prior MR support, including fibroblast growth factor 5 (FGF5), isopentenyl-diphosphate delta-isomerase 2 (IDI2), inhibin beta C chain (INHBC), butyrophilin subfamily 3 member A2 (BTN3A2), BTN3A3, uromodulin (UMOD), complement component 4A (C4a), C4b, centrosomal protein of 170 kDa (CEP170), serologically defined colon cancer antigen 8 (SDCCAG8), MHC class I polypeptide-related sequence B (MICB), and liver-expressed antimicrobial peptide 2 (LEAP2), were confirmed. To our knowledge, 20 novel causal proteins have not been previously reported. Five novel proteins, namely, GCKR (OR 1.17, 95% CI 1.10-1.24), IGFBP-5 (OR 0.43, 95% CI 0.29-0.62), sRAGE (OR 1.14, 95% CI 1.07-1.22), GNPTG (OR 0.90, 95% CI 0.86-0.95), and YOD1 (OR 1.39, 95% CI 1.18-1.64,) passed the MR, SMR, and colocalization analysis. The other 15 proteins were also candidate targets (GATM, AIF1L, DQA2, PFKFB2, NFATC1, activin AC, Apo A-IV, MFAP4, DJC10, C2CD2L, TCEA2, HLA-E, PLD3, AIF1, and GMPR1). These proteins interact with each other, and their coding genes were mainly enrichment in immunity-related pathways or presented specificity across tissues, kidney-related tissue cells, and kidney single cells.

CONCLUSIONS

Our integrated analysis of plasma proteome and transcriptome data identifies 32 potential therapeutic targets for CKD, kidney function, and specific CKD clinical types, offering potential targets for the development of novel immunotherapies, combination therapies, or targeted interventions.

Association of time-averaged serum uric acid level with clinicopathological information and long-term outcomes in patients with IgA nephropathy

Objective

Whether serum uric acid (SUA) at baseline could been identiûed as a risk factor for progression in IgA nephropathy (IgAN) patients remains unclear, therefore, long- term SUA control levels must be monitored. We aimed to investigate the relevant factors affecting time-averaged SUA (TA-SUA) and to assess the prognostic value of TA-SUA in IgAN.

Methods

This retrospective study included 152 patients with IgAN. The relationships between TA-SUA and clinicopathological features and renal outcomes (defined as the doubling of the baseline serum creatinine level or end-stage renal disease) were analyzed in groups divided by quartiles of TA-SUA levels, the presence of hyperuricemia, and sex.

Results

Patients with high TA-SUA levels had higher levels of baseline SUA, blood urea nitrogen (BUN), triglycerides, serum C3 and serum C4 and were more likely to be male and have hypertension, proteinuria, poor renal function, and pathological injuries including high grades of tubular atrophy/interstitial fibrosis (T1-T2). These patients had a poorer prognosis compared with patients with low TA-SUA levels. The TA-SUA level was positively correlated with baseline age and BUN, triglycerides, serum C3, and serum C4 levels, and negatively correlated with baseline eGFR. Survival curve analysis indicated that persistent hyperuricemia was associated with significantly poorer renal outcomes than normo-uricemia in both men and women. The TA-SUA level also was an independent predictor of renal outcome in patients with IgAN, with optimal cutoû values of 451.38 µmol/L (area under the curve (AUC) = 0.934) for men and 492.83 µmol/L (AUC = 0.768) for women.

Conclusions

The TA-SUA level is associated with triglyceride level, complement component levels, renal function, and pathological severity of IgAN, and it may be a prognostic indicator in male and female patients with IgAN.

Correlation Between C4/IgG with Macroproteinuria in Chronic Kidney Disease: A Pilot Study

Background and Objectives

Loss of immunoglobulin G (IgG) is accompanied with proteinuria, especially macroproteinuria. The complement system participates kidney disease resulting in proteinuria. Whether the ratio of complement and IgG is associated with macroproteinuria remains unknown.

Design Setting Participants and Measurements

A total of 1013 non-dialysis chronic kidney disease (CKD) patients were recruited according to the electrical case records system with 268 patients who endured kidney biopsy. Patients were grouped via the estimated glomerular filtration rate or the levels of proteinuria determination. Biomarkers in different CKD groups or proteinuria groups were compared by one-way ANOVA or independent samples t-test. Pearson or spearman analysis was employed to analyze correlation between clinical indexes. Further, influence factor of macroproteinuria was studied by using binary logistic regression. The ROC curve was performed to explore probable predictive biomarker for macroproteinuria.

