Effect of inhaled interleukin‐5 on eosinophil progenitors in the bronchi and bone marrow of asthmatic and non‐asthmatic volunteers

Abstract

Inhaled IL-5 modulated eosinophil progenitor numbers in both the airways and bone marrow of asthmatics and induced local eosinophilia in non-asthmatics.

Increased numbers of activated group 2 innate lymphoid cells in the airways of patients with severe asthma and persistent airway eosinophilia

“…46,47 It has been shown that numbers of IL-5-responsive EoPs are higher in the blood of patients with allergic asthma compared with healthy control subjects 44 and that these cells are increased within the airways after allergen or IL-5 challenge in patients with atopic asthma, where the increase in EoP precedes the development of airway eosinophilia. 42,48,49 Consistent with these findings, the current study demonstrated that EoP numbers are increased in the blood and airways of patients with severe compared with mild asthma. That bone marrow-derived progenitors can differentiate locally is inferred by findings that CD34 1 cells extracted from mucosal tissue undergo IL-5-stimulated proliferation and differentiation into eosinophil colonies in vitro.…”

Importance of Cytokines in Murine Allergic Airway Disease and Human Asthma

“…Consistent with this and with mouse studies, inhalation of recombinant human IL-4 induced AHR and sputum eosinophilic within 24 hours (234). Inhalation of recombinant human IL-5 by Chinese mild asthmatic subjects was also reported to induce AHR and airway eosinophilia in one study (235); however, these observations were not reproduced in a two studies in which British mild asthmatic subjects inhaled the same or a larger dose of recombinant human IL-5 from the same source (236, 237). …”

Tissue-Based and Bronchoalveolar Lavage–Based Biomarkers in Asthma

“…The reasons for these differences are not clear. 15 IL-5 has also been shown to increase in BAL fluid after segmental allergen challenge, but the IL-5 receptor seems to be shed from eosinophils found in BAL fluid, suggesting that eosinophils may become less responsive to IL-5 over time/with maturation. 16,17 Because IL-5 is believed to be produced primarily by lymphocytes, evaluating IL-5 protein in tissue is difficult.…”