CD40 siIL-induced immune suppression. (A) CD40 siILs inhibit allogenic T-cell proliferation in vitro. CD40 siIL-transfected BMDCs from C57/B6 mice were used as stimulators, and BALB/C splenocytes were used as effectors at 1:5 ratio in MLR. T-cell proliferation was measured by [³H]-thymidine incorporation, as described in “Mixed lymphocyte reaction.” (B) CD40 siILs inhibit KLH-specific recall response. Mice were immunized with KLH emulsified in CFA and simultaneously administered 15 μg CD40 siILs. Control groups included PBS, control siRNA, isotype IgG-coupled siILs. Naked siRNA was used as a positive control. T cells were isolated from the spleens of the siIL-treated mice and control mice, 12 days after KLH immunization and siIL treatment. Ag-specific T-cell response was assessed in the presence of 10 μg KLH antigen. Data presented are representative of 4 independent experiments (n = 3 or 4 mice/group). *P < .05.