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Development and Evaluation of a Robust Sandwich Immunoassay System Detecting Serum WFA-Reactive IgA1 for Diagnosis of IgA Nephropathy. Int J Mol Sci 2022; 23:ijms23095165. [PMID: 35563555 PMCID: PMC9104065 DOI: 10.3390/ijms23095165] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/28/2022] [Accepted: 05/03/2022] [Indexed: 02/04/2023] Open
Abstract
Aberrant glycosylation of IgA1 is involved in the development of IgA nephropathy (IgAN). There are many reports of IgAN markers focusing on the glycoform of IgA1. None have been clinically applied as a routine test. In this study, we established an automated sandwich immunoassay system for detecting aberrant glycosylated IgA1, using Wisteria floribunda agglutinin (WFA) and anti-IgA1 monoclonal antibody. The diagnostic performance as an IgAN marker was evaluated. The usefulness of WFA for immunoassays was investigated by lectin microarray. A reliable standard for quantitative immunoassay measurements was designed by modifying a purified IgA1 substrate. A validation study using multiple serum specimens was performed using the established WFA-antibody sandwich automated immunoassay. Lectin microarray results showed that WFA specifically recognized N-glycans of agglutinated IgA1 in IgAN patients. The constructed IgA1 standard exhibited a wide dynamic range and high reactivity. In the validation study, serum WFA-reactive IgA1 (WFA+-IgA1) differed significantly between healthy control subjects and IgAN patients. The findings indicate that WFA is a suitable lectin that specifically targets abnormal agglutinated IgA1 in serum. We also describe an automated immunoassay system for detecting WFA+-IgA1, focusing on N-glycans.
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Caliskan Y, Demir E, Karatay E, Ozluk Y, Mirioglu S, Dirim AB, Artan AS, Usta Akgul S, Oto OA, Savran Oguz F, Turkmen A, Lentine KL, Yazici H. Oxidative stress and macrophage infiltration in IgA nephropathy. J Nephrol 2021; 35:1101-1111. [PMID: 34787798 DOI: 10.1007/s40620-021-01196-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/27/2021] [Indexed: 12/21/2022]
Abstract
BACKGROUND The aim of this study was to evaluate the interactions among serum levels of galactose-deficient IgA1 (Gd-IgA1), oxidative stress and macrophage infiltration and their clinical correlates in patients with IgA Nephropathy (IgAN). METHODS A total of 47 patients with biopsy-proven primary IgAN, aged between 16 and 79 years, with a follow-up period ≥ 1 year or who showed progression to end stage kidney disease (ESKD) regardless the duration of follow-up were included. Study endpoint was the progression to ESKD. Serum Gd-IgA1 and advanced oxidation protein product (AOPP) levels were measured using ELISA assays. Kidney biopsies were evaluated according to the Oxford MEST-C scoring, with C4d and CD68 staining. RESULTS Seventeen patients (36%) experienced ESKD during a median follow-up time of 6 years (IQR 3.7-7.5). Serum AOPP levels were correlated with the intensity of glomerular C3 deposition (r = 0.325, p = 0.026), glomerular (r = 0.423, p = 0.003) and interstitial CD68 + cell count (r = 0.298, p = 0.042) and Gd-IgA1 levels (r = 0.289, p = 0.049). Serum Gd-IgA1 levels were correlated with the intensity of C3 deposition (r = 0.447, p = 0.002). eGFR at biopsy (adjusted HR (aHR) 0.979 p = 0.011), and E score (aHR, 8.305, p = 0.001) were associated with progression to ESKD in multivariate analysis. 5-year ESKD-free survival rate was significantly lower in patients with higher E score compared to patients with E score 0 [p = 0.021]. CONCLUSIONS An increased number of macrophages in the glomerular and tubulointerstitial area may play a role in oxidative stress and complement system activation. Endocapillary hypercellularity is a predictive factor for poor prognosis in IgAN.
