1 and 2). This relative stability

of the CD277 surface expression prompted us to further investigate the potential action of the CD277 engagement in immune cells. The role of CD277 engagement was investigated on TCR-induced cytokine production. Purified CD4+ T cells from healthy donors were cultured during 24–72 h with CD3+CD28 mAbs or CD3+CD277 mAbs or CD3 mAb+IgG1 (control condition). After 24 h of culture, IL-2 and IFN-γ production by CD4+ T cells were measured by ELISA. As expected, these two cytokines were secreted in large amounts after CD3+CD28 stimulation by comparison with the control condition (Fig. 1A: IL-2, 120 pg/mL, p=0.0079; Fig. 1B: IFN-γ, 7000 pg/mL, p=0.0317). Although the IL-2 levels produced by the CD3+CD277 co-activated CD4+ T cells were lower than the IL-2 levels obtained with CD3+CD28 Epigenetics inhibitor co-stimulation, the quantity of IL-2 induced by CD3+CD277

co-activation was significantly higher than that induced with the IgG1 control (Fig. 1A: IL-2, 40 pg/mL, p=0.0159). Moreover, click here IFN-γ secretion was strongly enhanced by CD3+CD277 co-activation (Fig. 1B: IFN-γ, 9000 pg/mL, p=0.0159) compared with the control situation, and, surprisingly, the production was even greater than that obtained after CD3+CD28 co-activation. A similar effect was obtained regarding the expression profile of the activation marker CD25 under CD3+CD277 co-stimulation (Fig. 1C). Altogether, these results suggest that the CD277 molecule acts as a T-cell co-stimulatory molecule for cytokine

production. To investigate whether similar co-stimulatory effects are obtained in NK cells, CD107 expression under P815-redirected cytotoxicity (Fig. 1D) and IFN-γ assays (Fig. 1E) were performed. The NK cells are stimulated via two different activation receptors, CD16 or NKp46, using specific mAbs, in the presence of isotypic control, CD277 mAb, anti-DNAM (positive control for a co-stimulation of the activation receptors) or anti-NKG2A (positive control for a co-inhibition of the activation receptors). The CD277 triggering tuclazepam alone did not induce any effect on NK cell stimulation. Moreover, in contrast to DNAM (co-stimulation) or NKG2A (co-inhibition), CD277 engagement fails to modulate CD16- or NKp46-induced NK cell activation, both for degranulation as evaluated by CD107a/b staining and IFN-γ secretion. These results show that CD277 is not involved in the regulation of NK cell activation, contrary to that which was observed with T cells. The BTN3/CD277-mediated positive signals shown in T-cell cytokine production (Fig. 1A and B) are not in accordance with previous work in which another CD277 mAb clone has been used 13. To further test the robustness of our results, we investigated the capacity of CD277 triggering to regulate TCR-induced early T-cell events such as signaling pathways.