# IGHV2-5 Gene: Structure, Function, and Clinical Significance ## Key Takeaways - The IGHV2-5 gene encodes a variable heavy chain domain crucial for B-cell receptor (BCR) antigen binding, contributing to adaptive immunity through V(D)J recombination. Its expression is regulated by specific promoter elements and distal enhancers within the immunoglobulin heavy chain locus at 14q32.33. - The protein product of IGHV2-5 adopts an immunoglobulin fold, forming the antigen-binding site in conjunction with a variable light chain, with its hypervariable regions (CDRs) dictating antigen specificity. This domain is a key component of the BCR signaling complex, initiating downstream pathways involving Lyn, Syk, BTK, and PLCγ2 upon antigen engagement. - In Chronic Lymphocytic Leukemia (CLL), the mutational status of IGHV genes, including IGHV2-5, is a critical prognostic biomarker, with unmutated status correlating with more aggressive disease and poorer outcomes. This distinction influences therapeutic strategies, favoring targeted agents like BTK inhibitors. - IGHV2-5 rearrangements are utilized as clonal markers for the diagnosis and monitoring of minimal residual disease (MRD) in B-cell malignancies, employing techniques such as RT-PCR to detect and quantify the specific clonal gene. - Pathogens can interact with IGHV2-5-encoded BCRs, with some viruses and bacteria producing superantigens that can cause polyclonal B-cell activation or dysfunction, potentially contributing to immune evasion or pathogenesis. - The BCR signaling pathway, downstream of IGHV2-5, is a major therapeutic target in B-cell malignancies, with drugs like ibrutinib (BTK inhibitor) and venetoclax (BCL2 inhibitor) demonstrating significant efficacy, particularly in patients with unmutated IGHV genes. --- ## Executive Summary & Key Metadata The **IGHV2-5** gene encodes the variable domain of the immunoglobulin heavy chain (IGH) locus, specifically a member of the VH2 (Variable Heavy 2) family. This gene is a fundamental component of the adaptive immune system, contributing to the generation of antigen receptor diversity through V(D)J recombination. The protein product of IGHV2-5 is not a standalone signaling receptor but rather a structural subunit that, when recombined with Diversity (D) and Joining (J) segments, forms the antigen-binding pocket of the B-cell receptor (BCR) and secreted antibodies. Its clinical significance is primarily rooted in its use as a clonal marker in B-cell malignancies, particularly chronic lymphocytic leukemia (CLL), where the mutational status of IGHV genes serves as a critical prognostic biomarker. Furthermore, the IGHV2-5 gene product is a target for specific therapeutic antibodies in the context of B-cell lymphomas. | **Attribute** | **Detail** | | :--- | :--- | | **HGNC Symbol** | IGHV2-5 | | **UniProt Accession** | P01817 | | **Representative PDB ID** | true (See Section 2) | | **Chromosomal Locus** | 14q32.33 (IGH locus, telomeric region) | | **Primary Molecular Function** | Antigen binding; component of the immunoglobulin heavy chain variable region | | **Disease & Pathology Associations** | Chronic Lymphocytic Leukemia (CLL), B-cell Non-Hodgkin Lymphoma (NHL), autoimmune disorders (as part of autoreactive BCRs) | --- ## 1. Genomic Locus, Chromosomal Organization & Isoforms ### 1.1 Chromosomal Context and Gene Coordinates The IGHV2-5 gene resides within the immunoglobulin heavy chain (IGH) locus on the long arm of human chromosome 14, specifically at cytogenetic band **14q32.33**. This locus is one of the most complex and dynamic regions of the human genome, spanning approximately 1.25 megabases (Mb). It is organized into three main clusters of gene segments: the Variable (V) region, the Diversity (D) region, and the Joining (J) region, followed by the Constant (C) region genes. The IGHV2-5 gene is located in the distal (telomeric) portion of the V region cluster, a position that influences its recombination frequency and usage in the expressed antibody repertoire. The precise genomic coordinates for IGHV2-5 (GRCh38/hg38 assembly) are approximately **chr14: 106,032,000 - 106,032,500** (coordinates are approximate and may vary slightly depending on the annotation source). The gene is oriented in the same transcriptional direction as the other V segments, allowing for direct recombination with downstream D and J segments. ### 1.2 Gene Structure and Regulatory Architecture The IGHV2-5 gene is a relatively compact genetic unit, spanning roughly **300-400 base pairs (bp)** of genomic DNA. Its structure is typical of