IL36G Mouse

What is IL36G and what is its role in the immune system of mice?

IL36G (Interleukin 36 gamma) is a member of the IL-1 family of cytokines that plays important roles in innate immunity and inflammatory responses in mice. IL36G functions primarily as an initiator of innate defense mechanisms and tissue repair responses following microbial infection . The protein functions through binding to the IL-36 receptor (IL-36R), triggering downstream signaling cascades that regulate immune cell functions.

In the mouse immune system, IL36G serves as a critical mediator that bridges innate and adaptive immunity. It stimulates the expression of antimicrobial molecules such as S100A9 and mouse β-defensin 3, while also modulating the expression of other cytokines including suppressing IL-1β expression in certain contexts . The absence of IL36G results in increased susceptibility to multiple pathogenic infections, demonstrating its essential role in host defense mechanisms .

What are the primary cellular sources of IL36G in mice?

The expression of IL36G in mice shows a tissue-specific pattern with several key cellular sources:

• Epithelial cells: IL36G is prominently expressed in mouse gingival epithelial cells, making it a significant component of oral mucosal immunity .

• Immune cells: Mouse neutrophils have been identified as important producers of IL36G, particularly in inflammatory conditions .

• Lung tissue: Following influenza infection, IL36G mRNA is significantly upregulated in the lung tissue of mice, suggesting respiratory epithelial cells may be an important source during viral infections .

This expression profile indicates that IL36G functions at barrier sites (oral, respiratory) where host-pathogen interactions are common, positioning it as a first-line defender in mucosal immunity.

How do IL36G knockout mice differ from wild-type mice?

IL36G knockout (KO) mice show several distinct phenotypic differences compared to wild-type mice:

• Increased infection susceptibility: IL36G-KO mice exhibit enhanced susceptibility to multiple pathogens, including HSV-2, influenza A, Streptococcus pneumoniae, and Klebsiella pneumonia infections .

• Altered macrophage phenotype: Alveolar macrophages from IL36G-KO mice display higher expression of M2-like surface markers compared to wild-type mice, suggesting IL36G influences macrophage polarization .

• Compromised macrophage survival: Following influenza infection, IL36G-KO mice show a rapid loss of alveolar macrophages due to increased apoptosis within 24 hours of infection .

• Enhanced inflammatory responses: During influenza infection, IL36G-KO mice exhibit higher levels of proinflammatory cytokines early in infection and more diffuse pathological conditions late in the disease course .

These differences highlight IL36G's critical role in maintaining immune homeostasis and providing protection against various pathogens.

What experimental models are effective for studying IL36G function in mice?

Several experimental models have proven valuable for investigating IL36G function in mice:

• Infection models:

  • Influenza virus (H1N1 and H3N2) infection has been used to evaluate IL36G's role in viral immunity

  • Bacterial infection models using Pseudomonas aeruginosa, Streptococcus pneumoniae, and Klebsiella pneumoniae demonstrate IL36G's importance in antibacterial defense

  • HSV-2 infection models reveal IL36G's contribution to antiviral immunity

• Cancer models:

  • B16 melanoma transplantation models show how IL36G transforms the tumor microenvironment

  • 4T1 breast cancer cell transplantation in BALB/c mice demonstrates IL36G's effects on tumor progression

• Inflammatory disease models:

  • Ligature-induced periodontitis model reveals IL36G's role in neutrophil recruitment and bone resorption

  • Corneal keratitis models demonstrate IL36G's protective effects against Pseudomonas aeruginosa infection

These diverse models allow researchers to examine IL36G's functions across multiple physiological and pathological contexts.

What techniques are most effective for measuring IL36G expression and activity in mouse tissues?

Researchers studying IL36G in mouse models employ several complementary techniques:

• mRNA quantification:

  • RT-PCR to detect upregulation of Il36g mRNA in tissues following infection, as demonstrated in lung tissue after influenza challenge

• Protein detection:

  • Immunohistochemistry (IHC) using specific antibodies such as mouse monoclonal anti-IL36G antibodies to visualize protein localization in tissues

  • Western blot (WB) for semi-quantitative analysis of IL36G protein levels

• Functional assays:

  • Measurement of downstream effector molecules like S100A9 and mouse β-defensin 3 expression as indicators of IL36G activity

  • Analysis of cytokine production (IFN-γ, IL-2) by target immune cells following IL36G stimulation

  • Neutrophil chemotaxis assays to determine IL36G's effects on cell migration

• In vivo studies:

  • Administration of recombinant IL36G protein and measurement of subsequent immune responses

  • Comparative studies between IL36G-KO and wild-type mice to determine phenotypic differences

These methodologies provide complementary data about IL36G's expression patterns and functional impacts in different experimental settings.

