In Tg mice. Immunofluorescence using a primary antibody (Iba-1) in conjunction with TRITC-conjugated secondary antibody was used to label microglia. Thiofalvin S staining was used to label the A plaque. A B Representative result of activated microglia in the brain of APPswe/PS1dE9 transgenic mice with systemic transplantation of UC-MSCs educated CD4+CD25+ T regulatory cells (A) and PBS (B). C The bar showed that systemic transplantation of UC-MSCs educated CD4+CD25+ T regulatory cells significantly reduced the number of the Iba-1 positive cells in the brain of Tg mice. 10457188 Data from 10 serial sections at an interval of every 5th section through the bilateral cortex and hippocampus were summed to derive representative values for each animal for positive cells and 6 mice per group. Data are reported as mean .E.M. *p<0.05. D E Representative results of A plaque in the cortex of PPswe/PS1dE9 transgenic mice with systemic transplantation of UCMSCs educated CD4+CD25+ T regulatory cells (D) and PBS (E). G H Representative results of A plaque in the hippocampus of APPswe/PS1dE9 transgenic mice with systemic transplantation of UC-MSCs educated CD4+CD25+ T regulatory cells (G) and PBS (H). F I The bar showed that Systemic transplantation of UC-MSCs educated CD4+CD25+ T regulatory cells significantly reduced the area of A plaque in the cortex (F) and hippocampus (I). Data from 10 serial sections at an interval of every 5th section through the bilateral cortex and hippocampus were summed to derive representative values for each animal for total plaque area and 6 mice per group. Data are reported as mean .E.M. **p<0.01. J K The bar showed that systemic transplantation of UC-MSCs educated CD4+CD25+ T regulatory cells significantly reduced the level of the whole brain soluble A1-42 (J) and A1-40 (K) by ELISA test. Data from 6 mice are reported as mean .E.M. *p<0.05.doi: 10.1371/journal.pone.0069129.gTregs Improved Impaired Cognition of ADFigure 4. Transplantation of UC-MSCs educated CD4+CD25+ T regulatory improved the impairments of learning and memory in Tg mice. A. Latency to find the platform during the training was reported as mean .E.M. Each point represented the mean daily values of four trials per day. The latency of the group with systemic transplantation of UC-MSCs educated CD4+CD25+ T regulatory cells was significantly lower than the group receiving vehicle after the last 3 days of training. *p 0.05. B C The bar graphs showed the number of platform location cross (B) and the time in the target section (C) during the probe trial within 60s were significantly improved in the group with systemic transplantation of UC-MSCs educated CD4+CD25+ T regulatory cells. Data are reported as mean .E.M. **p<0.01. D E Representative visible learning curve of transgenic mice with transplantation of UC-MSCs educated CD4+CD25+ T regulatory cells (D) and PBS (E) at day 5 of first training.doi: 10.1371/journal.pone.0069129.gto find the hidden platform (Figure 4D 4E). We also noticed although systemic transplantation UC-MSCs educated CD4+CD25+ T regulatory cells could decrease the escape latency, the transgenic mice still had the longer escape latency than the WT mice. There was no significant difference in the speed of three groups (data not show). After 24h of the last training, we removed the hidden platform and the mice were tested in probe trial for assessing the ability of memory. As illustrated in Figure 4B 4C, we observed that transplantation.