It is increasingly recognized that many patients with severe asthma have neutrophilic or mixed granulocytic inflammation of the lower airways [25, 37–40] and thus, the potential to act on both eosinophils and neutrophils by targeting the IL-5/IL-5R axis has exciting treatment potential for both asthma and other chronic lung diseases such as COPD [41]. This evidence concerns the gene IL5RA and asthma.