关键词: 弓形虫, 排泄分泌抗原, CD4+CD25+ Foxp3+ T细胞, 肺癌, 小鼠

Abstract: Objective　To investigate the effect of Toxoplasma gondii excretory?secretory antigens (ESA) on CD4+CD25+ Foxp3+ T (Treg) cells in mice carrying Lewis lung carcinoma, and examine the inhibitory effect of T. gondii ESA on tumor growth. Methods　C57BL/6 mice were randomly assigned into the PBS group (n = 14) and the Lewis group (n = 34). Mice in the Lewis group were subcutaneously injected with 2 × 105 Lewis lung carcinoma cells in the right axilla, while animals in the PBS group were injected with the same volume of sterile PBS. On day 7 post?injection (D7), mice in the PBS group were further divided into the PBS2 group and the PBS2 + ESA group, of 7 mice in each group, and mice in the Lewis group were further divided into the Lewis2 group and the Lewis2 + ESA group, of 17 mice in each group. Then, mice in the PBS2 + ESA group and the Lewis2 + ESA group were intraperitoneally injected with 100 μL of ESA. The mouse spleen coefficient was calculated in each group 7 days post?injection with ESA, and the changes of Treg cell counts and the long?term tumor growth were measured in tumor?bearing mice. Results　The spleen coefficient was significantly greater in the PBS2 + ESA group and the Lewis2 + ESA group than in the PBS2 (0.66% ± 0.09% vs. 0.30% ± 0.02%, P < 0.05) and Lewis2 groups (0.69% ± 0.07% vs. 0.33% ± 0.03%, P < 0.05) 7 days post?treatment with ESA, respectively, and the percentage of splenic Treg cells in splenocytes was significantly lower in the PBS2 + ESA group and the Lewis2 + ESA group than in the PBS2 (1.28% ± 0.14% vs. 2.06% ± 0.07%, P < 0.05) and Lewis2 groups (1.58% ± 0.14% vs. 2.44% ± 0.23%, P < 0.05), respectively. T. gondii ESA treatment caused a delay in tumor growth, and the tumor size was significantly smaller in the Lewis2 + ESA group than in the Lewis2 group (P < 0.05). Conclusion　T. gondii ESA may reduce the proportion of splenic Treg cells in splenocytes and inhibit tumor growth in mice carrying Lewis lung carcinoma.

Key words: Toxoplasma gondii, Excretory?secretory antigen, CD4+CD25+ Foxp3+ T cell, Lung carcinoma, Mouse