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Title: Neutrophils in bacterial pneumonia : influx and clearance
Author: Lawson, Roderick A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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A rabbit model of pneumonia was used. Bacteria were instilled bronchoscopically into a localised area, allowing strict timing of pneumonia onset, and study of subsequent evolving processes. Two organisms were used: 1) Streptococcus pneumoniae, an organism characteristic of pneumonia CAP and; 2) Escherichia coli, an organism characteristic of NP. It was hypothesised that in pneumonia due to the former (PneuS), the usual remarkably complete recovery witnessed clinically is due to the tissue load of neutrophils being carefully controlled. By contrast, pneumonia due to the latter (PneuE), is clinically much more severe and lung-damaging, due to a larger lung neutrophil burden. Radiolabelled neutrophils from donor animals were injected at intervals after induction of pneumonia to assess the magnitude of ongoing neutrophil recruitment. In PneuS, neutrophil influx was significantly elevated above control levels at 6 hour but not 30 hour or subsequent time points. In PneuE, neutrophil influx was at least as high at 30 hours as at 6 hours. This confirms the hypothesis that neutrophil influx is more prolonged in PneuE than in PneuS. The animal model demonstrated that neutrophil influx was more prolonged in PneuE than in PneuS. It is suggested this contributes to the more severe clinical manifestations of the former. CD18 was important to the influx of neutrophils in PneuE late as well as early in the disease. Anti-IL-8 antibody failed to inhibit neutrophil influx in either type of pneumonia. Evidence that neutrophil apoptosis is involved in their clearance during pneumonia was obtained, together with evidence that a factor is released to promote neutrophil apoptosis and thus provide negative feedback control of inflammation during pneumonia. The control may differ in PneuS and PneuE, affecting outcome.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available