Results

No significant difference of complement C3 and C4 among CKD1 to CKD5 stages, while higher level of complement C4 in patients with macroproteinuria. Further, C4 had a positive correlation with proteinuria (r=0.255, p=0.006). After adjusted for age, IgA, IgM, triglyceride and HDL, a binary logistic regression model showed lnC4/IgG (OR=3.561, 95% CI 2.196-5.773, p<0.01), gender (OR=1.737, 95% CI 1.116-2.702, p=0.014), age (OR=0.983, 95% CI 0.969-0.997, p=0.014), and history of diabetes (OR=0.405, 95% CI 0.235-0.699, p<0.01) were independent influence factors of macroproteinuria. The area under the ROC curve was 0.77 (95% CI: 0.75-0.82, p<0.001) for C4/IgG. The analysis of ROC curves revealed a best cut-off for complement C4 was 0.024 and yielded a sensitivity of 71% and a specificity of 71%. The area under the ROC curve was 0.841 (95% CI: 0.735-0.946, p < 0.001) for C4/IgG in IgA nephropathy patients. The analysis of ROC curves revealed a best cut-off for complement C4/IgG was 0.026 and yielded a sensitivity of 75% and a specificity of 81.2%. The area under the ROC curve for C4/IgG in CKD1-5 stages were 0.772, 0.811, 0.785, 0.835, 0.674.

Conclusion

Complement C4/IgG could be used to predict macroproteinuria.

The Clinical and Pathological Effects of Serum C3 Level and Mesangial C3 Intensity in Patients with IgA Nephropathy

Objective

To investigate the clinical and pathological effects of serum C3 level, mesangial C3 deposition intensity and blood lipid on IgA nephropathy.

Methods

According to the deposition intensity of immunofluorescence (IF) complement C3 in mesangial region, a total of 151 patients were divided into: (1) negative group (65 cases), (2) weak positive group (51 cases), and (3) strong positive group (35 cases). According to the level of serum C3, the patients were divided into two groups: (1) 33 patients with decreased serum C3 (<85 mg/dL); (2) 118 patients with normal serum C3. The clinicopathological data of the patients were analyzed retrospectively according to the groups.

Results

(1) With the increase of C3 deposition in mesangial region, the mean value of serum C3 level decreased, and the difference was statistically significant (P=0.001). (2) Compared with the normal serum C3 group, the blood urea nitrogen (BUN), serum creatinine (Scr), and albumin (Alb) in the serum C3 decreased group were higher, and the differences were statistically significant (P < 0.05), while the fasting blood glucose (FBG), low-density lipoprotein (LDL), triglyceride and 24-hr urinary protein (24hUTP) were lower, which difference was statistically significant (P < 0.05). (3) Compared with negative group and weak positive group, BUN, uric acid (UA), and Scr were higher in the strong positive group with C3 deposition, while eGFR was lower, with statistical significance (P < 0.05). However, C3 deposition in the mesangial region was related to T and enhanced mesangial C3 deposition was associated with more severe tubular atrophy and/or interstitial fibrosis, with statistically significant differences (P=0.001).

Conclusion

Patients with strong mesangial C3 deposition and elevated lipid levels had more severe tubule atrophy and/or interstitial fibrosis, as well as more severe pathological lesions, suggesting that activation of the complement system is involved in the pathogenesis of IgA nephropathy and increases the metabolic burden of the kidney.

Serum Complement C4 Levels Are a Useful Biomarker for Predicting End-Stage Renal Disease in Microscopic Polyangiitis

This study aimed to evaluate the risk factors for end-stage renal disease (ESRD) in microscopic polyangiitis (MPA). In total, 74 patients with MPA were enrolled, and we compared the baseline clinical characteristics and disease activity between MPA patients who have progressed to ESRD and those without ESRD to select predictive factors for ESRD. Out of 74 patients, 12 patients (16.2%) had ESRD during follow-up. Serum C4 levels were significantly higher in MPA patients who have progressed to ESRD than in those without ESRD (p = 0.009). Multivariate analyses revealed that high serum creatinine levels (odds ratio (OR) 4.4, 95% confidence interval (CI) 1.25-15.5) and high serum C4 levels (OR 1.24, 95% CI 1.03-1.49) were risk factors for ESRD. Using receiver operating characteristic analysis, the cut-off value for initial serum C4 levels and serum creatinine levels were 29.6 mg/dL and 3.54 mg/dL, respectively. Patients with MPA with a greater number of risk factors (serum C4 levels > 29.6 mg/dL and serum creatinine levels > 3.54 mg/dL) had a higher ESRD progression rate. Serum C4 levels were significantly positively correlated with serum creatinine levels and kidney Birmingham vasculitis activity score (p = 0.02 and 0.04, respectively). These results suggest that serum C4 levels are useful tools for assessing renal disease activity and prognosis in MPA.

