isolated tryptase-6, a serine protease that can activate PAR2, from the synovial fluid of patients with psoriatic arthritis (PsA) and observed increased levels of monocyte chemoattractant protein-1 (MCP-1) from PsA patient-derived monocytes/macrophages in response to PAR2 activation, highlighting a potential mechanism of PAR2-mediated recruitment of monocytes/macrophages to the PsA joint (68). This evidence concerns the gene CCL2 and psoriatic arthritis.