Salivary IgA concentration is influenced by the saliva collection method.

Measurement of salivary IgA is useful for the non-invasive assessment of secretory immunity, especially in children and infants. In our study, the influence of three commonly used methods ("spitting", "suction", "Salivette") of saliva collection on the yield of salivary IgA concentration was analysed in 54 samples of salivary secretion collected from six healthy children according to a cross over protocol. Nephelometrically determined IgA concentrations were significantly lower in saliva collected by the Salivette device (mean +/- SEM: 23 +/- 7 mg/l) than in saliva collected by the suction (46 +/- 8 mg/l) or spitting method (48 +/- 8 mg/l). Salivary flow assessed by the spitting method was inversely correlated with salivary IgA concentration. We conclude that salivary IgA assessment is influenced by the saliva collection method, and that studies dealing with this topic should accurately describe the methods used for collecting saliva so that data may be properly compared.     

609名中小学生唾液中IgA、IgG含量及相关因素分析

目的 了解中小学生唾液中免疫物质IgA、IgG含量水平,分析其相关影响因素.方法 采用分层整群抽样的方法于2010年10月-11月在吉林省靖宇、东辽两县随机抽取中小学生为研究对象进行问卷调查并收集唾液,共得有效问卷609张,应用固相夹心法酶联免疫吸附试验（ELISA）测定唾液中IgA、IgG含量,采用Excel 2010、SPSS13.0进行统计分析.结果 研究对象唾液中IgA、IgG平均含量分别为71.44（58.14,94.98）μg/ml、48.12（33.81,72.81）μg/ml;经多因素Logistic回归分析,年龄、家庭人均月收入、龋齿个数及每天锻炼时间等4方面因素与唾液中IgA的含量相关（P＜0.05）;年龄、母亲职业和文化程度、挑食或偏食情况、龋齿个数及每天锻炼时间等6方面因素与唾液中IgG含量相关（P＜0.05）.结论 研究对象唾液中IgA、IgG含量受年龄、母亲职业和文化程度、家庭人均月收入、龋齿个数及每天锻炼时间影响.     

IgA nephropathy

Summary Seventy-five biopsy samples from patients with chronic renal disorders were examined by the usual techniques of light microscopy and immunofluorescence; in fifteen patients IgA nephropathy was found. These patients were young adults; the onset of the disease was characterized by macrohematuria, and recurrent episodes of hematuria were observed. Histological examination revealed proliferative endothelio-mesangial glomerulonephritis at various stages of development with focal or diffuse patterns; immunofluorescence revealed constant and intense positive reactions for IgA mainly in association with C3. It is assumed that there is a relationship connecting the more advanced histological changes, a more severe clinical course and the presence of IgM deposits.     

血清IgA及IgA／C3比值在IgA肾病诊断中的价值

IgA肾病(IgA nephropathy,IgAN)是我国最常见的原发性肾小球肾炎,但至今其确切发病机制仍不明确.免疫反应和补体系统可能在IgAN的发生、发展中起重要作用,9%～70%的IgAN患者血清IgA升高[1],其血清C3水平是否下降仍有争议.     

IgA1-secreting cell lines from patients with IgA nephropathy produce aberrantly glycosylated IgA1

Aberrant glycosylation of IgA1 plays an essential role in the pathogenesis of IgA nephropathy. This abnormality is manifested by a deficiency of galactose in the hinge-region O-linked glycans of IgA1. Biosynthesis of these glycans occurs in a stepwise fashion beginning with the addition of N-acetylgalactosamine by the enzyme N-acetylgalactosaminyltransferase 2 and continuing with the addition of either galactose by beta1,3-galactosyltransferase or a terminal sialic acid by a N-acetylgalactosamine-specific alpha2,6-sialyltransferase. To identify the molecular basis for the aberrant IgA glycosylation, we established EBV-immortalized IgA1-producing cells from peripheral blood cells of patients with IgA nephropathy. The secreted IgA1 was mostly polymeric and had galactose-deficient O-linked glycans, characterized by a terminal or sialylated N-acetylgalactosamine. As controls, we showed that EBV-immortalized cells from patients with lupus nephritis and healthy individuals did not produce IgA with the defective galactosylation pattern. Analysis of the biosynthetic pathways in cloned EBV-immortalized cells from patients with IgA nephropathy indicated a decrease in beta1,3-galactosyltransferase activity and an increase in N-acetylgalactosamine-specific alpha2,6-sialyltransferase activity. Also, expression of beta1,3-galactosyltransferase was significantly lower, and that of N-acetylgalactosamine-specific alpha2,6-sialyltransferase was significantly higher than the expression of these genes in the control cells. Thus, our data suggest that premature sialylation likely contributes to the aberrant IgA1 glycosylation in IgA nephropathy and may represent a new therapeutic target.     

