Many patients with immunoglobulin A nephropathy (IgAN) progress to kidney failure even with optimal supportive care. An improved understanding of the pathophysiology of IgAN in recent years has led to the investigation of targeted therapies with acceptable tolerability that may address the underlying causes of IgAN or the pathogenesis of kidney injury. The complement system-particularly the lectin and alternative pathways of complement-has emerged as a key mediator of kidney injury in IgAN and a possible target for investigational therapy. This review will focus on the lectin pathway. The examination of kidney biopsies has consistently shown glomerular deposition of mannan-binding lectin (1 of 6 pattern-recognition molecules that activate the lectin pathway) together with IgA1 in up to 50% of patients with IgAN. Glomerular deposition of pattern-recognition molecules for the lectin pathway is associated with more severe glomerular damage and more severe proteinuria and hematuria. Emerging research suggests that the lectin pathway may also contribute to tubulointerstitial fibrosis in IgAN and that collectin-11 is a key mediator of this association. This review summarizes the growing scientific and clinical evidence supporting the role of the lectin pathway in IgAN and examines the possible therapeutic role of lectin pathway inhibition for these patients.
- MeSH
- glomerulus patologie MeSH
- IgA nefropatie * patologie MeSH
- imunoglobulin A metabolismus MeSH
- ledviny patologie MeSH
- lektiny metabolismus MeSH
- lidé MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
INTRODUCTION: IgA nephropathy is the most common primary glomerulonephritis worldwide. Immune complexes, composed of galactose-deficient IgA1 and Gd-IgA1 autoantibodies, are deposited in the mesangial area of the glomeruli where they induce complement-mediated inflammation. This may result in the reduced kidney function, which can progress to end-stage kidney disease. Treatment options are very limited. Treatments which directly affect the formation of pathogenic Gd-IgA1 antibodies and anti-Gd-IgA1 antibody-containing immune complexes are needed. AREAS COVERED: This article reviews potential therapies, namely monoclonal antibodies, that may affect the main axis of pathogenesis of IgA nephropathy with a discussion of their potential impact on the outcome of IgAN. PubMed was used to perform the literature search, which included papers on "treatment of IgA nephropathy"combined with "biological therapy", or 'monoclonal antibodies, atacicept, sibeprenlimab, rituximab, felzartamab, narsoplimab, iptacopan' published up to 2023. EXPERT OPINION: The new treatment options are aimed at the immunopathogenesis of IgAN, including depletion or modulation of Gd-IgA1 producing B cells, plasma cells, alternate or lectin pathway of complement. Monoclonal antibodies may target both B cells and T cells and also the factors needed for their activation and survival, e.g. BAFF or APRIL.
IL-6 is considered one of the well characterized cytokines exhibiting homeostatic, pro- and anti-inflammatory activities, depending on the receptor variant and the induced intracellular cis- or trans-signaling responses. IL-6-activated pathways are involved in the regulation of cell proliferation, survival, differentiation, and cell metabolism changes. Deviations in IL-6 levels or abnormal response to IL-6 signaling are associated with several autoimmune diseases including IgA nephropathy (IgAN), one of most frequent primary glomerulonephritis worldwide. IgAN is associated with increased plasma concentration of IL-6 and increased plasma concentration of aberrantly galactosylated IgA1 immunoglobulin (Gd-IgA1). Gd-IgA1 is specifically recognized by autoantibodies, leading to the formation of circulating immune complexes (CIC) with nephritogenic potential, since CIC deposited in the glomerular mesangium induce mesangial cells proliferation and glomerular injury. Infection of the upper respiratory or digestive tract enhances IL-6 production and in IgAN patients is often followed by the macroscopic hematuria. This review recapitulates general aspects of IL-6 signaling and summarizes experimental evidences about IL-6 involvement in the etiopathogenesis of IgA nephropathy through the production of Gd-IgA1 and regulation of mesangial cell proliferation.
