Recent studies revealed that IGHV-mutated CLL was derived from a previously unrecognized CD5+ CD27+ post-GC memory B cell subset (49), whereas IGHV-unmutated CLL was generated from pre-GC CD5+ CD27− B cells that were derived from naïve B cells, a separate lineage of B cell precursor or GC-independent memory B cells (4). The gene discussed is CD5; the disease is B-cell chronic lymphocytic leukemia.