['Ag-dependent activation of IgE-bearing mast cells is a critical first step in immediate hypersensitivity and other allergic responses. Recent studies have revealed Ag-independent effects of monoclonal mouse IgE molecules on mast cell survival and activation. However, no studies have been performed on the effects of polyclonal IgE molecules. Here, we tested whether polyclonal mouse and human IgE molecules affect survival and cytokine production in mast cells.', 'Mast cells were cultured in the presence of polyclonal mouse and human IgE molecules, and cell survival and cytokine production were analyzed.', 'Polyclonal mouse IgE molecules in sera from mice with atopic dermatitis-like allergic skin inflammation, enhanced survival and cytokine production in mast cell cultures. Similar to the effects of monoclonal IgE, the polyclonal IgE effects were mediated by the high-affinity IgE receptor, FcepsilonRI. Human polyclonal IgE molecules present in sera from atopic dermatitis patients were also capable of activating mast cells, and inducing IL-8 production in human cord blood-derived mast cells.'] Does polyclonal IgE induce mast cell survival and cytokine production?