Natural killer cell levels increased in COPD sputum
MedWire News: Levels of natural killer (NK) cells and NKT-like cells are higher and more cytotoxic in sputum from chronic obstructive pulmonary disease (COPD) patients than in sputum from “healthy” smokers and nonsmokers, UK researchers have found.
“Inflammation of the airways is present in COPD with increased numbers of inflammatory cells from both the innate and adaptive host response,” explain Lucy Fairclough (University of Nottingham) and team.
They add: “Many of these cells have the potential to cause the damage seen in the airways of patients with COPD, including three main heterogeneous and functionally distinct classes of human killer cells; namely CD8+ T lymphocytes, CD56+CD3- NK cells and CD56+CD3+ NKT-like cells.”
To investigate whether levels of these cells are increased in the airways of COPD patients, the researchers studied sputum samples collected from 11 participants with COPD who had a smoking history of at least 20 pack-years, an FEV1 below 80% of the predicted value, 10 healthy smokers without airway obstruction, and five healthy nonsmokers.
There were no significant differences among the groups regarding age, or between the COPD patients and healthy smokers regarding smoking history.
Flow cytometry revealed that sputum levels of NK cells and NKT-like cells were significantly higher in COPD patients (12.7% and 3.0%, respectively) than in healthy smokers (5.7% and 1.0%, respectively) and nonsmokers (4.2% and 0.8%, respectively).
The proportion of NK and NKT-like cells expressing the cytolytic protein perforin and the serine protease granzyme B were also significantly higher in COPD patients than healthy smokers and nonsmokers.
Using a lactate dehydrogenase-release assay, the researchers found that NK and NKT-like cells in sputum from COPD patients were significantly more cytotoxic than those in sputum from healthy smokers and nonsmokers.
Fairclough and team conclude in the journal Respiratory Research: “Here we report for the first time that NK cells (CD56+CD3-) and NKT-like cells (CD56+CD3+) from the induced sputum of COPD subjects are increased in both number and proportion and have a higher cytotoxic ability compared to healthy nonsmokers and smokers.”
They add that further research is needed to investigate whether these cells play a part in the pathogenesis of the disease or are a consequence of the underlying lung pathology.
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By Mark Cowen