Since CD5 seems to be located close to the surface IgBCR on the B cell surface (6) and seems to be a potential ligand of peculiar Ig heavy chain framework sequences in malignant B cells (5), these findings suggest that CD5 could be a self-antigen recognized by the CLL-IgBCRs, promoting survival and proliferation signaling. This evidence concerns the gene CD5 and B-cell chronic lymphocytic leukemia.