title: Identification of endogenous peroxidase-containing cells as eosinophils in the gastrointestinal system.
abstract: Endogenous peroxidase (EPX) activity in certain cells in the gastrointestinal system interferes with immunohistochemical methods based on the horseradish peroxidase-catalyzed substrate deposition. We studied the distribution and characteristics of these cells. We also report an effective and antigen-preserving EPX blocking method, to make possible the evaluation of immunoperoxidase stainings in cryostat sections. The EPX-containing cells (EPX cells) are present in every part of the gastrointestinal tract, predominantly in the tunica propria. We identified them as eosinophil cells in May-Grünwald-Giemsa stained sections. The complete match was confirmed by different fluorescence techniques. Firstly, the EPX cells were labeled by a red fluorochrome-conjugated substrate of peroxidase enzymes, rhodamine-tyramide, whereas the eosinophil cells were labeled by the green fluorochrome, l-hydroxy-3,6,8-pyrenetrisulfonic acid, which is known to label exclusively eosinophilic granules at pH 10. Secondly, all the EPX cells reacted with a monoclonal antibody against the eosinophil peroxidase enzyme. Finally, a set of commercially available leukocyte markers was used to characterize the EPX cells colabeled by fluorochrome-tyramides. Neither macrophages nor mast cells showed EPX activity. Increased numbers and altered distribution were seen in stressed rats and in ulcerated human stomach.
authors.affiliation: Laboratory of Cell Biology, National Institute of Mental Health, National Institute of Health, Bethesda, MD 20892, USA. bela@codon.nih.gov
authors.forename: B
authors.initials: B
authors.lastname: Hunyady
authors.forename: E
authors.initials: E
authors.lastname: Mezey
authors.forename: K
authors.initials: K
authors.lastname: Pacak
authors.forename: M
authors.initials: M
authors.lastname: Palkovits
mesh_terms: D000818:Animals; D004064:Digestive System / Q000166:cytology / Q000201:enzymology*; D004804:Eosinophils / Q000201:enzymology*; D006801:Humans; D008264:Macrophages / Q000201:enzymology; D008297:Male; D010544:Peroxidases / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical; D013276:Stomach Ulcer / Q000201:enzymology; D014018:Tissue Distribution
chemical_list: D010544:Peroxidases