MUC5AC and asthma: Previous research has shown that mucins are more abundant in the sputum of adults with asthma than in healthy control subjects,9 with MUC5AC predominating.13, 20 Mucin degradation in acute asthma has been shown to be inhibited in a protease-dependent manner,15 and tethering of MUC5AC to goblet cells impairs mucociliary clearance in asthma.14