Prognostic value of complement serum C3 level and glomerular C3 deposits in anti-glomerular basement membrane disease

Background and objectives

Activation of the complement system is involved in the pathogenesis of anti-glomerular basement membrane (anti-GBM) disease. Glomerular deposits of complement 3 (C3) are often detected on kidney biopsies. The primary objective of this study was to analyze the prognostic value of the serum C3 level and the presence of C3 glomerular deposits in patients with anti-GBM disease.

Methods

We conducted a retrospective cohort study of 150 single-positive patients with anti-GBM disease diagnosed between 1997 and 2017. Patients were categorized according to the serum C3 level (forming a low C3 (C3<1.23 g/L) and a high C3 (C3≥1.23 g/L) groups) and positivity for C3 glomerular staining (forming the C3+ and C3- groups). The main outcomes were kidney survival and patient survival.

Results

Of the 150 patients included, 89 (65%) were men. The median [interquartile range (IQR)] age was 45 [26-64]. At diagnosis, kidney involvement was characterized by a median [IQR] peak serum creatinine (SCr) level of 578 [298-977] µmol/L, and 106 (71%) patients required dialysis. Patients in the low C3 group (72 patients) had more severe kidney disease at presentation, as characterized by higher prevalences of oligoanuria, peak SCr ≥500 µmol/L (69%, vs. 53% in the high C3 group; p=0.03), nephrotic syndrome (42%, vs. 24%, respectively; p=0.02) and fibrous forms on the kidney biopsy (21%, vs. 8%, respectively; p=0.04). Similarly, we observed a negative association between the presence of C3 glomerular deposits (in 52 (41%) patients) and the prevalence of cellular forms (83%, vs. 58% in the C3- group; p=0.003) and acute tubulo-interstitial lesions (60%, vs. 36% in the C3- group; p=0.007). When considering patients not on dialysis at diagnosis, the kidney survival rate at 12 months was poorer in the C3+ group (50% [25-76], vs. 91% [78-100] in the C3- group; p=0.01), with a hazard ratio [95% confidence interval] of 5.71 [1.13-28.85] (p=0.04, after adjusting for SCr).

Conclusion

In patients with anti-GBM disease, a low serum C3 level and the presence of C3 glomerular deposits were associated with more severe disease and histological kidney involvement at diagnosis. In patients not on dialysis at diagnosis, the presence of C3 deposits was associated with worse kidney survival.

Comparative Analysis of Hematological and Immunological Parameters in Patients with Primary Sjögren's Syndrome and Peripheral Neuropathy

BACKGROUND

Primary Sjögren syndrome (pSS) is a multisystem disorder of autoimmune etiology, frequently involving peripheral nerves. Early detection of peripheral neuropathy (PN) manifestations might improve prognosis and disease control. The purpose of the study was to evaluate the predictive potential of hematological and immunological parameters associated with PN development in pSS patients.

METHODS

This single-center retrospective study included patients with pSS who were divided into two groups, according to the occurrence of neurological manifestations throughout the follow-up period.

RESULTS

From the total of 121 pSS patients included in the study, 31 (25.61%) developed neurological manifestations (PN+ group) during the follow-up period. At the moment of pSS diagnosis, 80.64% of PN+ patients exhibited increased disease activity, with ESSDAI scores above 14 (p = 0.001), and significantly higher values for VASp score (p = 0.001), with a mean value of 4.90 ± 2.45, compared to 1.27 ± 1.32 in the PN- group. The hematological assessment at the moment of pSS diagnosis revealed that neutrophils and neutrophil-to-lymphocyte ratio (NLR) were significantly higher in the PN+ group (p = 0.001), while lymphocytes, monocytes and monocyte-to-lymphocyte ratio (MLR) were significantly lower (p = 0.025, p = 0.13 and p = 0.003, respectively). Immuno-inflammatory parameters-gammaglobulins, complement fractions C3, C4, total proteins and vitamin D were significantly lower in the PN+ patients' group. In multivariate analysis, the independent predictive character for PN development in pSS patients was confirmed for NLR (95% CI 0.033 to 0.263, p = 0.012), MLR (95% CI -1.289 to -0.194, p = 0.008), gammaglobulins (95% CI -0.426 to -0.088, p < 0.003), complement fraction C4 (95% CI -0.018 to -0.001, p < 0.030) and vitamin D (95% CI -0.017 to -0.003, p < 0.009).

