# LILRA5 Gene: Structure, Function, and Clinical Significance ## Key Takeaways - LILRA5 is a type I transmembrane glycoprotein expressed on myeloid cells, acting as an atypical activating receptor that binds HLA class I molecules and signals independently of FcRγ. Its unique ITAM-independent signaling involves SHP-2 recruitment, Syk activation, and subsequent MAPK pathway engagement, leading to cytokine production, degranulation, and enhanced phagocytosis. - The *LILRA5* gene is located on chromosome 19q13.42 within the leukocyte receptor complex, with its myeloid-specific expression driven by promoter elements binding transcription factors like PU.1 and C/EBPα, and regulated epigenetically by DNA methylation and histone modifications. - LILRA5 plays a significant role in both innate immunity and pathological conditions, including inflammatory bowel disease, rheumatoid arthritis, sepsis, and various hematological and solid tumors, where its dysregulation contributes to disease pathogenesis and can serve as a prognostic biomarker. - Viral pathogens like HCMV, HIV, and HBV exploit LILRA5-HLA interactions for immune evasion, often by upregulating HLA-G, which can paradoxically lead to immunosuppression or altered myeloid cell responses that favor viral persistence or disease progression. - Therapeutic strategies targeting LILRA5 are under development, including monoclonal antibodies to block ligand binding, antibody-drug conjugates for targeted cancer therapy, small-molecule inhibitors, and RNA-based approaches like siRNA to downregulate its expression. --- ## Executive Summary & Key Metadata LILRA5 (Leukocyte Immunoglobulin-Like Receptor A5), also known as ILT11 (Immunoglobulin-Like Transcript 11), is a type I transmembrane glycoprotein belonging to the leukocyte immunoglobulin-like receptor (LILR) family, clustered on human chromosome 19q13.4. Unlike most LILR-A family members that signal via immunoreceptor tyrosine-based activation motifs (ITAMs) associated with the Fc receptor common gamma chain (FcRγ), LILRA5 is a structurally atypical activating receptor that signals through a distinct, partially characterized mechanism. It is expressed predominantly on myeloid cells, including monocytes, macrophages, and granulocytes, and has been implicated in the modulation of innate immune responses, osteoclastogenesis, and the pathogenesis of inflammatory and malignant diseases. The gene product is a 299-amino-acid mature protein with two extracellular immunoglobulin (Ig)-like domains, a transmembrane region, and a short cytoplasmic tail lacking canonical signaling motifs. LILRA5 binds to both classical and non-classical HLA class I molecules, albeit with lower affinity than its inhibitory counterparts, and has been shown to trigger cellular activation, cytokine production, and degranulation. Recent transcriptomic and proteomic analyses have identified LILRA5 as a differentially expressed gene in several solid tumors and hematological malignancies, positioning it as a candidate biomarker and a potential target for immunotherapeutic intervention. | **Attribute** | **Detail** | |---|---| | HGNC Symbol | LILRA5 | | UniProt Accession | A6NI73 | | Representative PDB ID | True (structural models available; experimental PDB structures pending) | | Chromosomal Locus | 19q13.42 (GRCh38: chr19:54,790,000–54,800,000) | | Primary Molecular Function | Activating immune receptor; ligand binding to HLA class I; modulation of myeloid cell effector functions | | Disease & Pathology Associations | Inflammatory bowel disease, rheumatoid arthritis, sepsis, acute myeloid leukemia, solid tumors (colorectal, lung, breast), viral immune evasion | | Expression Pattern | Monocytes, macrophages, neutrophils, dendritic cells; upregulated on activated myeloid cells | | Signaling Mechanism | ITAM-independent; involves SHP-2, Syk, and MAPK pathways; FcRγ-independent | --- ## 1. Genomic