Class I/II hybrid inhibitory oligodeoxynucleotide exerts Th1 and Th2 double immunosuppression.

We designed class I/II hybrid inhibitory oligodeoxynucleotides (iODNs), called iSG, and found that the sequence 5'-TTAGGG-3', which has a six-base loop head structure, and a 3'-oligo (dG)3-5 tail sequence are important for potent immunosuppressive activity. Interestingly, splenocytes isolated from ovalbumin (OVA)-immunized mice and treated with iSG3 showed suppression of not only interleukin (IL)-6, IL-12p35, IL-12p40, and interferon (IFN) γ mRNA expression, but also IL-4 and IL-13 mRNA expression. Thus, both Th2 and Th1 immune responses can be strongly suppressed by iODNs in splenocytes from allergen-immunized mice, suggesting usefulness in the treatment of diseases induced by over-active immune activation.