Role of phospholipase A2 and G-proteins in the IgE-dependent activation of mast cells and macrophages

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Abstract
The effect of para-bromophenacyl bromide (a selective inhibitor of phospholipase A2) and pertussis toxin has been investigated on IgE-dependent histamine release and on IgE-dependent macrophage-mediated cytotoxicity. Para-bromophenacyl bromide, inhibited dose-dependently IgE-dependent stimulation of mast cells and macrophages (IC50's of 5.0×10−7 M and 2.5×10−7 M, respectively). In contrast, pertussis toxin only inhibited the IgE-dependent stimulation of macrophages, whereas the IgE-dependent activation of mast cells was not affected. These results suggest that the transducing mechanisms following the activation of the high affinity receptor for IgE (FcεRI on mast cells) as well as the low affinity receptor for IgE (FcεRII on macrophages) induce the activation of phospholipase A2. FcεRII might be coupled to a pertussis toxin sensitive G-protein.

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