BACKGROUND: IgA nephropathy (IgAN) primary glomerulonephritis is characterized by the deposition of circulating immune complexes composed of polymeric IgA1 molecules with altered O-glycans (Gd-IgA1) and anti-glycan antibodies in the kidney mesangium. The mesangial IgA deposits and serum IgA1 contain predominantly λ light (L) chains, but the nature and origin of such IgA remains enigmatic. METHODS: We analyzed λ L chain expression in peripheral blood B cells of 30 IgAN patients, 30 healthy controls (HCs), and 18 membranous nephropathy patients selected as disease controls (non-IgAN). RESULTS: In comparison to HCs and non-IgAN patients, peripheral blood surface/membrane bound (mb)-Gd-IgA1+ cells from IgAN patients express predominantly λ L chains. In contrast, total mb-IgA+, mb-IgG+, and mb-IgM+ cells were preferentially positive for kappa (κ) L chains, in all analyzed groups. Although minor in comparison to κ L chains, λ L chain subsets of mb-IgG+, mb-IgM+, and mb-IgA+ cells were significantly enriched in IgAN patients in comparison to non-IgAN patients and/or HCs. In contrast to HCs, the peripheral blood of IgAN patients was enriched with λ+ mb-Gd-IgA1+, CCR10+, and CCR9+ cells, which preferentially home to the upper respiratory and digestive tracts. Furthermore, we observed that mb-Gd-IgA1+ cell populations comprise more CD138+ cells and plasmablasts (CD38+) in comparison to total mb-IgA+ cells. CONCLUSIONS: Peripheral blood of IgAN patients is enriched with migratory λ+ mb-Gd-IgA1+ B cells, with the potential to home to mucosal sites where Gd-IgA1 could be produced during local respiratory or digestive tract infections.
- MeSH
- galaktosa MeSH
- IgA nefropatie * MeSH
- imunoglobulin A metabolismus MeSH
- imunoglobulin G MeSH
- imunoglobulin M MeSH
- lidé MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Mucin-type O-glycosylation occurs on many proteins that transit the Golgi apparatus. These glycans impact structure and function of many proteins and have important roles in cellular biosynthetic processes, signaling and differentiation. Although recent technological advances have enhanced our ability to profile glycosylation of glycoproteins, limitations in the understanding of the biosynthesis of these glycan structures remain. Some of these limitations stem from the difficulty to track the biosynthetic process of mucin-type O-glycosylation, especially when glycans occur in dense clusters in repeat regions of proteins, such as the mucins or immunoglobulin A1 (IgA1). Here, we describe a series of nano-liquid chromatography (LC)-mass spectrometry (MS) analyses that demonstrate the range of glycosyltransferase enzymatic activities involved in the biosynthesis of clustered O-glycans on IgA1. By utilizing nano-LC-MS relative quantitation of in vitro reaction products, our results provide unique insights into the biosynthesis of clustered IgA1 O-glycans. We have developed a workflow to determine glycoform-specific apparent rates of a human UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltrasnfersase (GalNAc-T EC 2.4.1.41) and demonstrated how pre-existing glycans affect subsequent activity of glycosyltransferases, such as core 1 galactosyltransferase and α2,3- and α2,6-specific sialyltransferases, in successive additions in the biosynthesis of clustered O-glycans. In the context of IgA1, these results have potential to provide insight into the molecular mechanisms implicated in the pathogenesis of IgA nephropathy, an autoimmune renal disease involving aberrant IgA1 O-glycosylation. In a broader sense, these methods and workflows are applicable to the studies of the concerted and competing functions of other glycosyltransferases that initiate and extend mucin-type core 1 clustered O-glycosylation.
IgA nephropathy (IgAN) is the dominant type of primary glomerulonephritis worldwide. However, IgAN rarely affects African Blacks and is uncommon in African Americans. Polymeric IgA1 with galactose-deficient hinge-region glycans is recognized as auto-antigen by glycan-specific antibodies, leading to formation of circulating immune complexes with nephritogenic consequences. Because human B cells infected in vitro with Epstein-Barr virus (EBV) secrete galactose-deficient IgA1, we examined peripheral blood B cells from adult IgAN patients, and relevant controls, for the presence of EBV and their phenotypic markers. We found that IgAN patients had more lymphoblasts/plasmablasts that were surface-positive for IgA, infected with EBV, and displayed increased expression of homing receptors for targeting the upper respiratory tract. Upon polyclonal stimulation, these cells produced more galactose-deficient IgA1 than did cells from healthy controls. Unexpectedly, in healthy African Americans, EBV was detected preferentially in surface IgM- and IgD-positive cells. Importantly, most African Blacks and African Americans acquire EBV within 2 years of birth. At that time, the IgA system is naturally deficient, manifested as low serum IgA levels and few IgA-producing cells. Consequently, EBV infects cells secreting immunoglobulins other than IgA. Our novel data implicate Epstein-Barr virus infected IgA+ cells as the source of galactose-deficient IgA1 and basis for expression of relevant homing receptors. Moreover, the temporal sequence of racial-specific differences in Epstein-Barr virus infection as related to the naturally delayed maturation of the IgA system explains the racial disparity in the prevalence of IgAN.
