B6BMDCs were pretreated with diluent or SAHA and used as stimulators in MLR cultures as described in Methods. (A) BALB/c T cell proliferation after 72 h of culture. (B) IL-2 levels in supernatants at 48 h of culture. P = NS, control versus 0.1 μM SAHA. *P < 0.02, **P < 0.01 versus control. (C and D) Addition of (C) anti–TGF-β or (D) anti–IL-10 to SAHA-treated DC cultures did not reverse SAHA-treated DC–mediated suppression. P = NS, SAHA-treated versus control DCs. *P < 0.05 versus control. (E) Naive BALB/c T cells, or those obtained after 48 h of culture with C57BL/6 (B6) DCs pretreated with 0.5 μM SAHA, were restimulated in secondary cultures with control C57BL/6 DCs either separately or together at a 1:1 ratio. T cells cultured from primary SAHA-treated DCs were restimulated with third-party C3H/HeJ BMDCs. P = NS for all between-group comparisons. Data are mean ± SEM of quadruplicate cultures. (F and G) Cd74^–/– and HLA-G^–/– animals were irradiated and transplanted as described in Methods. Syngeneic (n = 3–4) and some allogeneic animals (n = 4–5) received 4 × 10⁶ to 5 × 10⁶ control B6BMDCs, while some allogeneic recipients (n = 5) received similar numbers of SAHA-treated B6BMDCs, on days –1, 0, and 2 relative to BMT. (F) Donor CD4⁺ cell number was evaluated in recipients’ spleens on day 7. **P < 0.001 versus allogeneic. Data (mean ± SEM) are from 1 of 3 similar experiments. (G) Donor CD8⁺ cell number was evaluated in recipients’ spleens on day 21. *P < 0.05 versus allogeneic. Data (mean ± SEM) are from 1 of 2 similar experiments.