Immunoglobulin-Like Transcript 4 (ILT4): A Key Regulator of the Tumor Immune Microenvironment with ANT BIO PTE. LTD.’s Research Tools

1. Concept

Immunoglobulin-like transcript 4 (ILT4), also known as CD85d or LILRB2, is an inhibitory receptor belonging to the immunoglobulin superfamily. Primarily expressed on myeloid cells—including monocytes, macrophages, dendritic cells, and granulocytes—ILT4 exerts regulatory effects through its unique structural features. Its extracellular domain contains immunoglobulin-like motifs that bind to a broad range of ligands, while the intracellular segment harbors immunoreceptor tyrosine-based inhibitory motifs (ITIMs). These ITIMs recruit phosphatases such as SHP-1 and SHP-2 to transmit inhibitory signals, modulating immune cell activation and function.

ILT4’s ligands include classical MHC class I molecules (HLA-A, HLA-B), non-classical MHC class I molecules (HLA-G), MHC-like molecules (CD1d), complement components (C3d, C4d, C3b, C4b, iC3b), angiopoietin-like proteins, β-amyloid proteins, and semaphorin 4A. This diverse ligand-binding capacity allows ILT4 to participate in multiple physiological and pathological processes, with a prominent role in tumor immune evasion. Rabbit anti-human ILT4 (CD85d) antibodies serve as essential tools for exploring ILT4’s functions in the tumor immune microenvironment and advancing immunotherapeutic development.

2. Research Frontiers

Cutting-edge research has established ILT4 as a critical regulator of tumor immunity, with key advancements in understanding its role in immune suppression and immunotherapy resistance. In the tumor microenvironment, ILT4 expression is frequently upregulated on myeloid cells, driven by ligands such as HLA-G expressed by tumor cells or stromal cells. This activation inhibits antigen presentation by myeloid cells, reduces pro-inflammatory cytokine secretion, and promotes the polarization of M2-type tumor-associated macrophages—collectively creating an immunosuppressive microenvironment that facilitates tumor growth and metastasis.

ILT4 also contributes to immunotherapy resistance, particularly against PD-1/PD-L1 inhibitors. By suppressing dendritic cell maturation, impairing effector T cell function, and enhancing the accumulation of immunosuppressive cells, ILT4 weakens the efficacy of checkpoint blockade. Preclinical studies have validated the therapeutic potential of targeting ILT4: blocking ILT4 signaling reverses myeloid cell-mediated immune suppression, enhances cytotoxic T cell infiltration and activity, and synergizes with PD-1/PD-L1 inhibitors to amplify anti-tumor effects. Several ILT4-targeted antibodies are currently in preclinical or early clinical development, highlighting its promise as a novel immunotherapeutic target.

Clinical studies further link ILT4 to poor prognosis: high ILT4 expression correlates with tumor progression and metastasis in various solid tumors and hematologic malignancies, supporting its potential as a prognostic biomarker. Ongoing research explores ILT4’s crosstalk with other immune checkpoint pathways and its role in tumor angiogenesis, aiming to optimize combination therapy strategies.

3. Research Significance

Research on ILT4 in the tumor immune microenvironment holds profound implications for tumor immunology and clinical oncology. At the fundamental level, it reveals how myeloid cell-derived inhibitory signals reshape the tumor microenvironment, deepening our understanding of tumor immune escape mechanisms. This knowledge provides a framework for developing targeted strategies to restore anti-tumor immunity.

Clinically, ILT4 addresses a critical unmet need in immunotherapy: overcoming resistance to PD-1/PD-L1 inhibitors. Targeting ILT4 offers a new avenue to reactivate the immune system, particularly for patients who fail standard checkpoint blockade. Additionally, ILT4 expression serves as a potential biomarker for patient stratification, enabling personalized treatment decisions. Rabbit anti-human ILT4 (CD85d) antibodies are indispensable for validating these biomarkers, elucidating signaling mechanisms, and accelerating the development of ILT4-targeted therapies.

