CD27 and rheumatoid arthritis: Following RTX treatment, a small number of IgD−CD27+ switched memory cells and DN cells are detectable in the peripheral blood of patients with RA and SLE [5, 6, 50] suggesting relative resistance to depletion by RTX, perhaps due to lower levels of CD20 on IgD−CD27+ switched memory cells and DN cells compared with IgD+CD27+ unswitched memory cells.