Effect of IB-MECA in the presence and absence of MRS 1220 on the clinical and pathological manifestations of adjuvant-induced arthritis. Rats were injected with an emulsion composed of incomplete Freund's adjuvant with 10 mg/ml heat-killed Mycobacterium tuberculosis. Treatment with IB-MECA (10 μg/kg) or the A3 adenosine receptor antagonist MRS 1220 (10 μg/kg), or a combination of both, was initiated on day 14. (a) Effect of IB-MECA on disease clinical score. (b) Effect of IB-MECA on paw thickness.