5 demonstrated the presence of CD5‐high B‐cells in fetal livers and their preferential abundance in young mice. Similarly, CD5‐high B‐cells are more frequently observed in human cord blood than in adult peripheral blood 6, and their percentage decreases with age. In adult human lymphoid tissue, CD5‐high B‐cells are located in the follicle mantle zone and comprise a large subpopulation of tonsillar B‐cells. In a mouse model, it has recently been shown that a subset of CD5‐high cells has a potential to give rise to B‐CLL‐like cells in adult animals 7. This evidence concerns the gene CD5 and B-cell chronic lymphocytic leukemia.