Increase of Peripheral Blood B Cells with Fc Receptor for IgA in Patients with IgA Nephropathy

A B-cell subset with Fc receptors for IgA (B alpha cells) has been observed in human peripheral blood. To investigate aberrations of B cells in a diseased state, the percentages of B alpha cells were enumerated in peripheral blood from patients with IgA nephropathy, which is characterized by preponderant deposition of IgA-dominant immune complexes in the glomerular mesangial area. The present study showed a significant increase in B alpha cells in peripheral blood from patients with IgA nephropathy but not in those with chronic proliferative glomerulonephritis without mesangial IgA deposition. Most Fc alpha R-bearing cells were observed in surface IgA bearing lymphocytes. No linear correlation was observed between the levels of serum IgA and the percentages of B alpha cells. The addition of aggregated IgA to cultures did not induce Fc alpha R-bearing B cells in vitro. It is postulated that B alpha cells might have some pathogenetic role in the development of IgA nephropathy and that some antigenic stimuli might play a role in the increase of peripheral blood B alpha cells in patients with IgA nephropathy.     

Regulatory B Cells and Mechanisms

Regulatory B cells have gained prominence in their role as modulators of the immune response against tumors, infectious diseases, and autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis, among others. The concept of regulatory B cells has been strongly associated with interleukin (IL)-10 production; however, there is growing evidence that supports the existence of other regulatory mechanisms, such as the production of transforming growth factor β (TGF-β), induced cell death of effector T cells, and the induction of CD4⁺CD25^?Foxp3⁺ regulatory T cells. The regulatory function of B cells has been associated with the presence and activation of molecules such as CD40, CD19, CD1d, and BCR. Alterations in signaling by any of these pathways leads to a marked defect in regulatory B cells and to increased clinical symptoms and proinflammatory signs, both in murine models and in autoimmune diseases in humans. B cells mainly exert their regulatory effect through the inhibition of proliferation and production of proinflammatory mediators, such as TNF-α, IFN-γ, and IL-17 by CD4⁺ T cells. A better understanding of how regulatory B cells function will offer new perspectives with regard to the treatment of various human diseases.     

Type 1 Regulatory T Cells and Regulatory B Cells Induced by Tolerogenic Dendritic Cells

Dendritic cells (DC) are professional antigen‐presenting cells that are capable of both activating immune responses and inducing tolerance. Several studies have revealed efficiency of therapeutic vaccination with tolerogenic DC (tolDC) in inhibition of experimental autoimmunity. The purpose of this study was to compare four different protocols for generation of tolDC – the antidiabetic drug troglitazone (TGZ DC), NF‐κB inhibitor BAY 11‐7082 (BAY DC), prostaglandin D2 metabolite 15d‐PGJ₂ (PGJ DC) and a combination of dexamethasone and 1α,25‐dihydroxyvitamin D3 (DexVD3 DC) regarding phenotype, cytokine production and T cell stimulatory capacity. TGZ DC and BAY DC had a phenotype comparable to immature DC, while DexVD3 DC were more macrophage like. Analysis of cytokine production using cell culture supernatants from all DC populations revealed that DexVD3 DC were efficient producers of IL‐10 and produced less pro‐inflammatory cytokines. T cells primed with DexVD3 DC showed reduced proliferation, and further analyses of these T cells revealed that functionally effective type 1 regulatory T cells (Tr1) but not FoxP3⁺ Treg were induced. Furthermore, DexVD3 DC promoted the induction of regulatory B cells (Breg). Together, these results indicate that DexVD3 DC have the best potential to be used in a tolerogenic antigen‐presenting cell‐based immunotherapy setting.     

