IL4 and chronic obstructive pulmonary disease: ST2/IL-1AcP signaling leads to the expression of type 2 cytokines (e.g., IL-5, IL-13, and IL-4), which are responsible for the activation of protective type 2 inflammatory responses during infection and tissue repair, as well as detrimental allergic responses, chronic obstructive pulmonary disease (COPD), and fibrosis [21, 22] (Fig. 2).