Secretory IgA as a measure of immunocompetence

The field of psychoimmunology has rapidly expanded in recent years and various parameters of the immune system have been examined in relation to psychological factors. The secretory immune system is one of the more interesting aspects of the entire immune system because it protects mucosal membranes from invading organisms. Stress-produced changes in secretory immunoglobulin A (s-IgA) as measured by radial immunodiffusion assays have been reported in several studies. We present three reasons why total s-IgA protein, the measure derived from radial immunodiffusion assays, may not be a reasonable measure of immune system functioning, and we suggest an alternative method for examining secretory IgA that focuses on s-IgA antibody response to a novel antigen.     

Some Properties of Secretory IgA Purified from Bovine Colostrum

The major component of a purified sample of secretory IgA (SIgA) in colostrum was revealed as a single peak on gel filtration with Sepharose 6B, having an estimated molecular weight of 540,000. The existence of a higher molecular weight component was suggested by a small shoulder on the ascending limb of the peak, but another component of IgA reported as IgA lacking the secretory component (SC) could not be found. When the purified SIgA was concentrated by dialysis against polyethylene glycol, its molecular size was apparently significantly decreased.

Analysis by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) showed that all SC in SIgA binds covalently. The band corresponding to the J chain was easily detected when a reduced and alkylated sample was analysed. Estimation of the molecular weight by SDS-PAGE gave the following values for each of the constituent polypeptide chains of bovine colostral SIgA: SC, 76,000; H chain, 62,000; L chain, 23,000; and J chain, 18,000. The molecular weight of the whole molecule was calculated to be 434,000.

Analysis of carbohydrates by gas-liquid chromatography showed 6.8% neutral and amino hexoses, consisting of 0.4% fucose, 1.8% mannose, 1.1% galactose and 3.5% glucosamine. Galactosamine, which has been found in bovine free secretory component from milk, could not be detected.     

Chromatographic Separation and Purification of Secretory IgA from Human Milk

Defatted and decaseinated human milk was concentrated and was fractionated on a preparative DEAE cellulose column. Elution with various concentrations of sodium chloride in Tris-HCl buffer (pH 8.0, 0.01 M) resulted in fractions that were rich in either secretory immunoglobulin A (SIgA) (0.1 M Nad) or free secretory component (SC) (0.05 M NaCl). The fractions, which were eluted with 0.10 M NaCl from the preparative column, were further fractionated on a G-200 Sephadex column. Repeated fractionation on this column resulted in a single purified fraction, which contained very high SIgA activity and showed immunological cross-reaction with both SC and serum IgA. Additional studies indicated that this fraction was homogeneous as shown by immunoprecipitin and disc gel electrophoresis. Injection of this purified SIgA into rabbits resulted in the production of monospecific antiscil.     

Isolation and Characterization of Proteins Associated with the Lung Surfactant System

Rabbit lung washings and purified lung surfactant were delipidated without precipitation or loss of protein. This enabled effective study of the proteins by electrophoretic and immunoelectrophoretlc techniques. The lung washings contained secretory immunoglobulin A and several serum proteins. The protein composition of purified lung surfactant was the same as the unfractionated lung washings confirming our previous study which indicated that there is no specific protein associated with surfactant phospholipids obtained by alveolar lavage with isotonic saline.     

Secretory IgA is a component of rabbit lung surfactant

Secretory IgA is a major protein component of rabbit lung surfactant purified by NaBr density gradient centrifugation from endobronchial lavage and minced lung tissue. Secretory IgA was found in both surfactant and non-surfactant fractions obtained from endobronchial lung washings. By contrast in minced-lung washings, which are not contaminated with proteins from the upper respiratory tree, secretory IgA is prominent only in the surfactant fraction. These findings indicate that in rabbit lung secretory IgA is present in the alveoli and is intimately associated with the surfactant system.     

Secretory IgA specific for Toxoplasma gondii

Secretory IgA specific for Toxoplasma gondii was identified in intestinal secretions of mice infected perorally with bradyzoites (encysted in brain) of the Me49 strain of T. gondii by using immunofluorescence microscopy and an ELISA. This activity was absorbed with tachyzoites of T. gondii but not mouse brain. To determine whether increased total amount of intestinal IgA might cause a nonspecific reaction in the ELISA for T. gondii-specific IgA, mice were immunized perorally with cholera toxin. This immunization produced intestinal IgA antibody to cholera toxin and increased the total amount of intestinal IgA, but there was no reactivity of intestinal secretions in the ELISA for T. gondii-specific IgA. Experiments in which ELISA were performed with monoclonal IgA, IgG, or IgM and antisera to IgA, IgG, or IgM demonstrated that the ELISA was specific for each Ig class. In addition, monoclonal IgA competed with the anti-Toxoplasma IgA activity of intestinal secretions obtained from mice infected with T. gondii.     

Secretory IgA in Urinary Tract Infections

Secretory IgA, measured by radial immunodiffusion, was compared in the urine of children with chronic and recurrent non-obstructive urinary tract infections with that in normal children. IgA, IgG, and IgM were also measured. Absent and low levels of IgA(s) were found in both groups; however, the mean levels of IgA(s) were significantly higher in the infected group compared with normals—3·3 to 0·78 mg./24 hours, respectively. Secretory IgA was found to be locally produced in the bladder. It is suggested that IgA(s) levels reflect an antibody response to infection.     

