IMMUNOHISTOCHEMICAL DETECTION OF HUMAN BASOPHILS IN LATE-PHASE SKIN REACTIONS

Background: Human basophils are difficult to detect with classic histo chemical stains at sites of allergic inflammation. The 2D7 anti-basoph il monoclonal antibody was used to identify basophils in skin during t he late-phase response to a cutaneous allergen challenge. Methods: The 2D7 monoclonal antibody was used on protease-digested sections of ski n biopsy specimens obtained 6 and 24 hours after an allergen or buffer challenge. The skin chamber technique was used to compare buffer- and allergen-challenged sites at 6 hours, and intradermal injection of al lergen was used to compare allergen-challenged sites at 6 and 24 hours . Results: Dramatic increases in the numbers of 2D7(+) cells and in ti ssue staining by 2D7 were observed Ci hours after allergen challenge c ompared with buffer challenge. Histamine levels in skin chamber fluid varied with 2D7(+) cell concentrations. By 24 hours, 2D7(+) cells and tissue staining appeared to diminish but were still detectable in tile allergen-challenged sites. Basophils localized primarily in and aroun d blood vessels, whereas mast cells remained mostly in the superficial dermis. Mast cells were 2D7(-) in both the allergen and buffer-challe nged skin. Metachromatic staining of 2D7(+) basophils with toluidine b lue was absent in these tissue sections. Conclusions: Tile 2D7 monoclo nal antibody provides a mole sensitive and precise marker than histoch emical staining for human basophil involvement during the late-phase r esponse to an allergen challenge. Basophil infiltration was observed a l: 6 tours only after allergen challenge and persisted at similar leve ls by 24 hours.