CD38 and systemic lupus erythematosus: Arce et al22 showed that, in patients with SLE, the plasma cell precursor subset (CD19+CD27+/++CD38++) tended to increase compared to that in the controls; however, there were no significant differences in the ratio of B cells (CD19+CD27‐CD38∓) to M‐Bs (CD19+CD27+CD38‐).