Recombinant Human ICOS ligand (ICOSLG)
Description
Molecular Structure and Characteristics of ICOSLG
ICOSLG, also known as B7 Homolog 2 (B7-H2), B7-Related Protein 1 (B7RP-1), or CD275, belongs to the immunoglobulin superfamily. Its structure incorporates distinctive immunoglobulin-like domains that are critical to its function as a co-stimulatory molecule.
Protein Structure and Domains
The ICOSLG protein exhibits a complex molecular architecture consisting of specific structural elements. It contains one Ig-like C2-type (immunoglobulin-like) domain and one Ig-like V-type (immunoglobulin-like) domain . These domains are characteristic of the B7 family of co-stimulatory molecules and are structurally related to B7-1 and B7-2 proteins. ICOSLG is configured as a transmembrane glycoprotein with extracellular IgV and IgC domains that interact with its receptor, ICOS, found on activated T cells .
When examining the structural features essential for its costimulatory function, research indicates that ICOSLG displays significant oligomerization potential, more closely resembling B7-1 than B7-2 . This oligomerization characteristic contributes to its ability to form higher-order complexes, which may enhance signaling strength during immune cell interactions.
Biological Functions of ICOSLG
ICOSLG serves as a crucial mediator in immune system regulation through its interaction with the ICOS receptor on T cells, orchestrating multiple immune responses.
T Cell and B Cell Regulation
The primary function of ICOSLG is acting as a costimulatory signal for T-cell proliferation and cytokine secretion . When engaged with ICOS on activated T cells, it delivers a positive costimulatory signal that is essential for optimal T-cell function . This interaction is fundamental for sustaining activated T cell responses beyond the initial activation phase.
In addition to T cell regulation, ICOSLG induces B-cell proliferation and differentiation into plasma cells . This dual capacity to modulate both T and B cell responses positions ICOSLG as a central regulator of adaptive immunity.
Role in Immune Response Modulation
ICOSLG plays an important role in mediating local tissue responses to inflammatory conditions . It also functions in modulating secondary immune responses by co-stimulating memory T-cell functions . The CD28/B7 and ICOS/B7-H2 pathways are both critical for co-stimulating T cell immune responses, with deficiency in either pathway resulting in defective T cell activation, cytokine production, and germinal center formation .
Expression Patterns
ICOSLG is widely expressed in lymphoid tissues including lymph nodes, leukocytes, and spleen . It is particularly detected on activated monocytes and dendritic cells, suggesting its upregulation during immune activation . In the pulmonary system, ICOS-ligand B7-H2 is expressed on human type II alveolar epithelial cells, where it plays a role in the pulmonary host defense system .
ICOSLG in Cancer Pathogenesis
Emerging research has identified significant roles for ICOSLG in various cancer types, with potential implications for diagnosis, prognosis, and therapeutic targeting.
Expression in Oral Squamous Cell Carcinoma
Expression in Glioblastoma Multiforme
ICOSLG expression exhibits subtype-specific patterns in glioblastoma multiforme (GBM). It is preferentially expressed in mesenchymal (MES) glioma stem cells (GSCs) compared to proneural (PN) GSCs . Flow cytometry analysis and quantitation indicated elevated ICOSLG protein levels in multiple MES GSC lines (MD13, 83, 30R, and 1123), while three PN GSC lines (146, 157, and 528) showed only marginal expression .
Immunocytochemistry confirmed higher expression of ICOSLG associated with the MES marker CD44 compared to the PN marker OLIG2 . This differential expression pattern suggests that ICOSLG may be a valid therapeutic target specifically in the mesenchymal subtype of GBM tumors .
Role in Colorectal Cancer Progression
In colorectal cancer (CRC), high expression of ICOS and ICOSLG has been identified as a significant factor in multiple analyses . Analysis of The Cancer Genome Atlas Colorectal Adenocarcinoma cohorts revealed higher ICOS mRNA levels in tumor tissues compared to paired non-tumor tissues (p=0.044) . Both ICOS (AUC = 0.739, CI = 0.704–0.775) and ICOSLG (AUC = 0.858, CI = 0.832–0.885) demonstrated accuracy in predicting colorectal normal and tumor outcomes .
Expression of ICOS and ICOSLG positively correlated with CD4+/Foxp3+ tumor-infiltrating lymphocyte (TIL) density and PD-1/PD-L1 expression, increasing sequentially with progression from precancerous tissues to carcinoma . The co-expression status of PD-1 and ICOS/ICOSLG could stratify patients with colorectal lesions into three risk groups (low, moderate, and high) .
Immunological Implications and Therapeutic Potential
The interactions between ICOSLG and immune system components have significant implications for immunotherapy approaches and potential therapeutic interventions.
