MUC5AC and Airway obstruction: Consistent with this effect and known biological activities, increased expression of mRNA for Il6, Cxcl1, Cxcl2 was also observed.(52, 53) Additionally, Muc5ac RNA was induced, which can contribute to airway obstruction and hypersensitivity in asthma.(54–57) These responses are normal and occur in response to a variety of pathogens and other foreign materials entering the respiratory tract, including other forms of PM.