ZAP70 and B-cell chronic lymphocytic leukemia: Taken together, overexpression of Lck and ZAP70 in T cells of CLL patients could be reflective of either T cell dysfunction related to inability to form an immunological synapse that has been reported associated with this disease50,51, or to the development of T cell populations that are skewed towards a memory and/or senescent CD8+ T cell phenotype52,53.