5+ Foxp3DTR+ mice compared with the controls.

The partial ablation of Treg cells did not inhibit the progressive growth of the NIT-1 tumor (Fig. 4A–C). However, as reported before Autophagy inhibitor price [34] and consistent with the adoptive transfer studies in Fig. 2A–D, the residual Treg cells were not sufficient to restrain autoimmune damage in the pancreatic islets [29, 34]; instead, partial Treg depletion caused complete destruction of the tissue. At the tumor site, partial depletion of Treg cells did not cause progression of autoimmune damage, as the inflammatory infiltrates remained at the periphery of tumor mass in both BDC2.5+ Foxp3DTR+ mice or littermate BDC2.5+ Foxp3 DTR− controls after DT treatment (Fig. 4D and E). The studies with insulinoma and lymphoma models identified a suppressive milieu against self-antigen-specific Teff cells, formed by the tumor microenvironment

in combination with Treg cells and MDSCs. Treg cells depend on CTLA4 for suppressive function [8]. CTLA4 is a prototypical inhibitor in antitumor immunity. In humans, expression of CTLA4 varies subtly due to polymorphisms in the CTLA4 locus. To examine how modest variation of CTLA4 impacts tumor destruction by self-antigen-specific Teff cells, we utilized a model of subtle CTLA4 reduction (∼60% in both mRNA and protein) constructed selleck by shRNA transgenesis, CTLA4KD7 [35], which mimics a natural reduction due to genetic variations. The CTLA4KD7 or PL4 vector control line [35]

was crossed with the OT1 transgenic mice. E.G7-OVA lymphoma cells were implanted into RIP-mOVA mice. The lymphoma-bearing mice were treated L-NAME HCl with activated CD8+ Teff cells from OT1.CTLA4KD7/B6 or OT1.PL4/B6 mice. Both CTLA4KD and PL4 control CD8+ Teff cells effectively destroyed healthy pancreatic β cells expressing the OVA antigen, as evidenced by the severe hyperglycemia (Fig. 5A). However, the transgenic CTLA4 shRNA significantly promoted the destruction of lymphoma cells expressing the OVA antigen in the same mice by the OT1 Teff cells (Fig. 5B). We did not detect any difference in circulating TGF-β1 levels between the groups receiving either CTLA4KD7 or control OT1 cells (Supporting Information Fig. 2B) To examine if a subtle reduction in CTLA4 also affects Treg cell potency, we reconstituted neonatal Foxp3-deficient B6 mice with Treg cells from either CTLA4KD7 or PL4 controls, and injected them with syngeneic EL4 lymphoma cells. There was no significant difference in lymphoma cell growth in the two groups of animals (Fig. 5C), indicating that CTLA4 reduction did not impair Treg cell functions in tumor-bearing mice. To further test this observation, we used a Foxp3-deficient BDC2.5 model. As shown in Fig. 1, the absence of Treg cells enabled the animals to reject NIT-1 tumor cells. The Treg cell-deficient mice were reconstituted with self-antigen-specific Treg cells from BDC2.5/NOD.CTLA4KD mice or BDC2.5/NOD.PL4 controls.