| abstract |
The present invention relates to an oligonucleotide containing two to four sequences each represented by the formula 5'-X1X2CpGX3X4-3 '(formula (I)) and has a length of 14 to 32 nucleotides. In formula (I), CpG represents a non-methylated CpG residue having a phosphate skeleton modification, X1X2 represents any one of AA, AT, GA and GT, and X3X4 represents any one of TT, AT, AC and CG. The oligonucleotide has at least one phosphate skeleton modification in a S-form stereoisomer located at a site other than CpG. |