Background: Mast cells are known to play a role in the pathophysiology of asthma. Determining their contribution to the development of asthma symptoms has been difficult as they remain tissue-resident and do not usually migrate into the airway lumen for detection using expectorated sputum.
Objectives: We investigated the presence and activity of mast cells in the blood and sputum of healthy controls and patients with moderate to severe asthma and the relationship with clinical characteristics of asthma and their associated microenvironment.
Methods: Cell-free sputum supernatant was used to detect levels of soluble tryptase and T2 and non-T2 cytokines by ELISA. RNA/cDNA isolated from sputum cells measured expression levels of eosinophil and mast cell-specific genes by digital PCR. Relevant clinical characteristics and measurements of lung function, airway hyperresponsiveness, FeNO, blood eosinophils, IgE and tryptase were collected.
Results: Tryptase was detectable in the fluid phase portions of sputum, irrespective of the inflammation based on the differential cell count, and was significantly different than healthy controls. Eosinophil and mast cell-specific genes were detected in sputum cells at levels significantly different than healthy controls. Sputum tryptase was not associated with any phenotype or severity of asthma but identified some associations with clinical characteristics. It is associated with a unique cytokine signature.
Conclusion: Differences were seen between eosinophilic and non-eosinophilic phenotypes in sputum supernatant and sputum cells. Eosinophil and mast cell-specific genes were detected in sputum cells but were not associated with asthma severity. Greater levels of cytokines IL-4 and IL-13 in sputum, suggest presence of mast cells in the airway epithelium that contribute to mucus secretion observed in patients with uncontrolled symptoms of asthma. Further investigations hope to identify the relationship of mast cells with the quantification of mucus in these patients to understand and confirm those with a predominant mast cell component. / Thesis / Master of Science (MSc) / In patients with asthma, mast cells are one of the inflammatory cells normally associated with allergies however, they also function by non-allergic mechanisms (bacteria, viruses, fungus, pollutants). Inflammatory cells cause swelling of the bronchial tubes, tightening/spasm of the bronchial muscles, and mucus production. The level of inflammation is measured in lung fluids such as sputum, but the mast cell remains in the lung tissue and therefore difficult to detect. When mast cells are activated they release mediators such as tryptase, that travel through the lung tissue. Tryptase was detected in the sputum of patients with moderate to severe asthma, with levels significantly greater than in healthy people. The level of sputum tryptase was independent of other inflammatory cells such as eosinophils, and was associated with biomarkers related to excess secretion of mucus. Further research hopes to understand if the mucus is related to the activity of the mast cell.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/29093 |
| Date | January 2023 |
| Creators | Kjarsgaard, Melanie |
| Contributors | Nair, Parameswaran, Medical Sciences (Division of Physiology/Pharmacology) |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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