CD4+ T cell immunity to Salmonella is transient in the circulation

While Salmonella enterica is seen as an archetypal facultative intracellular bacterial pathogen where protection is mediated by CD4⁺ T cells, identifying circulating protective cells has proved very difficult, inhibiting steps to identify key antigen specificities. Exploiting a mouse model of vaccination, we show that the spleens of C57BL/6 mice vaccinated with live-attenuated Salmonella serovar Typhimurium (S. Typhimurium) strains carried a pool of IFN-γ⁺ CD4⁺ T cells that could adoptively transfer protection, but only transiently. Circulating Salmonella-reactive CD4⁺ T cells expressed the liver-homing chemokine receptor CXCR6, accumulated over time in the liver and assumed phenotypic characteristics associated with tissue-associated T cells. Liver memory CD4⁺ T cells showed TCR selection bias and their accumulation in the liver could be inhibited by blocking CXCL16. These data showed that the circulation of CD4⁺ T cells mediating immunity to Salmonella is limited to a brief window after which Salmonella-specific CD4⁺ T cells migrate to peripheral tissues. Our observations highlight the importance of triggering tissue-specific immunity against systemic infections.     

Randomised trial of endoscopy with testing for Helicobacter pylori compared with non-invasive H pylori testing alone in the management of dyspepsia

ObjectiveTo compare the efficacy of non-invasive testing for Helicobacter pylori with that of endoscopy (plus H pylori testing) in the management of patients referred for endoscopic investigation of upper gastrointestinal symptoms.DesignRandomised controlled trial with follow up at 12 months.SettingHospital gastroenterology unit.Participants708 patients aged under 55 referred for endoscopic investigation of dyspepsia, randomised to non-invasive breath test for H pylori or endoscopy plus H pylori testing.ResultsIn 586 patients followed up at 12 months the mean change in dyspepsia score was 4.8 in the non-invasive H pylori test group and 4.6 in the endoscopy group (95% confidence interval for difference –0.7 to 0.5, P=0.69). Only 8.2% of patients followed up who were randomised to breath test alone were referred for subsequent endoscopy. The use of non-endoscopic resources was similar in the two groups. Reassurance value, concern about missed pathology, overall patient satisfaction, and quality of life were similar in the two groups. The patients found the non-invasive breath test procedure less uncomfortable and distressing than endoscopy with or without sedation. No potentially serious pathology requiring treatment other than eradication of H pylori was missed.ConclusionIn this patient group, non-invasive testing for H pylori is as effective and safe as endoscopy and less uncomfortable and distressing for the patient. Non-invasive H pylori testing should be the preferred mode of investigation.

What is already known on this topic

Endoscopy is a commonly used investigation for upper gastrointestinal symptoms, but its effectiveness has been questionedNon-invasive testing for Helicobacter pylori has been shown to predict endoscopic diagnosis in patients with dyspepsia

What this study adds

In patients less than 55 years of age with uncomplicated dyspepsia, non-invasive testing for H pylori is as effective and as safe as endoscopyNon-invasive H pylori testing is as reassuring to the patient as endoscopy and is less uncomfortable and distressing     

A biosensor of protein foldedness identifies increased “holdase” activity of chaperones in the nucleus following increased cytosolic protein aggregation

Chaperones and other quality control machinery guard proteins from inappropriate aggregation, which is a hallmark of neurodegenerative diseases. However, how the systems that regulate the “foldedness” of the proteome remain buffered under stress conditions and in different cellular compartments remains incompletely understood. In this study, we applied a FRET-based strategy to explore how well quality control machinery protects against the misfolding and aggregation of “bait” biosensor proteins, made from the prokaryotic ribonuclease barnase, in the nucleus and cytosol of human embryonic kidney 293T cells. We found that those barnase biosensors were prone to misfolding, were less engaged by quality control machinery, and more prone to inappropriate aggregation in the nucleus as compared with the cytosol, and that these effects could be regulated by chaperone Hsp70-related machinery. Furthermore, aggregation of mutant huntingtin exon 1 protein (Httex1) in the cytosol appeared to outcompete and thus prevented the engagement of quality control machinery with the biosensor in the cytosol. This effect correlated with reduced levels of DNAJB1 and HSPA1A chaperones in the cell outside those sequestered to the aggregates, particularly in the nucleus. Unexpectedly, we found Httex1 aggregation also increased the apparent engagement of the barnase biosensor with quality control machinery in the nucleus suggesting an independent implementation of “holdase” activity of chaperones other than DNAJB1 and HSPA1A. Collectively, these results suggest that proteostasis stress can trigger a rebalancing of chaperone abundance in different subcellular compartments through a dynamic network involving different chaperone–client interactions.     

