Recombinant Mouse Pro-interleukin-16 [Cleaved into: Interleukin-16 protein (Il16) (Active)
Description
Structure and Biochemical Properties of Recombinant Mouse IL-16
Recombinant mouse IL-16 protein represents a specific fragment of the larger Pro-IL-16 molecule and possesses distinct biochemical characteristics that enable its biological functions. The active form spans amino acid residues 1197 to 1322 of the full-length precursor protein, making it a relatively small functional unit compared to its precursor form . When produced recombinantly in expression systems such as Escherichia coli, this protein can be generated with high purity (>95%) and minimal endotoxin contamination (<1 EU/μg), which is crucial for experimental applications where biological activity needs to be assessed without interference from bacterial contaminants .
The amino acid sequence of the recombinant mouse IL-16 active fragment is: MHDLNSSTDSAASASAASDISVSEKEATVCTVTLEKTSAGLGFSLEGGKGSLHGDKPLTINRIFKGDRTGEMVQPGDEILQLAGTAVQGLTRFEAWNVIKALPDGPVTIVIRRKTSLQCKQTTASADS . This specific sequence confers the unique structural and functional properties that allow IL-16 to interact with its target receptors and mediate its biological effects. The protein's structure includes domains responsible for receptor binding and signaling activation, which ultimately translate into its chemoattractant and immunomodulatory functions.
The recombinant form of mouse IL-16 is suitable for various analytical techniques including SDS-PAGE for purity assessment and functional studies to evaluate its biological activity . This versatility makes it a valuable tool for researchers investigating IL-16-mediated immune responses and potential therapeutic applications.
Comparative Analysis of IL-16 Expression
Investigations into IL-16 expression patterns have revealed significant variations across different physiological and pathological states. In clinical studies, elevated IL-16 levels have been detected in the sera of influenza A virus (IAV)-infected children compared to healthy controls, indicating a potential role in the immune response to viral infection . This pattern of increased IL-16 expression during infection is consistently observed in mouse models as well.
Table 1: Comparative IL-16 Expression in Different Biological Samples During Influenza Infection
| Sample Type | Control Levels | IAV-Infected Levels | Time Post-Infection | Significance |
|---|---|---|---|---|
| Human Serum | Baseline | Significantly elevated | N/A | p<0.05 |
| Mouse Serum | Baseline | Elevated | Days 4-8 | p<0.05 |
| Mouse BALF | Baseline | Elevated | Days 4-8 | p<0.05 |
| Mouse Lung Homogenates | Baseline | Significantly elevated | Days 4-8 | p<0.05 |
The temporal dynamics of IL-16 expression during infection suggest that it plays a role in the host response to viral challenges. Interestingly, the elevation of IL-16 levels persists during the course of infection, with detection possible in multiple biological compartments including serum, bronchoalveolar lavage fluid (BALF), and lung tissue homogenates . This widespread increase implies a systemic induction of IL-16 during influenza infection rather than a localized response.
Production and Processing of Recombinant Mouse Pro-IL-16
Pro-interleukin-16 represents the inactive precursor form that must undergo specific proteolytic processing to generate the biologically active IL-16 protein. This precursor-to-active conversion represents a critical regulatory step in IL-16 biology. The production of recombinant mouse Pro-IL-16 typically involves expression in bacterial systems such as Escherichia coli, which allows for efficient generation of the protein in quantities suitable for research applications . Following expression, the protein undergoes purification procedures to achieve the high purity levels (>95%) required for downstream applications.
The conversion from the inactive Pro-IL-16 to the active IL-16 form occurs through proteolytic cleavage mediated by caspase-3 . This enzymatic processing represents a key regulatory mechanism that controls IL-16 activity in biological systems. The cleavage event generates the C-terminal fragment that constitutes the active IL-16 molecule, spanning amino acids 1197 to 1322 of the full-length precursor . This processing mechanism highlights the importance of caspase-3 activity in regulating IL-16 function and suggests potential connections between apoptotic processes (where caspase-3 is prominently involved) and the generation of active IL-16.
