CD27 and B-cell chronic lymphocytic leukemia: Notwithstanding the very low frequency of CD27 + mature B-cells we observed in FL and FBM, this would support the notion that CD5 + B-cell CLL with unmutated BCR might have its origin in FL B-1a-like B-cells, which also express CD5 and although they are selected once during fetal life they persist long-term in postnatal life [46], [47].