A room-temperature gas sensor based on 2D Ni-Co-Zn ternary oxide nanoflakes for selective and sensitive ammonia detection.

While most of the reports on NH3 gas sensors are either based on metal oxide composites with other 2D materials, polymers or noble metals or involve multi-step-based synthesis routes, this work is the first report on a pristine ternary metal oxide, 2D NiCo2ZnO4 nanoflake based room-temperature (RT) NH3 gas sensor. The 2D NiCo2ZnO4 nanoflakes were prepared by a one-step hydrothermal method. FESEM and TEM images displayed micro-flower like morphologies, containing vertically aligned interwoven porous 2D nanoflakes, whereas XPS and XRD data confirmed the successful growth of this ternary metal-oxide. This sensor revealed a good response, repeatability, linearity (R2 = 0.9976), a low detection limit of 3.024 ppb, and a response time of 74.84 s with excellent selectivity towards NH3 over six other VOCs. This improved performance of the sensor is ascribed to its large specific surface area (127.647 m2 g-1) resulting from the 2D nanoflake like structure, good electronic conductivity, variable valence states and abundant surface-active oxygen of NiCo2ZnO4. Thus, this highly selective 2D NiCo2ZnO4 based RT NH3 gas sensor can be an attractive solution for the fabrication of next-generation NH3 gas sensors.

The Determinants of B Cell Receptor Signaling as Prototype Molecular Biomarkers of Leukemia.

Advanced genome-wide association studies (GWAS) identified several transforming mutations in susceptible loci which are recognized as valuable prognostic markers in chronic lymphocytic leukemia (CLL) and B cell lymphoma (BCL). Alongside, robust genetic manipulations facilitated the generation of preclinical mouse models to validate mutations associated with poor prognosis and refractory B cell malignancies. Taken together, these studies identified new prognostic markers that could achieve characteristics of precision biomarkers for molecular diagnosis. On the contrary, the idea of augmented B cell antigen receptor (BCR) signaling as a transforming cue has somewhat receded despite the efficacy of Btk and Syk inhibitors. Recent studies from several research groups pointed out that acquired mutations in BCR components serve as faithful biomarkers, which become important for precision diagnostics and therapy, due to their relevant role in augmented BCR signaling and CLL pathogenesis. For example, we showed that expression of a single point mutated immunoglobulin light chain (LC) recombined through the variable gene segment IGLV3-21, named IGLV3-21R110, marks severe CLL cases. In this perspective, we summarize the molecular mechanisms fine-tuning B cell transformation, focusing on immunoglobulin point mutations and recurrent mutations in tumor suppressors. We present a stochastic model for gain-of-autonomous BCR signaling and subsequent neoplastic transformation. Of note, additional mutational analyses on immunoglobulin heavy chain (HC) derived from non-subset #2 CLL IGLV3-21R110 cases endorses our perspective. Altogether, we propose a model of malignant transformation in which the augmented BCR signaling creates a conducive platform for the appearance of transforming mutations.

Control of B Cell Responsiveness by Isotype and Structural Elements of the Antigen Receptor.

Expression of a functional B cell antigen receptor (BCR) plays a central role in regulating B cell development, maturation, and effector functions. Although IgM is solely expressed in immature B cell stages, the presence of both IgM- and IgD-BCR isotypes on mature naïve B cells raises the question of whether IgD has a unique role in B cell activation and function. While earlier studies suggested a broad functional redundancy between IgM and IgD, recent data point to an important immune regulatory role of IgD. Herein, we review these findings and discuss how the structural flexibility, mode of antigen binding, and co-receptor interactions, enable the IgD-BCR to act as a 'rheostat', regulating the activation and function of mature naïve B cells.

Survival of Igα-Deficient Mature B Cells Requires BAFF-R Function.

Expression of a functional BCR is essential for the development of mature B cells and has been invoked in the control of their maintenance. To test this maintenance function in a new experimental setting, we used the tamoxifen-inducible mb1-CreER(T2) mouse strain to delete or truncate either the mb-1 gene encoding the BCR signaling subunit Igα or the VDJ segment of the IgH (H chain [HC]). In this system, Cre-mediated deletion of the mb-1 gene is accompanied by expression of a GFP reporter. We found that, although the Igα-deficient mature B cells survive for >20 d in vivo, the HC-deficient or Igα tail-truncated B cell population is short-lived, with the HC-deficient cells displaying signs of an unfolded protein response. We also show that Igα-deficient B cells still respond to the prosurvival factor BAFF in culture and require BAFF-R signaling for their in vivo maintenance. These results suggest that, under certain conditions, the loss of the BCR can be tolerated by mature B cells for some time, whereas HC-deficient B cells, potentially generated by aberrant somatic mutations in the germinal center, are rapidly eliminated.

B cell antigen receptors of the IgM and IgD classes are clustered in different protein islands that are altered during B cell activation.

