While the majority of patients react to steady inhaled glucocorticoid (steroid) therapy, some are steroid resistant. Inflammation of the airway and activation of the immune system plays a significant part in Severe Asthma. Present asthma therapy guidelines have thus concentrated on the anti-inflammatory therapy use, mainly inhaled glucocorticoids (GCs). By airway inflammation reduction and immune activation, glucocorticoids are used to treat asthma. However, patients with steroid resistant asthma have advanced levels of airways immune activation than patients with steroid sensitive (SS) asthma.

Moreover, eosinophilia (eosinophil granulocytes in high concentration in the blood) or T cell activation found in steroid resistant asthmatics is not reduced by glucocorticoids. This persistent immune activation is related with immune system molecules IL-2 (interleukin 2), IL-4 and IL-5 in high levels in the airways of these patients.