(A) DCs were incubated with sCD40L monomer (MONO), CD40L multimer (MULTI), LPS, LPS and interferon-γ (LPS γ), or control (-) for 48 hours, washed and then co-cultured with allogeneic naïve CD4 T cells at a ratio of 1:10. After 6-7 days, the T cells were stained with CFSE and were mixed at various ratios with allogeneic DCs, from the original DC donor, matured overnight with R848 10uM (3M) (1:10, 1:30 and 1:300; DC: T cell ratio). After 3 days, CFSE dilution was analyzed by FACS. Data is shown for 3 donors with T cell proliferation (CFSE dilution) normalized to untreated T cells (T cells alone) stimulated with R848-DCs. *Represents a p-value < 0.05 and was considered significant. (B) The same anergy experiment was performed in the absence (-) MT or presence (+) MT of 1-MT a specific inhibitor of IDO activity. Data is shown for one donor, representative of 4 donor experiments.