Figure 4. OS-DC suppresses T_reg generation via IL-6-dependent mechanism.

(A) DC were incubated for 24 h in medium alone (control DC) or in the presence of 500 μM H₂O₂ (OS-DC)_. Cytokine profile was assessed in the supernatant of DC culture using Luminex assay; IL-6 levels were increased in OS-DC compared with control DC (*P<0.001; n=4 each group). The levels of other cytokines, including IL-4, IL-1β, TNF-α, and IL-9, did not differ significantly. (B) To assess the effect on T_reg generation, 1.0 × 10⁴ OS-DC or control DC (from C57BL/6 mice) were cocultured for 4 days with 1.0 × 10⁵ fully mismatched CD4⁺ T cells (isolated from BALB/c spleens) in the presence of TGF-β, with or without treatment with anti-IL-6. The percentage of CD4⁺FOXP3⁺ T cells generated when CD4⁺ cells were cocultured with OS-DC (11±6%) was lower than CD4⁺FOXP3⁺ T cells generated when CD4⁺ cells were cocultured with control DC (20±2%). Anti IL-6 therapy restored formation of T_regs in the OS-DC group (21±2%; *P<0.05; n≥3 in each group). (C) Representative flow plots showing FOXP3 expression (gated on CD4⁺), following coculturing with control DC, control DC with anti-IL-6, OS-DC, and OS-DC with anti-IL-6.