EXPRESSION AND FUNCTION OF AN IGE-BINDING ANIMAL LECTIN (EPSILON-BP) IN MAST-CELLS

epsilon BP (IgE-binding protein) is a 31,000 M(c) protein originally i dentified in rat basophilic leukemia (RBL) cells. The protein is compo sed of two domains with the amino-terminal domain containing a highly conserved repetitive sequence and the carboxyl-terminal domain contain ing consensus sequences shared by other beta-galactoside-binding solub le lectins. The protein has wide tissue distribution, is found on cell surfaces and in extracellular milieu. By combined efforts from severa l research groups including ours a multifunctional nature of this lect in began to emerge. This review emphasizes the following characteristi cs of epsilon BP: (i) epsilon BP is secreted by cells such as macropha ges; (ii) like many other lectins, epsilon BP functions at least bival ently; (iii) epsilon BP has specificity For distinct oligosaccharide s tructures that have a terminal galactose not masked by sialic acids; a nd (iv) in addition to binding IgE, epsilon BP binds to surfaces of va rious cell types via lectin-carbohydrate interaction. Importantly, eps ilon BP binds to the IgE receptor on mast cells. We propose that epsil on BP can function as a modulatory protein on various cells by cross-l inking critical cell surface glycoproteins. The proposed action of eps ilon BP on mast cells is presented as a model.