Autocrine IL-2 stimulation in the leukemic cells from smoldering/chronic ATL PBMCs. (A) FACS analysis of CD4, CD25, and CD3 expression of purified leukemic cells and PBMCs from patients with smoldering/chronic ATL. The data are representative of data from 4 independent experiments. (B) IL-2 and Tax mRNA expression by purified leukemic cells cultured alone for 2 days by TaqMan real-time RT-PCR. The copy numbers of IL-2 and Tax mRNA were normalized to the copy number of hypoxanthine guanine phosphoribosyl transferase 1 (HPRT1) mRNA. The IL-2 levels in the supernatants of 2-day purified leukemic cell cultures were also measured by ELISA. N.D: not detected. (C) FACS analysis of phospho-STAT5 in the purified leukemic cells at day 0 or cultured alone for 2 days in the ex vivo culture.