CD40 and viral infectious disease: Flow cytometry analysis revealed that the concomitant stimulation of circulating pDCs (Figure S6B) by CpG and IL-3 induced increased expression of the co-stimulatory molecules CD80, CD40 and CD86 but not HLADR when compared to controls (Figure 4B and Figure S6C) suggesting that IL-3 increased the ability of pDCs to prime T cells during viral infection.