Mouse bone marrow-derived mast cells differentiated in vitro and sensitized with monoclonal IgE respond to antigen-initiated activation with the release of histamine, β-hexosaminidase, chondroitin sulfate E proteoglycan, and leukotriene C 4 (LTC 4). The chondroitin sulfate E nature of the glycosaminoglycan side chain was established by demonstrating that the chondroitinase ABC disaccharide digestion products were composed of equal quantities of 4-sulfated and 4,6-disulfated N-acetyl-galactosamine. The single immunoreactive sulfidopeptide leukotriene, released and quantitated with a class-specific antibody, was identified as LTC 4 by its retention time on reverse-phase high-performance liquid chromatography and by its specific spasmogenic activity on the guinea pig ileum. The release of the preformed mediators, as well as of LTC 4, was related in a dose-response fashion to the concentration of monoclonal IgE used during the sensitization step and to the concentration of specific antigen used to initiate the activation-secretion response. The optimal concentrations of IgE for sensitization and of antigen for challenge were the same for the release of preformed mediators and of LTC 4. In addition, the time courses of their release were superimposable, with a plateau at 5 min after antigen challenge. The release of three preformed mediators and of LTC 4 after fixation of IgE, washing of the sensitized cells, and antigen challenge unequivocally indicates a bone marrow-derived mast cell origin for these products. Linear regression analyses of the net percent release of β-hexosaminidase to histamine and of 35S-chondroitin sulfate E to β-hexosaminidase yielded straight lines that intersected at the origin, which indicates that the three preformed mediators are localized in the secretory granules of the bone marrow-derived mast cells. The concomitant generation of 23 ng of LTC 4/10 6 sensitized bone marrow-derived mast cells represent the first examples of IgE-dependent release of substantial amounts of LTC 4, a component of slow reacting substance of anaphylaxis, from a mast cell population of > 95% purity. The IgE-dependent generation of LTC 4, rather than prostaglandin D 2, by the chondroitin sulfate E prosteoglycan-containing bone marrow-derived mast cells contrasts with the predominant generation of prostaglandin D 2 by heparin proteoglycan-containing mast cells. These differences together support the existence of two phenotypically different mast cell subclasses.
ASJC Scopus subject areas
- Immunology and Allergy