Th1/Th2 polarization in tonsillar lymphocyte form patients with IgA nephropathy

Imbalance of Th1/Th2 pro-inflammatory cytokines plays an important role in the development and progression of IgA nephropathy (IgAN). Clinical development and exacerbation of IgAN are frequently preceded by episodes of upper respiratory tract infection, and palatine tonsils represent the predominant immunocompetent tissue of the upper respiratory tract. This study examined tonsillar lymphocytes of IgAN who suffered from tonsillitis (n?=?22), and using tonsils derived from patients with chronic tonsillitis (n?=?24) but without renal disease as a control. We identified a polarization toward Th2 response in tonsils of IgAN patients. TH0 cells are differentially mobilized during contact sensitization and by adjuvants such as lipopolysaccharide (LPS) that induce T-helper type 1 (Th1) responses, or α-hemolytic streptococcus (HS) that induces T-helper type 2 (Th2) responses. Th1:Th2 ratio is correlated with proteinuria and renal pathologic changes in IgAN group. Our study suggests that IgAN is associated with the change in Th1/Th2 balance in favor of Th2 lymphocytes.     

Elevated production of polymeric and monomeric IgA1 by the bone marrow in IgA nephropathy

In bone marrow cultures of 15 patients with primary IgA nephropathy we found significantly (P = 0.02) increased synthesis of both monomeric and polymeric IgA1 compared to 23 controls, by using high performance liquid chromatography (HPLC) fractionation of culture supernatants. The relative contribution of polymeric to total IgA1 produced was not different for the two groups. Two-color immunofluorescence studies of the percentage of bone marrow IgA1 plasma cells able to bind secretory component in vitro showed no difference between patients and controls. In the sera of patients with primary IgA nephropathy the relative contribution of IgA1 polymers to total IgA1 was also similar to controls. These results indicate that in IgA nephropathy, the increased IgA production in the bone marrow is restricted to the IgA1 subclass. The production of both monomeric and polymeric IgA1 is increased in patients during a quiescent phase of the disease.     

Tonsillitis exacerbates renal injury in IgA nephropathy through promoting Th22 cells chemotaxis

Background

Tonsillitis can promote the progression of IgA nephropathy (IgAN) by aggravating immunopathologic response. Th22 cell disorder is involved in the pathogenesis of IgAN with tonsillitis. This study was determined to explore the possible mechanism of IgAN with tonsillitis underlying Th22 cell chemotaxis response to the effect of CCL20, CCL22, and CCL27.

Methods

This research was conducted on 65 subjects including 16 healthy controls (HC group), 5 patients with  renal carcinoma (HTC group) and 44 patients with IgAN between 2015 and 2016. According to clinical symptoms and results of throat swab culture, patients with IgAN were divided into two groups: IgAN with tonsillitis (IgAN + tonsillitis, n = 14) and IgAN patients without tonsillitis (IgAN, n = 30). Distribution of Th22 cells in IgAN patients was determined. The expression of CCL20, CCL22, and CCL27 in both peripheral blood and kidneys of IgAN patients was investigated. Severity of pathological lesions in IgAN patients was analyzed. Coculture assay and transwell assay were performed to explore the impacts of human mesangial cells (HMC) on Th22 cell chemotaxis and Th22 cell local accumulation under hemolytic streptococcus (HS) infection.

Results

Th22 cell percentages in IgAN patients increased compared with healthy controls. This increased Th22 cell percentage was positively correlated with the renal lesions of IgAN patients. Correspondingly, the expression of CCL20, CCL22, and CCL27 in renal tissue increased in IgAN patients. Tonsillitis exacerbated these overrepresentations of Th22 cells and chemokines. It was found that HMC could produce CCL20, CCL22, and CCL27. The supernatant of HMC was chemotactic for Th22 cells. This activity of HMC was stimulated by HS infection, whereas treatment of anti-CCL20, anti-CCL22, and anti-CCL27 antibodies partly blocked this chemoattractant effect of HMC.

Conclusions

Tonsil infection may aggravate the renal pathological lesions of IgAN by exacerbating Th22 cell accumulation. Our data suggested a collaboration between HMC and Th22 cells in IgAN with tonsillitis underlying the effects of CCL20, CCL22, and CCL27.

