CHARACTERIZATION OF A MARKER FOR TRACHEAL BASAL CELLS

An IgM monoclonal antibody (1D9/B3) is characterized, which specifical ly recognizes basal cells of the upper airway epithelium. Although mor phological features have been used to follow cell lineage and differen tiation, an objective assessment of differentiation can be enhanced by characterizing the expression of specific antigens that form the phen otypic profile of specialized cells. Mice were immunized with rabbit t racheal basal cells that had been obtained by pronase digestion and pu rified into a subpopulation of basal cells by flow cytometry. Sh immun ization experiments produced five hybridomas specific to epithelial: c ells. A hybridoma whose supernatant immunocytochemically stained the b asal cell subpopulation of rabbit tracheal cells was selected. The ant ibody reacted with tracheal basal cells in rabbit, rat, sheep, pig, an d human tracheal sections, and in cultured monolayers of tracheal epit helial cells of the same species. The antibody did not react with the basal cells of other rabbit tissue, including the skin, or other rabbi t epithelia. Confocal microscopy and exposure of tracheal epithelial c ells to fluorescent-tagged monoclonal antibody 1D9/B3 prior to loading on to flow cytometry showed that the basal cell antibody recognized a n intracellular epitope. The epitope for the 1D9/B3 antibody was chara cterized by Western blotting. The 1D9/B3 antibody appears to be a dist inct and specific marker to the airway epithelial basal cell and will be useful in studies of airway epithelial differentiation, injury, and regeneration.