Exacerbations of chronic obstructive pulmonary disease (COPD) are an increasing cause of hospitalisations and are associated with accelerated progression of airflow obstruction. Approximately half of COPD exacerbations are associated with bacteria and many patients have lower airways colonisation. This suggests that bacterial infection in COPD could be due to reduced pathogen removal. This study investigated whether bacterial clearance by macrophages is defective in COPD.Phagocytosis of fluorescently labelled polystyrene beads and Haemophillus influenzae and Streptococcus pneumoniae by alveolar macrophages and monocyte-derived macrophages (MDM) was assessed by fluorimetry and flow cytometry. Receptor expression was measured by flow cytometry.Alveolar macrophages and MDM phagocytosed polystyrene beads similarly. There was no difference in phagocytosis of beads by MDM from COPD patients compared with cells from smokers and nonsmokers. MDM from COPD patients showed reduced phagocytic responses to S. pneumoniae and H. influenzae compared with nonsmokers and smokers. This was not associated with alterations in cell surface receptor expression of toll-like receptor (TLR)2, TLR4, macrophage receptor with collagenous structure, cluster of differentiation (CD)163, CD36 or mannose receptor. Budesonide, formoterol or azithromycin did not suppress phagocytosis suggesting that reduced responses in COPD MDM were not due to medications.COPD macrophage innate responses are suppressed and may lead to bacterial colonisation and increased exacerbation frequency.

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Cell-wall mechanical properties play an integral part in the growth and form of Saccharomyces cerevisiae. In contrast to the tremendous knowledge on the genetics of S. cerevisiae, almost nothing is known about its mechanical properties. We have developed a micromanipulation technique to measure the force required to burst single cells and have recently established a mathematical model to extract the mechanical properties of the cell wall from such data. Here we determine the average surface modulus of the S. cerevisiae cell wall to be 11.1 ؎ 0.6 N͞m and 12.9 ؎ 0.7 N͞m in exponential and stationary phases, respectively, giving corresponding Young's moduli of 112 ؎ 6 MPa and 107 ؎ 6 MPa. This result demonstrates that yeast cell populations strengthen as they enter stationary phase by increasing wall thickness and hence the surface modulus, without altering the average elastic properties of the cell-wall material. We also determined the average breaking strain of the cell wall to be 82% ؎ 3% in exponential phase and 80% ؎ 3% in stationary phase. This finding provides a failure criterion that can be used to predict when applied stresses (e.g., because of fluid flow) will lead to wall rupture. This work analyzes yeast compression experiments in different growth phases by using engineering methodology.