Therapy of IgA Nephropathy

IgA nephropathy is the commonest form of glomerulonephritis worldwide, and is one of the major causes of terminal renal failure in most industrialised countries. It is defined by the dominance of IgA mesangial deposits in immunofluorescence studies. Corticosteroid-sensitive nephrosis lipoides (minimal change disease) with IgA deposits and superimposed crescentic glomerulonephritis are to be differentiated from primary IgA nephropathy (Berger's disease). In the latter, clinical manifestations are dominated by synpharyngitic macroscopic haematuria and permanent proteinuria. Terminal renal failure occurs in about 25% of patients after 10 years or more. Heavy proteinuria, hypertension, altered renal function and severe histological lesions at diagnosis are markers of poor prognosis. Primary IgA nephropathy is thought to be related to mesangial deposition of polymeric IgA1-containing immune complexes, owing to altered B cell responses to exogenous and endogenous antigens, together with hyperactivity of T helper type 1 and type 2 cells, both favoured by a genetic background. The 2 compartments of the IgA system (medullary and mucosal) may participate in the pathogenesis of the disease. Modulation of gut-associated lymphoid tissue and immune tonsillectomy are current lines of research. Although impressive results were obtained with an oligoantigenic diet, it is somewhat impractical. Pharmacological modulation of the mucosal immune response seems more promising. There is no proof that phenytoin, a drug which reduces bone marrow IgA synthesis, is beneficial. Emerging data suggest the potential of immune intervention in severely proteinuric patients before sclerotic lesions have occurred, using azathioprine and intravenous immunoglobulins. The benefit of early corticosteroid therapy is still unknown in both adults and children, and the efficiency of alkylating agents is unproven. The search for bacterial foci in primary IgA nephropathy is mandatory, as appropriate treatment may have a protective effect on renal function and help to improve or stabilise some patients. Slowing the progression of renal failure by a combination of ACE inhibitors, fish oil and, possibly, antiplatelet drugs is a promising therapeutic approach.     

Induction of IgA against Haemophilus parainfluenzae Antigens in Tonsillar Mononuclear Cells from Patients with IgA Nephropathy

Much evidence suggests that IgA production in vivo and in vitro is enhanced in patients with IgA nephropathy (IgAN). We have demonstrated glomerular deposition of the outer membranes of Haemophilus parainfluenzae (HP) antigens (OMHP) and the presence of HP-specific IgA in the serum of patients with IgAN. In this study, we investigated the production of IgA and several cytokines by tonsillar mononuclear cells (TMC) from IgAN patients induced by stimulation with OMHP. The spontaneous production of total IgA and TGF-β by TMC from IgAN patients was higher than that by TMC from patients with chronic tonsillitis (CT) (P < 0.05). Stimulation with OMHP in vitro enhanced the production of HP-specific IgA by TMC from IgAN patients (P < 0.01), but not by TMC from CT patients. OMHP stimulation also enhanced the production of TGF-β and IL-10 by TMC from IgAN patients (P < 0.001). These results suggest that the infection of HP in the tonsil may be involved in the etiology of IgAN.     

Effect of Adhesion Molecule P-selectin and Dendritic Cells on Tubulointerstitial Lesions in IgA Nephropathy

It is well appreciated that tubulointerstitial lesions (TILs)associated with renal insufficiency are frequently observedin IgA nephropathy. TILs may be induced by cell mediat ed immune responses and are closely related to the progno sis of the disease […     

Functional Characterization of Human B Cells Carrying the Lymphocyte Large Sialoglycoprotein gpl50

Human B cell-enriched populations were prepared from buffy coats of healthy donors. By means of affinity chromatography, the B cells were separated into two fractions, one enriched in and the other depleted of cells expressing gp150, the large sialoglycoprotein of lymphocytes. In the presence of autologous T cells, monocytes and pokeweed mitogen B cell populations enriched for gp150+ cells gave rise to significantly more plasma cells (cIg+ cells) and secreted significantly more IgG than gp150-depleted populations. In contrast, more or an equal amount of IgM was secreted in cultures containing gp150-depleted cells. The differences between the fractions could not be ascribed to uneven distribution of T3+ cells, OKM1+ cells or B1+ (CD20) cells. However, the gp150-enriched population contained significantly more B2+ (CD21) cells than the gp150-depleted population. These results suggest that the gp150+ B cells differ from gp150- B cells, not only in their responsiveness to T cell differentiation signals but also in their commitment to Ig heavy chain isotype secretion.     

