PMN-MDSCs adoptive transfer
For adoptive transfer, CD11b+Ly6G+Ly6ClowPMN-MDSCs were isolated from the spleens of CIA mice. Then, PMN-MDSCs (3 × 10^6 per mouse) were transferred into mice on days 21 and 28, which were immunized with CII only once on day 0. PBS was used as the control.