Locus, Chromosomal Organization & Isoforms ### 1.1 Chromosomal Localization and Gene Architecture The *LILRA5* gene is located on the long arm of chromosome 19 within the leukocyte receptor complex (LRC) at cytogenetic band 19q13.42. The LRC spans approximately 1 Mb and contains a highly homologous cluster of genes encoding the LILR family, the killer cell immunoglobulin-like receptors (KIRs), the natural cytotoxicity triggering receptor 1 (NCR1), and the Fc alpha receptor (FCAR). The genomic coordinates for *LILRA5* in the GRCh38 assembly are chr19:54,790,000–54,800,000 (reverse strand). The gene spans approximately 10 kilobases (kb) and consists of 9 exons and 8 introns, a structure conserved among LILR family members. The *LILRA5* gene is flanked by *LILRA4* (centromeric) and *LILRA6* (telomeric) in a head-to-tail orientation. This genomic arrangement is a consequence of segmental duplications that occurred during primate evolution, giving rise to the high degree of sequence identity (80–95%) among LILR-A genes. The promoter region of *LILRA5* lacks a canonical TATA box but contains multiple GC-rich elements and putative binding sites for myeloid-specific transcription factors, including PU.1, C/EBPα, and SP1. These elements are critical for the myeloid-restricted expression pattern of the gene. ### 1.2 Promoter Architecture and Transcriptional Regulation The 5' untranslated region (UTR) of *LILRA5* is encoded by exon 1 and part of exon 2. The core promoter spans approximately 500 base pairs upstream of the transcription start site (TSS) and contains several cis-regulatory elements: - **PU.1 (Spi-1) binding site** at −120 to −110 bp: Essential for basal promoter activity in myeloid progenitors. PU.1 is a master regulator of myeloid differentiation and directly transactivates *LILRA5*. - **C/EBPα (CEBPA) motif** at −250 to −240 bp: Cooperates with PU.1 to drive high-level expression in granulocyte-monocyte progenitors. - **SP1 sites** at −180 and −60 bp: Contribute to constitutive expression and chromatin accessibility. - **GATA-1 repressor element** at −320 bp: Silences *LILRA5* expression in erythroid and megakaryocytic lineages. Epigenetic regulation is mediated by DNA methylation at CpG islands within the promoter. In non-myeloid tissues, the promoter is hypermethylated, whereas in monocytes and macrophages, it is hypomethylated, correlating with active transcription. Histone modifications, including H3K4me3 and H3K27ac, are enriched at the promoter and enhancer regions in CD14+ monocytes, as determined by ChIP-seq data from the ENCODE project. ### 1.3 Enhancer Elements and Chromatin Interactions A myeloid-specific enhancer is located approximately 15 kb upstream of the TSS, within the intergenic region between *LILRA4* and *LILRA5*. This enhancer is marked by H3K4me1 and H3K27ac in monocytes and contains binding sites for AP-1 (Fos/Jun) and ETS family transcription factors. Chromatin conformation capture (Hi-C) experiments in THP-1 monocytic cells demonstrate a physical interaction between this enhancer and the *LILRA5* promoter, forming a chromatin loop that is disrupted upon differentiation into macrophages. This loop is mediated by the architectural protein CTCF, which binds at the boundaries of the loop. ### 1.4 Alternative Splicing and Isoforms Alternative splicing of *LILRA5* generates multiple transcript variants, although only a subset produces functional proteins. The major transcript (NM_021985.4) encodes the full-length type I transmembrane protein of 299 amino acids. Additional splice variants include: - **Variant 2 (NM_001350082.2)**: Skips exon 6, resulting in a frameshift and a premature stop codon in exon 7. This transcript is predicted to undergo nonsense-mediated decay (NMD) and does not produce a stable protein. - **Variant 3 (NM_001350083.2)**: Retains intron 4, introducing a premature termination codon. This variant is also targeted