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Citation Zhang H, Hu X, Liu X, Zhang R, Fu Q, Xu X. The Treg/Th17 Imbalance in Toxoplasma gondii-Infected Pregnant Mice. Am J Reprod Immunol 2012; 67: 112-121 Aim To evaluate whether impaired Treg/Th17 balance exists in the pregnant mice infected with Toxoplasma gondii. Method of Study Regulatory T (Treg) and T-helper type 17 (Th17) cells were measured in both placenta and spleens of the pregnant mice infected with and without T. gondii by flow cytometry. The mRNA and protein expression levels of transforming growth factor-β (TGF-β) and interleukin-17A (IL-17A) were analyzed using real-time PCR and enzyme-linked immunosorbent assay (ELISA). The mRNA expression levels of forkhead box P3 (Foxp3), retinoic acid-related orphan receptor γt (RORγt), and IL-6 were also analyzed using real-time PCR. The correlations of the ratio of Treg/Th17 to the mRNA or protein expression level of those factors were analyzed by Spearman's correlation analysis. Data were analyzed by unpaired t-test and paired t-test. Results The proportion of Tregs or Th17 cells in the placenta and spleens of the T. gondii-infected pregnant mice was significantly lower or higher than in those of non-infected mice, respectively. Upregulation of TGF-β and downregulation of IL-17A were found in the placenta of T. gondii-infected pregnant mice. The ratio of Treg to Th17 was significantly lower in the infected mice than that in the non-infected mice ( P < 0.01).The ratio of Treg to Th17 positively or negatively correlated with the protein expression level of TGF-β ( r = 0.6204, P < 0.05) or IL-17A ( r = −0.6296, P < 0.05), respectively. The ratio also positively correlated with the mRNA expression level of Foxp3 ( r = 0.7985, P < 0.01), but negatively correlated with the mRNA expression level of RORγt ( r = −0.6153, P < 0.05), and IL-6 ( r = −0.7492, P < 0.01). Conclusion TheTreg/Th17 imbalance exists in the pregnant mice infected with T. gondii, which is associated with the expression of related cytokine and key transcription factors. This result suggests that the embryo loss caused by this parasite may be associated with a reduced ratio of Treg to Th17 cell number. [ABSTRACT FROM AUTHOR]