CHARACTERIZATION OF A MARKER OF DIFFERENTIATION FOR TRACHEAL CILIATEDCELLS INDEPENDENT OF CILIATION

Although morphologic features have been used to follow cell lineage an d differentiation, an objective assessment of differentiation can be b est established by characterizing the expression of specific proteins that form the phenotypic profile of differentiated cells. Thus, specif ic markers or probes are required to unequivocally identify the variou s types of cells resulting from differentiation in a cell lineage. We report characterization of an IgM monoclonal antibody (5B4/H3), which recognized a surface antigen of approximately 130 kD unique to ciliate d cells. The antibody reacted with the lumenal surface of the ciliated cells in transmission electron micrographs, in immunohistochemical st aining of tracheal sections, and in cultured monolayers of tracheal ep ithelial cells. Flow cytometry, performed on enzymatically dispersed t racheal epithelial cells tagged with 5B4/H3 and fluorescent-labeled go at anti-mouse IgA/IgG/IgM, produced a population of fluorescent ciliat ed cells and a mixed nonfluorescent, nonciliated cell population. Cili ated cells were followed in vitro by time-lapse video microscopy for 4 8 to 72 h. Some of the ciliated cells lost their cilia under these cul ture conditions, but these cells were still found to react with the 5B 4/H3 antibody. The antigen detected by this antibody remained on the s urface of the cells after they lost their cilia. These results indicat e that 5B4/H3 recognized a cell surface antigen that is specific to th e ciliated cells and is independent of cell morphology. This marker wi ll be useful in tissue culture studies of airway epithelial lineage, o r differentiation, in which cell morphology is variable and cannot be used as a reliable marker of differentiation.