Figure 1.

Schematic representation of the potentially dichotomous role of inhaled corticosteroids (ICS) in the lower airway microbial host interphase in chronic obstructive pulmonary disease. On the left, ICS use reduces host susceptibility to microbes by reducing mucus secretion and bacterial nutrients, which can lead to a decrease in microbial burden and a more diverse microbiota. On the right, ICS affects the immune response with suppression of antimicrobial molecules, macrophage phagocytosis, and blunting IFN responses. These effects can collectively lead to the “blooming” of certain microbes within the lung microbiota (thus reducing diversity) and increase the risk of infection.