Regulatory T cell monitoring in severe eosinophilic asthma patients treated with mepolizumab

Severe eosinophilic asthma (SEA) has been associated with T‐helper type 2 (Th2) inflammatory response. A good understanding of T cell functions in asthma is important for therapy, especially in the choice of biological treatments for severe cases. Mepolizumab, an IL‐5 antagonist, is indicated for the treatment of severe asthma. Regulatory T cells (Tregs) suppress inflammation by secreting cytokines that inhibit Th2 cell proliferation. We investigated peripheral Treg, CD4, CD8, CD19 and NK cell percentages and their relationship to clinical and functional parameters, including peripheral eosinophils, before and after anti‐IL5 treatment. Subjects were 14 adult SEA patients (9 male, 54.1 ± 11.6 years), treated with mepolizumab, and 10 controls. T cells (CD4 and CD8), CD19, NK and Tregs were evaluated by flow cytometry. Comparison of lung function parameters before and after treatment with mepolizumab (T0 and T1) showed an increase in FEV1, FEV1/FVC ratio and a reduction in blood eosinophil percentages. CD8 and CD16/56+CD3+ were significantly higher in SEA patients than controls (P = .04 and P = .03, respectively). A decrease in CD45+, CD8 + and CD16/56+CD3+ cell percentages was observed between T0 and T1 (P = .02, P = .04, P = .03, respectively). A significant increase in Treg percentages (P = .0001) was recorded between T0 and T1. Mepolizumab therapy was found to modulate immune response, restoring immune balance in patients with SEA.