immunoglobulin variable genes, consisting of: - **5' Promoter Region:** Unlike many protein-coding genes, VH promoters are located immediately upstream of the transcription start site (TSS) and are characterized by the presence of a conserved **octamer motif (ATTTGCAT)** and a **heptamer motif**. These motifs are recognized by the transcription factors Oct-1 and Oct-2, which are essential for B-cell-specific expression. The promoter is positioned approximately 100-200 bp upstream of the leader exon. - **Leader Exon (L):** A short exon of ~60 bp that encodes a hydrophobic signal peptide. This peptide directs the nascent polypeptide chain into the endoplasmic reticulum (ER) for proper folding and secretion or membrane insertion. The leader peptide is cleaved off during post-translational processing. - **Intron:** A small intervening sequence of ~100 bp that separates the leader exon from the variable exon. This intron contains the recombination signal sequence (RSS) for the V gene. - **Variable Exon (V):** The main coding exon of ~300 bp, encoding the entire variable domain of the heavy chain (VH). This exon contains the framework regions (FR1, FR2, FR3) and the complementarity-determining regions (CDR1, CDR2). The CDR3 is not encoded by the V gene alone but is formed by the junctional diversity created during V(D)J recombination. - **3' Recombination Signal Sequence (RSS):** Located immediately downstream of the variable exon, this sequence is composed of a conserved heptamer (CACAGTG) and a nonamer (ACAAAAACC) separated by a 23-bp spacer. This "23-bp spacer" RSS is characteristic of V genes and pairs with the "12-bp spacer" RSS found on D segments during recombination. ### 1.3 Transcription Factor Binding and Enhancer Elements The expression of IGHV2-5 is tightly regulated by the interplay of its promoter and distal enhancer elements. The key regulatory elements include: - **Intronic Enhancer (Eμ):** Located in the intron between the J segments and the Cμ constant region, this enhancer is active early in B-cell development. It contains binding sites for multiple transcription factors, including E2A (E12/E47), EBF (Early B-Cell Factor), and PAX5. While it acts on the entire IGH locus, its proximity to the J-C region means it primarily influences rearranged genes. - **3' Regulatory Region (3'RR):** A complex of enhancers located downstream of the constant region genes. This region is crucial for high-level expression in mature B cells and plasma cells. It contains binding sites for IRF4, PU.1, and other factors that drive the massive antibody secretion seen in plasma cells. - **Locus Control Region (LCR):** The entire IGH locus is organized into a series of topologically associating domains (TADs). The V region is located in a large TAD that is brought into proximity with the D-J-C TAD during recombination and transcription. This 3D organization is mediated by CTCF and cohesin proteins. ### 1.4 Isoforms and Transcript Variants IGHV2-5 does not produce multiple protein-coding isoforms through alternative splicing in the traditional sense. The primary transcript is a precursor mRNA that includes the leader exon, the variable exon, and, after V(D)J recombination, the rearranged D-J-C region. The splicing machinery removes the introns to produce a mature mRNA. However, two main classes of transcripts are generated depending on the constant region used: 1. **Membrane-bound BCR (mIg):** The transcript is spliced to include the transmembrane (TM) and cytoplasmic (CY) exons of the constant region (e.g., Cμ for IgM). This results in a membrane-bound immunoglobulin that forms the BCR complex with Igα/Igβ (CD79a/CD79b). 2. **Secreted Antibody (sIg):** The transcript is spliced to a polyadenylation site upstream of the TM exons, resulting in a secreted form of the antibody. This is the primary product of plasma cells. Additionally, the IGHV2-5 gene can be found in two forms in the genome: a **functional allele** and a **pseudogene** or **open reading frame (ORF)** allele. The functional allele is capable of producing a complete, functional VH domain. The ORF allele may contain minor mutations that prevent proper folding or expression but can still be transcribed. The presence of these allelic variants contributes to the complexity of the IGH repertoire. --- ## 2. 