     

Immunoglobulin-producing cells in IgA nephropathy

The number of peripheral blood mononuclear cells (PBMC) producing IgA, IgG and IgM spontaneously, after in vitro polyclonal stimulation with pokeweek mitogen (PWM) and in response to autologous mixed lymphocyte reaction (AMLR), were determined by a protein A hemolytic plaque assay in 23 patients with IgA nephropathy confirmed by renal biopsies and in 24 normal controls. The geometric mean of circulating IgA-producing cells in Berger's disease (689 +/- 1.73 cells/10(6) PBMC) was increased when compared with the normal controls (332 X divided by 1.52 cells/10(6) PBMC; p less than 0.001). To a lesser degree, there was also an increase in the number of IgG-secreting cells (98 +/- 3.97 cells/10(6) PBMC vs. 38 +/- 2.90 cells/10(6) PBMC; p less than 0.05). After PWM stimulation, although the number of IgA-producing cells was increased in patients with IgA nephropathy, no significant differences were observed between the 2 groups. In response to AMLR, the number of IgA-secreting cells was significantly higher in the cases with Berger's disease (1,979 +/- 1.76 cells/10(6) non-T cells vs. 783 +/- 1.95 cells/10(6) non-T cells; p less than 0.001). Although it did not reach statistical significance, the patient group had also an increase in the number of IgG-producing cells (884 +/- 2.64 cells/10(6) non-T cells vs. 317 +/- 5.05 cells/10(6) non-T cells). These data support the existence of some abnormalities in the mechanisms regulating the synthesis of IgA in Berger's disease which might contribute to its pathogenesis.     

Charge-dependent binding of polymeric IgA1 to human mesangial cells in IgA nephropathy

BACKGROUND: IgA nephropathy (IgAN) is characterized by raised serum IgA1 and predominant mesangial IgA1 deposits of polymeric nature. The mechanism of polymeric IgA1 (pIgA1) deposition in the kidney mesangium is poorly understood in IgAN. It has been suggested that increased sialic acid content and anionic charge of the pIgA1 molecules may be operational in the IgA1 deposition in human mesangial cells (HMCs). The present study examined the binding of pIgA1 with different surface charges to HMCs. The binding characteristics of IgA1 to HMCs in the presence of polycation (poly-L-lysine) or polyanion (heparin) were also investigated. METHODS: IgA1 was purified in sera from patients with IgAN and from healthy controls by jacalin affinity chromatography. IgA1 was further separated into pIgA1 and monomeric IgA1 (mIgA1) by fast protein liquid chromatography (FPLC). pIgA1 or mIgA1 with different net charges on their surface were resolved by ion exchange chromatography (IEC) with a Mono Q column. The binding characteristics of pIgA1 and mIgA1 to HMCs in the presence or absence of polycation or polyanion were examined by flow cytometry. RESULTS: In patients with IgAN, the absolute amount of mIgA1 and pIgA1 is significantly higher than that of healthy controls (P < 0. 001). There was significant increase in binding of pIgA1 from patients with IgAN to HMC and cell lysate. pIgA1 that interacted strongly with the ion exchanger also bound more to HMCs when compared with IgA1 interacted weakly with the ion exchanger (P < 0. 001). The anionic charged pIgA1 from patients was significantly higher than that of healthy controls (P < 0.001). Preincubation with poly-L-lysine increased the binding of pIgA1 to HMCs. The binding of pIgA1 to HMCs was decreased by preincubation with heparin. CONCLUSIONS: The binding of IgA to HMCs is charge dependent. Polymeric IgA with the highest net negative charge binds more to HMCs. Preincubation with polyanion decreased the binding of polymeric IgA to HMCs. These results suggest an important role for anionic charge in IgA1 deposition onto the kidney mesangial cells.     

Abnormalities of IgA1 production in IgA nephropathy

SUMMARY: IgA nephropathy (IgAN) is characterized by the mesangial deposition of polymeric IgA1 (plgA1). the original view that this plgA1 is derived from the mucosal immune system can no longer be sustained. Studies of duodenal mucosa and marrow indicate increased production of plgA1 in the marrow and decreased production in the mucosa. These changes are consistent with immunization studies showing exaggerated and prolonged plgA responses to systemic immunization, and reduced mucosal responses to mucosal neoantigens. However, the IgA1 and IgG systemic responses to mucosal antigen are increased in IgAN, a finding consistent with impairment in oral tolerance, the process by which systemic immune responses, to mucosal antigen challenge are normally suppressed. Both IgA1 production and the induction of oral tolerance are under T-cell control. T-cell populations involved in these processes include γδ T cells, Tr cells and T-helper (Th)3 cells; cytokines with a key role in the control of IgA production include interleukin (IL)-10 and transforming growth factor (TGF)-β. There is evidence of abnormal γδ T-cell V region usage in both mucosa and marrow in IgAN. Increased expression of relevant cytokines has also been reported in circulating T cells in IgAN. the increased O-glycosylation of circulating IgA1 in IgAN may also be further evidence of a shift in the production of mucosal-type plgA1 from the mucosa to marrow. These findings suggest that the specific lymphocyte homing mechanisms that normally maintain oral tolerance and control the site of IgA production require further study in IgAN.     