Biological Functions of Interleukin-16
Interleukin-16 demonstrates multifaceted biological activities primarily centered on immune cell regulation and signaling. Its primary function involves stimulating migratory responses in CD4+ lymphocytes, monocytes, and eosinophils, effectively acting as a chemoattractant that directs immune cell trafficking and positioning . This chemotactic activity plays a crucial role in coordinating immune responses by facilitating the recruitment of relevant cell populations to sites of inflammation or infection.
Beyond its chemotactic properties, IL-16 also functions as a priming agent for CD4+ T-cells, enhancing their responsiveness to other cytokines, specifically IL-2 and IL-15 . This priming effect augments subsequent T-cell activation and proliferation, thereby amplifying immune responses. Additionally, IL-16 induces the expression of the interleukin-2 receptor on T-lymphocytes, further enhancing their capacity to respond to IL-2 signaling . A key molecular interaction underpinning these functions is IL-16's role as a ligand for CD4, the primary cellular receptor for this cytokine .
The complex interactions between IL-16 and various immune cell populations extend beyond direct activation. Evidence suggests that IL-16 participates in fine-tuning immune responses through modulation of cytokine networks. This regulatory role positions IL-16 as a potential critical factor in both normal immune function and pathological states characterized by immune dysregulation.
Modulation of Interferon Responses
A significant aspect of IL-16 biology is its capacity to modulate interferon responses, which has profound implications for antiviral immunity. Research indicates that IL-16 overexpression significantly reduces the levels of interferon-β (IFN-β) mRNA both before and after influenza virus infection . Similarly, the expression of interferon-stimulated gene 15 (ISG15) is decreased in cells overexpressing IL-16 following viral challenge . These findings suggest that IL-16 functions as a negative regulator of type I interferon responses.
Complementing these observations, IL-16 deficiency experiments reveal the opposite effect. Mouse embryonic fibroblasts lacking IL-16 exhibit elevated levels of IFN-β and ISG15 expression compared to wild-type cells, particularly following influenza virus infection . This pattern extends to in vivo settings, where IL-16 knockout mice show significantly higher IFN-β mRNA levels in lung tissue following influenza infection compared to wild-type animals . Protein level measurements confirm this trend, with higher IFN-β protein detected in both lung homogenates and bronchoalveolar lavage fluid samples from IL-16-deficient mice .
Mechanistic investigations further support IL-16's interferon-suppressive role, as IL-16 expression markedly blocks IFN-β and ISRE (Interferon-Stimulated Response Element) activation in luciferase reporter assays . This direct inhibition of type I interferon activation may explain how IL-16 negatively regulates interferon and interferon-stimulated gene expression, potentially contributing to its role in promoting influenza virus infection by dampening antiviral responses.
Role of IL-16 in Viral Infections with Focus on Influenza
Interleukin-16 plays a significant and complex role in viral infections, particularly in the context of influenza A virus (IAV) pathogenesis. Research has demonstrated that IL-16 levels increase substantially in both IAV-infected children and experimental mouse models, suggesting a consistent response across species . This elevation is detectable in multiple biological compartments including serum, bronchoalveolar lavage fluid, and lung homogenates, indicating a systemic rather than localized response to infection .
Functional studies have revealed that IL-16 enhances IAV infection in both human lung epithelial cells (A549) and mouse embryonic fibroblasts (MEFs) . When IL-16 is overexpressed in A549 cells, there is a marked increase in viral protein expression, including hemagglutinin (HA), nucleoprotein (NP), and non-structural proteins . Correspondingly, the mRNA levels of viral genes such as HA, M, and NA are significantly elevated, ultimately resulting in increased virus production as measured by plaque assays . These findings establish IL-16 as a factor that promotes rather than inhibits influenza virus replication in vitro.
The pro-viral role of IL-16 is further substantiated by loss-of-function studies. IL-16 knockout MEFs show significantly reduced expression of viral proteins and mRNAs following IAV infection compared to wild-type cells . Consistent with these observations, IL-16 deficiency markedly decreases the production of progeny viruses, confirming the importance of IL-16 in facilitating efficient viral replication .
