Based on our previous notion that CTLA-4 gene polymorphisms may influence CTLA-4 expression level in CLL cells [20, 22], it is possible that the high level of CTLA-4 expression in some of the CLL patients might result from the presence of specific alleles predisposing to upregulation of expression of the CTLA-4 molecule. This evidence concerns the gene CTLA4 and B-cell chronic lymphocytic leukemia.