Expression of NKG2D and NKp44 receptors and ligands on NK cells and the association with CNS leukemia. Box plots demonstrating the positive association between the expressions of (A) NKG2D/KLRK1 and (B) NKp44/NCR2, respectively, and CNS involvement in leukemia in the entire set of 86 primary BM samples. (C) Geometric mean fluorescence intensity of human NKG2D protein expression on T cells (CD45⁺/CD3⁺/CD56⁻/CD19⁻), natural killer T (NKT) cells (CD45⁺/CD3⁺/CD56⁺/CD19⁻), NK cells (CD45⁺/CD3⁻/CD56⁺/CD19⁻), and CD45⁺/CD3⁻/CD56⁻/CD19^+/− cells in a subset of 6 CNS-negative and 3 CNS-positive primary BM samples. (D) qRT-PCR of IL-15, NKG2D/KLRK1, MICA, MICB, ULBP1, ULBP2, and ULBP3 in the same set as C. mRNA values are normalized to SDHA expression. (E) Association of (ULBP1 + ULBP3/ULBP2) mRNA ratio and CNS involvement in leukemia in the entire set of BM samples. Data shown were derived through qRT-PCR after reverse transcription using RNA of BM mononuclear cells at initial diagnosis. The line within the box plots of A, B, and E corresponds to the median value, the star is the mean value, the box length is the interquartile range, and the lines emanating from the box (whiskers) extend to the smallest and largest observations; outliers are indicated. a.u., arbitrary units. Statistical analyses were done by applying the 2-tailed Student t-test.