Table 2: Effects of IL-16 on Influenza Virus Infection Parameters
Mechanisms of IL-16-Mediated Enhancement of Viral Infection
The mechanisms through which IL-16 promotes influenza virus infection appear multifaceted but center primarily on the modulation of antiviral immune responses rather than direct effects on viral entry. Interestingly, IL-16 overexpression does not affect IAV entry into host cells, as demonstrated by experiments measuring viral attachment and early internalization . This suggests that IL-16's pro-viral effects manifest during post-entry stages of the viral life cycle.
A key mechanism identified is IL-16's capacity to suppress type I interferon responses. IL-16 inhibits the expression of IFN-β and interferon-stimulated genes (ISGs) following influenza virus infection . This suppression of antiviral interferon signaling likely creates a more permissive cellular environment for viral replication. Supporting this model, IL-16 deficiency results in enhanced IFN-β and ISG expression following infection, corresponding with reduced viral replication .
At the molecular level, IL-16 appears to directly inhibit IFN-β promoter activation and interferon-stimulated response element (ISRE) activity, as demonstrated by luciferase reporter assays . This direct suppression of interferon signaling pathways provides a mechanistic explanation for how IL-16 promotes viral replication by dampening innate antiviral responses.
Research Applications of Recombinant Mouse IL-16
Recombinant mouse IL-16 serves as an essential tool in immunological research, enabling investigations into cytokine functions, immune cell activation, and disease pathogenesis. The availability of high-purity recombinant IL-16 (>95% purity, <1 EU/μg endotoxin) facilitates precise experimental manipulations without confounding effects from contaminants . This technical advantage allows researchers to confidently attribute observed biological effects to IL-16 activity rather than experimental artifacts.
The active nature of recombinant IL-16 necessitates careful handling in experimental settings. As noted in product information, "This product is an active protein and may elicit a biological response in vivo, handle with caution" . This caution reflects the potent immunomodulatory properties of IL-16 and its capacity to influence multiple aspects of immune function even at relatively low concentrations.
Mouse Models and In Vivo Applications
The development of IL-16 knockout mouse models has significantly advanced understanding of this cytokine's role in health and disease states. These models have been particularly valuable in elucidating IL-16's functions in viral infections. In influenza challenge studies, IL-16-deficient mice exhibit remarkable resistance to weight loss compared to wild-type animals, maintaining relatively normal body weight similar to mock-infected controls . This protection correlates with significantly reduced viral loads in lung tissue, suggesting that IL-16 deficiency constrains viral replication in vivo .
Histopathological analyses further reveal that IL-16 deficiency alleviates lung injury following influenza infection, providing additional evidence for IL-16's role in promoting viral pathogenesis . These in vivo findings complement cellular studies and strengthen the case for IL-16 as a factor that enhances host susceptibility to influenza virus infection.
Beyond influenza, IL-16's involvement in other viral infections has been documented. Previous research has implicated IL-16 in HIV replication within macrophages, dendritic cells, and monocytes, suggesting a broader role in viral pathogenesis beyond respiratory infections . This diverse involvement in multiple viral disease processes underscores the potential significance of IL-16 as a therapeutic target in various infectious contexts.
Product Specs
Target Background
Interleukin-16 (IL-16) stimulates migration in CD4+ lymphocytes, monocytes, and eosinophils. It primes CD4+ T-cells for responsiveness to IL-2 and IL-15 and induces interleukin-2 receptor expression in T-lymphocytes. IL-16 is a ligand for CD4. Isoform 1 functions as a membrane-anchoring scaffolding protein for ion channels. Isoform 2 is involved in T-cell cell cycle progression, regulating the transcription of SKP2, potentially as part of a transcriptional repression complex on the SKP2 gene's core promoter. It may also act as a scaffold for GABPB1 (the DNA-binding subunit of the GABP transcription factor complex) and HDAC3, maintaining transcriptional repression and inhibiting cell cycle progression in resting T-cells.
