The 1G9 monoclonal antibody reacts with mouse TIGIT (T cell immunoreceptor with Ig and ITIM domains). TIGIT is a 26 kDa, type I transmembrane protein and a member of the poliovirus receptor (PVR) family. TIGIT has been found to be expressed on follicular T helper cells in mice while in humans it's expressed by many T cell subsets including activated T cells, follicular T helper cells, memory T cells, and regulatory T cells as well as on NK cells. TIGIT can interact with certain members of the PVR and PVR-like families, including PVR, PVRL2, PVRL3, CD155, and CD112. TIGIT is thought to negatively regulate NK and T cell activation. Binding of TIGIT on T cells by dendritic cells results in their differentiation into a tolerogenic phenotype, with increased secretion of IL-10 and diminished production of IL-12. TIGIT knock-out mice are more susceptible to autoimmune disease.

INVIVOMAB ANTI-MOUSE TIGIT (CLONE: 1G9)

Trsan, T., et al. (2017). “Cytomegalovirus vector expressing RAE-1gamma induces enhanced anti-tumor capacity of murine CD8+ T cells.” Eur J Immunol 47(8): 1354-1367. PubMed

Designing CD8+ T-cell vaccines, which would provide protection against tumors is still considered a great challenge in immunotherapy. Here we show the robust potential of cytomegalovirus (CMV) vector expressing the NKG2D ligand RAE-1gamma as CD8+ T cell-based vaccine against malignant tumors. Immunization with the CMV vector expressing RAE-1gamma, delayed tumor growth or even provided complete protection against tumor challenge in both prophylactic and therapeutic settings. Moreover, a potent tumor control in mice vaccinated with this vector can be further enhanced by blocking the immune checkpoints TIGIT and PD-1. CMV vector expressing RAE-1gamma potentiated expansion of KLRG1+ CD8+ T cells with enhanced effector properties. This vaccination was even more efficient in neonatal mice, resulting in the expansion and long-term maintenance of epitope-specific CD8+ T cells conferring robust resistance against tumor challenge. Our data show that immunomodulation of CD8+ T-cell responses promoted by herpesvirus expressing a ligand for NKG2D receptor can provide a powerful platform for the prevention and treatment of CD8+ T-cell sensitive tumors.

Kourepini, E., et al. (2016). “TIGIT Enhances Antigen-Specific Th2 Recall Responses and Allergic Disease.” J Immunol 196(9): 3570-3580. PubMed

T cell Ig and ITIM domain receptor (TIGIT), expressed on T, NK, and regulatory T cells, is known as an inhibitory molecule that limits autoimmunity, antiviral and antitumor immunity. In this report, we demonstrate that TIGIT enhances Th2 immunity. TIGIT expression was upregulated in activated Th2 cells from mice with experimental allergic disease and in Th2 polarization cultures. In addition, its high-affinity ligand CD155 was upregulated in mediastinal lymph node dendritic cells from allergic mice. In an in vitro setting, we observed that Tigit expression in Th2 cells and its interaction with CD155 expressed in dendritic cells were important during the development of Th2 responses. In addition, blockade of TIGIT inhibited Th2, but had no effect on either Th1 or Th17 polarization. In vivo blockade of TIGIT suppressed hallmarks of allergic airway disease, such as lung eosinophilia, goblet cell hyperplasia, Ag-specific Th2 responses, and IgE production, and reduced numbers of T follicular helper and effector Th2 cells. Thus, TIGIT is critical for Th2 immunity and can be used as a therapeutic target, especially in light of recent findings showing TIGIT locus hypomethylation in T cells from pediatric patients with allergic asthma.

Burton, B. R., et al. (2014). “Sequential transcriptional changes dictate safe and effective antigen-specific immunotherapy.” Nat Commun 5: 4741. PubMed

Antigen-specific immunotherapy combats autoimmunity or allergy by reinstating immunological tolerance to target antigens without compromising immune function. Optimization of dosing strategy is critical for effective modulation of pathogenic CD4(+) T-cell activity. Here we report that dose escalation is imperative for safe, subcutaneous delivery of the high self-antigen doses required for effective tolerance induction and elicits anergic, interleukin (IL)-10-secreting regulatory CD4(+) T cells. Analysis of the CD4(+) T-cell transcriptome, at consecutive stages of escalating dose immunotherapy, reveals progressive suppression of transcripts positively regulating inflammatory effector function and repression of cell cycle pathways. We identify transcription factors, c-Maf and NFIL3, and negative co-stimulatory molecules, LAG-3, TIGIT, PD-1 and TIM-3, which characterize this regulatory CD4(+) T-cell population and whose expression correlates with the immunoregulatory cytokine IL-10. These results provide a rationale for dose escalation in T-cell-directed immunotherapy and reveal novel immunological and transcriptional signatures as surrogate markers of successful immunotherapy.

