USE OF A RADIOLABELED MONOCLONAL-ANTIBODY AGAINST E-SELECTIN FOR IMAGING OF ENDOTHELIAL ACTIVATION IN RHEUMATOID-ARTHRITIS

Objective, To determine the potential of In-111-labeled anti-E-selecti n monoclonal antibody (MAb) to image localized endothelial activation in rheumatoid arthritis (RA), Methods, Fourteen patients,vith RA were studied after intravenous administration of In-111-labeled F(ab')(2) f ragments of MAb against the cytokine-inducible endothelial cell activa tion antigen E-selectin (MAb 1.2B6). To compare uptake of 1.2B6 with t hat of nonspecific immunoglobulin, In-111-labeled polyclonal human imm unoglobulin (HIG) was separately administered to 6 of these patients a nd the relative uptake of each tracer was determined, Results, Promine nt and discrete uptake of the radiolabeled MAb 1.2B6 was clearly visib le in inflamed joints of all patients, Compared with In-111-HIG, In-11 1-1.2B6 provided superior images in terms of sensitivity and image int ensity, Furthermore, the distribution of uptake in inflamed joints was different for the 2 tracers, with 1.2B6 showing a more focal localiza tion in synovium, Conclusion, This study demonstrates that it is possi ble to objectively assess E-selectin expression on activated endotheli um in vivo in patients with RA, using a radiolabeled MAb, This techniq ue has considerable potential for monitoring disease activity and resp onse to therapy in inflammatory diseases.