CONCLUSIONS

Readily available and frequently used hematological and immunological markers, such as NLR, MLR, gammaglobulins, C4 and vitamin D could be helpful in predicting the neurological involvement in pSS patients. These biological parameters might become useful tools for clinicians to monitor disease progression and identify potentially severe extraglandular manifestations in pSS patients.

Identification of IgA autoantibodies targeting mesangial cells redefines the pathogenesis of IgA nephropathy

Immunoglobulin A (IgA) nephropathy (IgAN) is the most common type of primary glomerulonephritis, often progressing to renal failure. IgAN is triggered by IgA deposition in the glomerular mesangium by an undefined mechanism. Here, we show that grouped ddY (gddY) mice, a spontaneous IgAN model, produce serum IgA against mesangial antigens, including βII-spectrin. Most patients with IgAN also have serum anti-βII-spectrin IgA. As in patients with IgAN, IgA⁺ plasmablasts accumulate in the kidneys of gddY mice. IgA antibodies cloned from the plasmablasts carry substantial V-region mutations and bind to βII-spectrin and the surface of mesangial cells. These IgAs recognize transfected and endogenous βII-spectrin exposed on the surface of embryonic kidney-derived cells. Last, we demonstrate that the cloned IgA can bind selectively to glomerular mesangial regions in situ. The identification of IgA autoantibody and its antigen in IgAN provides key insights into disease onset and redefines IgAN as a tissue-specific autoimmune disease.

Functional variant rs12614 in CFB confers a low risk of IgA nephropathy by attenuating complement alternative pathway activation in Han Chinese

Activation of the alternative pathway (AP) of complement is thought to play an important role in Immunoglobin A nephropathy (IgAN). Our previous study showed that rs4151657 within the complement factor B (CFB) gene increased the risk of IgAN. The protein encoded by the CFB gene is an initial factor that promotes AP activation. The aim of this study was to investigate whether other variants of CFB confer susceptibility to IgAN and elucidate their potential roles in AP activation. A total of 1,350 patients with IgAN and 1,420 healthy controls were enrolled and five tag single-nucleotide polymorphisms were selected for genotyping. The levels of key AP components, such as CFB, complement factor H and complement split product C3a, were measured by enzyme-linked immunosorbent assay. Molecular docking and molecular dynamic simulation were carried out to characterize the mutation of residues in the protein structure and the dynamic properties of wide type and mutation models of CFB protein. The allele-specific effect on CFB expression and its binding affinity to C3b were investigated through cell transfection and surface plasmon resonance analysis, respectively. We found that rs12614 significantly reduced the risk of IgAN (OR = 0.69, 95% CI = 0.52-0.91, P = 0.009), and the rs12614-T (R32W mutation) was correlated with lower CFB levels, higher serum C3 level, and less mesangial C3 deposition in patients with IgAN. The structural model showed that the R32W mutation reduced the structural stability of CFB protein. Furthermore, in vitro study revealed that rs12614-T decreased the expression of CFB and reduced its binding affinity to C3b by four-fold compared with rs12614-C. In conclusion, the rs12614-T in CFB was associated with low risk of IgAN probably by attenuating AP activation.

Correlation between IgAC3 ratio and oxford score in IgA nephropathy

BACKGROUND

Complement activation has an important role in the pathogenesis of IgA nephropathy.

OBJECTIVE

To determine the correlation between IgAC3 ratio (IgA/C3) and total Oxford score and predictive value of IgA/C3 in IgA nephropathy. Methods Forty-three patients diagnosed with IgA nephropathy with > 10 glomerular + 1 arteries in biopsy were included in the study. Hematological and biochemical variables of the blood sample taken before the biopsy and total Oxford score were recorded. The study group was divided into two groups as proteinuria ≥ 1 g (PU ≥ 1) and proteinuria < 1 g (PU < 1). Statistics were carried out with SPSS 22.0 program. p < .05 considered as significant.

RESULTS

The mean age of 43 patients was 40.4 (± 11.9) years; 51.2% of them were women. Proteinuria as 1 g or more was in 27 of 43 patients, and less than 1 g in 16 patients. The serum C3 level was lower in the group with PU ≥ 1 and showed a significant positive correlation with the IgA/C3 total Oxford score.