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Affiliation(s)
- Yasar Caliskan
- Division of Nephrology, Saint Louis University School of Medicine, 3660 Vista Ave, Saint Louis, MO, USA. .,Division of Nephrology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
| | - Erol Demir
- Division of Nephrology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Ecem Karatay
- Department of Pathology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Yasemin Ozluk
- Department of Pathology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Safak Mirioglu
- Division of Nephrology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.,Division of Nephrology, Bezmialem Vakif University School of Medicine, Istanbul, Turkey
| | - Ahmet Burak Dirim
- Division of Nephrology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Ayse Serra Artan
- Division of Nephrology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Sebahat Usta Akgul
- Department of Medical Biology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Ozgur Akin Oto
- Division of Nephrology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Fatma Savran Oguz
- Department of Medical Biology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Aydin Turkmen
- Division of Nephrology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Krista L Lentine
- Division of Nephrology, Saint Louis University School of Medicine, 3660 Vista Ave, Saint Louis, MO, USA
| | - Halil Yazici
- Division of Nephrology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
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Ohyama Y, Renfrow MB, Novak J, Takahashi K. Aberrantly Glycosylated IgA1 in IgA Nephropathy: What We Know and What We Don't Know. J Clin Med 2021; 10:jcm10163467. [PMID: 34441764 PMCID: PMC8396900 DOI: 10.3390/jcm10163467] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/26/2021] [Accepted: 08/02/2021] [Indexed: 12/17/2022] Open
Abstract
IgA nephropathy (IgAN), the most common primary glomerular disease worldwide, is characterized by glomerular deposition of IgA1-containing immune complexes. The IgA1 hinge region (HR) has up to six clustered O-glycans consisting of Ser/Thr-linked N-acetylgalactosamine usually with β1,3-linked galactose and variable sialylation. Circulating levels of IgA1 with abnormally O-glycosylated HR, termed galactose-deficient IgA1 (Gd-IgA1), are increased in patients with IgAN. Current evidence suggests that IgAN is induced by multiple sequential pathogenic steps, and production of aberrantly glycosylated IgA1 is considered the initial step. Thus, the mechanisms of biosynthesis of aberrantly glycosylated IgA1 and the involvement of aberrant glycoforms of IgA1 in disease development have been studied. Furthermore, Gd-IgA1 represents an attractive biomarker for IgAN, and its clinical significance is still being evaluated. To elucidate the pathogenesis of IgAN, it is important to deconvolute the biosynthetic origins of Gd-IgA1 and characterize the pathogenic IgA1 HR O-glycoform(s), including the glycan structures and their sites of attachment. These efforts will likely lead to development of new biomarkers. Here, we review the IgA1 HR O-glycosylation in general and the role of aberrantly glycosylated IgA1 in the pathogenesis of IgAN in particular.
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Affiliation(s)
- Yukako Ohyama
- Department of Biomedical Molecular Sciences, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan;
| | - Matthew B. Renfrow
- Departments of Biochemistry and Molecular Genetics and Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; (M.B.R.); (J.N.)
| | - Jan Novak
- Departments of Biochemistry and Molecular Genetics and Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; (M.B.R.); (J.N.)
| | - Kazuo Takahashi
- Department of Biomedical Molecular Sciences, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan;
- Correspondence: ; Tel.: +81-(562)-93-2430; Fax: +81-(562)-93-1830
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Chiu YL, Lin WC, Shu KH, Fang YW, Chang FC, Chou YH, Wu CF, Chiang WC, Lin SL, Chen YM, Wu MS. Alternative Complement Pathway Is Activated and Associated with Galactose-Deficient IgA 1 Antibody in IgA Nephropathy Patients. Front Immunol 2021; 12:638309. [PMID: 34177889 PMCID: PMC8223746 DOI: 10.3389/fimmu.2021.638309] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 05/20/2021] [Indexed: 12/30/2022] Open
Abstract
Background Galactose-deficient IgA1 (Gd-IgA1) and alternative complement pathway activation are considered to be involved in the pathogenesis of IgA nephropathy (IgAN). Nevertheless, the relationships between alternative pathway activation and disease activity or Gd-IgA1 level remains unclear. Methods Ninety-eight biopsy-diagnosed IgAN, twenty-five primary focal segmental sclerosis (FSGS) patients and forty-two healthy individuals were recruited in this study. Among them, fifty IgAN patients received immunosuppression. Follow-up blood samples at 1 and 3~6 months after immunosuppression were collected. Plasma levels of complement C5a, factor Ba and Gd-IgA1 were measured and analyzed. Immunostaining for complement was performed in twenty-five IgAN and FSGS patients. Results At baseline, IgAN patients had higher levels of plasma C5a, factor Ba and Gd-IgA1 than control subjects. Gd-IgA1 levels positively correlated with plasma C5a and factor Ba. In addition, levels of factor Ba and Gd-IgA1 were positively associated with proteinuria and negatively associated with renal function. Immunostaining revealed positive staining for factor Bb and C3c in glomeruli in IgAN patients, but not in FSGS patients. At baseline, patients receiving immunosuppression had more severe proteinuria and higher factor Ba. After 6 months, eGFR declined and proteinuria persisted in patients without immunosuppression. In contrast, patients who received immunosuppression exhibited decreased plasma levels of C5a, factor Ba, and Gd-IgA1 as early as 1 month after treatment. Proteinuria decreased and renal function also remained stable 6 months after immunosuppression. Conclusions Our results indicate a close relationship between alternative complement pathway activation, Gd-IgA1 concentration and clinical severity of IgAN. Level of complement factor B may be a potential marker for disease activity and therapeutic target in IgAN patients.
