A new CD21low B cell population in the peripheral blood of patients with SLE

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(hi)IgD(+)CD24(hi)CD38(hi) were significantly expanded in SLE patients but also found in other autoimmune disorders. The population of plasmablasts (CD19(lo)CD21(lo)CD27(++)CD38(++)) was increased in active disease. Most interestingly, B cells in autoimmune disorders contain a so far uncharacterized subpopulation with an activated phenotype (CD19(hi)CD21(lo)CD38(lo)CD86(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. (C) 2004 Elsevier Inc. All rights reserved.