Asthma is a chronic inflammatory and obstructive condition affecting the airways. The disease is commonly associated with elevated blood eosinophils and tissue eosinophilia. Many aspects of the pathophysiological mechanisms and clinical symptoms are controlled by conventional therapies such as inhaled corticosteroids (ICS) and long acting β2 agonists. However, some patients remain clinically uncontrolled and need additional treatment such as direct targeting of eosinophil granulocytes by neutralizing the eosinophil-promoting cytokine interleukin 5 (IL5). Mepolizumab is a humanized monoclonal IL-5 neutralizing antibody that is used to treat patients with moderate-severe eosinophilic asthma. While a marked reduction of eosinophils is a key effect of mepolizumab, the exact mechanism of action is unknown. Apart from basophils, that also express the receptor for IL-5, other leukocytes are likely to be indirectly affected by the suppressed eosinophilia. In addition, it is largely unknown to what extent the few eosinophils remaining after anti-IL5 treatment differ from pre-treatment eosinophils.
The present study is a prospective observational asthma study that aims to use microscopic analysis to investigate the composition and subtypes of blood leukocytes collected before and after instantiated mepolizumab treatment. Comparisons are made to patients already on mepolizumab treatment, asthma patients without any biological treatment, and non-diseased control subjects.
