Conformational plasticity at the IgE-binding site of the B-cell receptor CD23

IgE antibodies play a central role in allergic disease. They recognize allergens via their Fab regions, whilst their effector functions are controlled through interactions of the Fc region with two principal cell surface receptors, Fc epsilon RI and CD23. Crosslinking of Fc epsilon RI-bound IgE on mast cells and basophils by allergen initiates an immediate inflammatory response, while the interaction of IgE with CD23 on B-cells regulates IgE production. We have determined the structures of the C-type lectin head domain of CD23 from seven crystal forms. The thirty-five independent structures reveal extensive conformational plasticity in two loops that are critical for IgE binding. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.