IL5 and Increased total eosinophil count: Increased membrane expression of the IL-5α receptor chain by eosinophils has been observed after treatment with anti-IL-5 (19), raising concern about a potentially enhanced response to endogenous IL-5 after treatment cessation, with rebound hypereosinophilia (i.e., posttreatment eosinophilia higher than baseline level), and/or eosinophil degranulation.