Figure 5.

Exogenous IL-15 protects NK cells from microvesicle (MV)-induced loss of cytotoxicity. (A) MV isolated from sera of AML patients decreased NK cell activity while exogenous IL-15 up-regulated it. In the presence of exogenous IL-15 (100 ng/mL for 24 h) NK cell activity was not impaired by the MV obtained from AML patients. MV obtained from normal controls (NC) did not alter NK cell activity. The data are mean LU±SE from experiments with eight AML samples. (A) NK cells obtained from NC were incubated in the presence of IL-15 and then MV isolated from the serum of an AML patient were added and after 60 min p-SMAD expression was measured by flow cytometry. (C) NK cells were incubated with or without MV isolated from an AML patients’ serum for 24 h in the presence or absence of exogenous IL-15 (100 ng/mL). NKG2D expression was measured by flow cytometry. In (A) and (B), gray-filled histograms indicate isotype control IgG.