Chitosan oligosaccharides (COS), hydrolyzed products of chitosan, was found to display various biological activities. Herein, we assessed the immunostimulatory activity of COS both in in vitro and in vivo studies. In vitro cytotoxicity studies to murine macrophage RAW264.7 revealed that COS is safe even at the maximum tested concentration of 1000 μg/mL. It also stimulates the production of nitric oxide (NO) and tumor necrosis factor (TNF-α) and enhances the phagocytosis in COS-stimulated RAW264.7. We have shown that the COS could significantly (P < 0.05) restore the reduced immune organs indices, phagocytic index, lymphocyte proliferation, natural killer cell activity, and antioxidant enzyme activities in a cyclophosphamide-induced immunosuppressed mice model. COS can also improve the survival rate in irradiation injury mice and significantly (P < 0.05) increased the spleen indices and up-regulates the CD4+/CD8+ ratio in splenocytes. In sum, the aforementioned results suggest that COS might has the potential to be used as an immunostimulatory agent in patients with immune dysfunctions or be a model for functional food development. PRACTICAL APPLICATION COS might has the potential to be used as an immunostimulatory agent in patients with immune dysfunctions or be a model for functional food development.

中文翻译：

---

壳寡糖对环磷酰胺诱导的小鼠免疫抑制和辐照损伤的保护作用

壳寡糖 (COS) 是壳聚糖的水解产物，被发现具有多种生物活性。在此，我们在体外和体内研究中评估了 COS 的免疫刺激活性。对鼠巨噬细胞 RAW264.7 的体外细胞毒性研究表明，即使在 1000 μg/mL 的最大测试浓度下，COS 也是安全的。它还刺激一氧化氮 (NO) 和肿瘤坏死因子 (TNF-α) 的产生，并增强 COS 刺激的 RAW264.7 中的吞噬作用。我们已经表明，COS 可以显着（P < 0.05）恢复环磷酰胺诱导的免疫抑制小鼠模型中降低的免疫器官指数、吞噬指数、淋巴细胞增殖、自然杀伤细胞活性和抗氧化酶活性。COS还可以提高辐射损伤小鼠的存活率，显着(P < 0.05)增加脾脏指数，上调脾细胞中CD4+/CD8+比率。总之，上述结果表明 COS 有可能用作免疫功能障碍患者的免疫刺激剂或成为功能性食品开发的模型。实际应用 COS 有可能被用作免疫功能障碍患者的免疫刺激剂或成为功能性食品开发的模型。