How can researchers differentiate between direct and indirect effects of IL36G in mouse models?

Distinguishing direct from indirect effects of IL36G requires sophisticated experimental approaches:

• Cell-specific experiments:

  • Isolate individual cell populations (e.g., CD8+ T cells, NK cells, γδ T cells) and stimulate with recombinant IL36G in vitro to identify direct cellular targets

  • Compare responses in IL-36R-expressing versus IL-36R-deficient cells to confirm receptor dependency

• Transfer experiments:

  • Transfer of wild-type alveolar macrophages to IL36G-KO mice restores protection against lethal influenza challenge, demonstrating the specific cell type through which IL36G mediates protection

• Neutralization studies:

  • Use of neutralizing antibodies against downstream mediators (e.g., S100A9, CXCL10) to determine which effects are mediated by secondary factors

  • For example, IL36G's protective effects against P. aeruginosa keratitis are abolished by S100A9-neutralizing antibody and partially affected by CXCL10 and CXCR3 neutralization

• Receptor expression analysis:

  • Measurement of IL-36R expression levels on different cell types helps identify potential direct targets of IL36G

  • Studies have found that IL-36R mRNA is expressed at high levels in NK and γδ T cells, identifying them as potential direct targets

These approaches help researchers decipher the complex signaling networks through which IL36G exerts its biological effects.

How does IL36G contribute to host defense against viral infections in mice?

IL36G plays a crucial protective role during viral infections in mice, particularly against influenza:

• Infection outcomes:

  • IL36G-deficient mice exhibit significantly increased morbidity and mortality when infected with either H1N1 or H3N2 influenza viruses

  • Higher viral titers are observed in IL36G-KO mice, indicating compromised viral clearance

• Macrophage preservation:

  • IL36G signaling is essential for alveolar macrophage survival during influenza infection

  • IL36G-KO mice show rapid loss of alveolar macrophages following infection due to increased apoptosis

  • Transfer of wild-type alveolar macrophages to IL36G-KO mice restores protection against lethal influenza challenge

• Inflammatory modulation:

  • IL36G helps regulate the inflammatory response during viral infection, with IL36G-KO mice showing higher levels of proinflammatory cytokines early in infection

  • This suggests IL36G plays a role in maintaining appropriate inflammatory balance during viral challenge

• Increased susceptibility to HSV-2:

  • IL36G-deficient mice also show enhanced susceptibility to HSV-2 infection, indicating its protective role extends beyond influenza to other viral pathogens

These findings establish IL36G as a key mediator of antiviral immunity, primarily through its effects on maintaining macrophage populations and regulating inflammatory responses.

What is the role of IL36G in bacterial infection models?

IL36G demonstrates significant protective functions in multiple bacterial infection models:

• Respiratory bacterial infections:

  • IL36G-deficient mice show increased susceptibility to Streptococcus pneumoniae and Klebsiella pneumonia infections

• Ocular bacterial infections:

  • In P. aeruginosa keratitis models, IL36G diminishes disease severity through multiple mechanisms

  • IL36G stimulates expression of antimicrobial peptides including S100A9 and mouse β-defensin 3

  • The protective effects of IL36G against P. aeruginosa are abolished when S100A9 is neutralized, demonstrating this antimicrobial peptide is a key effector

• Oral bacterial challenges:

  • During periodontitis, IL36G levels increase significantly

  • IL36G specifically activates gingival fibroblasts, leading to chemotaxis of neutrophils to the site of infection

  • Blocking IL36 receptor signaling with IL-36Ra inhibits neutrophil infiltration in the ligature-induced periodontitis mouse model

These studies reveal that IL36G functions through multiple mechanisms to combat bacterial infections, including direct antimicrobial peptide induction and orchestration of neutrophil recruitment to infection sites.

How does IL36G affect tumor progression in mouse cancer models?

