Circulating mast cell progenitors correlate with reduced lung function in allergic asthma

Background Studies using mouse models have revealed that mast cell progenitors are recruited from the blood circulation to the lung during acute allergic airway inflammation. The discovery of a corresponding human mast cell progenitor population in the blood has enabled to study the relation of circulating mast cell progenitors in clinical settings. Objectives To explore the possible association between the frequency of mast cell progenitors in the blood circulation and allergic asthma, we assessed the relation of this recently identified cell population with asthma outcomes and inflammatory mediators in allergic asthmatic patients and controls. Methods Blood samples were obtained, and spirometry was performed on 38 well‐controlled allergic asthmatic patients and 29 controls. The frequency of blood mast cell progenitors, total serum IgE and 180 inflammation‐ and immune‐related plasma proteins were quantified. Results Allergic asthmatic patients and controls had a similar mean frequency of blood mast cell progenitors, but the frequency was higher in allergic asthmatic patients with reduced FEV1 and PEF (% of predicted) as well as in women. The level of fibroblast growth factor 21 (FGF‐21) correlated positively with the frequency of mast cell progenitors, independent of age and gender, and negatively with lung function. The expression of FcεRI on mast cell progenitors was higher in allergic asthmatic patients and correlated positively with the level of total IgE in the controls but not in the asthmatic patients. Conclusion Elevated levels of circulating mast cell progenitors are related to reduced lung function, female gender and high levels of FGF‐21 in young adults with allergic asthma