Evaluation of cell-surface IgE receptors on the canine mastocytoma cell line C2 maintained in continuous culture

Objective-To assess expression and function of cell-surface IgE receptors on the canine mastocytoma cell line C-2 maintained in continuous culture. Sample Population-C-2 Cells maintained in medium lacking IgE for up to 10 passages before being stored at -80 C. Procedure-Cells were thawed, cultured in medium without IgE for 1 to 3 passages, sensitized for 7 days with IgE-rich serum from dogs naturally sensitized to Ascaris suum, and stimulated with antigen Asc S1 from A suum, goat polyclonal anti-canine IgE, or calcium ionophore and phorbol myristate acetate (PMA). Percentage of intracellular beta-hexosaminidase released and concentration of tumor necrosis factor-alpha (TNF-alpha) synthesized after stimulation were determined. Expression of cell-surface IgE receptors was assessed by use of a flow cytometry. Results-Immunologic stimulation (antigen or anti-IgE) failed to induce release or synthesis of detectable amounts of P-hexosaminidase or TNF-alpha. In contrast, nonimmunologic stimulation (calcium ionophore and PMA) led to release of beta-hexosaminidase (mean +/- SEM maximum release, 23.95 +/- 1.96%) and synthesis of TNF-alpha (maximum concentration, 34.34 +/- 2.34 pg/10(6) cells). As revealed by use of flow cytometry, C-2 cells expressed surface IgE receptors that bound canine IgE in vitro. Conclusions-Continuous culture of the canine mastocytoma cell line C-2 in medium without exogenous IgE or cytokines and other growth factors resulted in cell-surface expression of nonfunctional IgE receptors. However, C-2 cells maintained in continuous culture may still be a useful tool for the evaluation of mast cell responses to nonimmunologic stimulation and IgE receptor differentiation and maturity.