Preparation of mononuclear cells
The spleens and ankle/wrist joints were dissected from the CIA mice. Spleens were passed through 40 𝜇m cell strainers, then the erythrocytes were lysed with red blood cell lysis buffer. The skins of joints were peeled off, then the joints were digested in the RPMI 1640 (MULTICELL) containing 1 mg/ml collagenase D (Sigma-Aldrich) and 0.2 mg/ml DNase Ⅰ (Sigma-Aldrich) at 37℃ for 45 min. The joints cells were passed through 40 𝜇m cell strainers, and red blood cell lysis buffer was performed afterwards. The cell suspension was washed and resuspended in the culture medium for further analysis.