IgM and IgG but not cytokine secretion is restricted to the CD27 super(+) B lymphocyte subset

In a recent study we reported that CD27 is expressed on a subpopulation of human B lymphocytes and presented circumstantial phenotypic evidence that CD27 expression may be acquired late during B cell differentiation. Here we present functional data showing that, after in vitro stimulation, CD27 super(+) but not CD27 super(-) B cells secrete large amounts of both IgM and IgG. Using double immunofluorescence staining of CD27 and IgD, three functionally different B cell subsets representing distinct stages of B cell differentiation can be isolated: 1) the CD27 super(-)IgD super(+) B cells, which do not secrete appreciable Ig; 2) the CD27 super(+)IgD super(+) B cells, which exclusively secrete IgM; and 3) the CD27 super(+)IgD super(-) B cells which comprise the IgG-producing cells.