FIELD : medicine.SUBSTANCE : invention relates to an oligonucleotide that can be used in medicine, the oligonucleotide contains two to four sequences, each represented by formula 5' -X1X2CpGX3X4-3' , having a length of 17 to 32 nucleotides, where CpG is unmethylated CpG having no phosphate backbone modifications, where the oligonucleotide includes a phosphate backbone modification, including thiophosphate of an Sp-type stereoisomer at a site, with the exception of the parts represented by formula 5' -X1X2CpGX3X4-3' , where X1X2 represents any one of AA, AT, GA or GT without phosphate backbone modifications, and where X3X4 is a TT, AT, AC, TC or CG without phosphate backbone modifications, and the oligonucleotide includes any one of the sequences, where * represents an Sp stereoisomer : Sequence NumberSequence1T*C*GTCGTT*T*T*GTCGTT*T*T*GTCGGG2G*G*GTCGTT*T*T*GTCGTT*T*T*GTCGGG3T*C*AACGTT*T*C*AACGTT*T*T4T*C*AACGTT*T*C*AACGTT*T*T*GG5T*C*AACGTT*T*C*AACGTT*G*G6T*C*AACGTT*T*C*AACGTT*G*G*G*G7T*C*AACGTT*T*T*AACGTT*T*T*AACGGG10T*C*AACGTT*T*A*AACGTT*T*A*AACGGG11T*C*AACGTTAACGTTAACGGG12T*C*GACGTT*T*T*GACGTT*T*T*GACGGG21T*C*GACGTT*T*A*AACGTT*T*A*AACGTT*T*A*AACGGG22T*C*GACGTT*T*A*AACGTT*T*A*GACGTT*T*A*AACGGG23T*C*GACGTTAACGTTAACGTTAACGGG24GGGACGTT*T*A*AACGTCTAGACGGG26T*C*GACGTT*T*T*GACGTT*T*T*G*A*C*G*G*G29T*C*GACGTT*T*T*GACGTT*T*T*GACGG*G*G30T*C*GACGTT*T*T*GACGTT*T*T*GACGT*G*G31T*C*GACGTT*T*T*GACGTT*T*T*GACGTG*G*G32T*C*GACGTT*T*T*GACGTT*T*T*G*A*C*G*G*G33T*C*GACGTT*T*T*GACGTT*T*T*GACGG*G*G*G*G36T*C*GACGTT*T*T*GACGTT*T*T*GACG*G*G*G*G39T*C*ATCGAT*T*T*ATCGAT*T*T*ATCGGG42G*G*GACGATATCGTCG*G*G*G*G*G43G*G*GACGACGTCGTCG*G*G*G*G*G49T*C*ATCGAT*T*T*ATCGAT*T*T*A*A*C*G*G*G50T*C*GACGTTTTGACGTT*T*T*G*A*C*G*G*G51T*C*GACGTTTTGACGTTTT*G*A*C*G*G*G60T*C*GACGTT*T*T*GACGTT*T*T*G*G*G*G*G61T*C*GACGTT*T*T*GACGTT*T*T*G*A*G*G*G*G62T*C*GACGTT*T*T*GACGTT*T*T*G*T*G*G*G*G64C*C*GACGTT*T*T*GACGTT*T*T*GACG*G*G65T*C*GACGTT*T*A*GACGTT*T*A*GACG*G*G66T*C*GACGTT*T*T*GACGTT*T*T*GACG*A*A67T*C*GACGTT*T*T*GACGTT*T*T*GACG*T*T68T*C*AACGTT*T*T*AACGTT*T*T*GACG*G*G69T*C*GACGTT*T*T*GACGTT*T*T*GGG70T*C*GACGTT*T*T*GACGTT*T*T*GACGTTGG71T*C*GACGTT*GACGTT*G*G*G75T*C*GACGTA*GACGTA*GACG*G*G76T*A*GACGAT*T*C*GTCGTC*T*A*GACG*G*G81T*C*ATCGAT*T*T*ATCGAT*T*T*GACG*G*G82T*C*ATCGAT*T*T*ATCGAT*T*T*ATCGA*T*G*G*G83T*C*ATCGAT*T*T*ATCGAT*T*T*AT*C*G*G*G84T*C*ATCGAT*T*T*ATCGAT*T*T*ATCGAT*T*T*ATCG*G*G85T*C*ATCGAT*T*T*ATCGAT*T*T*ATCGAT*T*T*A*T*C*G*G*G86T*C*ATCGAT*T*T*ATCGAT*T*T*ATCGAT*A*T*C*G*G*G87T*T*ATCGAT*T*T*ATCGAT*T*T*G*A*C*G*G*G88T*C*ATCGATATCGAT*T*T*G*A*C*G*G*G89TCATCGAT*T*T*ATCGAT*T*T*A*T*C*G*G*G90T*C*ATCGAT*T*T*ATCGAT*T*T*G*A*C*G*A*T95T*C*GACGTTTGACGTTT*G*A*C*G*G*G96T*C*ATCGAT*T*T*ATCGAT*T*T*A*T*C*G*G*G97G*G*GACGATATCGTCG*G*G*G*G*G99G*G*GACGACGTCGTCG*G*G*G*G100T*C*GACGACGTCGTCG*G*G*G*G*G101T*C*GACGACGTCGTCT*T*T*G*G*G102T*A*GACGACGTCGTCT*T*T*G*G*G103T*T*GACGACGTCGTCA*A*A*G*G*G106T*C*ATCGATATCGATT*T*T*G*G*G107T*T*ATCGATATCGATA*A*A*G*G*G109T*C*GACGAC*T*T*GACGAC*T*T*G*A*C*G*G*G110T*C*GACGAC*T*T*GTCGTC*T*T*G*A*C*G*G*G111T*T*ATCGATATCGATA*T*C*G*A*T*G*G*G112T*T*ATCGATATCGATT*T*A*A*A*G*G*G113T*C*ATCGAT*T*T*ATCGAT*T*T*G*A*C*G*T*T118T*C*GTCGTTGTCGTTG*A*C*G*A*C*G*G*GSee table.EFFECT : provided is CpG oligonucleotide, possessing high stability and low cytotoxicity for the production of interferon-α.6 cl, 3 dwg, 11 tbl, 6 ex, sequence list