Objective Proteinase-activated receptor-2 (PAR₂) has been implicated in inflammatory articular pathology. Using the collagen-induced arthritis model (CIA) the authors have explored the capacity of PAR₂ to regulate adaptive immune pathways that could promote autoimmune mediated articular damage.

Methods Using PAR₂ gene deletion and other approaches to inhibit or prevent PAR₂ activation, the development and progression of CIA were assessed via clinical and histological scores together with ex vivo immune analyses.

Results The progression of CIA, assessed by arthritic score and histological assessment of joint damage, was significantly (p<0.0001) abrogated in PAR₂ deficient mice or in wild-type mice administered either a PAR₂ antagonist (ENMD-1068) or a PAR₂ neutralising antibody (SAM11). Lymph node derived cell suspensions from PAR₂ deficient mice were found to produce significantly less interleukin (IL)-17 and IFNγ in ex vivo recall collagen stimulation assays compared with wild-type littermates. In addition, substantial inhibition of TNFα, IL-6, IL-1β and IL-12 along with GM-CSF and MIP-1α was observed. However, spleen and lymph node histology did not differ between groups nor was any difference detected in draining lymph node cell subsets. Anticollagen antibody titres were significantly lower in PAR₂ deficient mice.

Conclusion These data support an important role for PAR₂ in the pathogenesis of CIA and suggest an immunomodulatory role for this receptor in an adaptive model of inflammatory arthritis. PAR₂ antagonism may offer future potential for the management of inflammatory arthritides in which a proteinase rich environment prevails.