ISOLATION AND PROPERTIES OF SECRETORY GRANULES FROM RAT ISLETS OF LANGERHANS : I. Isolation of a Secretory Granule Fraction

A method has been devised for the isolation of a secretory granule fraction from isolated rat islets of Langerhans. The islets were homogenized in buffered sucrose, and the homogenate was separated into nuclear, mitochondrial, secretory granule, and microsomal fractions by differential centrifugation. The secretory granule fraction was purified by differential centrifugation in discontinuous sucrose density gradients. A greater degree of purification could be achieved by the use of two successive gradients of this type, although the final yield was greatly reduced. Biochemical and morphological characterization of the fractions was obtained; the secretory granule fraction contained both insulin and glucagon. The limiting membranes of the granules remained intact and the general appearance of the granules was similar to that seen within the whole islet cells.     

Isolation of the Chromocenter Fraction from Mouse Liver Nuclei

A new method for isolation of the constitutive heterochromatin (chromocenters) from interphase nuclei of mouse liver has been developed. This method allows separation of chromocenters of different size. Chromocenter fractions are essentially free of nucleoli and other contaminants. In contrast to nuclei and nucleoli, the chromocenter fraction is characterized by simpler protein composition, this fraction having a reduced number of proteins (especially high molecular weight proteins). Chromocenters contain all histone fractions; however, the relative proportion of histone H1 is lower and histone H3 is higher than in the total nuclear chromatin. The amount of non-histone proteins of 51, 63, 73, and 180 kD is higher in the chromocenter fraction than in nuclei and nucleoli. The use of immunocytochemistry and immunoblotting methods revealed the presence of the specific kinetochore component, CENP A protein. This suggests tight association of some molecular kinetochore components with chromocenters in the interphase.     

Isolation and Characterization of a Cytokinin-Binding Protein from the Water-Soluble Fraction of Tobacco Leaves

Cytokinin-binding protein (CBPI) was purified from the watersoluble fraction of tobacco leaves by successive chromatographyon benzyladenine-linked (BA-linked) Sepharose 4B, TSK-Gel G3000SWXL,t-zeatin-linked Sepharose 6B and TSK-Gel G3000SWXL. CBPI wasobtained as a monomer with a molecular weight of 31 kDa. Ithas one cytokinin-binding site, which shows a high affinityfor BA (Kd=1.1x10^–7 M) and other cytokinins. Biologicallyactive cytokinins competed with BA for binding to this protein,while biologically inactive analogues of adenine did not. Inall cases, cytokinin-binding activity was assayed by equilibriumdialysis. ¹ Present address: National Institute for Basic Biology, Okazaki,444 Japan.     

Isolation and Characterization of a Novel Noncoding RNA from Nickel-Induced Lung Cancer

Noncoding RNAs have drawn significant attention in carcinogenesis. In this study, we identified a novel gene named nickel-related gene1 (NRG1) associated with nickel-induced cancer. By using rapid amplification of cDNA end PCR, we obtained the full length of the cDNA. The sequence was analyzed by using related bioinformatics software and comparative genomics methods. The results showed that NRG1 was located on chromosome 2q12, within intron2 of ADAMTS6, a disintegrin and metalloproteinase with thrombospondin motifs. And, NRG1 had a high level of homology (76?%) to rat LINE1 sequence RL1.3 (long interspersed middle repetitive DNA). What's more, there was no continuous open reading frame present in NRG1 sequence. Taken together, these data demonstrate that NRG1 is a novel noncoding RNA, and we predicted it may be a transposon-like gene. The identification of NRG1 emphasized the potential role of noncoding RNA in nickel carcinogenesis.     

Electron Transport Systems of Nitrosomonas: Isolation of a Membrane-Envelope Fraction

Freezing and thawing of Nitrosomonas, followed by centrifugation of the homogenate at 3,000 x g, resulted in a fraction which appeared to consist of an intact membrane-envelope complex and contained approximately 50% of the cell protein and more than 90% of the ubiquinone and cytochrome A-type mammalian cytochrome c oxidase activity. The supernatant fraction, resulting from subsequent centrifugation of the extract at 100,000 x g, contained approximately 50% of the cell protein and more than 80% of the B- and C-type cytochrome and P-463 and the enzymes glutamate dehydrogenase; hydroxylamine dehydrogenase; nitrite synthetase; nitrite reductase; and 2,6-dichlorophenolindophenol-, p-phenylenediamine-, pyrogallol-, and hydroquinone-oxidase. Data on the concentration of electron transport components in Nitrosomonas are presented.     

从狗肺中分离到流行性出血热病毒

1984—1985年,从安徽省EHF疫区收集78只狗肺,用IFAT检测,5只EHF抗原阳性,阳性率为6.4％,并从EHF抗原阳性的狗肺中分离到两株EHFV,从而首次证明狗可自然感染EHFV。狗有捕食鼠类的习性,与人接触密切,其传播EHF的作用需要进一步研究。