ODNs were purchased from Hokkaido System Science (Hokkaido, Japan). The sequences of ODNs were 5′-TCCATGACGTTCCTGATGCT-3′ (CpG ODN1668), 5′-TCCATGAGCTTCCTGATGCT-3′ (non-CpG ODN1720), 5′-gggggACGATCGTCgggggG-3′ (A-type ODN2216), 5′-TCGTCGTTTTGTCGTTTTGTCGTT-3′ (CpG ODN2006), 5′-TGCTGCTTTTGTGCTTTTGTGCTT-3′ (GpC ODN2006) and 5′-TCGACGTTTTGACGTTTTGACGTTTT-3′ (26-mer CpG ODN). Capital letter means PO bond and lower-case

letter means PS bond. B-type ODN1668 has the same sequence as CpG ODN1668 and all bonds of it were substituted by PS bonds. ODN1668 fluorescently labeled by Alexa488 was purchased from FK228 Nihon Bioservice Laboratories (Saitama, Japan). All deoxynucleosides, dNMPs and dNTPs were purchased from Sigma. Plasmid vector pCMV-Luc, a CpG motif replete circular double-stranded DNA, was constructed as previously reported 44. pCMV-Luc has 33 Pur-Pur-CpG-Pyr-Pyr sequences including two GACGTT, a most potent CpG motif for mice 45. pCpG-ΔLuc, another plasmid with no CpG motifs, was constructed as previously reported 46. The plasmid DNA (pDNA)/LA2000

complex was prepared at a ratio of 2 μL LA2000 and 1 μg pDNA according SCH727965 solubility dmso to the manufacturer’s instructions. ODN1720 or pDNA was treated with DNase I or DNase II to prepare degraded DNA samples according to the manufacturers’ protocols of the enzymes. In brief, 1 μg DNA was incubated with 0.5 units DNase I or DNase II at 37°C overnight, and the DNA solution was incubated at 80°C for 10 min to inactivate the DNase in the DNA solution. The degradation of DNA was confirmed by 1% agarose gel electrophoresis (pDNA) or 21% PAGE (ODN). All degraded DNA samples were not detected, indicating sufficient degradation of DNA by DNases. Separately, DNase I-treated ODN1720 and ODNs Vildagliptin with a variety of length were run on a 21% non-denaturing PAGE and stained with CYBR Gold (Invitrogen) as shown in Supporting Information Fig. 4. ODNs with 4 nucleotides or longer were

stained with CYBR Gold, but ODN with a length of 2 nucleotides was not. No bands were observed with DNase I-treated ODN1720, suggesting that the DNase I-treated ODN1720 was ODNs with less than 4 nucleotides. DNase I-treated DNA was treated with alkaline phosphatase according to the manufacturers’ protocols of the enzyme. In brief, 1 μg DNase I-treated DNA was incubated with 0.013 units alkaline phosphatase at 37°C overnight. Then, the phosphatase was inactivated by the addition of 1 μmol EGTA followed by an incubation at 65°C for 10 min. To minimize the activation of cells by contaminated LPS, pDNA samples were extensively purified with Triton X-114, a nonionic detergent, before use according to a previously published method 47. The level of contaminated LPS was checked by a Limulus amebocyte lysate assay using the Limulus F Single Test kit (Wako Pure Chemical, Osaka, Japan).