The biological role of heat-aggregated IgGa during the secretory process of rat mast cells and rat basophilic leukaemia (RBL) cells was analysed. Incubation of normal rat mast cells and rat basophilic leukaemia cells with heat-aggregated IgGa alone leads to a stabilization of the cells resulting in a reduction of mediator secretion and ion influx. When mast cells from Nippostrongylus brasiliensis-infected animals were incubated with heat-aggregated IgGa and subsequently challenged with anti-IgE, a dual effect with regard to ion influx and histamine release was observed, depending on the concentration of heat-aggregated IgGa or anti-IgE either a pronounced decrease or a marked enhancement was apparent. Our data suggest that heat-aggregated IgGa as well as immune complexes modulate the secretory response of mast cells and may thus play an important role in the allergic disease process.
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