IL-15Rα is expressed on leukemic CD8 T cells from IL-15Tg mice. (A) Expression of mouse IL-15Rα mRNA in leukemic cell lines but not in normal CD8 T cells. Twenty micrograms of total RNA was resolved in a formaldehyde agarose gel and transferred to a nylon membrane, which was probed with a 32P-labeled mouse IL-15Rα fragment. As a loading control, the 18S ribosomal RNA was visualized with ethidium bromide staining. Origins of RNA were CD8 T cells from normal WT mice, from the B1 leukemia cell line, and from the K2 leukemia cell line. (B) Detection of IL-15Rα expression by an anti-mouse IL-15Rα antibody in CD8 T cells from IL-15Tg mice. IL-15Rα expression on CD8 T cells from IL-15Tg mice of different ages (solid lines) with staining of CD8 T cells from an IL-15Rα−/− mouse shown as a control (shaded area). Results represent 3-month-old (i), 9-month-old (ii), and leukemic 19-month-old (iii) IL-15Tg mice, with 3-6 mice in each age group. The averages of IL-15Rα mean fluorescent intensity in IL-15Rα−/− mice and IL-15Tg mice in groups i, ii, and iii were 4.2 ± 0.9, 6.8 ± 0.8, 7.6 ± 1.4, and 33.4 ± 10.2, respectively. (C) Acquisition of IL-15Rα expression in the leukemic phase, but not in the benign phase, by CD8 T cells in IL-15Tg mice. RNA was extracted from CD8 T cells purified from spleens, and 10 μg total RNA was loaded onto each lane and probed with a 32P-mouse IL-15Rα fragment. Origins of RNA were resting dendritic cells (DCs) (i), activated (poly I:C) DCs (ii), cells from the B1 cell line (iii), cells from the K2 cell line (iv), CD8 T cells from a young (3-month-old) IL-15Tg mouse (v), CD8 T cells from an 8-month-old IL-15Tg mouse (vi), IL-15Rα–IL-15 double-Tg cells from a 3-month-old mouse (vii), and CD8 T cells from a leukemic 13-month-old IL-15Tg mouse (viii). Densitometry analysis was performed, and the levels of IL-15Rα RNA expression normalized to that of 18S ribosomal RNA are indicated.
