OBJECTIVE: To evaluate the efficacy of gecko polysaccharide on the cyclophosphamide-induced suppressed immune response in mice.METHODS: Polysaccharides were extracted from fresh gecko for the first time using an orthogonal method and protein was removed using Sevag reagent(chloroform∶N-butanol, 5∶1, v/v). The gecko polysaccharide(GPCE) content was determined by the phenol-concentrated sulfuric acid method. An immunocompromised mouse model was established by intraperitoneally injecting cyclophosphamide at 100 mg/kg into 48 mice. The effects of GPCE on immune regulation in mice were assessed by a thymus-spleen index, serum hemolysin levels,and the proliferation of splenic lymphocytes.Spleen cell CD4+, CD8+, and the CD4+/CD8+ ratio were evaluated by flow cytometry and the tumor necrosis factor-α(TNF-α) levels were measured by ELISA.RESULTS: The optimal extraction process for gecko polysaccharide included a 1∶20 ratio of material to liquid(v/v), an extraction temperature of 60 ℃ and a time of 2 h. The polysaccharide content of the extract was 65.74%. GPCE was analyzed by HPLC and primarily contained glucose and small amounts of mannose, rha, and gal. Compared with the model,the thymus index, the spleen index were indices for GPCE increased with dose, whereas the high and medium groups exhibited significant differences(P < 0.05, P < 0.01). Higher doses of GPCE increased serum TNF-α levels and there was a significant difference between the medium and high GPCE doses and the model(P < 0.05, P < 0.01); The number of CD4+ cells and the CD4+/CD8+ ratio in the gecko polysaccharide group were increased(P < 0.05) and there was no statistical difference in the number of CD8+ cells in the gecko polysaccharide group(P >0.05); The high GPCE dose significantly increased the level of serum hemolysin(P < 0.01).CONCLUSIONS: Gecko polysaccharide significantly improved the suppressed immune response induced by cyclophosphamide in mice and promoted the secretion of tumor necrosis factor. The mechanism of gecko polysaccharide as an antitumor agent warrants further study.