Cytokine secretion during DC differentiation. Cells were incubated with or without IL-4 plus GM-CSF (50 ng/mL) for 5 days at 37°C in a 5% CO₂ atmosphere. After this period, supernatants were collected and assayed for IL-6 and TNF-α production by enzyme-linked immunosorbent assay. Data in bars are expressed as picomoles per milliliter of IL-6 (A) or TNF-α (B). Open bars represent supernatant obtained from culture of cells derived from noninfected individuals (CTR; n = 7), and shaded bars represent supernatant obtained from culture of cells derived from HTLV-1–infected donors (n = 15). Data are mean ± SD. *Significantly different from control (P < .05).