- IL-16 production contributes to lung damage in Staphylococcus aureus pneumonia; its neutralization enhances bacterial clearance and reduces lung pathology. PMID: 24736233
- Knockdown of translocator protein TSPO by siRNA does not affect TNF-α, IL-1β, and IL-6 production in LPS-stimulated BV-2 microglia cells. PMID: 25200148
- IL-16 promotes cardiac fibrosis and myocardial stiffening in heart failure with preserved ejection fraction. PMID: 23894370
- Pro-IL-16 overexpression impairs resting B cell proliferation by regulating NF-κB activation; siRNA knockdown of pro-IL-16 decreases p27kip1 and increases Skp2 levels. PMID: 23297678
- Ovalbumin (OVA)-sensitized mice exhibit increased systemic TNF-α levels; serum or BAL fluid stimulation of bronchial epithelial cells induces IL-16 production. PMID: 12594062
- IL-16 induces greater migration in Th1 cells than in Th2 cells. PMID: 14607889
- IL-16 and its precursor are involved in T lymphocyte activation and growth. PMID: 15253385
- Pro-IL-16 mRNA and protein expression are dynamically regulated during CD4+ T cell activation via a calcineurin-dependent mechanism; pro-IL-16 may influence T cell cycle regulation. PMID: 15728482
- Caspase-3-mediated IL-16 production by infiltrating CD4+ T cells contributes to neuroinflammation by attracting additional CD4+ T cells. PMID: 16271292
- After femoral artery ligation, CD8+ T cells infiltrate collateral vessel growth sites and recruit CD4+ mononuclear cells via IL-16 expression. PMID: 16380545
- Antibody therapy to inactivate IL-16 or IL-16 deficiency prevents ischemia-reperfusion kidney injury, reducing serum creatinine and blood urea nitrogen. PMID: 18004294
- Bleomycin-induced lung fibrosis is independent of IL-16. PMID: 19232499
- CD4+ T cells are recruited to the lung in an IL-16-dependent, dendritic cell-independent process, reducing neutrophil recruitment via increased IL-10 production. PMID: 19641139
Q&A
What is the structural relationship between pro-IL-16 and mature IL-16 in mice?
Pro-IL-16 is synthesized as a large (~80 kDa) inactive precursor protein stored intracellularly prior to activation. Upon appropriate cellular stimulation, caspase-3 mediates the proteolytic cleavage of pro-IL-16, resulting in the release of two functional proteins with distinct biological roles. The cytokine function is exclusively attributed to the secreted C-terminal region (~14 kDa, amino acids 1205-1322 in mice), while the N-terminal product remains intracellular and appears to function in cell cycle control .
The mature mouse IL-16 protein corresponds specifically to the C-terminal fragment and exhibits biological activities including stimulation of CD4+ lymphocyte migration, monocyte and eosinophil recruitment, and priming of T-cells for IL-2 and IL-15 responsiveness .
How is IL-16 processed and secreted in experimental systems?
Despite its important biological functions, IL-16 lacks a conventional secretory signal peptide, suggesting an unconventional secretion pathway . In experimental settings, caspase-3 mediates the critical cleavage of pro-IL-16, releasing the mature C-terminal fragment that possesses cytokine activity. Commercial recombinant preparations are engineered to circumvent this processing requirement by directly expressing the mature C-terminal segment.
For researchers investigating the natural processing pathway, experimental approaches include:
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In vitro cleavage assays with recombinant caspase-3
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Cell-based studies with caspase inhibitors
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Site-directed mutagenesis of the caspase-3 recognition sequence
In recombinant systems, mouse IL-16 can be produced using various expression platforms, with HEK293 cells yielding properly folded protein with minimal bacterial contamination, while E. coli systems provide higher yields but may require additional purification steps .
What are the primary cellular sources of IL-16 in mouse models?
IL-16 is produced by a diverse array of immune and non-immune cells in mouse models. The primary cellular sources include:
| Cell Type | IL-16 Production | Research Significance |
|---|---|---|
| T cells | High | Major source in adaptive immunity |
| Eosinophils | Moderate | Important in allergic responses |
| Neutrophils | Moderate | Relevant in acute inflammation |
| Dendritic cells | Moderate | Impact on antigen presentation |
| Fibroblasts | Variable | Tissue repair contexts |
| Epithelial cells | Variable | Mucosal immunity |
| Neuronal cells | Detected | Neuroimmune interactions |
During viral infections such as influenza, increased IL-16 production has been documented in multiple tissues. Studies have shown significantly elevated IL-16 levels in serum samples, bronchoalveolar lavage fluid (BALF), and lung homogenates from influenza A virus (IAV)-infected mice compared to uninfected controls .
