Comparisons of the intracellular distribution of multimerin, von Willebrand factor, P-selectin, and CD63. Paired, epifluorescent microscopic images of structures in the cytoplasm of double-immunolabeled, quiescent, permeabilized endothelial cells are shown. Primary antibodies included monoclonal (a, vWf; b and c, multimerin; d, CD63) and polyclonal antisera (a and c, P-selectin; b, vWf; d, multimerin). Single-labeled coverslips, processed in parallel, showed the same pattern of labeling. Identical granules were labeled by antibodies to P-selectin and von Willebrand factor, but multimerin was found in a different distribution than von Willebrand factor, P-selectin, and CD63 (N indicates cell nuclei). Cells labeled with polyclonal antimultimerin (d) showed more background labeling of nongranular structures than the cells labeled with monoclonal antimultimerin (b and c).