Abstract: Objective: To determine whether the immunopotentiator chitosan oligosaccharide(COS)can recover the reproductive functions of pathological ovarian recession mice and improvetheir immunity. Methods: Forty-three fertile female mice (at around 2 months),in addition to a normal control group (n=8), injected intraperitoneally with busulfan and cyclophosphamide to construct premature ovarian failure mod-els. Three of them were used to test whether the infertility model was constructed successfully by HE staining. Then the models were randomly divided into four groups (n=8) and treated with different dosages of COS by gavage, after which compared different groups' organ ratios (the weight of immune organs and ovary/body weight), ovarian follicles and peritoneal macrophages' phagocytosis as well as estragon(E₂) and pro-gesterone(P) levels in peripheral blood. In addition, we measured the expression dynamics of the ovarian protein reproductive cell marker mouse vasa homolog(MVH), germ stem cell marker OCT-4 in ovarian surface epithelium (OSE) and part of immune factors including tumor necrosis factor (TNF-α),interleukin-2(IL-2)as well as IL-6 to analyze the correlativity between germline stem cells marker dynamics and im-mune factors expression changes. Results: With increasing dosages of COS, organ ratios of ovaries, thymus and spleen both went up syn-chronously; The whole number of follicles and every stages of follicles are all presenting with progressive tendency; E₂ level in peripheral blood ascends, however, progesterone level declined relatively; Neutral red experiment revealed the phagocytosis ability of peritoneal macrophages became stronger with increasing dosages of COS; the results of Western blot had shown that no matter the expression level of germ stem cells marker or immune factors were all presenting increasing tendency, which means that the expression level dynamics of germ stem cell marker has a positive correlation with immune factors expression changes. The results were statistically significant. Conclusion: COS could improve the immunity of mice with pathological ovarian recession and at the same time it would promote the proliferation and differentiation of female germ line stem cells (FGSCs), and then helped saving ovarian functionsto some extent.

Key words: COS, immunity, POF, FGSCs, restoration of ovarian function