Browsing by Author "Murray, Graeme"

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    Microbial ligand costimulation drives neutrophilic steroid-refractory asthma
    (Public Library of Science, 2015) Hadebe, Sabelo; Kirstein, Frank; Fierens, Kaat; Chen, Kong; Drummond, Rebecca A; Vautier, Simon; Sajaniemi, Sara; Murray, Graeme; Williams, David L; Redelinghuys, Pierre; Reinhart, Todd A; Junecko, Beth A Fallert; Kolls, Jay K; Lambrecht, Bart N; Brombacher, Frank; Brown, Gordon D
    Asthma is a heterogeneous disease whose etiology is poorly understood but is likely to involve innate responses to inhaled microbial components that are found in allergens. The influence of these components on pulmonary inflammation has been largely studied in the context of individual agonists, despite knowledge that they can have synergistic effects when used in combination. Here we have explored the effects of LPS and β-glucan, two commonly-encountered microbial agonists, on the pathogenesis of allergic and non-allergic respiratory responses to house dust mite allergen. Notably, sensitization with these microbial components in combination acted synergistically to promote robust neutrophilic inflammation, which involved both Dectin-1 and TLR-4. This pulmonary neutrophilic inflammation was corticosteroid-refractory, resembling that found in patients with severe asthma. Thus our results provide key new insights into how microbial components influence the development of respiratory pathology.
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    The role of scavenger receptor B1 in infection with Mycobacterium tuberculosis in a murine model
    (Public Library of Science, 2009) Schäfer, Georgia; Guler, Reto; Murray, Graeme; Brombacher, Frank; Brown, Gordon D
    BACKGROUND: The interaction between Mycobacterium tuberculosis (Mtb) and host cells is complex and far from being understood. The role of the different receptor(s) implicated in the recognition of Mtb in particular remains poorly defined, and those that have been found to have activity in vitro were subsequently shown to be redundant in vivo . Methods and FINDINGS: To identify novel receptors involved in the recognition of Mtb, we screened a macrophage cDNA library and identified scavenger receptor B class 1 (SR-B1) as a receptor for mycobacteria. SR-B1 has been well-described as a lipoprotein receptor which mediates both the selective uptake of cholesteryl esters and the efflux of cholesterol, and has also recently been implicated in the recognition of other pathogens. We show here that mycobacteria can bind directly to SR-B1 on transfected cells, and that this interaction could be inhibited in the presence of a specific antibody to SR-B1, serum or LDL. We define a variety of macrophage populations, including alveolar macrophages, that express this receptor, however, no differences in the recognition and response to mycobacteria were observed in macrophages isolated from SR-B1 −/− or wild type mice in vitro . Moreover, when wild type and SR-B1 −/− animals were infected with a low dose of Mtb (100 CFU/mouse) there were no alterations in survival, bacterial burdens, granuloma formation or cytokine production in the lung. However, significant reduction in the production of TNF, IFNγ, and IL10 were observed in SR-B1 −/− mice following infection with a high dose of Mtb (1000 CFU/mouse), which marginally affected the size of inflammatory foci but did not influence bacterial burdens. Deficiency of SR-B1 also had no effect on resistance to disease under conditions of varying dietary cholesterol. We did observe, however, that the presence of high levels of cholesterol in the diet significantly enhanced the bacterial burdens in the lung, but this was independent of SR-B1. CONCLUSION: SR-B1 is involved in mycobacterial recognition, but this receptor plays only a minor role in anti-mycobacterial immunity in vivo . Like many other receptors for these pathogens, the loss of SR-B1 can be functionally compensated for under normal conditions.