Thus far, it seems that anti-IL-5 is most efficacious in patients with high blood eosinophil counts; however, it is possible that eosinophils’ plasticity and adaptability and their pleiotropic responses to the most disparate stimuli are at the basis of the relative impossibility, at least with the currently available drugs, to definitively “cure” from severe asthma. This evidence concerns the gene IL5 and asthma.