Objective Cystic fibrosis (CF) is a genetic condition that causes abnormal mucus secretions in affected organs. MUC5AC and MUC5B are gel-forming mucins and frequent targets for investigations in CF tissues. Our objective was to qualify MUC5AC and MUC5B immunohistochemical techniques to provide a useful tool to identify, localize and interpret mucin expression in ferret tissues. Results MUC5AC and MUC5B mucins were detected most commonly in large airways and least in small airways, consistent with reported goblet cell density in airway surface epithelia. We evaluated whether staining method affected the detection of goblet cell mucins in serial sections of bronchial surface epithelia. Significant differences between stains were not observed suggesting common co-expression MUC5AC and MUC5B proteins in goblet cells of airway surface epithelia. Gallbladder and stomach tissues are reported to have differential mucin enrichment, so we tested these tissues in wildtype ferrets. Stomach tissues were enriched in MUC5AC and gallbladder tissues enriched in MUC5B, mucin enrichment similar to human tissues. Mucin immunostaining techniques were further qualified for specificity using lung tissue from recently generated MUC5AC −/− and MUC5B −/− ferrets. Qualified techniques for MUC5AC and MUC5B immunohistochemistry will be useful tools for mucin tissue studies in CF and other ferret models.

Objective Inflammation is present in many diseases and identification of immune cell infiltration is a common assessment. CD138 (syndecan-1) is a recommended immunohistochemical marker for human plasmacytes although it is also expressed in various epithelia and tumors. Similarly, CD138 is a marker for murine plasmacytes, but its tissue immunostaining is not well-defined. Endogenous CD138 expression is an important confounding factor when evaluating plasmacyte infiltration. We studied two plasmacyte markers (CD138 and Kappa light chains) for endogenous immunostaining in five organs and one tumor from B6 mice. Results Plasmacytes in Peyer's patches were positive for CD138 and Kappa markers without endogenous immunostaining. Endogenous CD138 immunostaining was widespread in liver, kidney, lung and a malignant peripheral nerve sheath tumor (MPNST) versus regionalized immunostaining in skin and small intestine wall. Endogenous Kappa immunostaining was absent in all tissues except for plasmacytes. Tissues with widespread endogenous CD138 immunostaining were contrasted by absence of endogenous Kappa immunostaining. Here, plasmacytes would not be distinguished by CD138, but would be obvious by Kappa immunostaining. Our study suggests that utility of immunostaining for plasmacytes by CD138 is tissue dependent in mice. Additionally, Kappa immunostaining may be a useful alternative in mouse tissues with confounding endogenous CD138 immunostaining.