IL 19 Mouse

What is IL-19 and what is its fundamental role in mouse immune systems?

IL-19 is a member of the IL-10 family of cytokines that functions as a negative-feedback regulator to limit proinflammatory responses of macrophages and microglia in various inflammatory diseases. Unlike IL-10 which is predominantly anti-inflammatory, IL-19 exhibits more complex regulatory functions. In neuroinflammatory diseases like Multiple Sclerosis (MS) and its mouse model experimental autoimmune encephalomyelitis (EAE), IL-19 suppresses pathogenesis by inhibiting macrophage antigen presentation, limiting Th17 cell expansion, and reducing subsequent inflammatory responses . IL-19 signals through the IL-20 receptor A/B (IL-20RA/B) heterodimer, which activates the transcription factor Signal Transducer and Activator of Transcription 3 (STAT3) . Its expression by and regulatory effects on cells of the monocyte lineage highlight its importance in myeloid cell function within the immune system.

How should researchers measure IL-19 levels in mouse experimental samples?

The standard quantitative method for measuring IL-19 in mouse samples is sandwich ELISA. According to available mouse IL-19 ELISA kits, researchers should consider the following specifications and methodological approach:

For accurate measurement, researchers should prepare samples appropriately, establish a standard curve using reference standards, and carefully follow incubation times and washing steps . When analyzing diverse sample types, it's essential to validate potential matrix interference by performing dilution linearity and spike recovery experiments before proceeding with full experimental analysis.

How do genetic backgrounds influence IL-19 knockout phenotypes in mice?

The genetic background significantly influences phenotypic manifestations of IL-19 deficiency in mice. IL-19-deficient mice on a mixed 129xBL6 background demonstrate decreased percentages of CD11c+ cells in bronchoalveolar lavage (BAL) compared to wild-type mice. This phenotype results from the interaction between IL-19 deficiency and traits inherited from the 129 mouse strain .

When IL-19-/- mice are fully backcrossed to C57BL/6 or BALB/c backgrounds (for 6 to 10 generations, respectively), the abundance of CD11c+ cells in BAL becomes comparable to wild-type mice . Intercross and backcross experiments between IL-19-/- 129xBL6 and IL-19-/- C57BL6 mice, as well as backcrosses with wild-type C57BL/6 mice, confirmed that the decreased abundance of CD11c+ cells is determined by the interaction between IL-19 deficiency and specific 129 strain traits .

These observations underscore the importance of considering genetic background when designing experiments with IL-19-deficient mice, as strain-specific genetic factors can significantly modify phenotypic outcomes. Researchers should report complete backcrossing information and use appropriate genetic controls to ensure result reproducibility.

What are the primary immune cell alterations in IL-19 knockout mice?

IL-19 knockout mice exhibit several significant alterations in immune cell populations and functions compared to wild-type mice:

Cell Population Changes:

• Decreased percentages of CD11c+ cells in BAL (dependent on genetic background)

• 3-5 fold reduction in CD11c+ cells co-expressing CD205 in BAL and lungs

• Presence of eosinophils in BAL samples from IL-19-/- 129xBL6 mice

Cell Surface Marker Expression:

• Significantly reduced MHCII expression on CD11c+ cells at baseline and following inflammatory challenges

• Reduced MHCII expression on other cell types including monocytes/macrophages and B cells

• Lower levels of extracellular Notch2 but increased transmembrane/intracellular Notch2 on lung monocytes

Functional Alterations:

• IL-19-deficient splenic macrophages express elevated levels of co-stimulatory molecules

• Increased production of Th17 differentiation-associated cytokines (IL-1β, IL-6, IL-23, TGF-β1, and TNF-α) by splenic macrophages

• Altered response to T cell-dependent inflammatory challenges while maintaining similar responses to T cell-independent challenges

These immune cell alterations suggest that IL-19 plays important roles in regulating immune cell development, antigen presentation capabilities, and inflammatory responses, particularly in the context of T cell-dependent immunity.

How does IL-19 deficiency impact experimental autoimmune encephalomyelitis progression?

