The presence of synovial PAR-2 was confirmed in wild-type (PAR-2+/+) C57BL/6J mice by western blotting using SAM-11 (Santa Cruz, USA). The anti-inflammatory potential of this antibody, which inhibits PAR-2 activation by preventing release of its activating ligand, was investigated by intra-articular administration of SAM-11 to mice prior to induction of acute joint inflammation (under halothane/O2/N2O anaesthesia) by injection of 20 μl 2% carrageenan and 4% kaolin (C/K) into the knee joint. Joint swelling was assessed by comparing caliper-measured knee joint diameter pre and 24 hours post-injection. The swelling response was compared in untreated, and in two parallel groups of inflamed mice that had received intra-articular injection of SAM-11 at 5 ng or 10 ng, 5 min prior to C/K administration. Selectivity of SAM-11 for PAR-2 was confirmed by immunohistochemical analysis (in combination with the Animal Research Kit Dako, USA) of the wild-type mouse brain, which expresses PAR-1, PAR-2, PAR-3 and PAR-4 compared with that of PAR-2 gene-disrupted (PAR-2-/-) mice.