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Affiliation(s)
- Yen-Ling Chiu
- Graduate Program in Biomedical Informatics and Graduate Institute of Medicine, Yuan Ze University, Taoyuan, Taiwan.,Department of Medical Research, Far Eastern Memorial Hospital, New Taipei City, Taiwan.,Graduate Institute of Clinical Medicine, National Taiwan University, Taipei, Taiwan
| | - Wei-Chou Lin
- Department of Pathology, National Taiwan University Hospital, Taipei, Taiwan
| | - Kai-Hsiang Shu
- Graduate Program in Biomedical Informatics and Graduate Institute of Medicine, Yuan Ze University, Taoyuan, Taiwan
| | - Yi-Wen Fang
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Fan-Chi Chang
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Yu-Hsiang Chou
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Ching-Fang Wu
- Department of Internal Medicine, E-Da Hospital, Kaohsiung, Taiwan
| | - Wen-Chih Chiang
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Shuei-Liong Lin
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.,Graduate Institute of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Yung-Ming Chen
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Ming-Shiou Wu
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
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Utility of glomerular Gd-IgA1 staining for indistinguishable cases of IgA nephropathy or Alport syndrome. Clin Exp Nephrol 2021; 25:779-787. [PMID: 33743099 DOI: 10.1007/s10157-021-02054-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 03/11/2021] [Indexed: 12/13/2022]
Abstract
BACKGROUND Pathological findings in Alport syndrome frequently show mesangial proliferation and sometimes incidental IgA deposition, in addition to unique glomerular basement membrane (GBM) changes including thin basement membrane and/or lamellation. However, similar GBM abnormalities are also often observed in IgA nephropathy. Both diseases are also known to show hematuria, proteinuria, and sometimes macrohematuria when associated with viral infection. Therefore, it can be difficult to make a differential diagnosis, even based on clinical and pathological findings. Some recent articles demonstrated that galactose-deficient IgA1 (Gd-IgA1)-specific monoclonal antibody (KM55) could potentially enable incidental IgA deposition to be distinguished from IgA nephropathy. METHODS We performed comprehensive gene screening and glomerular Gd-IgA1 and type IV collagen α5 chain immunostaining for five cases with both IgA deposition and GBM changes to confirm that Gd-IgA1 can help to distinguish these two diseases. RESULTS Four of the cases were genetically diagnosed with Alport syndrome (Cases 1-4) and one was IgA nephropathy with massive GBM changes, which had a negative gene test result (Case 5). In Cases 1-4, glomerular Gd-IgA1 deposition was not detected, although there was positivity for IgA in the mesangial area. In Case 5, glomerular Gd-IgA1 deposition was observed. CONCLUSION Gd-IgA1 expression analysis could clearly differentiate these two disorders. This approach can be applied to identify these two diseases showing identical clinical and pathological findings.
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Characterization of IgA Deposition in the Kidney of Patients with IgA Nephropathy and Minimal Change. J Clin Med 2020; 9:jcm9082619. [PMID: 32806730 PMCID: PMC7464421 DOI: 10.3390/jcm9082619] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 08/05/2020] [Accepted: 08/09/2020] [Indexed: 12/04/2022] Open
Abstract
Approximately 5% of patients with IgA nephropathy (IgAN) exhibit mild mesangial lesions with acute onset nephrotic syndrome and diffuse foot process effacement representative of minimal change disease (MCD). It is not clear whether these unusual cases of IgAN with MCD (IgAN-MCD) are variant types of IgAN or coincidental deposition of IgA in patients with MCD. In a retrospective multicenter cohort study of 18 hospitals in Korea, we analyzed 46 patients with IgAN-MCD. Patients with endocapillary proliferation, segmental sclerosis, and crescent were excluded, and the clinical features and prognosis of IgAN-MCD were compared with those of pure MCD. In addition, we performed galactose-deficient IgA1 (KM55) staining to characterize IgAN-MCD. Among the 21,697 patients with glomerulonephritis enrolled in the database, 46 patients (0.21%) were diagnosed with IgAN-MCD, and 1610 patients (7.4%) with pure MCD. The 46 patients with IgAN-MCD accounted for 0.6% of primary IgAN patients (n = 7584). There was no difference in prognosis between patients with IgAN-MCD and those with only MCD. IgA and KM55 showed double positivity in all patients with IgAN-MCD (n = 4) or primary IgAN (n = 5) under double immunofluorescent staining. However, in four patients with lupus nephritis, mesangial IgA was deposited, but galactose-deficient-IgA1 (Gd-IgA1) was not. These findings suggest that IgAN-MCD is a dual glomerulopathy in which MCD was superimposed on possibly indolent IgAN. We confirmed by KM55 staining that IgAN-MCD is true IgAN, enabling better characterizations of the disease. Furthermore, IgAN-MCD shows a good prognosis when treated according to the usual MCD treatment modality.
