CD27 and rheumatoid arthritis: Previous studies of atypical memory B cells (CD27–CD21lo/–), that by definition include DN2 and DN3 cells, in the context of malaria and HIV viral infection have reported these B cells to display impaired BCR signaling and proliferative responses (43, 44), a finding that has also been demonstrated in atypical memory B cells from patients with rheumatoid arthritis and Common Variable Immunodeficiency (45, 46).