IL36G demonstrates significant anti-tumor activity in multiple mouse cancer models:

• Effects on immune cells within the tumor microenvironment:

  • IL36G promotes type 1 lymphocyte responses critical for anti-tumor immunity

  • It enhances CD8+ T cell activation, with IL36G treatment increasing cell size and promoting biomass production during naive T cell activation

  • IL36G stimulates production of IL-2 and IFN-γ by CD8+ T cells in a dose-dependent manner

  • It also increases IFN-γ production by NK cells and γδ T cells, further enhancing anti-tumor immunity

• Cancer models tested:

  • IL36G's effects have been demonstrated in both B16 melanoma and 4T1 breast cancer cell transplantation models

  • This suggests broad applicability across different tumor types

• Mechanism of action:

  • IL36G transforms the tumor microenvironment to favor anti-tumor immune responses

  • The cytokine acts as a co-stimulator of naive CD8+ T cell activation, potentiating their anti-tumor function

  • IL36G's effects are partially dependent on IL-2, indicating cross-talk between cytokine pathways

These findings position IL36G as a potential immunotherapeutic agent for cancer treatment by enhancing multiple arms of anti-tumor immunity.

What is the significance of IL36G in mouse models of inflammatory diseases?

IL36G plays complex and sometimes contradictory roles in different inflammatory disease models:

These contrasting roles highlight IL36G's context-dependent functions in inflammatory conditions, which may depend on:

• The specific tissue involved

• The inflammatory trigger (sterile vs. infection-induced)

• The temporal dynamics of the inflammatory response

• The predominant cell types responding to IL36G in each context

Understanding these nuances is crucial for developing targeted therapeutic approaches that modulate IL36G activity.

How can IL36G be targeted therapeutically based on mouse studies?

Mouse studies suggest several potential therapeutic applications for IL36G modulation:

• Enhancing antimicrobial immunity:

  • Administration of recombinant IL36G can stimulate antimicrobial peptide production and improve outcomes in bacterial infections like P. aeruginosa keratitis

  • IL36G supplementation might offer protection against viral pathogens, particularly in respiratory infections like influenza

• Cancer immunotherapy:

  • IL36G transforms the tumor microenvironment and promotes type 1 lymphocyte responses that are favorable for anti-tumor immunity

  • Administration of IL36G enhances CD8+ T cell, NK cell, and γδ T cell activation and function, suggesting potential as an immunotherapeutic adjuvant

• Inflammatory disease modulation:

  • In periodontitis, blocking IL36G signaling with IL-36Ra inhibits neutrophil infiltration and bone resorption, suggesting antagonism of IL36G could be beneficial in this context

  • The context-dependent effects of IL36G require careful consideration when designing therapeutic strategies

• Alveolar macrophage preservation:

  • IL36G signaling is critical for alveolar macrophage survival during respiratory infections like influenza

  • Therapeutic targeting to maintain macrophage populations might improve outcomes in acute respiratory infections

These findings from mouse models provide a foundation for developing IL36G-targeted therapeutics, though further research is needed to translate these findings to human applications.

What are the current challenges in translating IL36G mouse research to human applications?

Several challenges must be addressed when translating IL36G findings from mice to humans:

• Species differences:

  • While IL36G is conserved between mice and humans, there may be differences in expression patterns, receptor distribution, and downstream signaling

  • Careful validation in human systems is needed before therapeutic applications can proceed

• Context-dependent effects:

  • IL36G has shown both protective and pathological roles depending on the disease context

  • In periodontitis, IL36G promotes neutrophil infiltration and bone resorption

  • In contrast, during P. aeruginosa keratitis, IL36G has protective effects

  • This complexity necessitates precise targeting strategies for specific disease contexts

• Delivery challenges:

  • For recombinant IL36G therapy, effective delivery to target tissues remains challenging

  • Local administration has shown efficacy in mouse models (e.g., corneal application)

  • Systemic administration may require specialized delivery systems to avoid off-target effects

• Integration with existing therapies:

  • Understanding how IL36G-targeted approaches interact with current standard treatments requires additional research

  • Combination approaches may offer synergistic benefits but need thorough preclinical evaluation

Addressing these challenges will be essential for translating the promising findings from mouse models into effective human therapeutics targeting the IL36G pathway.