IgA1-containing immune complexes in IgA nephropathy differentially affect proliferation of mesangial cells

BACKGROUND: Sera of patients with IgA nephropathy (IgAN) contain circulating immune complexes (CIC) composed of galactose-deficient IgA1 complexed with antiglycan antibodies. The role of these CIC in the pathogenesis of IgAN is not known. METHODS: We studied how proliferation of cultured mesangial cells (MC) is affected by CIC prepared from sera of IgAN patients and healthy control subjects using size-exclusion chromatography. CIC-containing fractions were added to serum-starved MC in culture, and cell proliferation was measured using (3)H-thymidine incorporation. The results were confirmed by staining MC using an antibody against proliferating cell nuclear antigen. RESULTS: The incubation of starved MC with serum fractions with M(r) 800 to 900 kD, rich with galactose-deficient IgA1, stimulated proliferation, while fractions with smaller complexes were inhibitory. Furthermore, CIC-containing larger molecular mass fractions isolated from serum of an IgAN patient collected during an episode of macroscopic hematuria stimulated MC proliferation more than CIC obtained during a subsequent quiescent phase. To examine the role of IgA, we removed IgA1 from serum before fractionation. The resultant IgA1-depleted fractions were devoid of stimulatory IgA-CIC. Sera of IgAN patients were also fractionated after addition of desialylated galactose-deficient polymeric IgA1 to form additional immune complexes. Supplementation with a small quantity of this IgA1 increased cellular proliferation in assays using serum fractions of M(r)>/=800 to 900 kD; uncomplexed IgA1 did not affect MC proliferation significantly. In contrast, supplementation with a larger quantity of this IgA1 inhibited cellular proliferation in assays using serum fractions of M(r) 700 to 800 kD. CONCLUSION: Overall, these findings suggest that CIC containing aberrantly glycosylated IgA1 affect proliferation of MC in vitro and, thus, likely play a role in the pathogenesis of IgAN.     

Contribution of macromolecular IgA1 to IgA abnormality in IgA nephropathy

To evaluate the contribution of macromolecular IgA₁ to IgA abnormality in childhood IgA nephropathy, serum samples from 29 healthy children and 26 patients with IgA nephropathy in different age-groups (7–9, 10–12, and 13–15 years) were each separated by sucrose density gradient ultracentrifugation and assayed for IgA₁ using an enzyme-linked immunosorbent assay. IgA₁ in fraction I (sedimentation coefficient >11.4s) was significantly greater in patients 7–15 years of age (median 36.3–57.0 mg/dl) than in the age-matched controls (median 8.8–10.4 mg/dl). IgA₁ in fraction II (11.4–9.3s) was significantly greater in patients 10–15 years of age (median 46.7–52.6 mg/dl) than in the controls (median 27.8–35.5 mg/dl), and IgA₁ in fraction III (<9.3s) was significantly greater in patients 13–15 years of age (median 156.9 mg/dl) than in the controls (median 120.7 mg/dl). The ratio of IgA₁ in fractions I–III was higher in the patients of each age-group (median 0.233–0.314) than in the controls (median 0.067–0.082), while the ratio of IgA₁ in fractions II–III was not significantly high in patients 7–12 years old (median 0.268 to 0.318) compared with the controls (median 0.182–0.264). Thus, IgA abnormality in childhood IgA nephropathy would be better represented by an increase in macromolecular IgA₁ of >11.4s than by an increase in IgA₁ in fractions of 11.4–9.3s or <9.3s. Received: 8 December 1999 / Revised: 2 March 2000 / Accepted: 2 May 2000     

Analysis of IgA1 O-glycans in IgA nephropathy by fluorophore-assisted carbohydrate electrophoresis.

