When antioxidants and Nrf2 activators were used to reduce oxidative stress and thereby PI3Kδ activity, the expression of HDAC2 was increased and the efficacy of GCs was improved in macrophages obtained from these patients [34], clearly indicating a role of HDAC2 in modulating GCI in patients with severe asthma and COPD. Here, HDAC2 is linked to chronic obstructive pulmonary disease.