Numbers and cytotoxicities of CD3+CD56+ T lymphocytes in peripheral blood of patients with acute myeloid leukemia and acute lymphocytic leukemia

Recent reports have highlighted the role of cellular immunity in anti-tumor defenses. T lymphocytes are known to play important part in anti-cancer immunity. The number and function of T lymphocytes are altered in chronic leukemia patients. CD3⁺CD56⁺ T lymphocytes have also been found to be abnormal in cancer patients. We therefore investigated changes in the number and cytotoxicity of CD3⁺CD56⁺ T lymphocytes in the peripheral blood of acute leukemia (AL) patients (excluding acute promyelocytic leukemia), to improve our understanding of the role of this T lymphocyte subset. We analyzed CD3⁺CD56⁺ T lymphocyte numbers and cytotoxicities in healthy controls, AL patients, and AL patients with complete remission. Lymphocyte counts were performed in peripheral blood and flow cytometry was used to determine cell numbers and cytotoxicities. The absolute number of CD3⁺CD56⁺ T lymphocytes was increased in AL patients (including acute myeloid AML] and acute lymphocytic leukemia ALL]) compared with healthy controls (P < 0.05), but their functioning was significantly reduced (P < 0.05). The number of CD3⁺CD56⁺ T lymphocytes in AML and ALL patients who achieved remission following chemotherapy was close to healthy controls (P > 0.05), but their functioning was still significantly reduced (P < 0.05). In addition, the number of CD3⁺CD56⁺ T lymphocytes increased significantly in AML patients with increased peripheral blood white blood cell (WBC) counts, and in ALL patients without increased WBCs. These results suggest that cellular immunity may respond to AML and ALL, but that lymphocyte cytotoxicity remains impaired. Dysfunction of CD3⁺CD56⁺ T lymphocytes in AML and ALL patients may contribute to the failure of the host immune response against leukemic blasts.