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

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 micrograms/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.