Correlation with Other Immune Checkpoints
ICOSLG shows positive correlation with other immune checkpoint molecules, including PD-L1, CSF1R, CTLA4, IDO1, IL10, and PD1 . This correlation suggests a potential regulatory network involving multiple immune checkpoint pathways that could be simultaneously targeted for enhanced therapeutic efficacy.
Potential for Targeted Therapy
Tumor cell-derived ICOSLG could serve as an efficient marker for patient stratification in precision immunotherapy . The ICOS/ICOS-L pathway is currently under clinical investigation as an immune checkpoint blockade target, given that dysregulation of this pathway has been implicated in autoimmune diseases and cancer .
Crystal structures of ICOS and ICOS-L in complex with monoclonal antibodies under clinical evaluation in immunotherapy reveal that antibody paratopes closely mimic receptor-ligand binding core interactions, in addition to contacting peripheral residues to confer high binding affinities . This structural insight has direct implications for ongoing development of therapeutic interventions targeting immune checkpoint receptors.
Regulatory T-cell Expansion Mechanism
ICOSLG expressed on gastric cancer cells and melanoma can induce the activation of IL-10–producing CD4+ T cells . In glioblastoma, ICOSLG-mediated regulatory T-cell expansion and IL-10 production have been observed, suggesting a potential mechanism by which tumors may evade immune surveillance .
Future Research Directions and Clinical Applications
The growing body of evidence regarding ICOSLG's role in immune regulation and cancer pathogenesis points to several promising avenues for future research and clinical applications.
Development of Targeted Therapeutics
Given the correlation between ICOSLG expression and poor clinical outcomes in various cancers, the development of targeted therapies against this molecule represents a promising approach. Monoclonal antibodies targeting the ICOS/ICOS-L interaction are already under clinical evaluation, but further refinement based on structural insights could enhance their efficacy .
Biomarker Development
The differential expression of ICOSLG across cancer types and subtypes suggests its potential utility as a biomarker for patient stratification. In particular, its expression in oral squamous cell carcinoma and mesenchymal glioblastoma could guide personalized treatment approaches .
Combination Therapy Approaches
The positive correlation between ICOSLG and other immune checkpoint molecules indicates potential synergies in targeting multiple immune regulatory pathways simultaneously. Exploration of combination therapies that target both ICOSLG and other immune checkpoints (such as PD-1/PD-L1) may yield enhanced therapeutic outcomes, particularly in cancers with high expression of these molecules .
Product Specs
Note: We prioritize shipping the format currently in stock. However, if you have specific format requirements, please indicate them in your order remarks. We will fulfill your request if possible.
Note: All our proteins are shipped with standard blue ice packs. If you require dry ice shipment, please inform us in advance as additional fees will apply.
Generally, the shelf life of liquid form is 6 months at -20°C/-80°C. The shelf life of lyophilized form is 12 months at -20°C/-80°C.
Target Background
Q&A
What is Recombinant Human ICOS Ligand (ICOSLG)?
Recombinant Human ICOS Ligand (ICOSLG) is a protein fragment typically comprising amino acids 19-258 of the native human protein, produced in expression systems such as HEK 293 cells with high purity (>95%) and low endotoxin levels (<1 EU/μg) . ICOSLG functions as the ligand for the T-cell-specific cell surface receptor ICOS (Inducible T-cell COStimulator), playing crucial roles in immune regulation . The recombinant form is engineered for research applications and typically includes features such as His-tags for purification, while maintaining the functional properties of the native protein .
What are the alternative nomenclatures for ICOSLG in scientific literature?
ICOSLG appears in scientific literature under multiple designations, which can create confusion when reviewing research. The protein is variously known as CD275, B7H2, B7RP1, ICOSL, KIAA0653, ICOSLG, ICOS ligand, B7 homolog 2, B7-like protein Gl50, B7-related protein 1, B7-H2, and B7RP-1 . Researchers should be aware of these alternative designations when conducting literature reviews to ensure comprehensive coverage of relevant studies. These names reflect both the protein's discovery history and its membership in the B7 family of costimulatory molecules .
How does ICOSLG signaling influence T cell function and differentiation?
ICOSLG engagement with its receptor ICOS triggers complex signaling cascades that significantly impact T cell biology. Upon interaction with ICOS, ICOSLG functions as a costimulatory signal that promotes T-cell proliferation and cytokine secretion . This signaling axis is particularly important for CD4+ T cell activation and differentiation pathways .
