As regards p27KIP1 expression, in CLL patients, CTLA-4 blockade resulted in an increase in the median proportions of p27KIP1-positive cells compared to corresponding cells under stimulating conditions, although this increase was statistically significant only after 24 h of blocking culture (Figs. 6, 7). This evidence concerns the gene CDKN1B and B-cell chronic lymphocytic leukemia.