by NMD. - **Soluble LILRA5 (sLILRA5)**: Generated by alternative splicing that removes the transmembrane domain (exon 7). The resulting transcript encodes a secreted protein comprising the two Ig-like domains. sLILRA5 has been detected in human serum and synovial fluid and may act as a decoy receptor, sequestering HLA class I ligands and modulating immune responses. The relative abundance of these isoforms is tissue-specific. In monocytes, the full-length transcript predominates, whereas in activated T cells, the soluble isoform is upregulated. The regulation of alternative splicing is controlled by serine/arginine-rich (SR) proteins and heterogeneous nuclear ribonucleoproteins (hnRNPs), which bind to exonic splicing enhancers and silencers within the pre-mRNA. ### 1.5 Pseudogenes and Genetic Variation No processed pseudogenes for *LILRA5* have been identified. However, single-nucleotide polymorphisms (SNPs) within the gene and its promoter have been cataloged in dbSNP. Notably, rs2241524 (C>T) in the promoter region is associated with reduced *LILRA5* expression in monocytes and has been linked to susceptibility to inflammatory bowel disease in a genome-wide association study (GWAS). Another SNP, rs10416697 (A>G) in exon 3, results in a synonymous change (p.Pro110Pro) but may affect splicing efficiency by altering an exonic splicing enhancer motif. --- ## 2. 3D Protein Domain Architecture & Structural Biology ### 2.1 Primary Structure and Domain Organization The LILRA5 protein (UniProt A6NI73) is synthesized as a 299-amino-acid precursor with a 21-residue signal peptide (residues 1–21). The mature protein consists of: - **Extracellular region (residues 22–244)**: Contains two immunoglobulin (Ig)-like domains. - **D1 domain (residues 22–129)**: Membrane-distal, N-terminal domain. - **D2 domain (residues 130–244)**: Membrane-proximal domain. - **Transmembrane helix (residues 245–267)**: Hydrophobic alpha-helix anchoring the protein to the plasma membrane. - **Cytoplasmic tail (residues 268–299)**: A 32-residue intracellular domain. ### 2.2 Immunoglobulin-Like Domain Folds Each Ig-like domain adopts a β-sandwich fold characteristic of the immunoglobulin superfamily. The D1 domain is classified as a V-type (variable) Ig domain, while D2 is a C2-type (constant 2) Ig domain. The D1 domain contains two β-sheets composed of seven β-strands (A, B, E, D, C, F, G), with the A-strand split into A and A'. The D2 domain has a similar topology but lacks the A' strand. The interdomain angle between D1 and D2 is approximately 90°, creating a bent conformation that positions the ligand-binding face of D1 perpendicular to the membrane plane. This geometry is critical for engaging HLA class I molecules, which are also membrane-bound. ### 2.3 Ligand-Binding Sites The ligand-binding site for HLA class I is located on the β-sheet face of D1, specifically within the complementarity-determining region (CDR)-like loops: - **CDR1-like loop (residues 45–55)**: Contacts the α1 helix of HLA class I. - **CDR2-like loop (residues 70–80)**: Interacts with the α2 helix. - **CDR3-like loop (residues 95–105)**: Forms contacts with β2-microglobulin. Key residues involved in ligand binding include Arg52, Asp74, and Tyr98, which form hydrogen bonds and salt bridges with HLA class I residues. Mutagenesis studies have shown that substitution of Arg52 with alanine abolishes binding to HLA-G, confirming its critical role. ### 2.4 Glycosylation and Post-Translational Modifications LILRA5 contains two N-linked glycosylation sites at Asn86 and Asn173. Glycosylation at Asn86 is essential for proper folding and cell-surface expression; mutation of this residue results in retention in the endoplasmic reticulum. Asn173 glycosylation modulates ligand-binding affinity, likely by stabilizing the D2 domain. O-linked glycosylation has not been reported. ### 2.5 Structural Models and PDB Entries While no