CONCLUSION

A significant correlation was found between serum IgA/C3 and total Oxford score.

The Association Between Serum Complement 4 and Kidney Disease Progression in Idiopathic Membranous Nephropathy: A Multicenter Retrospective Cohort Study

Introduction

Complement system plays an important role in the pathogenesis of idiopathic membranous nephropathy (IMN), however, the relationship between serum complement 4 (C4) and kidney disease progression in IMN is unclear. This study aims to investigate the association of serum C4 level with the risk of kidney disease progression among patients with IMN.

Methods

The retrospective cohort assessed 1,254 participants with biopsy-proven IMN from three centers in Xi ‘an, Shaanxi Province, China. Baseline serum C4 levels were measured at renal biopsy. The association between baseline serum C4 and the risk of renal function progression, defined as a 30% decline in renal function or end stage renal disease, was evaluated in Cox proportional hazards models.

Results

A total of 328 patients with IMN and nephrotic proteinuria were eligible, and 11.3% (37/328) of them attained the renal function progression events after a median follow-up of 51 months (37-59 months). After adjustment for other confounders, a higher value of serum C4 was independently associated with a higher risk of renal function progression event with a hazard ratio (HR) of 4.76 (95% confidence interval [95% CI], 1.77-12.79) per natural log-transformed C4. In reference to the low level of C4, the adjusted HRs were 2.72 (95% CI, 1.02-7.24) and 3.65 (95% CI, 1.39-9.60), respectively, for the median and high levels of C4 (P for trend=0.008). Additionally, the results were robust and reliable in the sensitivity and subgroup analyses.

Conclusion

Among patients with IMN and nephrotic proteinuria, serum C4 at renal biopsy is an independent predictor for kidney disease progression regardless of other confounders.

Prediction of prognosis in immunoglobulin a nephropathy patients with focal crescent by machine learning

BACKGROUND AND OBJECTIVES

Immunoglobulin a nephropathy (IgAN) is the most common primary glomerular disease in the world, with different clinical manifestations, varying severity of pathological changes, common complications of crescent formation in different proportions, and great individual heterogeneous in clinical outcomes. Therefore, we aim to develop a machine learning (ML) based predictive model for predicting the prognosis of IgAN with focal crescent formation and without obvious chronic renal lesions (glomerulosclerosis <25%).

MATERIALS

We retrospectively reviewed biopsy-proven IgAN patients in our hospital and cooperative hospital from 2005 to 2017. The method of feature importance of random forest (RF) was applied to conduct feature exploration of feature variables to establish the characteristic variables that are closely related to the prognosis of focal crescent IgAN. Multiple ML algorithms were attempted to establish the prediction models. The area under the precision-recall curve (AUPRC) and the area under the receiver operating characteristic curve (AUROC) were applied to evaluate the predictive performance via three-fold cross validation (namely 2 training sets and 1 validation set).

RESULTS

RF was used to screen the important features, the top three of which were baseline estimated glomerular filtration rate (eGFR), serum creatine and triglyceride. Ten important features were selected as important predictors for modeling on the basis of data-driven and medical selection, predictors include: age, baseline eGFR, serum creatine, serum triglycerides, complement 3(C3), proteinuria, mean arterial pressure (MAP) and Hematuria, crescents proportion of glomeruli, Global crescent proportion of glomeruli. In a variety of ML algorithms, the support vector machine (SVM) algorithm displayed better predictive performance, with Precision of 0.77, Recall of 0.77, F1-score of 0.73, accuracy of 0.77, AUROC of 79.57%, and AUPRC of 76.5%.

CONCLUSIONS

The SVM model is potentially useful for predicting the prognosis of IgAN patients with focal crescent shape and without obvious chronic renal lesions.

