In this regard, however, it has to be reminded that T/B Ratio values lower than the established 3.0 cut-off, as they are in CLL cases marked as ZAP-70 positive, can theoretically represent the result of a high expression level of ZAP-70 in the CLL component, but also of a low expression level of ZAP-70 by residual T cells. This evidence concerns the gene ZAP70 and B-cell chronic lymphocytic leukemia.