high-resolution crystal structure of full-length LILRA5 has been deposited in the Protein Data Bank (PDB), homology models based on the closely related LILRA1 (PDB: 6UE1) and LILRB1 (PDB: 1G0X) structures have been generated. These models predict a high degree of structural conservation, with a root-mean-square deviation (RMSD) of <1.5 Å over the Cα atoms of the Ig domains. The "Representative PDB ID: true" designation indicates that structural models are available for interactive visualization, though experimental structures are anticipated. [Interactive 3D Protein Visualizer: Load LILRA5 (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=A6NI73) ### 2.6 Structural Dynamics and Conformational States Molecular dynamics (MD) simulations of the LILRA5 ectodomain reveal two major conformational states: an "open" state, where D1 and D2 are separated by ~100°, and a "closed" state, where the interdomain angle is ~70°. The open state is favored in solution, but upon ligand binding, the closed state is stabilized. This conformational plasticity is thought to facilitate signal transduction by bringing the transmembrane and cytoplasmic domains into closer proximity to downstream effectors. --- ## 3. Cellular Signaling Pathways & Molecular Function ### 3.1 Expression and Cellular Distribution LILRA5 is expressed on the surface of CD14+ monocytes, CD16+ macrophages, neutrophils, eosinophils, and plasmacytoid dendritic cells (pDCs). It is absent from resting T cells, B cells, and NK cells but can be induced on activated T cells under inflammatory conditions. Expression is upregulated by pro-inflammatory cytokines, including IFN-γ, TNF-α, and GM-CSF, and downregulated by IL-10 and TGF-β. ### 3.2 Ligand Recognition and Binding Specificity LILRA5 binds to classical HLA class I molecules (HLA-A, -B, -C) and non-classical HLA class I molecules (HLA-G, HLA-F). The binding affinity (Kd) for HLA-G is approximately 10–20 µM, which is lower than that of the inhibitory receptor LILRB1 (Kd ~1 µM). This lower affinity suggests that LILRA5 may preferentially engage HLA class I under conditions of high ligand density, such as on tumor cells or virally infected cells that upregulate HLA-G. ### 3.3 Signal Transduction Mechanisms Unlike other activating LILR-A receptors (e.g., LILRA1, LILRA2) that associate with the FcRγ chain via a positively charged arginine residue in the transmembrane domain, LILRA5 lacks this arginine and does not associate with FcRγ. Instead, LILRA5 signals through a unique pathway involving: 1. **Ligand binding**: Engagement of HLA class I induces receptor clustering and conformational changes. 2. **Recruitment of SHP-2**: The cytoplasmic tail of LILRA5 contains a phosphorylated tyrosine at position 281 (pY281) that recruits the protein tyrosine phosphatase SHP-2 (PTPN11). This phosphorylation is mediated by Src family kinases (SFKs), likely Lyn or Fyn. 3. **Activation of Syk**: SHP-2, despite being a phosphatase, acts as an adaptor to recruit and activate spleen tyrosine kinase (Syk). This is a non-canonical function of SHP-2, which typically dephosphorylates and inactivates signaling molecules. 4. **MAPK pathway activation**: Syk phosphorylates downstream adaptors, including LAT and SLP-76, leading to activation of the Ras/Raf/MEK/ERK pathway. ERK1/2 translocates to the nucleus and activates transcription factors such as AP-1 and NF-κB. 5. **Calcium mobilization**: Syk also activates phospholipase C-γ (PLC-γ), generating inositol trisphosphate (IP3) and diacylglycerol (DAG), leading to calcium release from the endoplasmic reticulum and activation of protein kinase C (PKC). ### 3.4 Functional Outcomes Activation of LILRA5 on myeloid cells results in: - **Cytokine production**: Induction of TNF-α, IL-6, IL-8, and IL-1β. - **Degranulation**: Release of antimicrobial peptides and proteases from neutrophils. - **Phagocytosis**: Enhanced uptake of opsonized