Airway mucus consists of various proteins such as long mucins MUC5AC and MUC5B, both of which contribute greatly to the proper gel-like consistency of this most essential bodily fluid. UNC School of Medicine researchers led by mucin expert Mehmet Kesimer, Ph.D., had previously discovered that the total mucin concentrations in the lungs are associated with COPD disease progression and could be used as diagnostic markers of chronic bronchitis, a hallmark condition for patients with COPD. Kesimer and colleagues now report that one of these mucins, MUC5AC, is more closely and reliably associated with the development of COPD than is its brother, MUC5B.