Research indicates that ICOSLG-ICOS interactions contribute to T cell subset development and function, with notable effects on regulatory T cells (Tregs). In oral squamous cell carcinoma (OSCC), high ICOSLG expression correlates with diminished CD4+ T cells and increased Foxp3+ regulatory T cells at the tumor invasion front . This suggests that ICOSLG may participate in creating immunosuppressive microenvironments by modulating T cell subset distribution and functionality. The downstream effects include altered cytokine production profiles and immune response characteristics that may promote tumor progression in cancer contexts .
What role does ICOSLG play in the tumor microenvironment?
ICOSLG exhibits multifaceted functions within tumor microenvironments that appear to be context-dependent. In oral squamous cell carcinoma (OSCC), ICOSLG is ubiquitously expressed across tumor cells, cancer-associated fibroblasts, and tumor-infiltrating lymphocytes . High expression levels in tumor cells (ICOSLGTCs) or tumor-infiltrating lymphocytes (ICOSLGTILs) correlate with advanced TNM staging and lymph node metastasis .
The tumor-promoting mechanisms of ICOSLG involve complex immune modulation. Research demonstrates that high ICOSLG expression correlates with immunosuppressive changes in the tumor milieu, including decreased CD4+ T cell populations and increased regulatory T cells (Tregs) . Furthermore, ICOSLG expression in tumors positively correlates with multiple immune checkpoint molecules, including PD-L1, CSF1R, CTLA4, IDO1, IL10, and PD1, suggesting its involvement in broader immunosuppressive networks . These observations indicate that ICOSLG may contribute to immune evasion strategies employed by tumor cells, facilitating disease progression and metastasis.
How does ICOSLG expression correlate with clinical outcomes in cancer patients?
Multivariate analysis reveals that ICOSLG expression correlates with clinicopathological parameters including advanced TNM stage and lymph node metastasis . Moreover, research indicates that ICOSLG expression patterns in peripheral blood correlate with altered immune cell profiles, with high ICOSLGTCs patients showing significantly lower absolute counts of CD3+ T cells, CD3+CD4+ T cells, and CD3+CD8+ T cells in peripheral blood . These findings collectively suggest that ICOSLG expression may serve as both a prognostic indicator and a potential stratification marker for precision immunotherapy approaches.
What techniques are recommended for analyzing ICOSLG expression in clinical samples?
Multiple complementary techniques can be employed to comprehensively analyze ICOSLG expression in clinical samples:
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Immunohistochemistry (IHC): Provides spatial information about ICOSLG expression across different cell types within tissue architecture. In OSCC research, IHC has been effectively used to distinguish ICOSLG expression in tumor cells, cancer-associated fibroblasts, and tumor-infiltrating lymphocytes . Serial section IHC allows correlation of ICOSLG expression with infiltrating immune cell populations.
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Flow Cytometry: Enables quantitative assessment of ICOSLG expression and simultaneous characterization of multiple markers. This approach has been used to analyze ICOSLG in relation to lymphocyte subsets in both peripheral blood and tumor samples . Proper gating strategies should include lymphocyte identification, followed by subsetting into CD3+, CD3+CD4+, CD3+CD8+, and CD3-CD16+CD56+ populations.
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Western Blotting: Provides information about protein expression levels and can confirm antibody specificity. For recombinant ICOSLG, SDS-PAGE analysis confirms protein identity and purity .
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HPLC: Useful for verifying the purity of recombinant ICOSLG preparations intended for experimental use .
When designing expression analysis studies, researchers should consider using multiple detection methods to overcome the limitations of individual techniques and provide more robust data.
How can researchers evaluate the functional activity of recombinant ICOSLG?
Functional evaluation of recombinant ICOSLG should employ assays that detect its biological activities:
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T Cell Proliferation Assays: Since ICOSLG provides costimulatory signals for T cell proliferation, researchers can measure the ability of recombinant ICOSLG to enhance T cell division in the presence of primary TCR stimulation. Typical readouts include tritiated thymidine incorporation, CFSE dilution, or Ki-67 expression .
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Cytokine Production Analysis: Functional ICOSLG enhances cytokine secretion from activated T cells. Researchers can measure cytokines using ELISA, cytometric bead arrays, or intracellular cytokine staining by flow cytometry following ICOSLG stimulation .
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B Cell Differentiation Assays: ICOSLG induces B cell proliferation and differentiation into plasma cells. Researchers can evaluate these activities by culturing B cells with recombinant ICOSLG and measuring proliferation, plasma cell markers, and antibody production .
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Neutrophil Transmigration Assays: In endothelial cell models, researchers can assess whether recombinant ICOSLG facilitates neutrophil transmigration in response to chemoattractants like CXCL8/IL8 or N-formyl-methionyl peptides (fMLP) .
Appropriate controls should include blocking antibodies against ICOS or ICOSLG to confirm specificity of observed effects.
What considerations are important when designing ICOSLG knockout or overexpression experiments?