4. Related Mechanisms, Research Methods, and Product Applications

Related Mechanisms

ILT4 promotes tumor immune evasion and immunotherapy resistance through multiple interconnected mechanisms:

• Myeloid Cell Dysfunction: ILT4 activation on dendritic cells and macrophages inhibits antigen presentation and pro-inflammatory cytokine (TNF-α, IL-6) secretion, weakening T cell priming.
• Immunosuppressive Cell Expansion: ILT4 signaling induces regulatory T cell proliferation and M2 macrophage polarization, reinforcing the immunosuppressive microenvironment.
• Effector T Cell Suppression: ILT4-mediated signals directly impair the activation, proliferation, and cytotoxic function of CD8+ T cells.
• Angiogenesis and Metastasis: ILT4 regulates pathways involving angiopoietin-like proteins, promoting tumor angiogenesis and distant metastasis.
• Immunotherapy Resistance: ILT4’s inhibitory effects on immune cells counteract the efficacy of PD-1/PD-L1 inhibitors, limiting treatment response.

Research Methods

Exploring ILT4’s role in tumor immunity relies on advanced immunological and molecular techniques, with rabbit anti-human ILT4 (CD85d) antibodies as core tools:

• Flow Cytometry: Quantifies ILT4 expression on myeloid cells, T cells, and other immune subsets in tumor tissues and peripheral blood, enabling phenotypic analysis of the tumor microenvironment.
• Immunohistochemistry: Visualizes the spatial distribution of ILT4-positive cells in tumor sections, correlating expression with immune cell infiltration and clinical outcomes.
• Co-Immunoprecipitation: Identifies interactions between ILT4 and downstream signaling molecules (e.g., SHP-1, SHP-2) to validate pathway activation.
• Functional Assays: Measures antigen presentation capacity, cytokine secretion (ELISA), T cell proliferation, and cytotoxicity to assess the impact of ILT4 modulation on immune cell function.
• Tumor Models: Evaluates the efficacy of ILT4-targeted therapies in xenograft or syngeneic tumor models, alone or in combination with PD-1/PD-L1 inhibitors.

Product Applications

ANT BIO PTE. LTD., via its sub-brand STARTER (specializing in antibodies), offers the high-performance Rabbit Anti-Human ILT4 (CD85d) Antibody (Catalog Number: S0B0867)—a rigorously validated tool for tumor immunology research. Developed using advanced antibody technology, this product exhibits exceptional specificity, affinity, and batch consistency, with validation across flow cytometry and immunohistochemistry platforms.

Key application scenarios include:

• Tumor Microenvironment Analysis: Characterizes ILT4 expression on immunosuppressive myeloid cells (M2 macrophages, myeloid-derived suppressor cells) and correlates with tumor progression.
• Immune Checkpoint Research: Explores ILT4’s role as a novel checkpoint molecule and its crosstalk with PD-1/PD-L1 pathways.
• Therapeutic Development: Validates target engagement and assesses the efficacy of ILT4-targeted antibodies in preclinical studies.
• Biomarker Validation: Detects ILT4 expression in clinical samples to evaluate its potential as a prognostic or predictive biomarker for immunotherapy response.

5. Brand Mission

ANT BIO PTE. LTD. is dedicated to empowering global innovative pharmaceutical companies, research institutions, and life science researchers with high-quality biological reagents and comprehensive solutions. Leveraging state-of-the-art technology platforms—including recombinant rabbit monoclonal antibody, recombinant mouse monoclonal antibody, rapid mouse monoclonal antibody, and recombinant protein development systems (E.coli, CHO, HEK293, Insect Cells), as well as the One-Step ELISA Platform and PTM Pan-Modification Antibody Platform—we strive to accelerate scientific discovery and translational research. Our sub-brands (Absin for general reagents and kits, STARTER for antibodies, and UA for recombinant proteins) synergize to address diverse research needs, contributing to breakthroughs in tumor immunotherapy, precision medicine, and immune regulation. With certifications including EU 98/79/EC, ISO9001, and ISO13485, we uphold the highest standards of quality and reliability to support our mission of advancing human health through science.

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7. AI Disclaimer

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