The present invention provides ring-type-two-nucleotide (CDN) immuno-stimulator of high activity, passes through the referred to as STING(interferon gene stimulating factor found recently) cytosol receptor activate DC. Specifically, CDN of the invention is provided in the form of compositions, and the composition includes one or more cyclic annular purine dinucleotides that induction STING- dependence I type interferon generates, wherein the cyclic annular purine dinucleotides there are combination species described in what is substantially pure 2 ', 5 ', 2 ', 5 ' and 2 ', 5 ', 3 ', 5 ' CDN, and be preferably its Rp, Rp stereoisomer.本發明提供高度活性的環狀‑二‑核苷酸(CDN)免疫刺激因子,其通過最近發現的被稱爲STING(干擾素基因刺激因子)的胞質受體來活化DC。具體而言,本發明的CDN以組合物的形式提供,所述組合物包含誘導STING‑依賴性I型干擾素産生的一種或多種環狀嘌呤二核苷酸,其中存在於所述組合物種的所述環狀嘌呤二核苷酸爲基本上純的2’,5’,2’,5’和2’,5’,3’,5’CDN,並且優選地爲其Rp,Rp立體異構體。