Leukemic LGLs express PDGF-BB and PDGFR-β. (A) PDGF-BB mRNA expression levels in NK cells from patients with NK-LGL leukemia and normal controls, and in T cells from patients with T-LGL leukemia and normal controls, were determined by real-time quantitative RT-PCR (expressed as the ratio of PDGF-BB mRNA copies/18S control mRNA copies; *P < .05). (B) Western blot analysis was performed for PDGF-BB production in cells lysates of CD16⁺/CD56⁺ cells from patients with NK-LGL leukemia or CD8⁺ cells from patients with T-LGL leukemia as well as in their counterpart cells from normal controls. GAPDH detection was used to confirm equal loading of total protein in each sample. Densitometry was performed on these Western blot results to determine the average level of PDGF-BB protein expression. *P < .05. (C) PDGF-BB protein expression in plasma samples from 10 normal controls, 9 NK-LGL leukemia patients, 10 T-LGL leukemia patients, 4 HTLV-I–infected persons, and 4 HTLV-II–infected persons was determined by ELISA; *P < .05 compared with plasma sample levels from normal controls. (D) PDGF-BB protein ICC/IF staining as visualized by confocal microscopy in LGL leukemia cells compared with normal T or NK cells. Nuclei staining was visualized by DAPI (blue); PDGF-BB, by Cy5 fluorescent staining in the cytoplasm compartment (red). CD8 surface marker on T cells was visualized by FITC-fluorescent staining on the cell membrane (green). (D1-2) NK cells from a patient with NK-LGL leukemia and a normal control. Nuclei staining (D1A,2A), PDGF-BB staining (Dib-iib), and merged image (Dic-iic). (D3-4) CD8⁺ cells from a patient with T-LGL leukemia and a normal control. Nuclei staining (D3A-4A), PDGF-BB staining (D3B,4B), CD8 surface marker (D3C,4C), and merged image (D3D,4D). (D5-6) PDGFR-β staining on NK cells and T cells from a patient with NK-LGL (D5) and T-LGL leukemia (D6), respectively. Nuclei staining: D5A, D6A; PDGFR-β: D5B, D6B; and merged images: D5C, D6C.