I-Delta1^ext-myc promoted T/NK cell differentiation, which was enhanced by IL-7. Culture plates were precoated with anti-myc 9E10 F(ab′)₂ and CH-296. (a) CD34⁺CD38^– precursors (400 cells per well) were cultured for 3 weeks in serum-free medium containing 5GF with or without IL-7 (100 ng/ml) and either 1 μg/ml of Delta1^ext-myc (I-Delta) or the same volume of control medium (Control). Data are representative of four independent experiments. Numbers in corners are the percentage of gated events within that quadrant. cy CD3, cytoplasmic CD3. (b) RNA was extracted from freshly obtained peripheral T cells (lane 1), freshly obtained peripheral granulocytes (lane 2), fresh CD34⁺CD38^– cells (lane 3), cells cultured for 3 weeks with I-Delta1^ext-myc (lane 4), cells cultured with I-Delta1^ext-myc and IL-7 (lane 5), cells cultured in control medium (lane 6), and cells cultured in control medium and IL-7 (lane 7). Equal amounts of RNA were subjected to RT-PCR, followed by electrophoresis on an agarose gel and ethidium bromide staining (see Methods). (c) CD34⁺CD38^– precursors (400 cells per well) were cultured for 5 weeks with 5GF, with or without IL-7 (100 ng/ml), and either I-Delta1^ext-myc or control medium. Cells were stained with FITC-conjugated CD7 (4H9) and PE-conjugated CD34 antibody. Mean numbers of CD34⁺ cells, CD34⁺CD7⁺ cells, and CD34^–CD7⁺ cells in six wells are shown. Data are representative of three independent experiments. MW, molecular weight.