CpG oligonucleotides locating to early or late endosomes induce innate or adaptive immune responses, respectively, in PDCs.
PDCs are very rare in the body (making up less than 1% of the cells in the blood) but are important for antiviral immune responses. Activation of the endosomal receptor TLR9 by viral DNA can induce PDCs either to mount an innate response (marked by their ability to produce IFN-α) or to mature into antigen-presenting adaptive immune cells. How these two fates are determined was unclear.
The two fates can also be induced using three different classes of synthetic oligonucleotides called CpG immunostimulatory sequences. CpG-A normally induces IFN-α production, CpG-B induces maturation, and CpG-C can induce both. Now, Guiducci et al....