3D Protein Domain Architecture & Structural Biology ### 2.1 The Immunoglobulin Fold The protein product of the IGHV2-5 gene, the VH domain, is a paradigm of the **immunoglobulin (Ig) fold**. This domain is approximately 110-120 amino acids in length and adopts a compact, globular structure composed of two antiparallel β-sheets. This "β-sandwich" architecture is stabilized by a highly conserved **intra-domain disulfide bond** between a cysteine in FR1 (Cys23) and a cysteine in FR3 (Cys104). The disulfide bond is buried in the hydrophobic core of the protein and is essential for the structural integrity of the domain. ### 2.2 Domain Boundaries and Structural Regions The VH domain can be structurally divided into several distinct regions: - **Framework Regions (FR1, FR2, FR3, FR4):** These are the relatively conserved β-strand regions that form the structural scaffold of the domain. They are designated FR1 (residues 1-30), FR2 (residues 36-49), FR3 (residues 66-94), and FR4 (residues 103-113). The FRs are critical for maintaining the overall fold and for mediating interactions with the light chain (VL) domain and the chaperone proteins (BiP) during assembly. - **Complementarity-Determining Regions (CDR1, CDR2, CDR3):** These are the hypervariable loops that protrude from the β-sandwich and form the antigen-binding site. They are designated CDR1 (residues 31-35), CDR2 (residues 50-65), and CDR3 (residues 95-102). The CDRs are the most variable parts of the molecule, and their sequence and conformation determine the specificity and affinity of the antibody. The CDR3 is the most diverse, as it is generated by the imprecise joining of V, D, and J segments, including N-nucleotide addition. - **Loop Regions:** The loops connecting the β-strands are structurally important. The "elbow" or "switch" region at the base of the V domain interacts with the constant domain (CH1) and is crucial for the relative orientation of the Fab (fragment, antigen-binding) arm. ### 2.3 Structural Features of the IGHV2-5 Gene Product The IGHV2-5 gene belongs to the **VH2 clan**, which is characterized by specific structural features: - **CDR1 and CDR2 Length:** VH2 family members typically have CDR1 and CDR2 loops of moderate length. The CDR1 is often 5-7 residues, and CDR2 is 16-19 residues. The specific conformation of these loops is dictated by the canonical structures (Chothia classes) determined by key residues in the FRs. - **CDR3 Conformation:** The CDR3 loop is the most variable in length and structure. In IGHV2-5, the CDR3 can adopt a variety of conformations, from short, rigid loops to long, flexible structures that can penetrate deep into antigen cavities. - **Hydrophobic Core:** The interior of the β-sandwich is packed with hydrophobic residues that are highly conserved across all VH domains. This core provides the thermodynamic stability required for the domain to function in the extracellular environment. - **Glycosylation Sites:** The VH domain itself is generally not N-glycosylated, but the adjacent constant domains are. However, some VH genes may contain potential N-glycosylation sites (Asn-X-Ser/Thr) in their CDRs, which can affect antigen binding and are sometimes associated with disease states. ### 2.4 Interaction with the Light Chain and Antigen The VH domain does not function in isolation. It pairs with a variable light chain (VL) domain (either kappa or lambda) to form the antigen-binding site (Fv). The VH-VL interface is formed by the packing of the hydrophobic faces of the FRs, particularly FR2 and FR4. The CDR loops of both VH and VL are juxtaposed at the top of the Fv, creating a contiguous surface of ~600-900 Ų that interacts with the antigen. The IGHV2-5 gene product can pair with a wide variety of VL domains, contributing to the immense diversity of the antibody repertoire. ### 2.5 Interactive 3D Visualizer To explore the three-dimensional structure of the IGHV2-5 gene product and its interaction with antigen, use the interactive visualizer below. This tool loads the representative PDB structure and allows for detailed analysis of domain architecture, CDR loops, and potential ligand-binding pockets. [Interactive 3D Protein Visualizer: Load IGHV2-5 (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=P01817) --- ## 3. Cellular Signaling Pathways & Molecular Function ### 3.1 The B-Cell Receptor (BCR) Signaling Complex The primary molecular function of the IGHV2-5 gene product is to serve as the antigen-recognition subunit of the BCR. The BCR is a multi-protein complex composed of: 1. **Membrane-bound Immunoglobulin (mIg):** The product of the rearranged IGHV2-5 gene (VH domain) paired with a VL domain and the constant heavy chain (e.g., μ, δ, γ, α, ε). This provides the antigen-binding site. 2. **Igα/Igβ (CD79a/CD79b) Heterodimer:** These are the signal-transducing subunits of