MUC5AC and infection: The biomarkers of CF exacerbation include MUC5AB and MUC5AC degradation, due to increased sialyation during infection, as well increased serum/blood or BALF levels of granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-8, TNF-alpha, and neutrophil protein calprotectin, as compared to healthy subjects [2,4,37,39,44,45,63].