MMP9 and bronchiolitis: Our study investigated the influence of various serum inflammatory cytokines including Th1 cytokines (IL2, TNF-α), Th2 cytokines (IL4, IL5, and IL13), chemokine (MIP-1α), matrix metalloproteinases and their tissue inhibitors (TIMP-1 and MMP-9) and epithelial cell-drived cytokines (TSLP, IL25, and IL33), on the subsequent development of asthma after hospitalization for bronchiolitis in early life.