3e). At all the doses tested, there was no significant difference in IL-2 production by T cells activated by SD-4+/+ versus SD-4−/− selleck chemicals llc DC. Altogether, SD-4 deletion had no impact on T-cell responses in the absence of accessory signals delivered by DC, but it augmented the DC-induced response (enhanced co-stimulatory signals resulting from lack of the inhibitory function

of DC-HIL/SD-4 between APC and T cells). Since SD-4−/− T cells were hyper-reactive to allo-antigen in the mixed lymphocyte reaction (Fig. 3a), we examined their effect on acute GVHD (Fig. 4). BALB/c mice were γ-irradiated at a sub-lethal dose and then infused with T-cell-depleted allogeneic BM cells (from C57BL/6 mice) with or without CD3+ T cells isolated from KO or WT mice. Body weight was noted weekly and survival was noted daily through to day 100. All mice lost about 30% of initial body weight within a week after BM transplantation,

but recovered some weight during the 2nd week. Thereafter, differentially treated mice displayed disparate HIF-1 cancer outcomes (Fig. 4a). Mice that received BM cells alone completely recovered their weight 3 weeks post-BM transplantation and survived for at least 100 days. Mice that received BM cells plus SD-4+/+ T cells partially recovered their weight, with 50% dying by day 32, and the rest survived for at least 100 days (Fig. 4b). By contrast, mice that received BM cells plus SD-4−/− T cells lost weight progressively (up to 40%) due to severe diarrhoea, with 50% dying by day 14, and all dead by day 32. We also examined proliferation of infused T cells in recipients, by measuring the number of donor-derived T cells (H-2Kb+) in spleen and liver of mice at day 5 post-BM transplantation (Fig. 4c,d). In spleen (Fig. 4c), there was twofold to threefold greater CD4+ and CD8+ SD-4−/− T cells than SD-4+/+ T cells, and also more CD69+ (activated) cells than in recipients of SD-4+/+ T cells. Similar results were observed in liver, which is another major target of acute GVHD (Fig. 4d).[1] These results indicate that infusion of T cells devoid

of SD-4 worsens morbidity and mortality of acute GVHD, most likely through hyper-reactivity to allo-antigen. Because donor-derived Treg cells are known to play a pivotal cAMP role in preventing GVHD induced by co-injection of BM cells and T cells isolated from C57BL/6 mice into total body γ-irradiated BALB/c mice,[24] we studied the influence of SD-4 deletion on the T-cell-suppressive activity of Treg. We examined expression of SD-4 on conventional CD4+ Foxp3− T cells (Tconv) versus CD4+ Foxp3+ Treg cells (Fig. 5). The Tconv and Treg cells freshly isolated from naive WT mice represented 90% and 10%, respectively, and neither expressed SD-4. In contrast, PD-1 was expressed by a minuscule fraction of Tconv cells (4·6%) and by some Treg cells (22% of Foxp3+ cells) (Fig. 5a). The Tconv and Treg cells were activated by culture for 2 days with immobilized anti-CD3/CD28 antibody.