Altered miR-155 Expression in Allergic Asthmatic Airways.

We and others have previously identified microRNAs (miRNAs) with pathological roles in animal models of asthma, where miR-146a and miR-155 have been described to play important roles in inflammatory responses. To date, few studies have investigated miRNA expression in human asthmatics. In the current study, significantly lower levels of miR-155 were detected in cell-free sputum from allergic asthmatics compared to healthy controls. Induced sputum isolated from allergic asthmatics in and out of pollen season revealed that miR-155 expression, but not miR-146a, is reduced in lymphocytes in season compared to post-season. In contrast, miR-155 was found to increase, whereas miR-146a decreased in PBMCs and cell-free PBMC culture media upon T cell receptor stimulation via αCD3/CD28 in both allergic asthmatics and healthy controls. Our findings suggest that miR-155 is differentially expressed ex vivo in airways of allergic asthmatics compared to healthy controls, which may have implications in the local immune response in allergic asthma.