Markers specific of marginal zone B cells shared by blood and spleen IgM⁺IgD⁺CD27⁺ subsets. Purified B cells from blood and spleen are analyzed separately for IgM, CD21, CD23, and CD1c surface expression after gating of the 3 different CD19⁺ lymphocyte subsets distinguished by IgD and CD27 labeling. These data correspond to 1 representative case out of 4 different individuals. Naive B cells (IgD⁺CD27^-) are indicated by the bold line; IgD⁺CD27⁺ B cells, the gray shadow; IgD^-CD27⁺ cells, the thin line. Percentages of cells in the 2 CD27⁺ quadrants are indicated. The absence of IgM⁺ cells among the IgD^-CD27⁺ subset is noticeable.