Quantitative Rather than Qualitative Differences between Monocytes with Respect to IgE Fc Receptor Expression as Studied by Flow Cytofluorometry

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Abstract
In this study we have used aggregated human IgE, conjugated with fluoroisothiocyanate, as a ligand in flow cytofluorometry to detect the low-affinity Fc receptor for IgE on human leukocytes. The percentage of IgE-binding monocytes increased up to 44%, in a dose-related manner, as the concentration of aggregated IgE in the fluid phase increased to the highest concentration (300 μg/ml) used in this study. No such dose-related increase was shown for granulocytes (1.8% IgE-binding cells) or lymphocytes (2.1 % IgE-binding cells). The IgE-binding was inhibited by IgE but not by IgG, whereas the opposite effect was obtained for IgG binding. We could not verify a distinct IgE-binding subpopulation of monocytes in peripheral blood. The results rather indicate that most monocytes bind IgE to a variable degree depending on the concentration of the ligand in the fluid phase.