the BCR. They are disulfide-linked to each other and non-covalently associated with the mIg. Each contains an immunoreceptor tyrosine-based activation motif (ITAM) in its cytoplasmic tail. ### 3.2 Signal Transduction Cascade Antigen binding to the BCR initiates a complex signaling cascade that is critical for B-cell survival, activation, proliferation, and differentiation. The pathway is initiated by the phosphorylation of ITAMs on Igα/Igβ by the Src-family kinase **Lyn**. This creates docking sites for the tyrosine kinase **Syk**, which binds to the phosphorylated ITAMs via its SH2 domains. Syk then becomes activated and phosphorylates downstream adaptor proteins, including **BLNK (SLP-65)**. The signaling cascade branches into several major pathways: - **PLCγ2/Ca²⁺ Pathway:** BLNK recruits **Bruton's tyrosine kinase (BTK)** and **PLCγ2** to the plasma membrane. BTK phosphorylates and activates PLCγ2, which cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 binds to IP3 receptors on the ER, causing a release of Ca²⁺ into the cytoplasm. DAG activates Protein Kinase C β (PKCβ). The increase in intracellular Ca²⁺ and PKCβ activity leads to the activation of transcription factors such as **NF-κB**, **NFAT**, and **AP-1**. - **Ras/MAPK Pathway:** The activation of BLNK also leads to the recruitment of the guanine nucleotide exchange factor **SOS**, which activates Ras. Ras then triggers the Raf/MEK/ERK kinase cascade, leading to the activation of transcription factors like **Elk-1** and **c-Fos**. - **PI3K/Akt Pathway:** The BCR also activates **PI3K**, which generates PIP3 at the plasma membrane. PIP3 recruits **Akt** and **PDK1** to the membrane, where Akt is phosphorylated and activated. Akt promotes cell survival and proliferation by inhibiting pro-apoptotic proteins like Bad and FoxO. ### 3.3 Regulation and Feedback Loops BCR signaling is tightly regulated to prevent autoimmunity and uncontrolled proliferation. Key negative regulators include: - **CD22 and FcγRIIB1:** These co-receptors recruit the phosphatase **SHP-1**, which dephosphorylates and inactivates key signaling molecules like Syk and BLNK. - **Cbl:** An E3 ubiquitin ligase that targets activated kinases for degradation. - **SHIP-1:** An inositol 5-phosphatase that degrades PIP3, thereby terminating PI3K/Akt signaling. ### 3.4 Protein-Protein Interaction Networks The IGHV2-5 gene product (as part of the BCR) participates in a complex protein-protein interaction network. Key interactions include: - **With Igα/Igβ:** The non-covalent association between the mIg and the Igα/Igβ heterodimer is essential for BCR surface expression and signaling. - **With Chaperones:** During B-cell development, the unassembled heavy chain (including the VH domain) binds to the chaperone **BiP (GRP78)** in the ER. This interaction prevents aggregation and allows for proper folding until the light chain is synthesized. - **With Antigen:** The primary interaction is with the specific antigen. The affinity and avidity of this interaction determine the strength and duration of the signaling response. - **With Co-receptors:** The BCR can associate with the CD19/CD21/CD81 complex, which amplifies signaling by recruiting PI3K. ### 3.5 Mermaid Diagram: BCR Signaling Pathway ```mermaid sequenceDiagram participant Ag as "Antigen" participant BCR as "BCR (IGHV2-5 + Igα/Igβ)" participant Lyn as "Lyn Kinase" participant Syk as "Syk Kinase" participant BLNK as "BLNK (SLP-65)" participant BTK as "BTK" participant PLC as "PLCγ2" participant IP3R as "IP3 Receptor (ER)" participant NFAT as "NFAT" participant NFkB as "NF-κB" Ag->>BCR: Binds to CDRs BCR->>Lyn: Conformational change Lyn->>BCR: Phosphorylates ITAMs BCR->>Syk: Recruits via SH2 domains Syk->>Syk: Autophosphorylation & activation Syk->>BLNK: Phosphorylates BLNK->>BTK: Recruits BLNK->>PLC: Recruits BTK->>PLC: Phosphorylates & activates PLC->>IP3R: Generates IP3 IP3R->>NFAT: Releases Ca²⁺, activates calcineurin NFAT->>NFAT: Dephosphorylated, translocates to nucleus NFAT->>NFkB: Co-activates transcription Note over NFAT,NFkB: Gene expression for survival, proliferation, differentiation ``` --- ## 4. Pathogenic Hotspot Mutations & Clinical Differentials ### 4.1 The Role of Somatic Hypermutation (SHM) The IGHV2-5 gene is a major target of **somatic hypermutation (SHM)**, a process that introduces point mutations into the rearranged V(D)J genes at a rate of ~10⁻³ per base pair per cell division. This process occurs in the germinal centers of secondary lymphoid organs and is mediated by **Activation-Induced Cytidine Deaminase (AID)**. AID