IL-19 deficiency significantly exacerbates experimental autoimmune encephalomyelitis (EAE), providing key insights into regulatory mechanisms of neuroinflammation:

Disease Progression Effects:

• IL-19 deficiency aggravates EAE severity by promoting enhanced IL-17-producing helper T cell (Th17) infiltration into the central nervous system (CNS)

• The exacerbated disease phenotype suggests endogenous IL-19 serves a protective role in limiting EAE severity

Immunological Mechanisms:

• IL-19-deficient splenic macrophages exhibit elevated expression of MHC class II and co-stimulatory molecules, enhancing their antigen presentation capacity

• These macrophages produce increased amounts of cytokines that promote Th17 cell differentiation, including IL-1β, IL-6, IL-23, TGF-β1, and TNF-α

• The enhanced antigen presentation combined with pro-inflammatory cytokine production creates an environment favoring Th17 expansion and more severe disease manifestation

Therapeutic Implications:

• Treatment with recombinant IL-19 significantly abrogates EAE progression in mice

• This therapeutic effect suggests IL-19 supplementation could potentially benefit MS patients

These findings establish IL-19 as a critical negative regulator of neuroinflammation through multiple mechanisms: inhibiting macrophage antigen presentation, limiting pathogenic Th17 expansion, and suppressing inflammatory cytokine production. Researchers studying neuroinflammatory conditions should consider IL-19 as both a potential biomarker for disease activity and a promising therapeutic target.

What molecular mechanisms explain IL-19's regulation of MHCII expression in airway CD11c+ cells?

IL-19 critically regulates MHCII expression on CD11c+ cells through several interconnected molecular mechanisms:

Baseline MHCII Regulation:

• CD11c+ cells from BAL of IL-19-deficient mice demonstrate significantly reduced MHCII expression even in resting conditions

• This suggests IL-19 provides constitutive signals necessary for maintaining normal MHCII levels

Response to Inflammatory Stimuli:

• Wild-type mice challenged with microbial products or inflammatory cytokines show dramatic (10-100 fold) increases in MHCII expression on CD11c+ airway cells

• This increase is significantly blunted in IL-19-deficient mice following challenges with Aspergillus antigen, lipopolysaccharide, or IL-13

• The effect extends beyond CD11c+ cells to other MHCII-expressing cells including monocytes/macrophages and B cells

Notch2 Signaling Pathway:

• IL-19 regulates Notch2 expression on lung monocytes, which are precursors to airway CD11c+ cells

• IL-19 deficiency results in lower extracellular Notch2 but increased transmembrane/intracellular Notch2

• Intranasal administration of recombinant IL-19 restores extracellular Notch2 expression

• Given that Notch signaling is a known regulator of immune cell development and function, this pathway likely contributes to IL-19's regulation of MHCII expression

Functional Consequences:

• The decreased MHCII expression correlates with ameliorated responses to T cell-dependent challenges but not T cell-independent challenges

• This differential effect highlights how IL-19-mediated regulation of MHCII impacts antigen presentation and subsequent T cell activation

These findings establish IL-19 as a key regulator in the molecular network controlling MHCII expression, with significant implications for antigen presentation and adaptive immune responses in the lungs.

How does IL-19 regulate Notch2 expression and what are the implications for myeloid cell differentiation?

IL-19 exhibits complex domain-specific regulation of Notch2 on myeloid cells with significant implications for their differentiation and function:

Domain-Specific Regulation:

• Lung monocytes from IL-19-deficient mice show significantly reduced extracellular Notch2 expression compared to wild-type

• Conversely, these cells exhibit increased transmembrane/intracellular Notch2 expression

• This pattern suggests IL-19 may influence Notch2 processing, potentially affecting its signaling capacity

Direct Regulatory Effects:

• Intranasal administration of recombinant IL-19 to IL-19-deficient mice significantly increases extracellular Notch2 expression on lung monocytes

• Dendritic cells cultured from bone marrow cells in the presence of IL-19 show upregulated extracellular Notch2

• These observations establish a direct regulatory relationship between IL-19 and Notch2 expression

Implications for CD11c+CD205+ Cell Development:

• Wild-type mice have a predominance of CD11c+ cells that co-express high levels of CD205 in BAL and lungs