Abnormal O-glycosylation of IgA1 may contribute to pathogenic mechanisms in IgA nephropathy (IgAN). Observations of altered lectin binding to IgA1 in IgAN suggest that the O-glycan chains may be undergalactosylated, but precise structural definition of the defect has proved technically difficult, and it remains unconfirmed. This is the first study using fluorophore-assisted carbohydrate electrophoresis (FACE) to analyze IgA1 O-glycans in IgAN and controls. IgA1 was purified from serum, and the intact O-glycans were released by hydrazinolysis at 60 degrees C. After re-N-acetylation, the glycans were fluorophore-labeled and separated by polyacrylamide gel electrophoresis. Sequential exoglycosidase digestions of IgA1 allowed identification of the different O-glycan bands on FACE gels, and their relative frequencies in IgA1 samples were measured by ultraviolet densitometry. Lectin binding of the IgA1 samples was also measured. In some patients with IgAN, FACE analysis demonstrated a significant increase in the percentage of IgA1 O-glycan chains consisting of single N-acetyl galactosamine (GalNAc) units rather than the more usual galactosylated and sialylated forms. This finding was confirmed using both desialylated IgA1 and enzymatically released O-glycans. Good correlation was also found between O-glycan agalactosylation on FACE analysis and IgA1 lectin binding in IgAN, supporting the value of lectins as tools for detection of this abnormality. This is the first study in which all of the predicted O-glycan forms of IgA1 have been analyzed simultaneously, and demonstrates that in IgAN, the IgA1 Oglycan chains are truncated, with increased terminal GalNAc. This abnormality has the potential to significantly affect IgA1 behavior and handling with pathogenic consequences in IgAN.     

Role of endothelial cells in IgA nephropathy

Summary: Various polyspecific autoantibodies have been described in the sera of patients with IgA nephropathy, including anti-IgG, anti-IgA, antigalactosyl, antifibronectin and antimesangial antibodies. We and other authors have demonstrated the presence of antivascular endothelial cell (VEC) antibodies, in up to 32% of patients with IgA nephropathy. These antibodies were directed against molecules on the endothelial cell surface. Some of these antibodies were directed against HLA class I antigens; the majority, however, were reactive against antigens present on unstimulated endothelial cells, as prior stimulation of the cells with interferon-γ or interleukin 1 did not result in an increase in anti-VEC activity of the sera. The clinical significance of these anti-VEC antibodies in IgA nephropathy is unknown. A significant correlation was demonstrated between these antibodies and the presence of heavy proteinuria. A significant association was also shown between the presence of these antibodies and the histopathologic markers of activity such as crescents and focal and segmental necrotizing lesions, as well as immunoglobulin and C3 deposition in the vessel walls.     

IgA肾病患者血清IgA1与系膜细胞共培养上清诱导足细胞凋亡

目的 探讨IgA肾病(IgAN)患者血清IgA1与系膜细胞共培养上清对足细胞凋亡的影响。 方法 用Jacalin 亲和层析柱和Sephacryl S-200 分子筛纯化蛋白。单体IgA1（mIgA1）热聚合为聚合体IgA1（aIgA1）。实验分为患者上清组、健康上清组和对照组，系膜细胞分别与IgAN患者的aIgA1、健康对照的aIgA1和5%胎牛血清共培养，收集上清，与同步化的足细胞作用。流式细胞仪检测细胞凋亡情况。实时定量PCR 检测凋亡相关基因Bcl-2、Bax、Fas和Fas-L表达情况。 结果 患者上清可诱导足细胞凋亡，其凋亡率显著高于健康上清组和对照组[（28.5±5.9）%比（22.5±5.8）%、（20.5±4.5）%， 均P < 0.05]。患者上清可诱导足细胞Fas mRNA 升高，为对照组的1.89倍（P < 0.05）， 而Bcl-2 mRNA下调为对照组的72%（P < 0.05）。患者上清组的AngⅡ和TGF-β1水平均高于健康上清组[（13.2±3.4） ng/L比（8.2±2.3） ng/L，P < 0.05；（15.4±3.4） ng/L比（10.8±3.2） ng/L，P < 0.05]。 结论 IgAN患者血清IgA1与系膜细胞共培养上清可诱导足细胞凋亡，可能参与IgAN的进展。     

Light-chain composition of serum IgA1 and in vitro IgA1 production in IgA nephropathy.

