Distribution and valency of receptor for IgE on rodent mast cells and related tumour cells

Abstract

MONOMERIC IgE binds tightly to the surface of mast cells and basophils without, by itself, causing any known perturbation. Interaction of the IgE with an appropriate antigen (or experimentally with anti-IgE) causes the cells to degranulate. Little is known about the initial molecular events in IgE-mediated triggering, but there is considerable evidence that crosslinking of the IgE molecules is a critical step (see refs 1 and 2 for discussion). The available data suggest that only limited bridging rather than an aggregation-induced extensive redistribution of the surface IgE^3,4 is required; indeed if the bridging is extensive enough to induce such gross redistribution within the time that degranulation would ordinarily be expected, the latter is inhibited^3,5. Since bridging of the IgE, and therefore of the receptor to which it is bound, seems to be a critical signal, it is important to know if the cellular binding sites for IgE are integrated into larger functional units; the receptor molecules themselves might be multivalent, or individual receptors might be connected to each other by some other component (Fig. 1). The experiments described here were directed towards investigating this point. We saturated cells with a mixture of two distinguishable types of rat IgE and determined whether by redistributing one of them with specific antibody, the other would comigrate.