deaminates cytosines to uracils in the DNA, leading to a cascade of error-prone DNA repair that introduces mutations, primarily in the CDRs. The **mutational status** of the IGHV genes is a critical prognostic marker in CLL. The presence of >2% mutation in the IGHV gene (compared to the germline sequence) defines the "mutated" subtype, which is associated with a more indolent disease course. Conversely, <2% mutation defines the "unmutated" subtype, which is associated with aggressive disease and poorer outcomes. This distinction is so significant that it is incorporated into the CLL-IPI (International Prognostic Index) scoring system. ### 4.2 Specific Mutations and Their Consequences While IGHV2-5 is not a classic oncogene, specific mutations or features of the rearranged IGHV2-5 gene have clinical implications: - **B-Cell Receptor Stereotypes:** In CLL, approximately 30% of cases express BCRs with stereotyped heavy chain CDR3s. IGHV2-5 is one of the genes involved in these stereotyped subsets. For example, **subset #2** is defined by the use of IGHV3-21, but other subsets utilize IGHV2-5. The presence of a stereotyped BCR suggests that the disease is driven by specific antigenic stimulation. - **Autoreactivity:** Certain amino acid substitutions in the CDRs of IGHV2-5 can confer autoreactivity to the BCR. This is particularly relevant in the context of autoimmune diseases like Rheumatoid Arthritis (RA) and Systemic Lupus Erythematosus (SLE), where B cells producing autoreactive antibodies are pathogenic. The VH2 family has been implicated in the production of antibodies against various self-antigens, including double-stranded DNA (dsDNA) and rheumatoid factor (RF). - **Loss of Function Mutations:** In the germline, the IGHV2-5 gene can exist as an ORF allele with mutations that prevent its expression. These are not pathogenic per se but contribute to the diversity of the germline repertoire. However, in the context of a rearranged BCR, a non-synonymous mutation in a framework region could destabilize the domain, leading to a loss of BCR expression and potentially contributing to B-cell anergy or apoptosis. ### 4.3 Clinical Differentials and Diagnostic Use The primary clinical use of IGHV2-5 is as a **clonal marker**. In B-cell malignancies, the detection of a clonal IGHV2-5 rearrangement is used to: - **Diagnose B-cell lymphoma/leukemia:** The presence of a dominant, clonal B-cell population can be detected by PCR amplification of the rearranged IGH gene. This is a standard diagnostic test. - **Monitor Minimal Residual Disease (MRD):** After treatment, the level of the clonal IGHV2-5 rearrangement can be measured to detect residual disease. This is a powerful predictor of relapse. - **Prognosticate CLL:** As mentioned, the mutational status of the IGHV gene (including IGHV2-5) is a key prognostic indicator. --- ## 5. Host-Pathogen & Viral Interactions ### 5.1 Viral Evasion and Superantigens The IGHV2-5 gene product, as part of the BCR, is a target for various pathogens that have evolved mechanisms to subvert the immune system. - **Viral Superantigens:** Some viruses, such as **Epstein-Barr Virus (EBV)** and **Cytomegalovirus (CMV)**, encode proteins that can act as superantigens. These proteins bind to the framework regions of the VH domain, outside the conventional antigen-binding site, and stimulate a large fraction of B cells expressing specific VH genes. This polyclonal activation can lead to B-cell proliferation and, in the context of EBV, contribute to the development of B-cell lymphomas. While the most well-studied superantigens target VH3 and VH4 families, the potential for VH2-specific superantigens exists. - **HIV-1:** The HIV-1 envelope protein gp120 has been shown to interact with the BCR of B cells expressing specific VH genes. This interaction can lead to B-cell dysfunction and exhaustion, contributing to the immunodeficiency seen in HIV infection. Some studies have suggested that VH2 family members may be involved in this interaction. - **Bacterial Superantigens:** Certain bacterial toxins, such as **Protein A from *Staphylococcus aureus*** and **Protein G from *Streptococcus* species**, bind to the Fc region of antibodies. However, some bacterial proteins, like **Protein L from *Peptostreptococcus magnus***, bind to the VH domain of the light chain (VL), not the heavy chain. The interaction with VH2 is less well-characterized but remains a field of active research. ### 5.2 Immune Evasion Mechanisms Pathogens can also exploit the IGHV2-5 gene to evade the immune response: - **Molecular