EXPRESSION OF FUNCTIONAL HIGH-AFFINITY IMMUNOGLOBULIN-E RECEPTORS (FC-EPSILON-RI) ON MONOCYTES OF ATOPIC INDIVIDUALS

Suggestive evidence indicates that immunoglobulin E (IgE)-dependent ac tivation of mononuclear phagocytes plays an important pathogenic role in allergic tissue inflammation. Prevailing opinion holds that low aff inity IgE receptors are the relevant IgE-binding structures on monocyt es/ macrophages and that functional events occurring after cross-linki ng of membrane-bound IgE on these cells are mediated by these receptor s. Here we demonstrate that peripheral blood monocytes can bind monome ric IgE via the high affinity IgE receptor (Fc epsilon RI) and that Fc epsilon RI expression on these cells is upregulated in atopic persons . Further, we demonstrate that, upon monocyte adherence to substrate, bridging of monocyte Fc epsilon RI is followed by cell activation. We propose that direct interaction of multivalent allergen with Fc epsilo n RI(+)-bound IgE on mononuclear phagocytes results in cell signaling via Fc epsilon RI and that the biological consequences of this event m ay critically influence the outcome of allergic reactions.