Abstract
An immunoperoxidase method has been developed for staining heparin in the granules of mast cells. The method employs human platelet factor 4 (or anti-heparin) and a rabbit antiserum to this polypeptide. Platelet factor 4 binds to mast cell heparin and provides the basis for immunoperoxidase staining using the rabbit antiserum. Preliminary studies of mast cells in various tissues indicate that the stain is quite specific for the content of mast cell granules, presumably heparin and possibly other glycosaminoglycans.