- MeSH
- B-lymfocyty imunologie MeSH
- galaktosa MeSH
- IgA nefropatie epidemiologie virologie MeSH
- imunoglobulin A metabolismus MeSH
- infekce virem Epsteina-Barrové epidemiologie MeSH
- kojenec MeSH
- lidé MeSH
- prevalence MeSH
- rasové skupiny * MeSH
- virus Epsteinův-Barrové fyziologie MeSH
- Check Tag
- kojenec MeSH
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- Geografické názvy
- Česká republika MeSH
GalNAc-type O-glycans are often added to proteins post-translationally in a clustered manner in repeat regions of proteins, such as mucins and IgA1. Observed IgA1 glycosylation patterns show that glycans occur at similar sites with similar structures. It is not clear how the sites and number of glycans added to IgA1, or other proteins, can follow a conservative process. GalNAc-transferases initiate GalNAc-type glycosylation. In IgA nephropathy, an autoimmune disease, the sites and O-glycan structures of IgA1 hinge-region are altered, giving rise to a glycan autoantigen. To better understand how GalNAc-transferases determine sites and densities of clustered O-glycans, we used IgA1 hinge-region (HR) segment as a probe. Using LC-MS, we demonstrated a semi-ordered process of glycosylation by GalNAc-T2 towards the IgA1 HR. The catalytic domain was responsible for selection of four initial sites based on amino-acid sequence recognition. Both catalytic and lectin domains were involved in multiple second site-selections, each dependent on initial site-selection. Our data demonstrated that multiple start-sites and follow-up pathways were key to increasing the number of glycans added. The lectin domain predominately enhanced IgA1 HR glycan density by increasing synthesis pathway exploration by GalNAc-T2. Our data indicated a link between site-specific glycan addition and clustered glycan density that defines a mechanism of how conserved clustered O-glycosylation patterns and glycoform populations of IgA1 can be controlled by GalNAc-T2. Together, these findings characterized a correlation between glycosylation pathway diversity and glycosylation density, revealing mechanisms by which a single GalNAc-T isozyme can limit and define glycan heterogeneity in a disease-relevant context.
- MeSH
- biokatalýza MeSH
- glykosylace MeSH
- imunoglobulin A metabolismus MeSH
- lidé MeSH
- N-acetylgalaktosaminyltransferasy metabolismus MeSH
- polysacharidy biosyntéza chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
BACKGROUND/AIMS: IgA nephropathy is associated with aberrant O-glycosylation of IgA1, which is recognized by autoantibodies leading to the formation of circulating immune complexes. Some of them, after deposition into kidney mesangium, trigger glomerular injury. In patients with active disease nonresponding to angiotensin-converting enzyme inhibitors or angiotensin II blockers, corticosteroids are recommended. METHODS: The relationship between the corticosteroid therapy and serum levels of IgA, aberrantly O-glycosylated IgA1, IgA-containing immune complexes and their mesangioproliferative activity was analyzed in IgA nephropathy patients and disease and healthy controls. RESULTS: Prednisone therapy significantly reduced proteinuria and levels of serum IgA, galactose-deficient IgA1, and IgA-IgG immune complexes in IgA nephropathy patients and thus reduced differences in all of the above parameters between IgAN patients and control groups. A moderate but not significant reduction of mesangioproliferative potential of IgA-IgG immune complexes and IgA sialylation was detected. CONCLUSION: The prednisone therapy reduces overall aberrancy in IgA1 O-glycosylation in IgA nephropathy patients, but the measurement of IgA1 parameters does not allow us to predict the prednisone therapy outcome in individual patients.
- MeSH
- glukokortikoidy farmakologie terapeutické užití MeSH
- glykosylace účinky léků MeSH
- IgA nefropatie diagnóza farmakoterapie MeSH
- imunoglobulin A krev imunologie metabolismus MeSH
- imunokomplex krev MeSH
- lidé MeSH
- prednison terapeutické užití MeSH
- prognóza MeSH
- protilátky krev MeSH
- studie případů a kontrol MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
AIMS: TheAIM of the study was to investigate gastrointestinal comorbidities, identify risk factors and detect the early stages of autoimmune gastrointestinal diseases, such as Crohn's disease, ulcerative colitis and coeliac disease in patients with psoriasis. METHODS: This was a hospital-based case-control study. Patients with chronic plaque psoriasis were included as cases. The control group consisted of patients with other skin diseases and who complied with the same selection criteria as cases. Two controls were selected per one case. We analysed the following antibodies (ASCA, AEP, p-ANCA, AGC, EMA, ARA, tTG, AGA) and non-specific signs of gastrointestinal diseases. RESULTS: There were significant differences between cases and controls in several parameters. Leucocyte count, CRP, total protein, transglutaminase IgA antibodies and p-ANCA were statistically significant between groups (P < 0.05). In the binary logistic model, leucocyte count and p-ANCA (for all parameters included in the logistic model P ≤ 0.001) were associated with psoriasis. CONCLUSION: Patients with psoriasis should be regularly screened for coeliac and inflammatory bowel disease. Early diagnosis of gastrointestinal diseases and risk factors may prevent complications and greatly improve the patient's quality of life.
