Sun et al. Journal of Experimental & Clinical Cancer Research 2011, 30:82 http://www.jeccr.com/content/30/1/82 Page 7 of 10 Figure 3 Inductive effect of CHO cells with IDO transfection on Tregs. (A) Representative FACS scatter plots of the CD4+CD25+CD127- T cells in CD3+ T cells 7 days after incubation. (B) Representative FACS scatter plots of CD4+CD25+CD127- T cells 7 days after co-culture with CHO/ EGFP cells. (C) Representative FACS scatter plots of CD4+CD25+CD127- T cells 7 days after co-culture with IDO+ CHO cells. (D) Representative FACS scatter plots of CD4+CD25+CD127- T cells 7 days after co-culture with IDO+ CHO cells and inhibitor 1-MT. (P2 region represents CD4+ T cells, Q4 region represents CD4+CD25+CD127- T cells.) (E) Relative percentages of CD4+CD25+CD127- T cells in CD4+ T cells. The columns showed the average (%) ± SD from 3 independent experiments. IDO+ CHO cells had more Tregs in T cells after co-culture than in control groups. The differences were statistically significant (P < 0.05). patients with breast cancer, a mechanism may exist that can increase the proportion of Tregs. We also added 1- MT, the specific inhibitor of IDO in the co-culture system composing of CHO/IDO cells and CD3+T cells to eluci- date the regulatory effect of IDO both in promoting apop- tosis and increasing Tregs. It demonstrated that 1-MT could efficiently reversed enhancement of T cells apoptosis and increased Tregs proportion in vitro. It implied that IDO is indeed responsible for the changes observed in vitro. Some studies have indicated a close relationship between IDO and regulatory T cells. Some dendritic