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Members of the Leukocyte Immunoglobulin-like Receptor B (LILRB) family act as negative regulators of myeloid cell activation. LILRBs are Type I transmembrane glycoproteins that function as immunosuppressive receptors; currently known members of the LILRB family include LILRB1, LILRB2, LILRB3, LILRB4, and LILRB5.

Leukocyte Immunoglobulin-like Receptor Subfamily B Member 1 (LILRB1)—also known as Immunoglobulin-like Transcript (ILT) 2, Monocyte/Macrophage Ig-like Receptor (MIR) 7, and CD85j—possesses inhibitory functions. LILRB1 consists of an extracellular region containing four Ig-like domains and a cytoplasmic tail containing four ITIM motifs. Due to alternative splicing, LILRB1 exists in 13 distinct isoforms. Like other LIRs, LILRB1 is also expressed as a soluble isoform, which is capable of binding to ligands and may interfere with the interactions between ligands and cell-surface LILRB1 receptors. LILRB1 is expressed in a variety of immune cells—including macrophages and certain cytotoxic lymphocytes—and modulates diverse immune responses by interacting with classical and non-classical Human Leukocyte Antigen (HLA) Class I molecules. This inhibitory receptor for HLA Class I molecules is expressed by numerous immune cells, including certain cytotoxic lymphocytes and macrophages. Recently, HLA Class I expression was shown to protect cancer cells from macrophage-mediated phagocytosis through its interaction with LILRB1, thereby establishing LILRB1 as a "phagocytosis checkpoint."

The Jurkat E6.1 Human LILRB1 Effector Reporter Cell Model—effectively simulates the signal transduction process of LILRB1*in vivo*. The underlying principle is illustrated in the figure below.

Figure 1. Schematic Diagram of theJurkat E6.1 Human LILRB1 Effector Reporter Cell  Model

Figure 2.Dose Response of LILRB1 Blocking Antibody in LILRB1 Effector Reporter Cell (C13)With B2M-associated HLA-G/aAPC Cell (C15).

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.