Increases of IgA milk concentrations correlate with IgA2 increment

IgA, IgA1, and IgA2 concentrations were determined in 81 defatted human milk samples: colostrum (days 1-5, n = 42), transitional milk (days 6-14, n = 18) and mature milk (days 15-75, n = 21) by immunonephelometry. Correlations were found between total IgA levels and the concentrations of both IgA subclasses (P < 0.0001). The levels of the three molecules decreased over lactation with significant differences (P < 0.05) between colostrum and transitional milk levels and between colostrum and mature milk. Colostral IgA1 and IgA2 mean concentrations dropped respectively from 10.89 +/- 2.12 g/L, and 15.41 +/- 2.10 g/L to 1.83 +/- 0.73 g/L and 3.40 +/- 1.25 g/L in transitional milk reaching finally to 0.36 +/- 0.07 g/L and 0.27 +/- 0.06 g/L in mature milk. IgA2 concentrations were higher than those of IgA1 when the total IgA level was high. The IgA2 levels in colostrum could be an adaptation resistance of IgA to potentially harmful pathogens able to secrete IgA proteases and also a way to regulate colonization of the microflora in the newborn.     

膜型IgA肾病

肾病是我国常见的肾小球疾病，病理类型很多，但膜型ＩｇＡ肾病极罕见。本文报告３例膜型ＩｇＡ肾病。病理特点是系膜增生的同时，肾小球毛细血管基底膜增厚，并有钉突形成。患者有大量蛋白尿。系膜区有大量ＩｇＡ沉积，毛细血管基底膜外侧有ＩｇＧ沉积。超微结构显示在系膜区及基底膜上皮细胞下均有电子致密物。本文通过免疫荧光和免疫电镜的研究认为，膜型ＩｇＡ肾病是膜型肾小球肾炎与系膜增生型ＩｇＡ肾病的相互重叠。     

Impairment of jacalin binding to serum IgA in IgA nephropathy

A test was set up to analyze the direct binding of serum IgA to the lectin jacalin. Under the testing conditions, jacalin bound to both IgA subclasses and reacted similarly with monomeric and polymeric IgA. A jacalin index was defined to quantify serum IgA binding to this lectin. The jacalin index appeared significantly lower in IgA nephropathy than in controls. This may be related to abnormal IgA glycosylation, which could explain, at least in part, the mesangial deposition responsible for the renal disease.     

Differential susceptibility of human IgA immunoglobulins to streptococcal IgA protease

IgA protease, a proteolytic enzyme found in human saliva and colonic fluid, hydrolyzes human serum IgA immunoglobulins to yield Fab(alpha) and Fc(alpha) fragments. The enzyme is produced by organisms in the normal human microflora and can be purified from culture filtrates of the common human oral organism Streptococcus sanguis (American Type Culture Collection no. 10556). IgA protease is inactive against all other protein substrates examined including the other classes of human immunoglobulins. The role of this enzyme in affecting the function of the secretory IgA immune system is unknown.To further characterize and explain this unusual substrate specificity, the susceptibility of 31 human IgA myeloma proteins of both subclasses was investigated. 16 IgA1 and 15 IgA2 myeloma paraproteins were treated with enzyme and the extent of proteolysis was determined by cellulose actate electrophoresis, immunoelectrophoresis, polyacrylamide gel electrophoresis, and column chromatography. All IgA1 proteins were enzymatically cleaved to Fab(alpha) and Fc(alpha) fragments, but all IgA2 proteins were resistant, yielding no fragments after prolonged enzymatic treatment. N-terminal amino acid sequence analysis of the purified Fc(alpha) fragment of a single IgA1 paraprotein was as follows: Thr-Pro-Ser-Pro-?-Thr-Pro-Pro-Thr-Pro-Ser-Pro-Ser. Comparison of this sequence to that reported for the IgA1 heavy chain shows that the enzyme-susceptible peptide bond is a Pro-Thr in the IgA1 hinge region. The most likely explanation of the resistance of the IgA2 subclass to IgA protease is a deletion in the heavy chain which commences with the critical threonine of the susceptible Pro-Thr bond.     