- MeSH
- C-reaktivní protein metabolismus MeSH
- časná diagnóza MeSH
- celiakie komplikace diagnóza epidemiologie MeSH
- chronická nemoc MeSH
- Crohnova nemoc komplikace diagnóza epidemiologie MeSH
- imunoglobulin A metabolismus MeSH
- kvalita života MeSH
- lidé MeSH
- počet leukocytů MeSH
- protilátky proti cytoplazmě neutrofilů metabolismus MeSH
- psoriáza komplikace epidemiologie MeSH
- studie případů a kontrol MeSH
- transglutaminasy metabolismus MeSH
- ulcerózní kolitida komplikace diagnóza epidemiologie MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika epidemiologie MeSH
BACKGROUND AND AIMS: Advances in the diagnosis and treatment of multiple myeloma (MM), place increasing demands on accurate stratification of patients as the starting point for optimal individualized therapy. The present study focused on assessing the association between HLC levels and the HLC-r to parameters of MM activity, prognosis and tumor mass volume.The objective was to assess the correlation of immunoglobulin (Ig), heavy/light chain (HLC) pairs (IgG-κ and-λ, IgA-κ and -λ HLC) and the ratio of monoclonal involved-HLC (i-HLC) to polyclonal uninvolved (u-HLC) Ig concentrations assessed by the Hevylite(TM) method with the free light chain κ/λ ratio (FLC-r), selected prognostic laboratory parameters i.e. Hb, platelets, albumin, β2-microglobulin (β2-M), Ca, lactate dehydrogenase (LDH), creatinine and the Durie-Salmon (D-S) and International Staging System (ISS), stages (1-3) for MM. METHODS: Hevylite assays were done on the sera of 132 MM patients at the time of diagnosis (IgG 94, IgA 38). HLC-r was calculated in the case of i-HLC-κ from the i-HLC-κ/u-HLC-λ ratio and for i-HLC-λ from the i-HLC-λ/u-HLC-κ ratio. D-S and ISS stages were evenly distributed. RESULTS: Md IgG-κ HLC-r was 64.8 (2.7-2222) and of IgG-λ HLC-r 49.6 (0.7-465.1), in the case of IgA-κ, Md HLC-r was 408.9 (3.4-3966) and for IgA-λ HLC-r the Md was 180.0 (0.1-3110). Normal levels of HLC pairs and HLC-r did not always rule out the diagnosis of MM. HLC-r correlated with FLC-r in IgG (r = 0.244, P = 0.018), but not in the IgA type. For IgG, HLC-r values were significantly different in patients with abnormal vs normal levels of Hb (P < 0.0001), albumin (P < 0.043), β2-M (P < 0.0001) and creatinine (P = 0.034) but not thrombocyte count, Ca or LDH. For the IgA isotype, we found a significant difference in HLC-r values only for thrombocyte count (P = 0.026) and β2-M (P = 0.016) but not for Hb, albumin, Ca, LDH or creatinine. For the IgG isotype there was a significant relationship of HLC-r index to stages 1-3 (P = 0.038) and substage A vs B (P = 0.048) according to D-S, and with high significance to stages 1-3 according to ISS (P = 0.005) and between stages 1 vs 3 (P = 0.001). For the IgA isotype, we found significant differences in HLC-r only between stages 1-3 (P = 0.025) according to D-S but not in the case of ISS. There were no significant correlations between i-HLC Ig levels and D-S or ISS stages in both IgG-κ and λ and IgA-κ and λ. Exceptions were significant differences for stages 1 vs 3 (P = 0.012) and 2 vs 3 (P = 0.017) for the IgG-λ isotype. There were no correlations of the HLC-r and u-HLC levels for either D-S or ISS stratifications in all HLC isotypes. CONCLUSION: We found a significant positive contribution of HLC-r using the i-HLC/u-HLC ratio even in the case of i-HLC-λ i.e. i-HLC-λ/u-HLC-κ. Variable results for the relationship of important laboratory parameters and D-S and ISS stratifications (stage 1-3) to HLC-r values in IgG and IgA isotypes make separate interpretation of the Hevylite method results necessary in clinical practice.
- MeSH
- dospělí MeSH
- imunoglobulin A metabolismus MeSH
- imunoglobulin G metabolismus MeSH
- lidé středního věku MeSH
- lidé MeSH
- mnohočetný myelom krev klasifikace diagnóza MeSH
- prognóza MeSH
- prospektivní studie MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- těžké řetězce imunoglobulinů metabolismus MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