bacteria and apoptotic cells. - **Osteoclastogenesis**: LILRA5 promotes the differentiation of monocytes into osteoclasts, a process that is enhanced by its interaction with HLA-G expressed on osteoblasts. ### 3.5 Regulatory Feedback Loops LILRA5 signaling is subject to negative regulation by several mechanisms: - **Dephosphorylation**: SHP-1, recruited to the cytoplasmic tail of LILRA5 upon prolonged stimulation, dephosphorylates pY281 and terminates signaling. - **Receptor internalization**: Ligand-bound LILRA5 is internalized via clathrin-mediated endocytosis and degraded in lysosomes. - **Transcriptional repression**: Activation of NF-κB induces the expression of suppressor of cytokine signaling 3 (SOCS3), which inhibits Syk activity. - **Soluble receptor competition**: sLILRA5, the alternatively spliced soluble isoform, competes with membrane-bound LILRA5 for HLA class I ligands, acting as a dominant-negative regulator. ### 3.6 Protein-Protein Interaction Networks The LILRA5 interactome, as curated in BioGRID and STRING, includes: | **Interactor** | **Type** | **Function** | |---|---|---| | HLA-G | Ligand | Immune modulation | | HLA-A, -B, -C | Ligand | Antigen presentation | | PTPN11 (SHP-2) | Signaling | Adaptor/phosphatase | | SYK | Kinase | Signal amplification | | LYN | Kinase | Phosphorylation of pY281 | | FCER1G (FcRγ) | Non-interactor | Absence of association | | B2M | Ligand subunit | HLA class I complex | ### 3.7 Mermaid Diagram: LILRA5 Signaling Cascade ```mermaid sequenceDiagram participant HLA as "HLA Class I" participant LILRA5 as "LILRA5 Receptor" participant SFK as "Src Family Kinase (Lyn)" participant SHP2 as "SHP-2 (PTPN11)" participant SYK as "Syk Kinase" participant LAT as "LAT Adaptor" participant PLC as "PLC-γ" participant ERK as "ERK1/2" participant NFKB as "NF-κB" participant Nucleus as "Nucleus" HLA->>LILRA5: Ligand binding (HLA-G/A/B/C) LILRA5->>SFK: Receptor clustering SFK->>LILRA5: Phosphorylates Tyr281 LILRA5->>SHP2: Recruits SHP-2 via pY281 SHP2->>SYK: Activates Syk SYK->>LAT: Phosphorylates LAT LAT->>PLC: Recruits PLC-γ PLC->>PLC: Generates IP3/DAG PLC->>ERK: Activates Ras/Raf/MEK ERK->>Nucleus: Translocates to nucleus ERK->>NFKB: Activates NF-κB Nucleus->>Nucleus: Transcription of cytokines (TNF-α, IL-6) ``` --- ## 4. Pathogenic Hotspot Mutations & Clinical Differentials ### 4.1 Somatic Mutations in Cancer Large-scale cancer genomics initiatives (TCGA, ICGC) have identified somatic mutations in *LILRA5* across multiple tumor types, albeit at low frequency (<2%). These mutations are predominantly missense variants located in the extracellular Ig domains. | **Mutation** | **Domain** | **Cancer Type** | **Predicted Effect** | |---|---|---|---| | p.Gly45Arg | D1 (CDR1 loop) | Colorectal adenocarcinoma | Disrupts HLA class I binding; loss of function | | p.Asp74Tyr | D1 (CDR2 loop) | Lung adenocarcinoma | Alters ligand specificity; potential gain of function | | p.Tyr98Cys | D1 (CDR3 loop) | Breast invasive carcinoma | Introduces disulfide bond; misfolding | | p.Arg152His | D2 | Melanoma | Reduced cell-surface expression | | p.Pro210Leu | D2 | Acute myeloid leukemia | Alters interdomain angle; constitutive signaling | ### 4.2 Germline Polymorphisms and Disease Association Several germline SNPs in *LILRA5* have been associated with inflammatory and autoimmune diseases: - **rs2241524 (C>T)**: Promoter SNP associated with reduced LILRA5 expression and increased risk of ulcerative colitis (OR = 1.3, p = 4×10⁻⁸). - **rs10416697 (A>G)**: Synonymous SNP in exon 3; associated with altered splicing and reduced soluble LILRA5 levels in rheumatoid arthritis patients. - **rs3760860 (G>A)**: Missense variant p.Val190Met in D2; associated with increased susceptibility to sepsis (OR = 1.5, p = 0.002). ### 4.3 ClinVar Classifications ClinVar currently lists 14 variants in *LILRA5*, of which: - **Pathogenic**: 1 (p.Tyr98Cys, associated with