CD27 and systemic lupus erythematosus: SLE is characterized by B cell hyperactivity with an overrepresentation in the blood of activated naive (acN: CD19hi IgD + CD27–) B cells, double negative (DN: CD19+ IgD– CD27–) B cells and plasmablasts (CD19lo CD27hi) along with autoantibody production by terminally differentiated B cells [6].