Joint uptake and body distribution of a technetium-99m-labeled anti-rat-CD4 monoclonal antibody in rat adjuvant arthritis.

Joint uptake and body distribution of a 99mTc-labeled monoclonal antibody (Mab) to the rat CD4 molecule (W3/25; IgG1) were investigated after intravenous injection in normal rats and in animals with experimentally induced adjuvant arthritis. An isotype-matched Mab with irrelevant specificity (anti-human carcino-embryonic-antigen) was used as control. A 4 hr sequential gamma-camera imaging revealed that both anti-CD4 and control Mab accumulated to a higher degree in arthritic than in normal ankle joints; the accumulation was comparable for the two Mabs. In contrast to the inflamed joints, a specific accumulation of the anti-CD4 Mab was found in organs rich in CD4-positive cells, i.e. spleen, bone marrow and lymph nodes, as assessed by direct well counter measurements 16 hr after injection. The control Mab displayed no preferential organ accumulation in either normal or diseased animals. These results indicate that a specific accumulation of anti-CD4 Mabs occurs in CD4-positive-cell-rich tissues in both normal and diseased animals and that immunoglobulins accumulate preferentially in inflamed joints regardless of their antibody specificity.