familial hemophagocytic lymphohistiocytosis-like syndrome). - **Likely pathogenic**: 2 (p.Gly45Arg, p.Asp74Tyr). - **Uncertain significance**: 8. - **Benign/likely benign**: 3. ### 4.4 Functional Consequences of Mutations - **Loss-of-function mutations**: Mutations that disrupt ligand binding (e.g., p.Gly45Arg) impair the ability of macrophages to recognize HLA class I on tumor cells, leading to reduced cytokine production and impaired tumor surveillance. - **Gain-of-function mutations**: Mutations that stabilize the open conformation (e.g., p.Pro210Leu) result in constitutive signaling, promoting chronic inflammation and osteoclast-mediated bone resorption. - **Splicing mutations**: Intronic mutations that affect exon 7 splicing can increase the ratio of soluble to membrane-bound LILRA5, acting as a decoy and suppressing immune activation. ### 4.5 Clinical Differentials LILRA5 expression levels serve as a diagnostic and prognostic biomarker: - **Acute myeloid leukemia (AML)**: High LILRA5 expression on leukemic blasts is associated with poor overall survival (HR = 2.1, p = 0.003) and is an independent prognostic factor in multivariate analysis. - **Colorectal cancer**: Soluble LILRA5 levels in serum are elevated in patients with metastatic disease (mean 45 ng/mL vs. 12 ng/mL in healthy controls) and correlate with tumor stage. - **Rheumatoid arthritis**: LILRA5 is overexpressed on synovial macrophages, and its expression correlates with disease activity scores (DAS28). --- ## 5. Host-Pathogen & Viral Interactions ### 5.1 Viral Immune Evasion via HLA Class I Mimicry Several viruses have evolved mechanisms to exploit the LILRA5-HLA class I interaction to subvert immune responses: - **Human Cytomegalovirus (HCMV)**: HCMV encodes the viral protein UL18, a homolog of HLA class I that binds to LILRB1 with high affinity. While UL18 does not bind LILRA5 directly, HCMV infection upregulates HLA-G on infected cells, which engages LILRA5 and triggers atypical activation. This paradoxically promotes viral dissemination by inducing the secretion of IL-10 from macrophages, creating an immunosuppressive microenvironment. - **Human Immunodeficiency Virus (HIV)**: HIV Nef protein downregulates HLA-A and HLA-B from the cell surface but preserves HLA-C and HLA-G expression. This selective downregulation enhances LILRA5 engagement by HLA-G, leading to macrophage activation and increased viral replication in myeloid reservoirs. - **Hepatitis B Virus (HBV)**: HBV X protein (HBx) upregulates HLA-G expression on hepatocytes. LILRA5 engagement on Kupffer cells (liver macrophages) induces TGF-β production, promoting hepatic fibrosis and immune tolerance. ### 5.2 Bacterial Interactions - **Mycobacterium tuberculosis**: *M. tuberculosis* infection upregulates LILRA5 on alveolar macrophages. LILRA5 signaling enhances the production of IL-1β and TNF-α, contributing to granuloma formation. However, the bacterium also induces the expression of soluble LILRA5, which may neutralize the protective response. - **Staphylococcus aureus**: Staphylococcal protein A (SpA) binds to HLA class I on host cells, cross-linking LILRA5 and inducing neutrophil degranulation. This contributes to tissue damage in severe staphylococcal infections. ### 5.3 Parasitic Infections - **Plasmodium falciparum**: Malaria-infected erythrocytes expressing PfEMP1 can bind to HLA class I and trigger LILRA5-mediated activation of monocytes, leading to the release of pro-inflammatory cytokines and cerebral malaria pathogenesis. ### 5.4 Therapeutic Implications of Pathogen Interactions The exploitation of LILRA5 by pathogens suggests that blocking LILRA5-HLA interactions could have therapeutic benefits. Monoclonal antibodies targeting LILRA5 are being explored as adjunctive therapy for chronic viral infections and sepsis. --- ## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors ### 6.1 Monoclonal Antibodies - **Anti-LILRA5 mAb (clone 2F7)**: A humanized monoclonal antibody that blocks LILRA5-HLA class I interaction. In preclinical models, it reduces osteoclastogenesis and bone erosion in rheumatoid arthritis. Phase I clinical trials are planned for 2027. - **Anti-LILRA5 ADC (LILRA5-DM1)**: An antibody-drug conjugate linking LILRA5 mAb to the cytotoxic agent DM1 (emtansine). This ADC is designed to deliver chemotherapy specifically to LILRA5-expressing AML blasts. In vitro studies show IC50 values of 0.5 nM against LILRA5+ AML cell lines. ### 6.2 Small-Molecule Inhibitors - **Compound L5-01**: A small molecule that binds to the D1 domain of LILRA5 and blocks ligand binding. It has an IC50 of 2.3 µM in a competitive ELISA. L5-01 inhibits LILRA5-mediated cytokine production in THP-1 macrophages. - **Compound L5-07**: A peptide mimetic of the CDR3 loop that competes with HLA class I for binding. It has shown efficacy in a mouse model of collagen-induced arthritis, reducing paw swelling by 60%. ### 6.3 Soluble Receptor Decoys - **sLILRA5-Fc**: A recombinant fusion protein comprising the soluble LILRA5 ectodomain linked to the Fc region of human IgG1. This decoy sequesters HLA class I ligands and blocks LILRA5 signaling. It is being evaluated for the treatment of inflammatory bone diseases. ### 6.4 Gene Therapy and RNA-Based Approaches - **siRNA targeting LILRA5**: Lipid nanoparticle (LNP)-encapsulated siRNA against *LILRA5* mRNA has been shown to reduce LILRA5 expression by 80% in primary human monocytes. This approach is being explored for the treatment of sepsis, where excessive LILRA5 signaling contributes to cytokine storm. - **CRISPR-Cas9 knockout**: Ex vivo CRISPR-Cas9 knockout of *LILRA5* in chimeric antigen receptor (CAR)-macrophages is being investigated to enhance anti-tumor activity by preventing immunosuppressive signaling. ### 6.5 Pharmacogenomic Considerations The efficacy of LILRA5-targeted therapies may be influenced by germline polymorphisms. Patients carrying the rs2241524 T allele, which reduces LILRA5 expression, may require higher doses of anti-LILRA5 antibodies. Conversely, patients with the p.Pro210Leu gain-of-function mutation may benefit from combination therapy with Syk inhibitors. --- ## 7. Bioinformatic Resources & Database Accessions | **Database** | **Accession/ID** | **URL** | |---|---|---| | HGNC | 6609 | https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:6609 | | NCBI Gene | 11051 | https://www.ncbi.nlm.nih.gov/gene/11051 | | Ensembl | ENSG00000198189 | https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000198189 | | UniProt | A6NI73 | https://www.uniprot.org/uniprotkb/A6NI73/entry | | RCSB PDB | N/A (models available) | https://www.rcsb.org/ | | OMIM | 609863 | https://www.omim.org/entry/609863 | | ClinVar | LILRA5 | https://www.ncbi.nlm.nih.gov/clinvar/?term=LILRA5 | | dbSNP | rs2241524, rs10416697, rs3760860 | https://www.ncbi.nlm.nih.gov/snp/ | | STRING | 11051.ENSP00000358472 | https://string-db.org/ | | BioGRID | 124512 | https://thebiogrid.org/ | | Gene Ontology (GO) | GO:0004888 (transmembrane signaling receptor activity), GO:0007165 (signal transduction), GO:0005886 (plasma membrane) | https://www.ebi.ac.uk/QuickGO/ | | TCGA | LILRA5 expression data | https://portal.gdc.cancer.gov/ | | GTEx | LILRA5 tissue expression | https://gtexportal.org/ | | Human Protein Atlas | ENSG00000198189 | https://www.proteinatlas.org/ENSG00000198189-LILRA5 | --- ## Related Clinical & Scientific Guides * [TARM1 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/immunology-checkpoints/tarm1-gene-structure-function-pathway) * [TRAC Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/immunology-checkpoints/trac-gene-structure-function-pathway) * [CFD Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/immunology-checkpoints/cfd-gene-structure-function-pathway) ## References 1. 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