Ultrastructural analysis of mucin granules isolated from goblet cells of well-differentiated NHBE cells in culture. Primary antibody incubations were followed by 12 nm gold-labeled secondary antibody. Gold appears as black dots indicating the presence of the primary antibody. A) Mucin granule membranes (arrows) near a magnetic dynal bead (B); B) hCLCA1 localized to mucin granule membranes as demonstrated by gold-labeled immunostaining; C) positive control: gold-labeled pan mucin antibody (17Q2) shows the presence of mucin within the granules; D) Rabbit IgG negative control; E) Mouse IgG negative control. Magnification is at 40Kx.