A predominant expression of IgA1 in mesangial deposits, serum, and bone marrow culture supernatants has been shown in IgA nephropathy (IgAN). Furthermore an excess of lambda light chains in both mesangial deposits and serum IgA has been observed. However, the origin of mesangial IgA remains controversial. In the present study, we have examined the IgA1 light chain type in IgAN. Total IgA1, IgA1 kappa and IgA1 lambda were measured by ELISA in serum and culture supernatants from spontaneous and pokeweed-mitogen (PWM)-stimulated peripheral blood mononuclear cells (PBMC). We observed an increase in IgA and IgA1 serum concentrations in IgA nephropathy patients, with a ratio of serum IgA1 to total serum IgA identical between patients and controls. The concentration of serum IgA kappa did not differ between patients and controls but patients had a significantly higher concentration of serum IgA lambda. The IgA1 kappa to IgA1 lambda ratio was 1.06 +/- 0.42 in IgAN patients versus 1.55 +/- 0.36 in controls (P less than 0.01). By contrast, the concentrations of IgA1 kappa and IgA1 lambda in PBMC culture supernatants, both spontaneous and PWM-stimulated, were identical in patients and controls. Therefore, there is a specific increase in IgA1 lambda in patients' sera. This contrasts with the normal IgA1 production by PBMC, which are derived from mucosal-associated lymphoid tissues. This suggests that IgA isotypic deregulation is confined to the bone marrow compartment and is not a generalised defect of the IgA system.     

Pathogenetic significance of aberrant glycosylation of IgA1 in IgA nephropathy

IgA nephropathy (IgAN), the most common form of primary glomerulonephritis worldwide, is defined by predominant IgA1 deposits in the glomerular mesangium. Among abnormalities of the IgA immune system reported so far in IgAN, aberrant O-linked glycosylation in the hinge region of IgA1 is the most consistent finding. IgA1 molecules bearing abnormal glycosylation have been found in serum, in tonsillar lymphocytes, and in eluate from mesangial deposits, and characterized by decreased O-linked N-acetylgalactosamine residues with or without alteration in the terminal sialylation of the O-linked sugars. IgA1 with incomplete galactosylation has a tendency to accumulate in glomerular mesangium by self-aggregation or immune complex formation. Glomerular mesangial cells exposed to immune complexes of these IgA1 can proliferate and secrete cytokines, chemokines, growth factors, and extracellular matrix components promoting inflammatory reactions in the glomeruli. Although genes encoding enzymes involved in the O-glycosylation process, such as C1GALT1, have been reported to be responsible for susceptibility to IgAN, recent evidence suggests that the abnormality is restricted to a small fraction of B cell populations and arises from dysregulated IgA1 production and secretion in mucosal immune system. This review will focus on and discuss the role of incompleteness of IgA1 O-galactosylation in the pathogenesis of IgAN and propose a possible mechanism in which abnormal IgA1 occurs in IgAN. Presented at the 37th Eastern Regional Meeting of the Japanese Society of Nephrology.     

Mass spectrometry proves under-O-glycosylation of glomerular IgA1 in IgA nephropathy

BACKGROUND: The IgA1 molecule, which is predominantly deposited in glomeruli in IgA nephropathy (IgAN), is a unique serum glycoprotein because it has O-glycan side chains in its hinge region. Our study was conducted to investigate the O-glycan structure in the glomerular IgA1 in IgAN. METHODS: The IgA1 was separated from 290 renal biopsy specimens of 278 IgAN patients and from four serum IgA1 samples (IgAN, 2; control, 2). The variety of O-glycan glycoform was determined by estimating the precise molecular weights of the IgA1 hinge glycopeptides using matrix-assisted laser desorption ionization time of flight mass spectrometry. RESULTS: The peak distribution of IgA1 hinge glycopeptides clearly shifted to lesser molecular weights in both glomerular and serum IgA1 in IgAN compared with the serum IgA1 of controls. In the five major peaks of IgA1 hinge glycopeptides in each sample, the numbers of carbohydrates composing O-glycans (GalNAc, Gal, and NANA) in the deposited and serum IgA1 in IgAN patients were significantly fewer than those in the serum IgA1 in the control groups. CONCLUSION: The O-glycan side chains in the hinge of the glomerular IgA1 were highly underglycosylated in IgAN. These results indicate that the decreased sialylation and galactosylation of the IgA1 hinge glycopeptides play a crucial role in its glomerular deposition in IgAN.