AC-derived DCs induced activation and proliferation of naive allogenic T cells. (A) Graded numbers of irradiated DCs cultured with or without TNF-α were used as stimulator cells for 10⁵ allogenic CD45RA⁺CD3⁺ T cells or 10⁵ allogenic CD45RA⁺CD8⁺CD3⁺ T cells. IL-2 was added at 50 U/mL when indicated. Cell proliferation was evaluated by a 12-hour pulse with ³H-TdR. ³H-TdR incorporation of purified naive T cells ± IL-2 were substracted. Results are representative of four experiments using DCs and T cells from two distinct donors. (B) After 5 days of coculture of 10⁴ TNF-α–treated DCs and 10⁵ allogenic CD45RA⁺ CD3⁺ naive T lymphocytes, cells were obtained and stained with PE-CD4 or PE-CD8 MoAbs and FITC–HLA-DR or FITC-CD25 MoAbs. Negative controls were obtained with irrelevant isotype-matched murine MoAbs. No viable CD1a⁺ DC was detectable at this time. At the beginning of coculture, less than 1% of T cells expressed HLA-DR and less than 3% expressed CD25.