Cross-species immunoreactivity of airway mucin as revealed by monoclonal antibodies directed against mucins from human, hamster, and rat

Airway mucin plays crucial role in host-defense and has been implicated in pathophysiology of various airway diseases including asthma and cystic fibr osis. The analysis of airway mucin has been hampered mostly by the lack of specific and efficient methods for the detection of mucin. Recent productio n of antibodies against airway mucin from several species and also the deve lopment of immunoassay procedures make it more efficient to study the airwa y mucin. However, the cross-species immunoreactivity of antibodies against airway mucin has not been clearly demonstrated and this prompted us to inve stigate the cross-species immunoreactivity of monoclonal antibodies against human (HM02), hamster (HTA), and rat airway mucin (RT03), which is three m ost widely used species in the study of mucin. All the monoclonal antibodie s (MAbs) used in this study is IgM isotype and recognizes N-acetyl-galactos amine-linked carbohydrate core or backbone portion of airway mucin. In enzy me-linked immunoadsorbent assay (ELISA), Western blot, immunoprecipitation, and immunohistochemical staining experiments, it was demonstrated that hum an and hamster airway mucin showed strong cross-species immunoreactivity. H owever, rat airway mucin did not show any cross-species immunoreactivity ag ainst human and hamster airway mucin. Endotoxin-induced secretory cell meta plasia and hence the increase in mucin release from hamster airway mucin co uld be detected with antibodies against hamster and human airway mucin in v ivo and in vitro. However, the same increase from rat airway could only be detected with antibody against rat airway mucin but not with antibodies aga inst human and hamster airway mucin. In addition, the increase in mucin rel ease from asthmatic patients could be detected with antibodies against huma n and hamster airway mucin but not with the antibody against rat airway muc in. The data from the present study implicates that the carbohydrate chain of human and hamster airway mucin, but not that of rat airway mucin, share common antigenic structure. In case of the interspecies use of the antibodi es against airway mucin, it would be more desirable to clearly identify the cross-species immunoreactivity otherwise might lead to erroneous results.