MCs induce increase of CD138 expression on naive B cells. Surface expression of CD138 on B cells was analyzed by flow cytometry after 72 hours of B-cell and MC cocultures in the same condition of Figure 2. (A) Histograms of cell numbers on the y-axis plotted against log fluorescence intensity of CD138 on x-axis. A representative histogram is shown here of 2 independent experiments. Filled histograms (left, gray) indicate isotype control antibody. (B) The mean fluorescence intensity (MFI) of CD138 expression on naive B cells (B) and on activated B cells (Bact) at baseline and in coculture with nonsensitized MCs (MC) or activated MCs (MC/IgE-Ag) is shown. Results shown are representative of at least 2 independent experiments.