Mast cells are effector cells known to contribute to allergic airway disease. When activated, mast cells release a broad spectrum of inflammatory mediators, including the mast cell-specific protease carboxypeptidase A3 (CPA3). The expression of CPA3 in the airway epithelium and lumen of asthma patients has been associated with a Th2-driven airway inflammation. However, the role of CPA3 in asthma is unclear and therefore, the aim of this study was to investigate the impact of CPA3 for the development and severity of allergic airway inflammation using knockout mice with a deletion in the Cpa3 gene. We used the ovalbumin (OVA)- and house-dust mite (HDM) induced murine asthma models, and monitored development of allergic airway inflammation. In the OVA model, mice were sensitized with OVA intraperitoneally at seven time points and challenged intranasally (i.n.) with OVA three times. HDM-treated mice were challenged i.n. twice weekly for three weeks. Both asthma protocols resulted in elevated airway hyperresponsiveness, increased number of eosinophils in bronchoalveolar lavage fluid, increased peribronchial mast cell degranulation, goblet cell hyperplasia, thickening of airway smooth muscle layer, increased expression of IL-33 and increased production of allergen-specific IgE in allergen-exposed mice as compared to mocktreated mice. However, increased number of peribronchial mast cells was only seen in the HDM asthma model. The asthma-like responses in Cpa3^-/- mice were similar as in wild type mice, regardless of the asthma protocol used. Our results demonstrated that the absence of a functional Cpa3 gene had no effect on several symptoms of asthma in two different mouse models. This suggest that CPA3 is dispensable for development of allergic airway inflammation in acute models of asthma in mice.

Background: Mast cells (MCs) develop from a rare population of peripheral blood circulating MC progenitors (MCps). Here, we investigated whether the frequency of circulating MCps is altered in asthma patients sensitized to birch pollen during pollen season, compared to out of season.Methods: Asthma patients were examined during birch pollen season in late April to early June (May), and out of season in November–January. Spirometry measurements, asthma and allergy‐related symptoms, asthma control questionnaire (ACQ), and asthma control test (ACT) scores were assessed at both time points. The MCp frequency was determined by flow cytometry in ficoll‐separated blood samples from patients with positive birch pollen‐specific IgE, and analyzed in relation to basic and disease parameters.Results: The frequency of MCps per liter of blood was higher in May than in November (p = .004), particularly in women (p = .009). Patients that reported moderate to severe asthma symptoms (<.0001), nose or eye symptoms (p = .02; p = .01), or reduced asthma control (higher ACQ, p = .01) had higher MCp frequency in May than those that did not report this. These associations remained significant after adjusting for sex and BMI. The change in asthma control to a lower ACT score in May correlated with an increase in MCp frequency in May (p = .006, rho = 0.46).Conclusions: The data suggest that the frequency of MCps increases in symptomatic patients with allergic asthma. Our results unravel a link between asthma symptoms and circulating MCps, and bring new insight into the impact of natural allergen exposure on the expansion of MCs.

Asthma is a chronic inflammatory airway disease and a serious health problem in horses as well as in humans. In humans and mice, mast cells (MCs) are known to be directly involved in asthma pathology and subtypes of MCs accumulate in different lung and airway compartments. The role and phenotype of MCs in equine asthma has not been well documented, although an accumulation of MCs in bronchoalveolar lavage fluid (BALF) is frequently seen. To characterize the phenotype of airway MCs in equine asthma we here developed a protocol, based on MACS Tyto sorting, resulting in the isolation of 92.9% pure MCs from horse BALF. We then used quantitative transcriptome analyses to determine the gene expression profile of the purified MCs compared with total BALF cells. We found that the MCs exhibited a protease profile typical for the classical mucosal MC subtype, as demonstrated by the expression of tryptase (TPSB2) alone, with no expression of chymase (CMA1) or carboxypeptidase A3 (CPA3). Moreover, the expression of genes involved in antigen presentation and complement activation strongly implicates an inflammatory role for these MCs. This study provides a first insight into the phenotype of equine MCs in BALF and their potential role in the airways of asthmatic horses.

Sensitization to shrimp and house dust mites in a Swedish population-based study: Influence on allergic disorders and lung functionIda Waern1, Magnus Molin2, Robert Movérare2,3, Jonas Lidholm2, Andrei Malinovschi4, Magnus P. Borres2,5, Christer Janson3.1Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden2Thermo Fisher Scientific, Uppsala, Sweden3Department of Medical Sciences: Respiratory, Allergy and Sleep Research, Uppsala University, Uppsala, Sweden4Department of Medical Sciences: Clinical Physiology, Uppsala University, Uppsala, Sweden5Department of Maternal and Child Health, Uppsala University, Uppsala, Sweden