Results obtained from three independent experiments showed

that although Treg cells from uninfected animals are able to suppress proliferation at various degrees (36.1–85.7%), Treg cells from infected mice induced a significantly higher suppression of target cells proliferation (84.3–97.4%); as expected, Treg cells alone were unable to proliferate under these conditions. These results demonstrate that during infection, the residual activated Treg cells display an increased suppressive capacity. The activated phenotype and the increased suppression capacity of the residual Treg cells could explain the apparent discrepancy between the immunosuppression www.selleckchem.com/products/Vorinostat-saha.html and the reduced proportion of Treg cells observed during infection. In a first attempt to evaluate the role of Treg cells in the observed immunosuppression, we injected animals with anti-CD25 mAb and examined whether proliferation was recovered. However, as we previously reported, treatment of C57BL/6J mice with anti-CD25 mAb before infection eliminates mainly activated cells, and thus the role of Treg cells is impossible to elucidate using this approach 38. Thus, we used Foxp3EGFP mice to directly

assess whether Treg cells mediate immunosuppression. Foxp3+ cells were eliminated by cell sorting (Fig. 4A) and proliferation of Foxp3− cells was analysed (Fig. 4B). As expected, proliferation of ungated, CD4+ and CD8+ lymphocytes was suppressed when unsorted splenocytes were assayed. These results are indistinguishable

from those shown in Fig. 1, demonstrating that the EGFP+ phenotype does not alter the Ku-0059436 datasheet immunosuppression pattern of T. gondii-infected mice. When Foxp3+ cells were eliminated from infected mice splenocytes, a proliferation recovery was clearly observed in the ungated population. CD4+ cells showed a strong proliferation, similar to that observed in cells from uninfected mice. CD8+ Casein kinase 1 cells from infected animals also recovered their proliferative response. Elimination of Foxp3+ cells from uninfected mice did not alter proliferation of CD4+ nor CD8+ cells. Statistical analysis of the data collected from two independent experiments confirmed that after Treg-cell removal the percentage of divided CD4+ cells from infected mice was significantly enhanced and was similar to that of cells from uninfected animals (Fig. 4C); a non-significant increase in the percentage of divided cells from the ungated and CD8+ subsets was observed. Since the percentage of divided cells only represents the proportion of the original population that responded by dividing 39 we also calculated the percentage of proliferating cells (cells found in any round of division). Figure 4D shows that when Treg cells are eliminated, the percentages of proliferating CD4+ and CD8+ cells are similar for uninfected and infected animals.