What methodologies are recommended for studying IL-16 function in viral infection models?
When investigating IL-16 function in viral infection contexts, researchers should consider this comprehensive experimental approach:
For in vivo infection studies:
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Use age-matched (6-8 weeks) IL-16 knockout and wild-type control mice
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Administer virus (e.g., influenza A) intranasally at appropriate dosage (8,000-10,000 PFU/mouse)
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Monitor weight loss daily as a disease severity indicator
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Collect samples at key timepoints (days 2, 4, 7 post-infection)
Sample collection should include:
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Serum for systemic IL-16 and cytokine measurements
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Bronchoalveolar lavage fluid for local IL-16 quantification
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Lung tissue for viral load determination and histopathology
Viral quantification is optimally performed through plaque assays using appropriate cell lines, while IL-16's immunomodulatory effects can be assessed through qRT-PCR and ELISA measurement of interferon-β and interferon-stimulated genes .
Studies have demonstrated that IL-16 knockout mice maintain normal body weight following influenza infection, whereas wild-type mice exhibit rapid weight loss reaching 25-30% by days 8-10 post-infection. This corresponds with significantly reduced viral titers in the lungs of IL-16 KO mice, supporting IL-16's role in enhancing viral susceptibility .
How should researchers evaluate recombinant mouse IL-16 quality and activity?
Quality assessment of recombinant mouse IL-16 should include multiple complementary approaches:
For purity evaluation:
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SDS-PAGE analysis (standard research grade requires >95% purity)
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Size exclusion chromatography to verify monomeric state
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Endotoxin testing with acceptable levels <1 EU/μg for in vivo applications
Functional validation should employ:
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CD4+ T-cell migration assays (gold standard)
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IL-2 receptor upregulation assessment on CD4+ lymphocytes
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Evaluation of priming effects for IL-2/IL-15 responsiveness
Commercial recombinant mouse IL-16 is typically engineered from cDNA sequences lacking signal sequences and purified from expression systems using anti-IL-16 monoclonal antibodies . Researchers should verify that preparations contain predominantly monomeric mature IL-16 and are free of bacterial contaminations that could activate TLR2/TLR4 pathways and confound experimental results .
What experimental design considerations are essential when investigating IL-16 effects on interferon signaling?
Given IL-16's role in modulating antiviral responses, careful experimental design is critical when studying its effects on interferon pathways:
Cell culture approaches:
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Compare IL-16 overexpression versus control vector in relevant cell lines
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Alternatively, utilize IL-16 knockout versus wild-type mouse embryonic fibroblasts
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Following appropriate treatments, assess:
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IFN-β and ISG expression by qRT-PCR at multiple timepoints
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IFN-β protein secretion by ELISA
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Promoter activity using luciferase reporter assays with IFN-β or ISRE constructs
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In vivo validation should include:
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Measurement of IFN-β expression in tissues from IL-16 KO versus WT mice following viral challenge
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Quantification of IFN-β protein in BALF and lung homogenates
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Assessment of ISG expression profiles in relevant tissues
Studies have demonstrated that IL-16 overexpression significantly suppresses IFN-β and ISG15 expression in virus-infected cells, while IL-16 deficiency enhances these responses, suggesting that IL-16 inhibits interferon-mediated antiviral immunity .
What molecular mechanisms underlie IL-16's enhancement of viral replication?
IL-16 enhances viral replication through several distinct molecular mechanisms:
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Suppression of interferon responses:
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Decreased IFN-β production following viral infection
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Reduced interferon-stimulated gene expression
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Inhibition of IFN-β and ISRE promoter activities
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Enhanced viral gene expression and protein production:
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Increased viral hemagglutinin (HA), nucleoprotein (NP), and nonstructural (NS) protein levels
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Elevated viral mRNA expression (HA, M, NA genes)
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Higher infectious virus production
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Experimental evidence demonstrates that A549 cells transfected with IL-16-expressing plasmids show significantly upregulated influenza virus protein levels compared to vector controls . Similarly, IL-16 knockout mouse embryonic fibroblasts (MEFs) exhibit reduced viral replication compared to wild-type cells .
