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TIGIT—also known as WUCAM, Vstm3, or VSIG9—is a co-inhibitory receptor belonging to the immunoglobulin superfamily. TIGIT consists of an extracellular immunoglobulin variable (IgV) domain, a type I transmembrane domain, and an intracellular domain containing both an ITIM motif and an Ig-tail tyrosine-like motif (ITT). TIGIT is expressed on activated conventional αβ T cells, as well as on memory T cells, Tregs, follicular helper T cells, and NKT cells. By activating inhibitory receptors within T cells, natural killer (NK) cells, and regulatory T cells (Tregs), TIGIT has emerged as a promising target for immunotherapy.

The ligands for TIGIT include CD112 and the Poliovirus Receptor (PVR—also known as CD155, Necl-5, and Tage4), with PVR serving as TIGIT's high-affinity cognate receptor. Furthermore, TIGIT competes with CD226 (DNAM-1) and CD96 (TACTILE) for ligand binding. TIGIT effectively blocks the binding of CD155 to either CD96 or CD226, thereby providing further evidence that TIGIT possesses the highest affinity for CD155. TIGIT not only competes with CD226 for ligands but can also directly bind to CD226 *in cis*, thereby preventing its homodimerization and rendering CD226 unable to bind to CD155 to exert its co-stimulatory function.

CD155 is primarily expressed on the surface of dendritic cells (DCs), T cells, B cells, and macrophages; it is also expressed to varying degrees in non-hematopoietic tissues, such as the kidneys, the nervous system, and the intestines. Additionally, CD155 has been reported to be highly expressed in various human malignancies, including melanoma, pancreatic cancer, colon cancer, lung adenocarcinoma, and glioblastoma. As a cell adhesion molecule, CD155 influences cellular proliferation, migration, invasion, and adhesion through tumor-associated signaling pathways. Serving as target cells for TIGIT NFAT-Luc Jurkat cells, CD155 TCR Activator CHO cells effectively mimic the in vivo signal transduction process of TIGIT; the underlying principle is illustrated in the figure below.

Figure 1. Schematic Diagram of the CD155/TCR Activator CHO-K1 Cell Model

Figure 2. Recombinant CD155/TCR Activator/CHO stably expressing CD155.

Figure 3. Dose Response of TIGIT Monoclonal Antibody in TIGIT NFAT-Luc Jurkat  (C26) with CD155 TCR activator CHO.

Cell Resuscitation
1)Rapidly thaw the frozen cells in a 37 °C water bath for approximately 60 seconds. Once thawed (which may take slightly less or more than 60 seconds), immediately transfer the cell suspension from the cryovial into a 15 mL centrifuge tube containing 10 mL of pre-warmed  CHO-K1 Human CD155/TCR Activator Cell complete culture medium.
2)Centrifuge cells at 1000 rpm for 5 min to remove medium, then resuspend cells in 5 mL of pre-warmed complete medium.
3)Transfer the cell suspension into a T25 culture flask and incubate at 37 °C with 5% CO₂.
4)After approximately 24–36 hours, replace the medium or passage the cells to remove non-adherent dead cells.

Subculturing procedure
1)When the cell density reaches the appropriate confluency for passaging, wash the cells with PBS, then add 1 mL trypsin to detach the cells. When more than 80% of the cells detach upon gently tapping the culture flask, add complete culture medium to terminate digestion. Gently pipette to obtain a single-cell suspension, transfer to a 15 mL centrifuge tube, and centrifuge at 1000 rpm for 5 minutes.

2)Discard supernatant after centrifugation. Resuspend cells in fresh medium to a single-cell suspension and transfer to a new culture flask for continued growth.

Cell Freezing
After trypsinization and centrifugation of cells from each T75 flask or 10 cm culture dish, discard the supernatant. Add 2 mL of cryopreservation medium (90% FBS + 10% DMSO), gently resuspend thoroughly, and aliquot into two cryovials. Immediately place the cryovials into a controlled-rate freezing container (e.g., Nalgene 5100-0001), fill with isopropanol to the indicated level, and store at −80 °C. After 24 hours, transfer the cryovials to liquid nitrogen for long-term storage.