IgE enhances Fc epsilon RI expression and IgE-dependent TNF-alpha release from canine skin mast cells

The role of IgE on mast cell (MC) activation is well known. Recent studies have demonstrated that IgE also has the ability to up-regulate the high affinity IgE receptor (Fc epsilon RI) on the surface of human and murine MC, leading to an increased production of cytokines and chemokines. In the present study, we have examined the influence of IgE levels on Fc epsilon RI expression, and its consequences on TNF-alpha production from canine skin MC. Mature MC were enzymatically dispersed from the skin biopsies of 6-8 dogs and were cultured for up to 5 days in medium supplemented with recombinant canine stem cell factor (SCF) (6 ng/ml), in the presence of increasing serum IgE concentrations (ranging from 0 to 80 microg/ml). Subsequently, skin MC were activated with anti-IgE, and TNF-alpha concentration was assessed 5h post-activation by a cytotoxic bioassay. Fc epsilon RI receptors were identified in MC surface by flow cytometry. MC cultured for up to 5 days in the presence of high serum IgE concentration (8 microg/ml) produced twice the quantity of TNF-alpha than MC cultured in the absence of serum IgE, in response to stimulation with anti-IgE. Moreover, the percentage of Fc epsilon RI-positive skin cells was found to be approximately double in cells cultured with serum IgE compared to that cultured in the absence of IgE, following saturation of IgE receptors. These results suggest that, as found in human and murine MC, IgE may induce an up-regulation of the Fc epsilon RI density and an enhancement in the secretory activity of canine skin MC. This study could be of great interest in designing new therapeutic strategies for controlling MC activation in inflammatory and allergic processes.