TLR9 and Arthritis: To confirm the differential roles of TLR9 in T cell‐dependent and T cell‐independent arthritic processes, we next investigated the involvement of TLR9 in the course of repeated SCW arthritis, which is characterized by a T cell‐independent initial phase after the first intra‐articular SCW injection, followed by a T cell‐dependent chronic phase after the fourth SCW reactivation.11 We induced SCW arthritis in TLR9−/− and control wild‐type mice, and quantified joint inflammation.