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Natural killer cell receptors (NKRs) are expressed on the surface of NK cells and T cells, participating in the regulation of downstream signal activation and inhibition, and actively involved in modulating immune responses. They possess C-type lectin-like domains that have lost the ability to bind Ca²⁺, instead participating in protein-protein interactions rather than carbohydrate binding.

  
The KLRB1 protein (NKR-P1A or CD161), a type II transmembrane protein belonging to the C-type lectin-like receptor family, is expressed on NK cells and subsets of CD4⁺ and CD8⁺ T cells. As an inhibitory receptor on mature NK cells, it inhibits NK cell cytotoxicity and cytokine secretion. Blocking or inactivation of CD161 can enhance T cell-mediated killing of gliomas, favoring the control of tumor growth in vivo.

  
Lectin-like transcript 1 (LLT1 or CLEC2D) is the ligand for the CD161 receptor expressed on natural killer cells and T cells. CD161 inhibits NK cell cytotoxicity and IFN-γ secretion by binding to LLT1 expressed on activated leukocytes. The LLT1/CD161 interaction shuts down NK cell activation while co-stimulating T cells.

The CD161 Effector Reporter Cell reporter gene drug target model effectively simulates the signal transduction process of CD161 in vivo, with the principle shown in the figure below.

Figure 1. Schematic of the CD161 Effector Reporter Cell Model.

Figure 2. Dose Response of CD161 Blocking Antibody in CD161 Effector Reporter Cell (C8) With CLEC2D aAPC Cell.

Cell Passage Procedures

1.This cell line grows in suspension.
2.Upon receipt, cells should be thawed immediately or stored in liquid nitrogen until use.
3.Before thawing, pre-warm the water bath and culture medium to 37 °C, and prepare a small amount of dry ice.
4.Remove the cryovial from storage and transport it to the cell culture laboratory on dry ice.
5.Rapidly thaw the cells in a 37 °C water bath. Once the cells are completely thawed, spray the cryovial with 70% ethanol for disinfection and transfer it to a biosafety cabinet.
6.Add 10 mL of pre-warmed culture medium into a 15 mL centrifuge tube. Transfer the contents of the cryovial into the tube and centrifuge at 1000 rpm for 5 minutes.
7.Carefully discard the supernatant. Resuspend the cell pellet in 5 mL of pre-warmed culture medium by gentle pipetting. Immediately perform cell counting and adjust the cell density to 3–6 × 10⁵ cells/mL based on the counting results, then transfer the cells into a culture flask.
8.Count the cells every 1–2 days. When the cell density exceeds 1 × 10⁶ cells/mL, passage the cells promptly or add fresh culture medium. Maintain the cell density between 2 × 10⁵ and 1 × 10⁶ cells/mL.

Suspension Cell Cryopreservation Procedure:

1.Collect 8 × 10⁶ cells, centrifuge, and discard the supernatant.
2.Add 1 mL of cell freezing medium (90% FBS + 10% DMSO) and gently pipette to mix thoroughly. Transfer the suspension into a cryovial.
3.Immediately place the cryovial into a controlled-rate freezing container (Nalgene 5100-0001), fill with isopropanol up to the indicated level, and store at −80 °C.
4.After 24 hours, transfer the cryovial to liquid nitrogen for long-term storage.