BISPECIFIC RECEPTOR GLOBULINS, NOVEL TOOLS FOR THE STUDY OF CELLULAR INTERACTIONS - PREPARATION AND CHARACTERIZATION OF AN E-SELECTIN P-SELECTIN BISPECIFIC RECEPTOR GLOBULIN

In recent years the functional consequences of receptor/ligand interac tions have been studied in vitro and in vivo using monospecific recomb inant immunoglobulin fusion proteins (recombinant/receptor globulins, Rg). These proteins are encoded by chimeric genes composed of a DNA fr agment encoding the extracellular domain of a cell surface protein gra fted onto a DNA fragment encoding immunoglobulin constant domains. In order to extend the range of applications of Rgs we investigated the p ossibility of preparing bispecific Rgs. These bispecific fusion protei ns contain the extracellular domains of two cell surface proteins held together in close proximity by the constant domains of an immunoglobu lin. Here we describe the preparation and characterization of a bispec ific Rg which contains the extracellular domains of two adhesion molec ules expressed by activated vascular endothelial cells, E-selectin and P-selectin. These two proteins play an important role in initiating l eukocyte adhesion to the vascular cell wall at sites of inflammation. Binding studies showed that the E-selectin/P-selectin bispecific immun oglobulin fusion protein (ELAM-1/GMP140 Rg) has an enhanced ability to bind to the myeloid cell line HL60 when compared to the monospecific Rg fusion proteins from which it was derived.