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Programmed Cell Death Protein 1 (PD-1), a receptor expressed on activated T cells, binds to its ligands PD-L1 and PD-L2 to negatively regulate immune responses. PD-1 ligands are present in most cancers, and the PD-1-PD-L1/2 interaction inhibits T cell activity, allowing cancer cells to evade immune surveillance. Binding of PD-1 to PDL1 can weaken T cell-mediated immune surveillance, leading to impaired immune responses and even T cell apoptosis. PD-1-PD-L1 inhibitors can relieve immune suppression of anti-tumor T cells, resulting in T cell proliferation, infiltration into the tumor microenvironment, and induction of anti-tumor responses. The PD-1-PD-L1 signaling pathway is an important component of tumor immune suppression, which can inhibit T lymphocyte activation, enhance tumor cell immune tolerance, and thus achieve tumor immune escape.

  
TIGIT, also known as WUCAM, Vstm3, or VSIG9, is a co-inhibitory receptor belonging to the immunoglobulin superfamily. TIGIT is highly expressed on effector CD4+ and CD8+ T cells, regulatory T cells, and NK cells. TIGIT ligands include CD112 and the poliovirus receptor (PVR, also known as CD155, Necl-5, and Tage4), with PVR being a high-affinity homologous receptor for TIGIT. Additionally, TIGIT competes with CD226 (DNAM-1) and CD96 (TACTILE) for ligands. TIGIT can effectively block the binding of CD155 to CD96 or CD226, further demonstrating TIGIT's highest affinity for CD155. TIGIT not only competes with CD226 for ligands but also directly cis-binds to CD226 to prevent its homodimerization, thereby preventing CD226 from binding to CD155 and exerting co-stimulatory effects.

  
Studies have shown that in mice treated with anti-PD1 therapy, blocking TIGIT (T cell immunoglobulin and ITIM domain) can enhance the effector activity of CD8+ T cells by secreting IFNγ and TNF-α, leading to significant tumor and viral clearance. TIGIT is highly upregulated on tumor-infiltrating T cells, and functional blockade of CD226 can counteract tumor regression induced by combination therapy in mice. This research reveals the potential of combined PD-1 and TIGIT therapy in improving immune responses in patients with cancer or chronic viral infections.

PDL1&CD155 TCR Activator CHO serves as target cells for PD1&TIGIT Dual Effector Reporter Cells, effectively mimicking the intracellular signal transduction process of PD1 and TIGIT in vivo. The principle is illustrated in the figure below.

Figure 1. Schematic diagram of the CHO-K1 Human PDL1&CD155 TCR Activator Cell model.

Figure 2. Dose Response of Blocking Antibodies in PD1&TIGIT Dual Effector Reporter Cell (C7) with PDL1&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 PDL1&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.