A recent study documented that Tregs decreased and returned to healthy levels in CLL patients receiving ibrutinib in first-line or for relapsed/refractory disease (28); in another, the number of Tregs remained unchanged, but the Tregs/CD4+ ratio was reduced under ibrutinib treatment but not with acalabrutinib (27), leaving this field open to further investigation. Here, CD4 is linked to B-cell chronic lymphocytic leukemia.