Mucosal IgA elaboration

Secretory IgA is the main immunoglobulin present along mucosal surfaces. It is elicited best by oral rather than parenteral administration of specific antigens. The role of antigen form on the development of a secretory IgA response is still unclear. IgA protects by preventing attachment of microorganisms or their toxic products to the surface epithelium. A wide variety of regulatory T cells are now known to be of considerable importance in optimizing the secretory IgA response. This regulation is at least partly due to the elaboration of small polypeptide products (lymphokines). These lymphokines have been shown to be key signals during the maturation of IgA precursor B cells to IgA-secreting plasma cells. By studying models of the mucosal immune system which closely approximate the natural mucosal immune response, it should be possible to develop vaccines against many pathogenic microorganisms, their toxic products, and to toxicants and carcinogens within the environment.     

Serum secretory IgA, IgA1 and IgA2 subclasses in inflammatory bowel and chronic liver diseases

Healthy controls and patients with autoimmune chronic active hepatitis (CAH), primary biliary cirrhosis (PBC), coeliac disease (GSE), Crohn's disease (CD) and ulcerative colitis (UC) were examined for serum immunoglobulin A (IgA), secretory IgA (sIgA) and subclasses IgA1 and IgA2 concentrations separately. Elevated secretory IgA levels are found in CAH and PBC. IgA2 level as well as the proportional part of IgA2 out of the serum total IgA are significantly increased in GSE and in CD, while in UC IgA1 levels are significantly decreased as compared to controls. Serial determinations of IgA subclasses may provide a differential diagnostic tool in inflammatory bowel diseases and the findings support the view that increased sIgA levels in CAH and PBC probably have a different origin.     

Experimental IgA nephropathy

An animal model for IgA immune complex nephritis was developed. IgA immune complexes formed in vitro with an IgA anti-dinitrophenyl (DNP) derived from MOPC-315 plasmacytoma, and dinitrophenylated bovine serum albumin (DNP-BSA) produced mild focal glomerulonephritis in mice. Similar, but more severe pathological changes were produced with complexes formed in vivo either in normal mice or MOPC-315 tumor-bearing mice. In contrast to the focal nature of the PAS-positive glomerular lesions observed by light microscopy, immunofluorescent examination revealed IgA deposits in all glomeruli. This discrepancy between immunofluorescent and histopathologic findings as well as the distribution of the immune complexes within the affected glomeruli, are some of the features which bear resemblance between this experimental model and human IgA nephropathy. Fixation of complements by DNP-BSA-IgA immune complexes, formed in vitro or in vivo, was shown to occur in the glomeruli of mice with IgA immune complex nephropathy. The pattern of C3 glomerular deposits was similar to that of IgA. However, complement proved to be nonessential for complex deposition. This conclusion is based on the observation that decomplemented mice, although showing no deposition of C3 in their glomerulus, developed glomerular immunohistological changes similar to those observed in experimental mice that were not decomplemented. Polymeric IgA was observed to be critical for renal deposition of complexes and induction of nephritic histological changes. In contrast, monomeric IgA immune complexes failed to produce glomerular deposits. This finding raises the possibility that secretory IgA, which is predominantly polymeric, may play a role in human IgA-associated glomerulonephritis.     

