Imaging rheumatoid arthritis joints with technetium-99m labelled specific anti-CD4- and non-specific monoclonal antibodies.

A direct comparison of the joint-imaging properties of inflammation-specific- and non-specific monoclonal antibodies (Mabs) was possible in a patient suffering from long-standing, severe rheumatoid arthritis (RA). This patient received an anti-CD4- and an anticarcinoembryonic antigen (anti-CEA) Mab, both labelled with technetium-99m, 9 days apart from each other. The anti-CD4 Mab was superior to the isotype-matched anti-CEA Mab in imaging inflamed joints. In the knee joint, the target-to-background ratio of the synovial membrane (SM) activity in comparison to that of adjacent large vessels was 1.22 (SM/muscle 1.55) for the anti-CD4 Mab and 0.53 (SM/muscle 0.92) for the anti-CEA Mab, in both cases 4 h after injection of the immunoglobulin. Since the CD4 antigen is present on the surface of T-helper lymphocytes and macrophages infiltrating the inflamed synovial membrane, imaging with the anti-CD4 Mab may allow more specific detection of inflammatory infiltrates in RA.