M1/MUC5AC mucin released by human airways in vitro

A series of monoclonal antibodies which bind to a mucin known as M1 (anti-M 1 MAbs) have also been shown to detect the product of the human gene MUC5AC . The aim of this investigation was to determine the concentration of the M 1 mucin in the surface epithelium of human bronchial preparations by means of immunohistochemistry and in the bronchial fluid derived from human airwa ys by means of an immunoradiometric assay. Human bronchial ring preparations from the resection material of 20 patient s were challenged with methacholine, leukotriene D-4, or anti-immunoglobuli n E. Experiments were performed In preparations with an intact epithelium a s web as in tissues in which the epithelium had been mechanically removed. The anti-Mi MAbs stained the goblet cells in the epithelium intensely and t here was also light and less uniform staining in the submucosa. The M1/MUC5 AC mucin in the fluids secreted by the bronchial preparations was not modif ied during either the experimental protocol or stimulation with the differe nt secretagogues. However in preparations in which the epithelium had been removed, there was a significant reduction in the amount of,M1/MUC5AC mucin detected. These data suggest that the M1/MUC5AC mucin detected in the biological flui ds produced by human airways in vitro may be released constantly, and princ ipally from the goblet cells in the epithelial layer.