Serum IgG, IgM and IgA concentration determined by the "linear plate" immunodiffusion technique in a normal population

Using the “linear plate” immunodiffusion technique, the authors have determined the serum IgG, IgM and IgA levels in normal populations. The incidence of storage of the samples at ?20° for a prolonged time was investigated and also the influence of age on immunoglobulin levels in a normal population. The reference sera were obtained by mixing a great number of serum samples (four pools were obtained for each immuniglobulin) containing the protein at markedly different levels. The immunoglobulin concentration of each pool was determined by comparison with a calibration curve obtained with well weighted quantities of immunochemical pure human IgG or IgM or IgA powder. The frequency distribution of the immunoglobulin levels in the populations investigated was found to be of the log normal type. The mean levels (1275 mg/100 ml for IgG; 74 mg/100 ml for IgM and 208 mg/100 ml for IgA) fit very well with the data reported by most authors using other methods. The determination of the IgG level was not influenced by storage of the samples at ?20°. A decrease of IgM and IgA was, however, observed when sera were kept frozen for a period of 3 months.No significant variation was found between the IgG and IgM levels of the different age classes. For the IgA's, however, the authors found a slight but significant increase between 20 and 30 years. Between the older age classes the increase is slower and between 40 and 60 there is no longer a significant change.     

Transglutaminase is essential for IgA nephropathy development acting through IgA receptors

IgA nephropathy (IgAN) is a common cause of renal failure worldwide. Treatment is limited because of a complex pathogenesis, including unknown factors favoring IgA1 deposition in the glomerular mesangium. IgA receptor abnormalities are implicated, including circulating IgA-soluble CD89 (sCD89) complexes and overexpression of the mesangial IgA1 receptor, TfR1 (transferrin receptor 1). Herein, we show that although mice expressing both human IgA1 and CD89 displayed circulating and mesangial deposits of IgA1-sCD89 complexes resulting in kidney inflammation, hematuria, and proteinuria, mice expressing IgA1 only displayed endocapillary IgA1 deposition but neither mesangial injury nor kidney dysfunction. sCD89 injection into IgA1-expressing mouse recipients induced mesangial IgA1 deposits. sCD89 was also detected in patient and mouse mesangium. IgA1 deposition involved a direct binding of sCD89 to mesangial TfR1 resulting in TfR1 up-regulation. sCD89-TfR1 interaction induced mesangial surface expression of TGase2 (transglutaminase 2), which in turn up-regulated TfR1 expression. In the absence of TGase2, IgA1-sCD89 deposits were dramatically impaired. These data reveal a cooperation between IgA1, sCD89, TfR1, and TGase2 on mesangial cells needed for disease development. They demonstrate that TGase2 is responsible for a pathogenic amplification loop facilitating IgA1-sCD89 deposition and mesangial cell activation, thus identifying TGase2 as a target for therapeutic intervention in this disease.     

Significance of serum IgA levels and serum IgA/C3 ratio in diagnostic analysis of patients with IgA nephropathy

Diagnostic analysis of clinical markers including serum IgA levels and serum IgA/C3 ratio in patients with IgA nephropathy is described. One hundred patients with IgA nephropathy (IgA nephropathy group) and 100 patients with other primary glomerular diseases (non-IgA nephropathy group) were examined. The analysis was performed to distinguish between these two groups using four clinical markers: 1) more than five red blood cells in urinary sediments, 2) persistent proteinuria (urinary protein of more than 0.3 g/day), 3) serum IgA levels of more than 315 mg/dl, and 4) a serum IgA/C3 ratio of more than 3.01. Patients with three or four clinical markers were easily diagnosed as having IgA nephropathy in this study. Furthermore, there was a significant difference in these clinical markers between the good prognosis and relatively good prognosis groups (Groups I and II) and the relatively poor prognosis and poor prognosis groups (Groups III and IV) of IgA nephropathy patients. It appears that the presence of microscopic hematuria and/or persistent proteinuria, high serum IgA levels, and the serum IgA/C3 ratio are useful for distinguishing IgA nephropathy from other primary renal diseases. It is postulated that these clinical markers are also useful for diagnosis of IgA nephropathy without renal biopsy.