Objective: To determine the potential of 111In-labeled anti-E-selectin monoclonal antibody (MAb) to image localized endothelial activation in rheumatoid arthritis (RA).
Methods: Fourteen patients with RA were studied after intravenous administration of 111In-labeled F(ab')2 fragments of MAb against the cytokine-inducible endothelial cell activation antigen E-selectin (MAb 1.2B6). To compare uptake of 1.2B6 with that of nonspecific immunoglobulin, 111In-labeled polyclonal human immunoglobulin (HIG) was separately administered to 6 of these patients and the relative uptake of each tracer was determined.
Results: Prominent and discrete uptake of the radiolabeled MAb 1.2B6 was clearly visible in inflamed joints of all patients. Compared with 111In-HIG, 111In-1.2B6 provided superior images in terms of sensitivity and image intensity. Furthermore, the distribution of uptake in inflamed joints was different for the 2 tracers, with 1.2B6 showing a more focal localization in synovium.
Conclusion: This study demonstrates that it is possible to objectively assess E-selectin expression on activated endothelium in vivo in patients with RA, using a radiolabeled MAb. This technique has considerable potential for monitoring disease activity and response to therapy in inflammatory diseases.