High expression levels of BTN3 transcripts could be found in human lymphoid tissues, mainly spleen, LNs and peripheral blood lymphocytes (PBLs) 1. Using an anti-CD277 monoclonal antibody, it was also demonstrated that BTN3A was expressed on most immune cells, including not only T and B lymphocytes, but also NK cells, monocytes,

DCs, as well as hematopoietic precursors and some tumor www.selleckchem.com/products/epacadostat-incb024360.html cell lines 1. Research on the counter-receptor of BTN3A showed that neither CD28, CTLA-4, ICOS, PD-1 nor BTLA were involved, and, except from some (but not all) acute T leukemia cell lines, was absent from both resting and activated T cells. Similar experiments were performed with BTN2A and showed that BTN2A mRNA was expressed in most human tissues, but protein expression was significantly lower in leukocytes. These experiments also revealed that a particular glycosylated form of BTN2A1 binds a lectin molecule, DC-SIGN, found on DCs, confirming the involvement of the BTN family as co-regulators of the immune system 10. Furthermore, the binding of human BTN2A1 to DC-SIGN was also dependent on heavy glycosylation of the receptor when expressed by tumor cells. In two recent studies, the recombinant murine BTNL2 protein bound an unidentified receptor on B cells and T cells 11, distinct from the known receptors of the B7 molecules Z-VAD-FMK nmr 12. Both groups demonstrated that the activation of mouse T cells,

through TCR engagement, was inhibited by the ligation of BTNL2 with its putative receptor on T cells. Recently, a report proposed that BTN3A1 is an additional co-inhibitor receptor of T-cell activation 13. However, the expression of BTN3A1 on lymphocytes as well

as on NK cells prompted us to investigate Thiamine-diphosphate kinase whether BTN3A1 was involved in the regulation of innate effectors (NK cells) as well as T lymphocytes ant to explore the potential role of BTN3 (CD277) on the regulation of T lymphocyte and NK cell activation. Our results show that CD277-triggering in CD4+ T cells considerably enhances TCR-induced signaling, cytokine production and CD4+ T-cell proliferation. In contrast, CD277 triggering is not involved in CD16- or NKp46-induced NK-cell activation. The differential behaviour of CD277 in these two immune cell types prompted us to investigate the relative expression of the different BTN3 isoforms in both T cells and NK cells. To identify possible differences at the protein level, detection of CD277 surface expression was performed on several T and NK differentiation subsets from healthy donors (n=4). Using multi-parametric flow cytometry, CD3+CD4+, CD3+CD8+ and NK cell populations were analyzed (see Supporting Information, Figs. 1 and 2). Staining with the CD277 mAb reveals a strong expression of CD277 in all cell types CD4+ helper T cells, cytolytic CD8+ T cells and NK cells (Figs. 1B and 2B).