Targeting of the IL-5 pathway in severe asthma reduces mast cell progenitors

BACKGROUND: Therapies targeting IL-5 or its receptor (IL-5Rα) are currently used to treat patients with severe eosinophilic asthma. OBJECTIVE: We sought to investigate the impact of anti-IL-5 and anti-IL-5Rα biological therapies on mast cells (MCs) and their progenitors. METHODS: Surface IL-5Rα expression was investigated on MCs and their progenitors in mouse lungs and bone marrow and in human lungs and blood. Isolated human MC progenitors cultured in the presence or absence of IL-5 were analyzed in vitro. Circulating MC progenitors were quantified in patients with severe asthma before and after anti-IL-5 (mepolizumab) or anti-IL-5Rα (benralizumab) therapy. Gene expression analysis of MC progenitors was performed before and after anti-IL-5Rα therapy. RESULTS: 2 cells. Finally, the blood MC progenitors remaining after anti-IL-5Rα (benralizumab) treatment exhibited a downregulated expression of genes involved in growth and proliferation. CONCLUSIONS: This study introduces the possibility that the clinical effects of targeting IL-5/IL-5Rα in severe asthma may also involve reduction of MC populations.