DIAMINE OXIDASE-GOLD ULTRASTRUCTURAL-LOCALIZATION OF HISTAMINE IN HUMAN SKIN BIOPSIES CONTAINING MAST-CELLS STIMULATED TO DEGRANULATE IN-VIVO BY EXPOSURE TO RECOMBINANT HUMAN STEM-CELL FACTOR

Stem cell factor (SCF) has a major role in hematopoiesis and in the re gulation of mast cell development and function. For example, recombina nt human SCF (rhSCF) can induce the development of human mast cells fr om precursor cells in vitro, stimulate mediator release from human ski n mast cells in vitro, and promote both the development and functional activation of human skin mast cells in vivo. In the present study, we used a new ultrastructural enzyme-affinity method, employing diamine oxidase (DAO)-conjugated gold particles (DAO-gold), to detect histamin e in skin biopsies obtained from patients with breast carcinomas who w ere receiving daily subcutaneous (SC) injections of rhSCF in a phase I study of this cytokine. We examined control biopsies obtained at site s remote from rhSCF injection as well as biopsies of rhSCF-injected sk in that were obtained within 2 hours and 30 minutes of the SC injectio n of rhSCF at that site. The rhSCF-injected sites (which clinically ex hibited a wheal-and-flare response), but not the control sites, contai ned mast cells undergoing regulated secretion by granule extrusion. Th e DAO-gold-affinity method detected histamine in electron-dense granul es of mast cells in control and injected skin biopsies; however, the a ltered matrix of membrane-free, extruded mast cell granules was largel y unreactive with DAO-gold. Notably, DAO-gold bound strongly to fibrin deposits and collagen fibers that were adjacent to degranulated mast cells. These findings represent the first morphologic evidence of hist amine secretion by classical granule exocytosis in human mast cells in vivo. (C) 1997 by The American Society of Hematology.