Imaging rheumatic joint diseases with anti-T lymphocyte antibody OKT-3

T lymphocytes play an important role in the pathogenesis of rheumatoid arthritis (RA). Murine monoclonal antibody OKT-3 (IgG2a), known to be specific for T lymphocyte 20 kD glycoprotein CD3 receptor was labelled with 5 mCi 99Tcm and given intravenously (i.v.) to seven RA and two psoriatic arthritis patients following informed consent to identify inflamed synovium. Anterior and posterior whole body scans and specific regional imaging was commenced 20 min later. At 1 h, approximately 20% of 99Tcm was associated with the lymphocytes. In these patients, all 41 asymptomatic joints and 43 joints with mild pain or minimal tenderness had normal scans. All 34 joints with moderate to severe pain had moderate to marked uptake of radioactivity. Two patients experienced shaking chills for 20-30 min within an hour of 99Tcm-OKT-3 infusion. These results suggest that 99Tcm-OKT-3 imaging serves as an objective surrogate for joint inflammation and could be useful as a measurement of therapeutic effectiveness in RA and other diseases with inflamed synovium. The side effect profile may limit the utility of 99Tcm-OKT-3 but other forms of antibodies directed toward lymphocyte subsets may be useful.