Genetics and Immunopathogenesis of IgA Nephropathy

IgA nephropathy (IgAN) is the most common glomerulonephritis in the world. The hallmark of IgAN is underglycosylation in the hinge region of IgA1. Increasing evidence supports the underglycosylated IgA-containing immune-complex including IgG antibodies against the glycans of the hinge region of IgA1 are key factors for mesangial deposition and then trigger inflammation and glomerular injury. The polymeric IgA is produced after aberrant mucosal IgA response. The displacement of mucosal B cells to systemic lymphoid organs and bone marrow may arise from abnormal trafficking of lymphocytes along the mucosa–bone marrow axis involving changes of chemokines and adhesion molecules. This review will summarize the works on the genetics, the mucosal and systemic IgA immune response, mechanism of underglycosylation of IgA1, and the pathological effect of mesangial IgA deposition in IgAN.     

Study on HLA System in IgA Nephropathy

Forty Japanese patients with IgA nephropathy were typed for HLA-A and HLA-B using local antisera. Thirty-seven of these patients were typed for HLA-D using homozygous cells "En", now known to be strongly related to DRw6. Forty-six patients with chronic hemodialysis were used as patient controls for renal disease and 115 healthy individuals were used as normal controls. The frequency of HLA-DEn was significantly increased in 17 out of 37 patients with IgA nephropathy, (46%) (normal controls 18.3%) (P less than 0.0007). Although the occurrence of HLA-B12 was high, it was not significant, i.e. 11 out of 40 (27.5%). These results suggest that some abnormality in the genes of patients with IgA nephropathy is more closely associated with the HLA-D region than the HLA-A or B regions.     

Phagocytosis of IgA Immune Complexes by Human U937 Cells

Human promonocytic cell line U937 can express both IgAFc receptors ( FcαRⅠ, CD89 ) and IgG Fc receptors(FcαγⅠ, FcγRⅡ and FcγRⅢ)[1]. These receptors canmediate a variety of cell reactions including phagocytosis ofimmune complexes ( ICs ), degranulation, respiratorybursts, release of cytokines and enhancement of antibody dependent cell mediated cytotoxicity (ADCC) [2]. AfterIgA and IgG form ICs with their corresponding antigens,the ICs are bound by FcR on phagocyt…     

IgA肾病中IgA1异常糖基化的致病机制

IgA肾病是最常见的原发性肾小球疾病,是发展为终末期肾病的主要病因,其病理机制复杂,临床表现多样化,组织形态学改变轻重不一。IgA肾病以肾小球系膜区IgA1沉积为病理特征,肾脏沉积的IgA1分子铰链区O-糖链半乳糖基减少,致使IgA1分子易于自身聚集并沉积在肾小球。糖基化酶缺乏、基因突变、免疫紊乱都可能导致IgA1异常糖基化的发生。IgA1分子的异常糖基化是IgA肾病发病的关键因素,但其具体产生原因和致病机制仍未明确,对IgA1异常糖基化的深入研究有助于了解IgA肾病的发病机制并提供新的治疗方向。     

Smoking-Related Renal Histologic Injury in IgA Nephropathy Patients

Purpose

Smoking reportedly exerts deleterious effects on renal function; however, its effects on histology have not been clarified in patients with IgA nephropathy (IgAN).

Materials and Methods

Renal histology was evaluated in a cohort of 397 patients diagnosed with IgAN according to smoking status and dose in relation to renal function.

Results

Among the study cohort, which was predominantly male (88.5%), 52 patients (13%) were current smokers. These current smokers demonstrated more frequent hypertension and higher serum creatinine levels than non/ex-smokers at the time of diagnosis, which was apparent with increased smoking dose. The percentages of global glomerulosclerosis and arteriolar hyalinosis increased with increased smoking dose, whereas tubulointerstitial fibrosis or arterial intimal thickening did not. Glomerular mesangial alpha-smooth muscle actin expression were similar between current and non/ex-smokers matched for age, gender, hypertension, and histologic severity, although the number of glomerular CD68+ cells was significantly fewer in smokers. Initial serum creatinine level, estimated glomerular filtration rate (eGFR), and global glomerulosclerosis were found to be risk factors of serum creatinine doubling in both smokers and non/ex-smokers by univariate analysis during a mean follow-up of 3.8 years.

Conclusion

In addition to dose dependent renal functional decline and hypertension, smoking contributes to renal disease progression by eliciting microvascular injury in IgAN patients.