MUC6 and infection: Additionally, MUC6 O-glycan chains carry terminal N-Acetylglucosamine residues, which have been reported to have a protective role against pathogen infection and are synthesized by the enzyme α1,4-N-Acetylglucosaminyltransferase, specifically produced by glandular mucous cells, where it co-localizes with the expression of MUC6 (Figure 1aII) [35,36,37].