CD3+/CD56+ Cells, but Not Natural Killer T Cells, Are Increased in Peripheral Blood of Untreated Patients with Leukemia

Despite recent interest in the use of natural killer T (NKT) cells for cancer immunotherapy, there remains confusion over the phenotype and function of these cells. We observed a population of CD3+/CD56+ cells in the peripheral blood (PB) of patients with acute myeloid leukemia (AML) at diagnosis. We therefore performed more detailed multiparametric flow cytometric analysis on PB from previously untreated patients with AML (n=30), chronic lymphocytic leukemia (CLL) (n=12) and healthy normal volunteers (n=17) to characterize these cells in more detail. Since we were assessing rare cell populations, at least 200,000 events were always acquired from the mononuclear and live cell gates. In healthy individuals CD3+/CD56+ cells comprise 1% to 8.6% (median 2.74%) of PB T cells, but these cells are significantly increased both in percentage of T cells as well as in absolute numbers in the PB of patients with AML (p=0.0009) and CLL (p