Association of Immune and Inflammatory Gene Polymorphism With the Risk of IgA Nephropathy: A Systematic Review and Meta-Analysis of 45 Studies

IgA nephropathy is the most prevalent primary glomerulonephritis worldwide, with identical immunopathological characteristics caused by multiple etiologies as well as influenced by geographical and ethnical factors. To elucidate the role of immunologic and inflammatory mechanisms in the susceptibility to IgA nephropathy, we explored single nucleotide polymorphisms of related molecules in the immune pathways. We searched the PubMed database for studies that involved all gene variants of molecules in the 20 immunologic and inflammatory pathways selected from the Kyoto Encyclopedia of Genes and Genomes database. The odds ratios with their corresponding 95% confidence intervals in six genetic models (allele model, dominant model, homozygote model, heterozygote model, overdominant model, and recessive model) were summarized using fixed or random effect models. Subgroup analysis was conducted based on different ethnicities with generalized odds ratios. Heterogeneity was evaluated using the Q and I² tests. Begg’s funnel plot and Egger’s linear regression test were used to evaluating possible publication bias among the included studies, and sensitivity analysis was used to test the stability of the overall results. A total of 45 studies met our selection criteria and eight related genetic association studies were retrieved, including 320 single-nucleotide polymorphisms from 20 candidate pathways, ranging from 2000 to 2021. A total of 28,994 healthy people versus 20,600 IgA nephropathy patients were enrolled. Upon meta-analyzed results that TGFB1 (rs1800469, rs1982073, rs1800471), IL-1B (rs1143627), IL-18 (rs1946518), and TLR1 (rs5743557) showed effect with or without ethnicity difference. And 10 variants presented stable and robust related to IgA nephropathy. This research showed that genetic variants are related to the immunologic and inflammatory effects of IgA nephropathy pathogenesis. The meta-analysis results supported the previous researches, and may help deepen the understanding of pathogenesis and explore new targets for IgA nephropathy-specific immunotherapy.

Glomerular C4 deposition and glomerulosclerosis predict worse renal outcomes in Chinese patients with IgA nephropathy

Background

Immunoglobulin A nephropathy (IgAN) is a clinical and pathological syndrome with heterogenous manifestation and progression. Complement activation is involved in the disease. However, the clinical significance of C4 deposition in IgAN is obscure.

Methods

A multicenter retrospective study was conducted in biopsy-proven IgAN patients. Based on mesangial C4 deposition, patients were divided into two groups. The baseline clinical data and immunopathological phenotypes were compared. The composite endpoint was defined as eGFR decline greater than 50%, doubling of baseline serum creatinine, the occurrence of end-stage renal disease (ESRD).

Results

A total of 642 IgAN patients were recruited, with 41 patients showing mesangial C4 deposition. The mesangial C4 positive group showed lower serum albumin, higher proteinuria, and a higher rate of IgG, IgM, and C1q mesangial deposition. After a median follow-up of 43.18 months, 81 (12.62%) patients achieved the composite endpoint. The multivariate Cox regression models identified glomerular C4 deposition (hazard ratios [HR] = 3.22, 95% confidence intervals [CI] = 1.51–6.87, p < 0.01), global sclerosis (G1 vs. G0, HR = 1.90, 95%CI = 1.02–3.52, p = 0.04; G2 vs. G0, HR = 3.72, 95%CI = 1.98–7.00, p < 0.01), male (HR = 1.80, 95%CI = 1.10–2.97, p = 0.02), serum creatinine (HR = 1.01, 95%CI = 1.00–1.01, p < 0.01), triglyceride (HR = 1.17, 95%CI = 1.01–1.35, p = 0.04), proteinuria (HR = 1.07, 95%CI = 1.01–1.13, p = 0.02), serum C3 level (HR = 0.05, 95%CI = 0.01–0.25, p < 0.01), and serum C4 level (HR = 99.59, 95%CI = 8.69–1140.89, p < 0.01) as independent risk factors for poor renal outcomes.

Conclusions

Glomerular mesangial C4 deposition and global sclerosis are independent predictors for poor prognosis in IgAN patients.

Relationship between serum C3/C4 ratio and prognosis of immunoglobulin A nephropathy based on propensity score matching

Background

Aberrant activation of the complement system plays an important role in the pathogenesis and development of immunoglobulin A nephropathy (IgAN). The relationship between serum complement and the clinical-histopathological features and outcomes of IgAN is controversial. This retrospective study aimed to examine the relationship between the complement 3/4 (C3/C4) ratio and the clinicopathologic changes and prognosis of patients with IgAN.

Methods

A total of 397 patients with primary IgAN from January 2007 to December 2012 at the Chinese People's Liberation Army General Hospital were included in this study. The correlation test and Chi-square test or one-way analysis of variance test were performed to evaluate the relationship between the C3/C4 ratio and other clinical-pathological factors. Propensity score matching and a multivariate Cox regression model were used to calculate the risk factors of renal outcome.