The specific signaling pathways through which IL-16 mediates these effects remain under investigation, but the inhibition of interferon signaling appears to be a critical mechanism, as IL-16 significantly suppresses IFN-β and ISG15 expression in virus-infected cells .
How can researchers address discrepancies between in vitro and in vivo IL-16 functional studies?
Reconciling in vitro and in vivo observations requires systematic approaches to address several common discrepancies:
| Challenge | Potential Causes | Methodological Solutions |
|---|---|---|
| Concentration differences | Non-physiological levels in vitro | Establish dose-response curves spanning physiological ranges; measure actual IL-16 levels in tissues |
| Cell-specific responses | Limited cell types in vitro | Use primary cells; employ co-culture systems; validate in tissue explants |
| Microenvironmental factors | Absence of matrix and tissue architecture | Incorporate 3D culture systems; include relevant matrix components |
| Processing variations | Differences in caspase-3 activity | Compare pro-IL-16 vs. mature IL-16; monitor processing in experimental systems |
When examining viral infection models, researchers should acknowledge that the complex interactions between IL-16 and multiple cell types in vivo may not be fully recapitulated in simplified in vitro systems. For example, while IL-16 deficiency significantly reduces viral titers in mouse lungs, analysis of individual myeloid cell subsets (alveolar macrophages, interstitial macrophages, dendritic cells, monocytes, and neutrophils) showed no significant differences in viral M2 protein expression between wild-type and IL-16 knockout mice .
What controls are essential when working with IL-16 knockout models?
Rigorous research with IL-16 knockout models requires comprehensive controls:
Genetic and validation controls:
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Confirm knockout status through:
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Genomic PCR for targeted locus
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RT-PCR verification of absent IL-16 mRNA
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Western blot/ELISA confirmation of protein absence
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Functional validation (e.g., reduced CD4+ T-cell chemotaxis)
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Consider potential compensatory mechanisms:
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Assess related cytokine pathways
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Evaluate baseline immune cell development and distribution
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Compare both steady-state and inflammatory conditions
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Experimental design considerations:
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Include age-matched comparisons (6-8 weeks commonly used)
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Perform rescue experiments with recombinant IL-16
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Examine responses at multiple timepoints to capture dynamic effects
Published research with IL-16 knockout mice has revealed significant protective effects against influenza A virus infection, with knockout mice maintaining normal body weight while wild-type mice experienced severe weight loss following infection . These phenotypic differences were associated with reduced viral loads in knockout mouse lungs and enhanced interferon responses, confirming the biological relevance of IL-16 in viral pathogenesis .
What expression systems are optimal for recombinant mouse IL-16 production?
Different expression systems offer distinct advantages for recombinant mouse IL-16 production:
| Expression System | Advantages | Limitations | Applications |
|---|---|---|---|
| HEK293 cells | - Proper protein folding - Minimal bacterial contamination - Native-like processing | - Higher cost - Lower yield | - Functional assays - In vivo studies |
| E. coli | - High yield - Cost-effective - Simplified purification | - Potential endotoxin contamination - May require refolding | - Structural studies - Antibody production |
Commercial sources utilize HEK293 cell expression systems to produce properly folded, biologically active mouse IL-16 that is purified using anti-IL-16 monoclonal antibodies . The resulting preparation contains predominantly monomeric mature IL-16 as determined by gel filtration . For E. coli-expressed IL-16, rigorous purification and endotoxin removal are essential, with acceptable endotoxin levels being <1 EU/μg for research applications .
How can researchers distinguish between tagged and untagged recombinant mouse IL-16 in experimental systems?