• IL-19-deficient mice show a 3-5 fold reduction in this cell population

• Given that lung monocytes are precursors to airway CD11c+ cells, the altered Notch2 expression likely influences their differentiation pathway

Developmental and Functional Consequences:

• Notch signaling is a critical regulator of immune cell fate determination and function

• The altered Notch2 expression pattern in IL-19-deficient mice may disrupt normal differentiation programs of myeloid cells

• These developmental alterations likely contribute to the observed changes in immune cell phenotypes and functions

This regulatory relationship between IL-19 and Notch2 represents a novel mechanism through which IL-19 influences myeloid cell development and function, with potential implications for understanding and targeting immune dysregulation in inflammatory conditions.

What methodological approaches should researchers use to investigate IL-19's differential effects on T cell-dependent versus T cell-independent inflammation?

Researchers investigating IL-19's role in different inflammatory pathways should implement these methodological approaches:

Experimental Models:

• T cell-dependent inflammation models:

  • Experimental autoimmune encephalomyelitis (EAE) induction through MOG peptide immunization

  • Aspergillus antigen sensitization followed by intranasal challenge

  • House dust mite or ovalbumin-based allergic airway inflammation models

• T cell-independent inflammation models:

  • Direct lipopolysaccharide (LPS) administration to naïve mice

  • Recombinant IL-13 administration to naïve mice

  • Acute lung injury models using direct irritants

Assessment Parameters:

Advanced Experimental Approaches:

• Genetic Models:

  • Compare fully backcrossed IL-19-/- mice on defined genetic backgrounds (C57BL/6, BALB/c)

  • Consider conditional knockout models targeting specific cell types

  • Utilize reporter mice to track IL-19-expressing cells during inflammation

• Mechanistic Interventions:

  • Administer recombinant IL-19 to IL-19-deficient mice to assess phenotype rescue

  • Use IL-19 neutralizing antibodies in wild-type mice during inflammatory challenges

  • Combine IL-19 manipulation with Notch pathway inhibition to dissect signaling interactions

• Cell-specific Analyses:

  • Isolate CD11c+ cells or monocytes for ex vivo functional assays

  • Perform antigen presentation assays with T cells from TCR transgenic mice

  • Conduct adoptive transfer experiments with wild-type or IL-19-deficient cells

By implementing these methodological approaches, researchers can systematically investigate the mechanisms through which IL-19 differentially regulates T cell-dependent versus T cell-independent inflammatory responses, potentially revealing new therapeutic targets for inflammatory conditions.

How can researchers reconcile conflicting data showing protective versus pathogenic roles of IL-19 in different inflammatory contexts?

The apparently contradictory roles of IL-19 across different inflammatory conditions can be reconciled through careful consideration of several experimental and biological factors:

Context-Dependent Mechanisms:

IL-19 exhibits divergent effects in different inflammatory settings:

• In EAE (CNS inflammation), IL-19 deficiency exacerbates disease through enhanced Th17 responses

• In Aspergillus antigen-induced airway inflammation, IL-19 deficiency ameliorates inflammation

• These opposing outcomes suggest IL-19's function is highly context-dependent

Tissue-Specific Microenvironments:

Experimental Design Considerations:

• Genetic Background Effects:

  • The mixed genetic background in some studies introduces confounding variables

  • Researchers should use fully backcrossed mice on defined backgrounds

  • Studies should report complete information on genetic background

• Temporal Aspects:

  • IL-19's effects may differ during initiation versus established inflammation

  • Consider kinetic studies examining IL-19 function at different disease phases

• Cell-Type Specific Functions:

  • IL-19 may have opposing effects on different cell populations

  • Cell-specific deletion or expression of IL-19 or its receptors could help dissect these effects

Methodological Recommendations:

To reconcile conflicting data, researchers should:

• Directly compare IL-19's function across different tissues in the same animals

• Use single-cell approaches to identify cell-specific responses to IL-19

• Investigate downstream molecular pathways (like Notch signaling) in different contexts

• Consider the influence of other cytokines and inflammatory mediators that might modify IL-19's effects

Understanding the context-dependent functions of IL-19 will be crucial for developing targeted therapeutic approaches that harness its protective effects while avoiding potential detrimental outcomes in specific disease settings.