Two MCs were the lowest in RA, MC02 (CD98dim/CD185+/IgD+) (HCs: 4.320%; RA: 1.871%; SSc: 3.223%; SLE: 5.761%) and MC03 (CD38−/CD98dim/CD185−/IgD−) (HCs: 2.606%; RA: 0.490%; SSc: 0.975%; SLE: 1.662%). Here, CD38 is linked to rheumatoid arthritis.