Selecting between tagged and untagged recombinant mouse IL-16 depends on specific experimental requirements:
| Feature | His-tagged IL-16 | Untagged IL-16 |
|---|---|---|
| Amino acid sequence | Contains MGSSHHHHHH tag | Matches native sequence |
| Molecular weight | Slightly higher (~1-2 kDa) | Native size (~14 kDa) |
| Detection methods | Anti-His and anti-IL-16 antibodies | Anti-IL-16 antibodies only |
| Purification strategy | IMAC (metal affinity) | Immunoaffinity or conventional chromatography |
| Potential limitations | Possible interference with function | More challenging to track |
Commercial His-tagged recombinant mouse IL-16 typically incorporates the tag at the N-terminus of the mature IL-16 fragment (amino acids 1205-1322) . While this facilitates purification and detection, researchers should consider potential effects on protein function, particularly for studies involving receptor interactions or oligomerization. Critical functional experiments may benefit from comparing both tagged and untagged versions to ensure the tag does not affect the biological activity of interest.
What protocols are recommended for studying IL-16's effects on influenza susceptibility?
To investigate IL-16's impact on influenza susceptibility, researchers should consider these methodological approaches:
In vitro infection models:
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Cell preparation:
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Transfect A549 cells with IL-16-expressing or control plasmids
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Alternatively, use IL-16 knockout versus wild-type mouse embryonic fibroblasts
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Viral infection:
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Infect cells with influenza A virus (typically PR8 strain) at MOI 0.1-5
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Harvest cells and supernatants at multiple timepoints (12, 24, 48 hours)
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Analysis methods:
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Immunoblotting for viral proteins (HA, NP, NS)
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qRT-PCR for viral gene expression (NA, HA, M)
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Plaque assays for infectious virus quantification
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qRT-PCR and ELISA for interferon pathway components
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In vivo infection protocol:
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Infect age-matched (6-8 weeks) IL-16 knockout and wild-type mice with influenza A virus (8,000-10,000 PFU/mouse) intranasally
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Monitor weight daily for 14 days
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Collect lungs at day 3 and day 7 post-infection for viral load determination
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Perform histopathological analysis of lung sections
This approach has revealed that IL-16 overexpression significantly enhances viral protein levels, mRNA expression, and virus production in cell culture models . Correspondingly, IL-16 knockout mice show remarkable resistance to influenza infection, maintaining normal body weight while wild-type mice experience severe weight loss . These findings establish IL-16 as a host susceptibility factor for influenza virus infection.
What are the emerging therapeutic implications of IL-16 research in viral infections?
The discovery that IL-16 enhances host susceptibility to influenza virus by suppressing interferon responses suggests several therapeutic possibilities worthy of investigation:
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IL-16 neutralization strategies:
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Development of neutralizing antibodies against IL-16
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Small molecule inhibitors targeting IL-16/receptor interactions
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Testing these approaches in pre-clinical models of viral infection
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Interferon pathway modulation:
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Combining IL-16 inhibition with interferon-enhancing therapies
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Identifying the specific interferon pathway components affected by IL-16
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Targeting these downstream mediators
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Cell-specific targeting approaches:
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Determining which IL-16-producing cells are most relevant during infection
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Developing cell-specific delivery systems for IL-16 inhibitors
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Evaluating effects on viral pathogenesis versus immune homeostasis
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Research has demonstrated that IL-16 knockout mice maintain normal body weight following influenza infection while wild-type mice experience severe weight loss and higher viral loads . This protective effect suggests that transient IL-16 inhibition during acute viral infections might represent a host-directed therapeutic strategy that complements direct antiviral approaches.
How might recombinant IL-16 be utilized as a research tool beyond viral infection models?
Recombinant mouse IL-16 has applications beyond viral pathogenesis research:
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T-cell biology:
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Investigation of CD4+ T-cell migration mechanisms
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Studies of IL-16's role in T-cell activation and proliferation
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Examination of effects on regulatory versus effector T-cell balance
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Inflammatory disease models:
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Asthma and allergic airway inflammation
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Autoimmune conditions
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Tissue-specific inflammatory responses
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Cancer immunology:
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Effects on tumor-infiltrating lymphocytes
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Potential role in modulating anti-tumor immunity
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Applications in immunotherapy enhancement
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Neurodegenerative conditions:
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Investigation of IL-16's neuronal functions
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Potential role in neuroinflammatory processes
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Therapeutic implications for conditions with immune components
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The pleiotropic effects of IL-16 on various immune and non-immune cells make it a valuable research tool for investigating diverse biological processes beyond infectious disease models .
