IL5 and asthma: An explanation for this finding is that the local generation of IL-5 within both upper and lower airways can result in higher circulating blood eosinophil levels, which are predictive biomarkers of a better response to Mepolizumab, suggesting that subjects with severe asthma, nasal polyps, and high blood eosinophils experience a better response to anti-IL-5 rather than to anti-IgE, irrespective of allergic status and IgE levels.