The B cell antigen receptors (BCRs) play an important role in the clonal selection of B cells and their differentiation into antibody-secreting plasma cells. Mature B cells have both immunoglobulin M (IgM) and IgD types of BCRs, which have identical antigen-binding sites and are both associated with the signaling subunits Igα and Igß, but differ in their membrane-bound heavy chain isoforms. By two-color direct stochastic optical reconstruction microscopy (dSTORM), we showed that IgM-BCRs and IgD-BCRs reside in the plasma membrane in different protein islands with average sizes of 150 and 240 nm, respectively. Upon B cell activation, the BCR protein islands became smaller and more dispersed such that the IgM-BCRs and IgD-BCRs were found in close proximity to each other. Moreover, specific stimulation of one class of BCR had minimal effects on the organization of the other. These conclusions were supported by the findings from two-marker transmission electron microscopy and proximity ligation assays. Together, these data provide evidence for a preformed multimeric organization of BCRs on the plasma membrane that is remodeled after B cell activation.

The nanoscale organization of the B lymphocyte membrane.

The fluid mosaic model of Singer and Nicolson correctly predicted that the plasma membrane (PM) forms a lipid bi-layer containing many integral trans-membrane proteins. This model also suggested that most of these proteins were randomly dispersed and freely diffusing moieties. Initially, this view of a dynamic and rather unorganized membrane was supported by early observations of the cell surfaces using the light microscope. However, recent studies on the PM below the diffraction limit of visible light (~250nm) revealed that, at nanoscale dimensions, membranes are highly organized and compartmentalized structures. Lymphocytes are particularly useful to study this nanoscale membrane organization because they grow as single cells and are not permanently engaged in cell:cell contacts within a tissue that can influence membrane organization. In this review, we describe the methods that can be used to better study the protein:protein interaction and nanoscale organization of lymphocyte membrane proteins, with a focus on the B cell antigen receptor (BCR). Furthermore, we discuss the factors that may generate and maintain these membrane structures.

Vitamin C prevents cigarette smoke induced atherosclerosis in guinea pig model.

AIM: Cigarette smoking is a major risk for developing atherosclerosis; however, the underlying mechanism is poorly understood. This paucity of knowledge is largely attributed to the lack of an animal model; therefore, our efforts were targeted towards establishing cigarette smoke (CS)-induced atherosclerosis in guinea pig. To understand the mechanism, we investigated apoptosis, an event implicated in atherosclerosis, in the aorta of CS-exposed animals. Since a major deleterious effect of CS is oxidative stress, we also examined the effect of vitamin C, an antioxidant, on CS- induced atherosclerosis. METHODS AND RESULTS: Guinea pigs on a diet with or without vitamin C supplement were exposed to CS for different time periods. Aortal sections from these animals were examined for atherosclerotic changes by staining with H&E and Oil red O. Atherogenic changes were observed in sections obtained from CS-exposed guinea pigs only. TUNEL assay showed the occurrence of apoptosis in CS-exposed guinea pig aorta. Our results revealed that CS-induced apoptosis could contribute to the progression but not to the initiation of the disease. Immunohistochemical analysis documents that CS-induced apoptosis in aortal sections is mediated at least in part by an increased Bax/Bcl2 ratio. In contrast, CS-exposed guinea pigs fed with vitamin C-supplemented diet exhibit little or no atherogenic changes. This anti-atherosclerotic activity of vitamin C can be attributed partly to its ability to inhibit CS-induced apoptosis and platelet activation. CONCLUSION: Exposure of guinea pigs to cigarette smoke causes the development of atherosclerosis, which can be prevented by vitamin C supplement.

cAMP stringently regulates human cathelicidin antimicrobial peptide expression in the mucosal epithelial cells by activating cAMP-response element-binding protein, AP-1, and inducible cAMP early repressor.

Little is known about the regulation of the innate host defense peptide cathelicidin at the mucosal surfaces. Expression is believed to be transcriptionally regulated, and several cis-acting elements have been identified in the cathelicidin putative promoter. However, the trans-acting factors have not been clearly defined. We have recently reported that bacterial exotoxins suppress cathelicidin expression in sodium butyrate-differentiated intestinal epithelial cells (ECs), and this may be mediated through inducible cAMP early repressor. Here we have shown that cAMP-signaling pathways transcriptionally regulate cathelicidin expression in various ECs. cAMP-response element-binding protein (CREB) and AP-1 (activator protein-1) bind to the cathelicidin putative promoter in vitro. Additionally, transcriptional complexes containing CREB, AP-1, and cathelicidin upstream regulatory sequences are formed within ECs. We have also shown that these complexes may activate cathelicidin promoter and are required for its inducible expression in ECs. This is underscored by the fact that silencing of CREB and AP-1 results in failure of ECs to up-regulate cathelicidin, and hepatitis B virus X protein may use CREB to induce cathelicidin. On the other hand, inducible cAMP early repressor competes with CREB and AP-1 for binding to the cathelicidin promoter and represses transcription, thus functioning as a counter-regulatory mechanism. Finally, both CREB and AP-1 were shown to play major roles in the regulation of cathelicidin in sodium butyrate-differentiated HT-29 cells. This is the first report of a detailed mechanistic study of inducible cathelicidin expression in the mucosal ECs. At the same time, it describes a novel immunomodulatory function of cAMP.