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Title: Characterisation of human pulmonary macrophage populations
Author: Chana, Kirandeep Kaur
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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In chronic obstructive pulmonary disease (COPD), alveolar macrophages increase in number, release more inflammatory mediators and respond poorly to glucocorticosteroids. Whether this is due to a change in macrophage phenotype or localised activation is unknown. It was hypothesised that different pulmonary macrophage phenotypes co-exist, maintaining lung homeostasis; however, in COPD these populations become skewed, driving pathophysiology. Macrophage populations were isolated from human lung tissue from non-smokers, smokers, and COPD patients using Percoll density gradients. Five populations were isolated at interfaces of each gradient (1.011-1.023; 1.023-1.036; 1.036-1.048; 1.048-1.061. 1.061-1.073 g/ml). The two least dense fractions were >90% apoptotic/necrotic, with remaining fractions >70% viable. COPD macrophages (1.036-1.048g/ml) were significantly less responsive to the glucocorticosteroid, budesonide, compared to those from non-smokers and smokers when stimulated with lipopolysacharride (LPS). Glucocorticosteroid insensitivity was selective for pro-inflammatory cytokines as budesonide inhibition of LPS-stimulated IL-10 release was similar from all macrophages. Macrophages of density 1.036-1.048g/ml from COPD subjects released higher levels of active MMP-9 compared with cells from non-smokers, with no difference between remaining fractions, suggesting this may be an alveolar macrophage population. Macrophages from non-smokers and smokers displayed receptor profiles akin to ‘alternative’ activation (CD163+, CD206+, CD14+, CD40-), whereas COPD macrophages were less defined showing significantly lower expression of all receptors investigated, with no differences associated with density. M-CSF cultured monocyte-derived macrophages (MDM) expressed higher levels of CD163 compared to cells differentiated in GM-CSF. COPD MDM showed lower expression of CD163 and CD206 compared to cells from non-smokers as observed with tissue macrophages. A population of HLA-DR+CD14-CD16- cells specific to COPD lung tissue were observed, and were also present in COPD MDM. Phenotyping macrophages via receptor profiling may not be sufficient when elucidating macrophage phenotypes based on cell maturation. However, identifying markers for the glucocorticosteroid-insensitive macrophage population from COPD subjects (1.036-1.048g/ml) may allow development of pharmacotherapies.
Supervisor: Donnelly, Louise Sponsor: Biotechnology and Biological Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available