Mimicry:** Some pathogens express antigens that mimic self-antigens recognized by IGHV2-5-encoded antibodies. This can lead to the production of cross-reactive antibodies that are ineffective at clearing the pathogen and may contribute to autoimmunity. - **B-Cell Anergy:** Chronic stimulation of B cells by a pathogen can induce anergy, a state of unresponsiveness. This is a mechanism of immune evasion, as the B cells are rendered non-functional. --- ## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors ### 6.1 IGHV2-5 as a Therapeutic Target The IGHV2-5 gene product is a unique target for therapeutic intervention due to its clonal expression on malignant B cells. - **Anti-Idiotype Antibodies:** The CDRs of the clonal IGHV2-5 BCR are unique to the malignant clone. Anti-idiotype antibodies can be generated to specifically target these CDRs. While this approach has been explored in clinical trials for B-cell lymphomas, it is highly personalized and technically challenging. The emergence of tumor cells that have lost or mutated the idiotype is a major limitation. - **Chimeric Antigen Receptor (CAR) T-Cell Therapy:** CAR-T cells can be engineered to target the BCR idiotype. This is a highly specific approach, but again, it is personalized and expensive. More commonly, CAR-T cells target pan-B-cell markers like CD19, which is effective but leads to B-cell aplasia. ### 6.2 Targeting the BCR Signaling Pathway Given the central role of BCR signaling in the survival and proliferation of malignant B cells, the downstream signaling components are major drug targets. These drugs are effective regardless of the specific IGHV gene used, but their efficacy can be influenced by the BCR signaling profile. - **BTK Inhibitors:** - **Ibrutinib (Imbruvica):** An irreversible, covalent inhibitor of BTK. It is FDA-approved for CLL, Mantle Cell Lymphoma (MCL), and Waldenström's Macroglobulinemia (WM). It is highly effective, but resistance can emerge through mutations in BTK (e.g., C481S) or through activation of alternative pathways. - **Acalabrutinib (Calquence):** A second-generation, more selective BTK inhibitor with fewer off-target effects. - **Zanubrutinib (Brukinsa):** Another next-generation BTK inhibitor with improved selectivity and bioavailability. - **PI3K Inhibitors:** - **Idelalisib (Zydelig):** A selective inhibitor of the PI3Kδ isoform, which is highly expressed in B cells. It is approved for CLL and follicular lymphoma. - **Duvelisib (Copiktra):** A dual inhibitor of PI3Kγ and PI3Kδ. - **SYK Inhibitors:** - **Fostamatinib (Tavalisse):** An inhibitor of SYK, approved for the treatment of chronic immune thrombocytopenia (ITP). It has also been investigated in B-cell malignancies. - **BCL2 Inhibitors:** - **Venetoclax (Venclexta):** An inhibitor of the anti-apoptotic protein BCL2. It is highly effective in CLL, particularly in patients with high-risk features, including unmutated IGHV status. ### 6.3 Pharmacogenomic Considerations The IGHV mutational status can predict response to certain therapies. For example, patients with unmutated IGHV genes (including IGHV2-5) have a poorer response to chemoimmunotherapy (e.g., FCR) but respond well to BTK inhibitors. This has led to a shift in treatment paradigms, with targeted agents being used as first-line therapy for high-risk patients. --- ## 7. Bioinformatic Resources & Database Accessions The following table provides key database accessions and resources for the IGHV2-5 gene and its product. | **Database** | **Accession / ID** | **Description** | | :--- | :--- | :--- | | **HGNC** | HGNC:5537 | Official gene symbol and name | | **NCBI Gene** | 28395 | Gene-specific information, genomic context, and links | | **Ensembl** | ENSG00000211964 | Genome annotation, transcripts, and variation | | **UniProt** | P01817 | Protein sequence, function, and structure | | **RCSB PDB** | true (e.g., 1HZH for a full antibody) | Experimentally determined 3D structures | | **IMGT** | IGHV2-5*01 | International ImMunoGeneTics information system for immunoglobulins | | **Gene Ontology (GO)** | GO:0003823 (antigen binding), GO:0002376 (immune system process) | Functional annotations | | **ClinVar** | N/A (no germline pathogenic variants) | Clinical significance of variants | | **COSMIC** | N/A (not a classic cancer gene) | Catalogue of somatic mutations in cancer | | **STRING** | P01817 | Protein-protein interaction networks | | **BioGRID** | P01817 | Protein-protein interaction data | --- ## 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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