Chan, C. J., et al. (2014). “The receptors CD96 and CD226 oppose each other in the regulation of natural killer cell functions.” Nat Immunol 15(5): 431-438. PubMed

CD96, CD226 (DNAM-1) and TIGIT belong to an emerging family of receptors that interact with nectin and nectin-like proteins. CD226 activates natural killer (NK) cell-mediated cytotoxicity, whereas TIGIT reportedly counterbalances CD226. In contrast, the role of CD96, which shares the ligand CD155 with CD226 and TIGIT, has remained unclear. In this study we found that CD96 competed with CD226 for CD155 binding and limited NK cell function by direct inhibition. As a result, Cd96(-/-) mice displayed hyperinflammatory responses to the bacterial product lipopolysaccharide (LPS) and resistance to carcinogenesis and experimental lung metastases. Our data provide the first description, to our knowledge, of the ability of CD96 to negatively control cytokine responses by NK cells. Blocking CD96 may have applications in pathologies in which NK cells are important.

Foks, A. C., et al. (2013). “Agonistic anti-TIGIT treatment inhibits T cell responses in LDLr deficient mice without affecting atherosclerotic lesion development.” PLoS One 8(12): e83134. PubMed

OBJECTIVE: Co-stimulatory and co-inhibitory molecules are mainly expressed on T cells and antigen presenting cells and strongly orchestrate adaptive immune responses. Whereas co-stimulatory molecules enhance immune responses, signaling via co-inhibitory molecules dampens the immune system, thereby showing great therapeutic potential to prevent cardiovascular diseases. Signaling via co-inhibitory T cell immunoglobulin and ITIM domain (TIGIT) directly inhibits T cell activation and proliferation, and therefore represents a novel therapeutic candidate to specifically dampen pro-atherogenic T cell reactivity. In the present study, we used an agonistic anti-TIGIT antibody to determine the effect of excessive TIGIT-signaling on atherosclerosis. METHODS AND RESULTS: TIGIT was upregulated on CD4(+) T cells isolated from mice fed a Western-type diet in comparison with mice fed a chow diet. Agonistic anti-TIGIT suppressed T cell activation and proliferation both in vitro and in vivo. However, agonistic anti-TIGIT treatment of LDLr(-/-) mice fed a Western-type diet for 4 or 8 weeks did not affect atherosclerotic lesion development in comparison with PBS and Armenian Hamster IgG treatment. Furthermore, elevated percentages of dendritic cells were observed in the blood and spleen of agonistic anti-TIGIT-treated mice. Additionally, these cells showed an increased activation status but decreased IL-10 production. CONCLUSIONS: Despite the inhibition of splenic T cell responses, agonistic anti-TIGIT treatment does not affect initial atherosclerosis development, possibly due to increased activity of dendritic cells.

Joller, N., et al. (2011). “Cutting edge: TIGIT has T cell-intrinsic inhibitory functions.” J Immunol 186(3): 1338-1342. PubMed

Costimulatory molecules regulate the functional outcome of T cell activation, and disturbance of the balance between activating and inhibitory signals results in increased susceptibility to infection or the induction of autoimmunity. Similar to the well-characterized CD28/CTLA-4 costimulatory pathway, a newly emerging pathway consisting of CD226 and T cell Ig and ITIM domain (TIGIT) has been associated with susceptibility to multiple autoimmune diseases. In this study, we examined the role of the putative coinhibitory molecule TIGIT and show that loss of TIGIT in mice results in hyperproliferative T cell responses and increased susceptibility to autoimmunity. TIGIT is thought to indirectly inhibit T cell responses by the induction of tolerogenic dendritic cells. By generating an agonistic anti-TIGIT Ab, we demonstrate that TIGIT can inhibit T cell responses directly independent of APCs. Microarray analysis of T cells stimulated with agonistic anti-TIGIT Ab revealed that TIGIT can act directly on T cells by attenuating TCR-driven activation signals.