Human peripheral B lymphocytes comprise four major subsets based on CD27 and IgD expression: unswitched memory B cells (CD27+IgD+), associated with early immune responses; switched memory B cells (CD27+IgD−); naive/transitional B cells (CD27−IgD+) from recent bone marrow generation; and double negative B cells (CD27−IgD−), a heterogeneous population linked to aging and systemic lupus erythematosus. This evidence concerns the gene CD27 and systemic lupus erythematosus.