We hypothesize that CLL leukemic B cells could represent a self-reactive (e.g., CD5+ expression and autoreactive-related usage of IGHV) regulatory B cell (e.g., production of IL-10, exspression of CD27) clone that is driven to proliferate by the common environment and the autoantigens that they recognize. This evidence concerns the gene CD27 and B-cell chronic lymphocytic leukemia.