CD4 and rheumatoid arthritis: We also found an expanded CCR2+CD4+ T cluster in ARIs, and our analysis using an external single-cell dataset further demonstrated that these CCR2+CD4+ T cells in the blood showed strong signatures of Th22 cells (e.g., CCR6+, IL-23R+, KLRB1/CD161+, IL-22+), supporting the possibility that expanded Th17/Th22 cells, which play important roles at mucosal sites, may contribute to the mucosal origin endotype of RA (24, 29).