Anti-IL-5 (mepolizumab) therapy reduces eosinophil activation ex vivo and increases IL-5 and IL-5 receptor levels

Anti-IL-5 therapy induces a dramatic and sustained decrease in blood eosinophilia (including CCR3+ cells), decreased eosinophil activation, and increased circulating levels of IL-5 in a variety of eosinophilic disorders. Increased levels of IL-5 receptor α and lymphocyte IL-5 production after anti-IL-5 therapy suggest an endogenous IL-5 autoregulatory pathway.