When manipulating ICOSLG expression experimentally, researchers should address several key considerations:
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Cell Type Selection: ICOSLG functions differ across cell types. Researchers should carefully select appropriate cell models based on research questions. For tumor studies, both cancer cells and relevant stromal cells should be considered for manipulation .
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Expression Verification: Both protein and mRNA level verification of knockout or overexpression efficiency should be performed. For ICOSLG, both membrane and cytoplasmic localization should be examined .
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Functional Readouts: Appropriate readouts should assess both direct ICOSLG effects and downstream consequences. In cancer models, consider measuring:
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Context Dependency: ICOSLG effects may be context-dependent. Researchers should evaluate phenotypes under different conditions (e.g., inflammatory stimuli, presence of different immune cell populations) to capture the complexity of ICOSLG biology .
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Validation Approaches: Use complementary approaches (CRISPR/Cas9, siRNA, expression plasmids) and rescue experiments to confirm specificity of observed phenotypes to ICOSLG manipulation.
How does ICOSLG expression relate to other immune checkpoint molecules in integrated immunotherapy approaches?
ICOSLG demonstrates significant correlations with multiple immune checkpoint molecules, suggesting its participation in complex immunoregulatory networks. Research in OSCC has revealed positive correlations between ICOSLG and several immune checkpoint molecules including ICOS, CD96, PD-L1 (CD274), CSF1R, CTLA4, HAVCR2, IDO1, IL10, and PD1 . This pattern implies that ICOSLG does not function in isolation but rather as part of an integrated immune checkpoint landscape.
From a therapeutic perspective, these correlations raise important questions about potential combination therapies. The ICOS-ICOSLG pathway shows promise as a target for immunotherapy in various tumors . Given the positive correlation between ICOSLG and established checkpoint targets like PD-L1 and CTLA4, researchers should investigate whether dual blockade of ICOSLG with these molecules might produce synergistic effects. Additionally, the relationship between ICOSLG expression and response to existing checkpoint inhibitors deserves exploration, as ICOSLG status might predict responsiveness to these therapies or indicate the need for alternative approaches.
What are the mechanisms through which ICOSLG influences tumor metastasis?
ICOSLG expression correlates significantly with lymph node metastasis in OSCC patients, suggesting its involvement in metastatic processes . Several potential mechanisms warrant investigation:
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Immune Landscape Modulation: High ICOSLG expression correlates with altered immune cell composition, including decreased CD4+ T cells and increased regulatory T cells, potentially creating an immunosuppressive environment permissive to metastasis .
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Direct Effects on Tumor Cells: The expression of ICOSLG on tumor cells themselves suggests possible autocrine or paracrine signaling mechanisms that might influence tumor cell behavior. Research in myeloma indicates that tumor cells with high ICOSLG expression demonstrate enhanced proliferative capacity .
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Stromal Interaction Effects: ICOSLG expression in cancer-associated fibroblasts might influence tumor-stromal interactions crucial for metastatic processes, though current research shows less prognostic significance for ICOSLG in CAFs compared to tumor cells and TILs .
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Relationship with Epithelial-Mesenchymal Transition: The correlation between ICOSLG and advanced tumor stages suggests potential involvement in processes like epithelial-mesenchymal transition that facilitate metastasis.
Understanding these mechanisms could identify stage-specific interventions targeting ICOSLG in metastasis prevention or treatment.
How might ICOSLG serve as a biomarker for patient stratification in precision immunotherapy?
ICOSLG expression patterns have significant potential as biomarkers for cancer patient stratification. Research in OSCC demonstrates that ICOSLG expression in tumor cells correlates with clinical outcomes and immune cell profiles . Based on these findings, several stratification approaches merit exploration:
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ICOSLG Expression Profiling: Comprehensive profiling of ICOSLG expression across tumor cells, TILs, and CAFs could identify patient subgroups with distinct prognostic characteristics and therapeutic vulnerabilities .
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Multi-Parameter Immune Checkpoint Analysis: Given ICOSLG's correlation with other immune checkpoint molecules, developing integrated checkpoint profiles that include ICOSLG alongside PD-L1, CTLA4, and others might enhance stratification accuracy .
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Peripheral Blood Correlates: The correlation between tumor ICOSLG expression and altered peripheral blood lymphocyte counts suggests the possibility of developing blood-based biomarkers that reflect tumor ICOSLG status, potentially offering less invasive monitoring options .
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Predictive Biomarker Development: Prospective studies should evaluate whether ICOSLG expression patterns predict response to immunotherapies, particularly checkpoint inhibitors, to guide therapeutic decision-making.
The development of standardized, clinically applicable ICOSLG assessment methods will be crucial for translating these research findings into practical stratification tools for precision medicine applications.
