Immunoglobulin a suppresses B cell receptor-mediated activation of mouse B cells with differential inhibition of signaling molecules.

CONTEXT: We previously reported that monoclonal mouse immunoglobulin (Ig) A, OA-4, attenuates sensitization in mice by suppressing B cell activation. OBJECTIVE: Here, it is demonstrated for the first time that mouse IgA inhibits mouse B cell activation in vitro under natural conditions (i.e. in the absence of chemical, physical, and genetic modifications of IgA and B cells). MATERIALS AND METHODS: Mouse splenocytes were stimulated with anti-B cell receptor (BCR) antibody or lipopolysaccharide (LPS) in the presence or absence of OA-4. Splenic B cell proliferation and the activation of several intracellular signaling molecules were measured. RESULTS: Anti-BCR antibody-induced proliferation was markedly inhibited by OA-4 or the commercially available mouse IgA S107, whereas LPS-induced proliferation was weakly attenuated by a high concentration of OA-4. Moreover, OA-4 markedly decreased the anti-BCR antibody-induced phosphorylation of p44/42 mitogen-activated protein kinase (ERK) and CD22 and decreased phosphorylated phospholipase (PLC) γ2 and intracellular Ca2+ levels moderately, whereas protein kinase B (Akt) phosphorylation was not affected by OA-4. The MAPK/ERK kinase-ERK and phosphoinositide 3-kinase-Akt pathways were found to play a role in the proliferation of splenocytes induced by anti-BCR antibody based on experiments with their inhibitors. In contrast to that in splenic B cells, ERK phosphorylation induced by anti-BCR antibody in A20 cells was not inhibited by OA-4. The modulatory effects of IgA were different among the cell types and signaling pathways. CONCLUSION: IgA is a potential immunoregulatory drug utilizing new mechanisms that affect splenic B cells but not A20 lymphomas.

Characterization of fluorophores released from three kinds of lake phytoplankton using gel chromatography and fluorescence spectrophotometry.

Three kinds of phytoplankton were cultivated, and the contribution of dissolved organic matter (DOM) released from the phytoplankton was examined to clarify the cause of organic pollution of Lake Biwa. Microcystis aeruginosa, Staurastrum dorcidentiferum, and Cryptomonas ovata were evaluated with regard to cultivation. A significant peak (M(w): <3000 Da) was mainly detected in the algal DOM released from plankton during cultivation by gel chromatography with a fluorescence detector (E(x) = 340 nm, E(m) = 435 nm). Since this peak corresponds to a peak with lower molecular weight in three peaks detected in the surface water of Lake Biwa, it can be concluded that the algal DOM released from the plankton during cultivation makes a considerable contribution to the refractory organic matter in Lake Biwa. Three fluorescence maxima were observed in the cultivation of three kinds of phytoplankton: two fulvic-like fluorescence peaks (A and B) and a protein-like fluorescence peak (C). These peaks became larger as their cell counts of plankton increased. As for the fractionations of algal DOM using DAX-8, the ratio of hydrophilic DOM is fairly high in DOM produced by three kinds of phytoplankton. The order of the amount of algal DOM per cell volume during cultivation was Cryptomonas ovata > Microcystis aeruginosa > Staurastrum dorcidentiferum. These results suggest that the increase of the refractory organic matter in Lake Biwa may be attributed to a change of the predominant phytoplankton.

Characterization of dissolved organic matter released from Microcystis aeruginosa.

The contribution of dissolved organic matter (DOM) released from phytoplankton (Microcystis aeruginosa) during cultivation and biodegradation was examined to clarify the causes of the organic pollution of Lake Biwa. Two peaks, peak 2 (retention time (RT) = 32 min) and peak 3 (RT = 35 min), were detected in the algal DOM released from Microcystis aeruginosa during cultivation and biodegradation by gel chromatography with a fluorescence detector (Ex = 340 nm, Em = 435 nm). As these peaks correspond with the peaks detected in the surface water of Lake Biwa, one can conclude that the algal DOM released from Microcystis aeruginosa during cultivation and biodegradation makes a considerable contribution to the refractory organic matter in Lake Biwa. Three fluorescence maxima were observed in the cultivation of Microcystis aeruginosa: a fulvic-like fluorescence peak (peak A) with Ex/Em values of 320/430 nm, a protein-like fluorescence peak (peak C) with Ex/Em values of 280/360 nm, and another peak with Ex/Em values of 240/370 nm. The fluorescence material of peak C has a larger MW than that of peak A. The algal-derived DOM from Microcystis aeruginosa has similar fluorescence to fulvic acid of soil origin but exhibits mainly hydrophilic characteristics. In the biodegradation of Microcystis aeruginosa, a fulvic-like fluorescence peak (peak B) with Ex/Em values of 250/440 nm and a peak with Ex/Em values of 320/380 nm were observed.

Highly sensitive determination of a polymeric hindered amine light stabilizer in polypropylene by reactive thermal desorption-gas chromatography using nitrogen-specific detection.

Highly sensitive and specific determination of trace amounts of a polymeric hindered amine light stabilizer (HALS) in polypropylene (PP) materials could be established by improving reactive thermal desorption-gas chromatography (RTD-GC) in the presence of an organic alkali, tetramethylammonium hydroxide. By using nitrogen-phosphorus detection, highly selective detection of the HALS-related components was attained. In addition, the use of a polar poly(ethylene glycol) separation column alleviated the adsorption of minor specific pyrolysis products. This modified RTD-GC method allowed the determination of the polymeric HALS (Mr 1900) in PP even for trace concentrations between 100 and 500 ppm, through observing selectively the characteristic products containing a tetramethylpiperidine moiety, which had been impossible to detect under the previous RTD-GC conditions using a non-polar separation column and conventional flame ionization detection.