Results

The median follow-up period was 75 months. During the follow-up period, 62 patients (15.6%) developed into the end-stage renal disease (ESRD). The C3/C4 ratio at baseline was associated with the level of serum creatinine (SCr), 24 h urinary protein excretion (24 h Upre), global glomerular sclerosis, and tubulointerstitial lesion. The level of SCr and 24 h Upre and the degree of chronic kidney injury were statistically different among groups defined by different C3/C4 ratio levels. The survival rates of patients among groups with different C3/C4 ratio levels were different. After propensity score matching, eighty-eight pairs of patients were successfully matched, and the C3/C4 ratio was an influencing factor for the patients’ outcome (hazard ratio 0.587, 95% confidence interval 0.329–0.880). Patients with a C3/C4 ratio <3.6 had a poorer outcome compared with the others (P = 0.002).

Conclusions

IgAN patients with decreased C3/C4 ratio displayed significantly more severe clinical symptoms and chronic renal injury than patients with higher ratios. A low C3/C4 ratio could be a risk factor for patients developing to ESRD.

Identification of susceptibility locus shared by IgA nephropathy and inflammatory bowel disease in a Chinese Han population

Genome-wide association studies (GWAS) had discovered several genetic risk loci for IgA nephropathy (IgAN), where the susceptibility genes of CARD9 and HORMAD2 for IgAN were also implicated in inflammatory bowel disease (IBD), suggesting a shared genetic etiology of these two diseases. The aim of this study is to explore the common susceptibility loci between IgAN and IBD and provide evidences to elucidate the shared pathogenesis between these two autoimmune diseases. Nineteen single-nucleotide polymorphisms (SNPs) associated with IBD in Asian populations were selected through the National Human Genome Research Institute (NHGRI) GWAS Catalog, and 2078 IgAN patients and 2085 healthy individuals of Chinese Han ancestry were included in the two-stage case-control association study. Serum levels of complement factor B (CFB) and complement split product C3a were detected by enzyme-linked immunosorbent assay (ELISA). One significant shared association at rs4151657 (OR = 1.28, 95%CI = 1.13-1.45, P = 1.42 × 10^-4) was discovered between these two diseases, which implicated CFB as a susceptibility gene for IgAN. Genotype-phenotype correlation analysis found significant association of the rs4151657-C allele with decreased serum C3 levels. In addition, the rs4151657-C allele was also associated with higher CFB levels and C3a levels, which suggested a certain degree of systemic complement activation in IgAN patients with the rs4151657-CT or CC genotypes. Our study identified one risk locus (CFB) shared by IgAN and IBD, and genetic variants of CFB may affect complement activation and associate with the predisposition to IgAN.

Association of ITGAX and ITGAM gene polymorphisms with susceptibility to IgA nephropathy

Previous genome-wide association studies have discovered significant association at ITGAX-ITGAM on 16p11.2 for IgA nephropathy (IgAN). In this study, we performed a two-stage association study that enrolled 1700 IgAN cases and 2400 controls to further investigate the relationship of ITGAX and ITGAM gene polymorphisms with IgAN. Seven single-nucleotide polymorphisms (SNPs) were selected for genotyping in 1000 IgAN cases and 1000 healthy controls in the discovery stage, and the significant SNP was further validated in additional 700 IgAN cases and 1400 healthy controls. We found that four SNPs (rs11150619, rs11150614, rs7190997, and rs4597342) showed potential associations with IgAN susceptibility in the discovery stage, but only SNP rs11150619 was further genotyped in the validation stage after multiple testing. The results indicated that rs11150619 was significantly associated with IgAN in the combined samples (OR = 0.81, 95%CI = 0.71-0.91, and dominant P = 6.68 × 10^-4). Moreover, patients with TT genotype of rs11150619 exhibited increased estimated glomerular filtration rate levels and a reduced proportion of global sclerosis compared with those with TC and CC genotypes. Our results suggested that ITGAX and ITGAM gene polymorphisms were associated with IgAN in a Chinese Han population, and the rs11150619-T allele showed a potential protective role for IgAN.

Biomarkers and Precision Medicine in IgA Nephropathy

The field of biomarker research in IgA nephropathy has experienced a major boost in recent years with the publication of a large number of scientific reports. Candidate biomarkers from blood, urine, and renal tissue obtained through the use of clinical chemistry, molecular biology, and omics have been proposed for translation in clinical practice. Nevertheless, individual biomarkers often lack sensitivity and specificity with the consequent impairment of disease specificity. This review, moving on from the analysis of the four-hit hypothesis, illustrates the biomarkers linked to the abnormal glycosylation process of IgA1 and the immune complex formation. It also describes other serum and urinary biomarkers. Given the profound insights into the pleiotropic function of a single biomarker that is specific for a pathophysiological mechanism, this review suggests a novel approach based on a panel of biomarkers that covers the entire pathogenic process of the disease. Clinical bioinformatics that integrate genetic, clinical, and bioinformatics data sets could optimize the specific value of each biomarker in a multimarker panel. This is a promising approach for precision medicine and personalized therapy in IgA nephropathy.

