The percentages of B cell subpopulations (CD19+ B cells, CD19+CD27+ B cells, CD19+CD20+CD27+ B cells, and CD19+CD20−CD27+ B cells) were analyzed by flow cytometry. a Percentages of CD19+ B cells, CD19+CD27+ B cells, CD19+CD20+ CD27+ B cells, and CD19+CD20−CD27+ B cells in RA and HCs. b Percentages of B cell subpopulations were compared between RA and HCs. *P < 0.05 vs. HCs.