COMPARISON OF (99)TCM-LABELED SPECIFIC MURINE ANTI-CD4 MONOCLONAL-ANTIBODIES AND NONSPECIFIC HUMAN-IMMUNOGLOBULIN FOR IMAGING INFLAMED JOINTS IN RHEUMATOID-ARTHRITIS

Inflamed joints in human rheumatoid arthritis (RA) can be imaged emplo ying Tc-99m-labelled anti-CD4 monoclonal antibodies (MAbs). These MAbs recognize the CD4 molecule expressed on T-helper cells and, with a lo wer density, on macrophages, which are both abundantly present in RA i nflammatory infiltrates. However, it is at present unclear whether spe cific binding to target molecules in the inflamed joint determines the joint uptake of anti-CD4 MAbs, i.e. whether the uptake of anti-CD4 MA bs differs from that of control immunoglobulins with irrelevant specif icity. Eight patients with severe, active RA were examined after intra venous injection of a Tc-99m-labelled murine anti-human CD4 MAb (MAX.1 6H5; 200-300 mug, 370-550 MBq) or polyclonal human immunoglobulin (HIG ; Technescan(R), MDH-67, Mallinckrodt Diagnostica; 1 mg, 370 MBq); fiv e patients received both the anti-CD4 MAb and HIG. Whole body and join t scans in anterior and posterior views were obtained 1, 4 and 24 h af ter injection. As early as 4 h after injection, the anti-human CD4 MAb showed a higher target-to-background ratio in arthritic knee and elbo w joints in comparison to polyclonal HIG used for conventional imaging , indicating that the anti-CD4 MAb allows more specific detection of i nflammatory infiltrates rich in CD4-positive cells.