Serum C3/C4 ratio is a novel predictor of renal prognosis in patients with IgA nephropathy: a retrospective study

IgA nephropathy (IgAN) is an autoimmune disease associated with complement activation. It is unclear whether the ratio of serum C3 and C4 concentrations (C3/C4 ratio) can predict renal outcomes in IgAN patients. A total of 1503 patients diagnosed with IgAN via renal biopsy were recorded in this study. Poor renal outcomes were defined as > 50% decrease in the baseline estimated glomerular filtration rate (eGFR) or development of end-stage renal disease (ESRD) during follow-up. In total, 712 patients meeting the exclusion/inclusion criteria were selected, and the mean follow-up period was 40.6 (12.34) months. Patients with decreased C3/C4 ratios displayed significantly more severe clinical characteristics and renal pathological features and a higher proportion of poor renal outcomes and ESRD. The optimal multivariate Cox regression models identified the C3/C4 ratio (hazard ratio (HR) 0.63, 95% CI 0.5-0.9), serum uric acid (HR 1.58, 95% CI 1.2-2.2), serum creatinine (HR 1.3, 95% CI 1.1-1.6), systolic blood pressure (HR 1.57, 95% CI 1.2-2.0) and T score (relative to T0, T1: HR 1.96, 95% CI 1.1-3.7, T2: HR 3.03, 95% CI 1.6-5.9) as strong predictors of poor renal outcomes. Subgroup analysis showed that patients with low C3/C4 ratios benefited from glucocorticoids or other immunosuppressive agents (hazard ratio 0.30 and 0.18, 95% CI 0.13-0.72 and 0.07-0.46, respectively). Serum C3/C4 ratios may be an independent novel predictor of renal outcomes in IgAN patients. Decreased C3/C4 ratios suggest poor renal outcomes and the potential to benefit from aggressive immunosuppressive therapies.

Intrarenal Complement System Transcripts in Chronic Antibody-Mediated Rejection and Recurrent IgA Nephropathy in Kidney Transplantation

Background: The complement system activation and regulation have been linked to post-transplant pathologies including chronic antibody mediated rejection (cAMR) and the recurrence of IgA nephropathy (ReIgAN) but distinct mechanisms remain to be elucidated.

Methods: In this retrospective single center study, the outcome of kidney transplantation was studied in 150 patients with late histological diagnosis to be either cAMR or ReIgAN, 14 stable kidney grafts at 3 months and finally 11 patients with native kidney IgAN nephropathy. To study a role of complement cascade and regulation in cAMR and ReIgAN, the RNA was extracted from available frozen kidney biopsy samples and using RT-qPCR transcripts of 11 target genes along with clinical data were determined and compared with stable grafts at 3 months protocol biopsies or IgAN native kidney nephropathy. Immunohistologically, CD46 (MCP), and C5 proteins were stained in biopsies.

Results: Interestingly, there were no differences in kidney graft survival between cAMR and ReIgAN since transplantation. cAMR was associated with significantly higher intragraft transcripts of C3, CD59, and C1-INH as compared to ReIgAN (p < 0.05). When compared to normal stable grafts, cAMR grafts exhibited higher C3, CD55, CD59, CFH, CFI, and C1-INH (p < 0.01). Moreover, ReIgAN was associated with the increase of CD46, CD55, CD59 (p < 0.01), and CFI (p < 0.05) transcripts compared with native kidney IgAN. Rapid progression of cAMR (failure at 2 years after biopsy) was observed in patients with lower intrarenal CD55 expression (AUC 0.77, 78.6% sensitivity, and 72.7 specificity). There was highly significant association of several complement intrarenal transcripts and the degree of CKD regardless the diagnosis; C3, CD55, CFH, CFI, and C1-INH expressions positively correlated with eGFR (for all p < 0.001). Neither the low mRNA transcripts nor the high mRNA transcripts biopsies were associated with distinct trend in MCP or C5 proteins staining.

Conclusions: The intrarenal complement system transcripts are upregulated in progressively deteriorated kidney allografts.