IgG-mediated histamine release from canine mastocytoma-derived cells

Background. Recent data suggest that normal tissue mast cells can express f unctional receptors for IgG under certain conditions. However, little is kn own about IgG receptor expression and functional consequences in mast cell neoplasms. Methods: In this study, neoplastic mast cells were obtained from a dog with cutaneous mastocytoma (CM-MC) and from a dog with visceral mast ocytoma NI-MC). Both cell populations were characterized morphologically an d functionally. Results: Most cells proliferated constantly in suspension w ithout particular supplements. Doubling times of CM-MC and VI-MC were 52.2 and 27.5 h, respectively. Both cell types were sensitive to formalin fixati on, did not contain heparin and were tryptase and chymase positive. Electro n microscopy showed fine granules with electron-dense content in both cell populations. The total histamine content of CM-MC and VI-MC was 0.25 and 0. 10 pg/cell, respectively. Calcium ionophore A23187 and substance P induced dose-dependent histamine release, whereas compound 48/80 had no effect. Mos t significantly, both cell types, when sensitized with monomeric dog IgG, r eleased histamine upon stimulation by anti-dog IgG. Conclusions: Dog mastoc ytoma-derived cells may be useful to study the regulation of neoplastic mas t cell growth and differentiation, as well as IgG receptor-mediated activat ion in neoplastic mast cells. Further research is required to clarify the p athophysiological significance of constitutive expression of IgG receptors in neoplastic (canine) mast cells. Copyright (C) 2001 S. Karger AG, Basel.