Involvement of IgE in con A-induced histamine release from human basophils in vitro

Abstract

CONCANAVALIN A (con A) induces the release of histamine from rat1 and hamster mast cells2 and human basophils. Time course, cationic requirements, enzymatic sequences and dose-response seem to be the same for con A-induced release as for antigen-induced release, which is mediated by reaginic antibody (reagin), believed to be bound by its Fc portion to a receptor in the membrane of the histamine-releasing cell. Human reagin is an antibody of the IgE class3. Antibodies4 specific for IgE can induce histamine release whereas the papain digest5 of those antibodies (which produces monomer anti-IgE) fails to elicit a response and can inhibit the intact anti-IgE-induced release6. The requirement for bridging to initiate histamine release has been established7–13. The types of sugar moieties to which con A binds have been studied14–17, and the physicochemical properties of con A15,18–22 indicate that at physiological pH it can bridge two or more of those sugar moieties. The question is raised as to whether con A is bridging sugar moieties at the receptor for reagin, or whether it is bridging sugar moieties which are directly attached to the reagin. The nature of the receptor remains to be established and the observation that con A can induce histamine release raised expectations that this interaction could elucidate some of the properties of this receptor.