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Title: Lipopolysaccharide of different bacteria : extraction methods, signalling and cytokine production
Author: Al-Hawi, Mohammad Abdullah Mubarak
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2007
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Different LPS extraction methods were utilized to investigate the differences between them in terms of producing proinflammatory immune response. A further application of a repurification method was to eliminate any possible protein contaminants. These purified LPS preparations were used for the other main approach this study in which different unpurified and repurified Bacteroides fragilis LPSs together with different heat killed B. fragilis populations were examined to elucidate their Toll-like receptor (TLR) specificity. Four different extraction methods were chosen to extract LPS from Escherichia coli O18K-, Pseudomonas aeruginosa Pa-O1, B. fragilis NCTC 9343 and Rhodobacter sphaeroides NCIMB 8253. All of these species, except of R. sphaeroides, were able to simulate the production of proinflammatory cytokines TNF-α and IL-1β with differences apparent between different LPS preparations according to their extraction methods. R. sphaeroides LPS was able to inhibit the ability of these LPSs to induce TNF-α production except for B. fragilis LPS which was not effected by R. sphaeroides LPS. All different B. fragilis LPSs showed the ability to exert an antagonist effect on different E. coli on production of TNF-α or IL-1β from both human monocytes and THP-1 cell lines, which indicated that there was not such a profound effect of the extraction method in totally changing the bioactivity of specific LPS. Moreover, unpurified or purified LPSs of B. fragilis on the one hand and heat killed bacteria of B. fragilis from different capsular polysaccharide populations on the other hand all showed an obvious TLR2 signalling specificity but not TLR4 specificity. This adds further evidence that different LPS extraction methods with or without applying a repurification procedure do not change the TLR specificity of the B. fragilis LPS.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available