CD3⁺/CD56⁺ PB T cells in AML compared with healthy donors. (A) Dot plot of CD3⁺/CD56⁺ T cells in PB of acute myeloid leukamia (AML) patients (n = 36) compared with healthy persons (n = 17). P value obtained using a Mann-Whitney unpaired 2-tailed t test. (B) Mean percentage ± SD of CD3⁺56⁺ and CD3⁺56⁻ cells expressing CD25 and CD69 in AML patients and healthy controls. CD25 and CD69 expression is significantly higher in CD3⁺56⁺ cells compared with CD3⁺56⁻ cells in healthy controls (■) and AML patients (□) and significantly higher in the CD3⁺56⁺ cells of AML patients (□) compared with healthy controls. (C) Size and granularity characteristics of CD3⁺56⁺ cells. The scatterplot shows CD3⁺56⁺ cells in blue backgated onto the FSC/SSC plot. Two populations of cells with different scatter characteristics are apparent. (D) Expression of perforin and granzyme B in the CD3⁺SSC^High and total CD3⁺56⁺ populations in these AML patients was compared with healthy persons. Although a higher mean percentage of CD3⁺56⁺ cells express cytotoxic granules compared with CD3⁺56⁻ cells, there is no difference in the percentage of cells that express these granules in AML (□) and healthy persons (■) until the LGL population is examined (CD3⁺SSC^High). Within this population, significantly fewer CD3⁺56⁺ cells express perforin and granzyme B compared with healthy controls.