A new CD21 low B cell population in the peripheral blood of patients with SLE

Abstract

A hallmark of systemic lupus erythematosus (SLE) is the production of autoantibodies. Recent reports suggest an abnormal peripheral blood B cell homeostasis in SLE patients without being conclusive. We analyzed by four color flow-cytometry peripheral blood B cell subpopulations of SLE patients, healthy donors, and patients with other systemic autoimmune diseases. IgM memory but not switched memory B cells of SLE patients were significantly decreased compared to healthy donors, whereas transitional B cells, characterized by CD19 +IgM hiIgD +CD24 hiCD38 hi, were significantly expanded in SLE patients but also found in other autoimmune disorders. The population of plasmablasts (CD19 loCD21 loCD27 ++CD38 ++) was increased in active disease. Most interestingly, B cells in autoimmune disorders contain a so far uncharacterized subpopulation with an activated phenotype (CD19 hiCD21 loCD38 loCD86 int). None of the identified subpopulations was associated with current or previous therapy and therefore may represent different aspects of the disturbed B cell homeostasis in patients with SLE.