CD27 and B-cell chronic lymphocytic leukemia: Since the normal cellular equivalent of a CLL cell is still a matter of debate (28–31), we used a database containing IGHV-IGHD-IGHJ sequences from several normal B-cell types generated with the same methodology, i.e., memory B cells (isotype-switched, sMem, and IgM only, mMem), marginal zone B cells (MZ), and IgD-CD27- (“double negative”, DN) B cells, as controls (32) (Figure 6).