Modulation by phorbol myristate acetate of arachidonic acid release and leukotriene synthesis by human polymorphonuclear leukocytes stimulated with A23187

Phorbol myristate acetate augmented the release of 3H-AA and the synthesis of leukotriene B4 and 5-hydroxyeicosatetraenoic acid by human polymorphonuclear leukocytes stimulated by A23187. PMA alone had no effect. Enhancement of the response to A23187 was not seen when the inactive phorbol ester 4-alpha phorbol didecanoate was added with A23187. These data are consistent with the hypothesis that activation of protein kinase C enhances AA release and metabolism in stimulated polymorphonuclear leukocytes.     

An immune paradox: How can the same chemokine axis regulate both immune tolerance and activation?

Chemokines (chemotactic cytokines) drive and direct leukocyte traffic. New evidence suggests that the unusual CCR6/CCL20 chemokine receptor/ligand axis provides key homing signals for recently identified cells of the adaptive immune system, recruiting both pro-inflammatory and suppressive T cell subsets. Thus CCR6 and CCL20 have been recently implicated in various human pathologies, particularly in autoimmune disease. These studies have revealed that targeting CCR6/CCL20 can enhance or inhibit autoimmune disease depending on the cellular basis of pathogenesis and the cell subtype most affected through different CCR6/CCL20 manipulations. Here, we discuss the significance of this chemokine receptor/ligand axis in immune and inflammatory functions, consider the potential for targeting CCR6/CCL20 in human autoimmunity and propose that the shared evolutionary origins of pro-inflammatory and regulatory T cells may contribute to the reason why both immune activation and regulation might be controlled through the same chemokine pathway.     

Analysis of the platypus genome suggests a transposon origin for mammalian imprinting

Background  

Genomic imprinting is an epigenetic phenomenon that results in monoallelic gene expression. Many hypotheses have been advanced to explain why genomic imprinting evolved in mammals, but few have examined how it arose. The host defence hypothesis suggests that imprinting evolved from existing mechanisms within the cell that act to silence foreign DNA elements that insert into the genome. However, the changes to the mammalian genome that accompanied the evolution of imprinting have been hard to define due to the absence of large scale genomic resources between all extant classes. The recent release of the platypus genome has provided the first opportunity to perform comparisons between prototherian (monotreme; which appear to lack imprinting) and therian (marsupial and eutherian; which have imprinting) mammals.     

The limnology of a Thermal Lake: Lake Rotowhero,New Zealand: I. General description and water chemistry

The topography, morphology, hydrography, temperature conditions and water chemistry of an acid thermal lake, Lake Rotowhero. North Island, New Zealand, were studied and related to lake biology. Results are given for analyses of O₂, pH, conductivity, Ca, Mg, Na, K, SO₄, Cl, Si, total-P, reactive-P, NH₄-N, NO₃ N, NO₂-N As, Fe, Mn, Zn, Cu, total dissolved solids, chlorophyll and total pigment. Sediment mineralogy and total carbon content are mentioned.     

A sensitive magnetic bead method for the detection and identification of tyrosine phosphorylation in proteins by MALDI‐TOF/TOF MS

Phosphorylation is one of the most important PTMs and is estimated to occur on 30% of the mammalian proteome. Its perturbed regulation has been implicated in many pathologies. The rarity of phosphotyrosine compared with phosphoserine or phosphothreonine is prompting the development of more sensitive approaches because proteomic technologies that are currently used to assess tyrosine phosphorylation in proteins are inadequate, identifying only a fraction of the predicted tyrosine phosphoproteome. Here we describe the development of a reproducible, high‐sensitivity methodology for the detection and mapping of phosphotyrosine residues by MS. The anti‐phosphotyrosine antibody 4G10 was coupled covalently to super para‐magnetic beads or by affinity to super para‐magnetic beads with protein G covalently attached. Using this approach, we successfully enriched phosphotyrosine peptides mixed with non‐phosphorylated peptides at a ratio of up to 1:200, enabling detection at a level representing the highest sensitivity reported for tyrosine phosphorylation. The beads were subsequently used to enrich tyrosine phosphopeptides from a digest of the in vitro‐phosphorylated recombinant β‐intracellular region of the granulocyte‐macrophage colony‐stimulating factor receptor, which was subsequently analysed by MALDI‐TOF/TOF MS. Our results define this methodology as a sensitive approach for tyrosine phosphoproteome analysis.