IL33 and asthma: In this study, we have characterized the activated macrophages in an experimental acute exacerbation of chronic asthma and shown that they have a phenotype that includes features of alternative activation; provided evidence that expression of IL-33 in the airways is enhanced in an acute exacerbation and that IL-33 can promote expression of proinflammatory cytokines by macrophages; and demonstrated that inhibition of IL-33 reduces the distal airway inflammation which characterizes an acute exacerbation of asthma.