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Zhao L, Peng L, Yang D, Chen S, Lan Z, Zhu X, Yuan S, Chen G, Liu Y, Liu H. Immunostaining of galactose-deficient IgA1 by KM55 is not specific for immunoglobulin A nephropathy. Clin Immunol 2020; 217:108483. [PMID: 32479989 DOI: 10.1016/j.clim.2020.108483] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 04/27/2020] [Accepted: 05/26/2020] [Indexed: 12/19/2022]
Abstract
BACKGROUND Immunoglobulin A nephropathy (IgAN nephropathy, IgAN) is named for the renal pathological features of IgA-dominant immunoglobulin deposition. IgA deposits, however, may also occur in other diseases, from liver disease and inflammation to chronic infections and tumors. Now increasing studies have suggested that galactose-deficient IgA1 (Gd-IgA1) plays a critical role in the pathogenesis of IgAN. This study aims to investigate whether the Gd-IgA1-specific antibody KM55 contributes to differentiating primary IgAN from other diseases with IgA deposits. METHODS In this retrospective study, we enrolled 100 Chinese patients with IgA deposits in renal biopsies, including IgAN(n = 40), IgAN with hepatitis B virus antigen deposits(n = 14), IgA vasculitis(n = 16), lupus nephritis(n = 11), incidental IgA deposits(n = 13) and negative controls(n = 6). Double immunostaining of Gd-IgA1 and IgA was performed in all biopsies. RESULTS There were similar patterns of Gd-IgA1 deposition in primary IgAN, IgA vasculitis, and IgAN with hepatitis B virus antigen deposits. Gd-IgA1 staining could also be seen in patients with lupus nephritis and incidental IgA deposits, but the intensity was significantly lower than IgAN, and the optimal cutoff was 2+ staining for differential diagnosis. Every increase in KM55 staining intensity of 1+ was associated with an increase in the odds of primary IgAN (OR: 4.399; 95% CI: 1.725-11.216). CONCLUSIONS Immunostaining for Gd-IgA1 by KM55 is not specific for IgA nephropathy, but weak or negative staining may favor incidental IgA deposits.
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Affiliation(s)
- Lu Zhao
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Liang Peng
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Danyi Yang
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Shi Chen
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Zhixin Lan
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Xuejing Zhu
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Shuguang Yuan
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Guochun Chen
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Yu Liu
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China
| | - Hong Liu
- Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China; Hunan Key Laboratory of Kidney Disease and Blood Purification, Changsha, Hunan, China.
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Analysis of O-glycoforms of the IgA1 hinge region by sequential deglycosylation. Sci Rep 2020; 10:671. [PMID: 31959827 PMCID: PMC6971281 DOI: 10.1038/s41598-020-57510-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 12/30/2019] [Indexed: 12/21/2022] Open
Abstract
A common renal disease, immunoglobulin A (IgA) nephropathy (IgAN), is associated with glomerular deposition of IgA1-containing immune complexes. IgA1 hinge region (HR) has up to six clustered O-glycans consisting of Ser/Thr-linked N-acetylgalactosamine with β1,3-linked galactose and variable sialylation. IgA1 glycoforms with some galactose-deficient (Gd) HR O-glycans play a key role in IgAN pathogenesis. The clustered and variable O-glycans make the IgA1 glycomic analysis challenging and better approaches are needed. Here, we report a comprehensive analytical workflow for IgA1 HR O-glycoform analysis. We combined an automated quantitative analysis of the HR O-glycopeptide profiles with sequential deglycosylation to remove all but Gd O-glycans from the HR. The workflow was tested using serum IgA1 from healthy subjects. Twelve variants of glycopeptides corresponding to the HR with three to six O-glycans were detected; nine glycopeptides carried up to three Gd O-glycans. Sites with Gd O-glycans were unambiguously identified by electron-transfer/higher-energy collision dissociation tandem mass spectrometry. Extracted ion chromatograms of isomeric glycoforms enabled quantitative assignment of Gd sites. The most frequent Gd site was T236, followed by S230, T233, T228, and S232. The new workflow for quantitative profiling of IgA1 HR O-glycoforms with site-specific resolution will enable identification of pathogenic IgA1 HR O-glycoforms in IgAN.
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