IL13 and asthma: In addition, stimulation of BCi-NS1.1 cells during ALI culture with IL-13, a cytokine known to play an important role in the pathology of asthma and COPD in vivo, resulted in alteration of the normal differentiation response with stimulated cells displaying increased secretory cell differentiation, and a corresponding decrease in Clara and ciliated cell differentiation consistent with previous studies using cultures of primary normal bronchial epithelial cells [53,55,56].