IL17F Mouse

What is IL-17F and how does it relate functionally to IL-17A?

IL-17F is a member of the IL-17 cytokine family that shares significant structural homology with IL-17A (commonly referred to as IL-17). While both cytokines regulate proinflammatory gene expression, IL-17F typically induces more moderate inflammatory responses than IL-17 at equivalent concentrations. Both cytokines utilize similar signaling mechanisms, requiring IL-17 receptor A (IL-17RA), tumor necrosis factor receptor-associated factor 6 (TRAF6), and Act1 to mediate their biological effects . In experimental systems, detailed dose comparison between IL-17 and IL-17F in inducing IL-6 production in mouse embryonic fibroblasts (MEFs) reveals that IL-17 consistently demonstrates greater potency .

What cellular sources express IL-17F in mouse models?

IL-17F is predominantly co-expressed with IL-17 in T cells, particularly in Th17 cells. Analysis of protein expression patterns using IL-17F-specific antibodies reveals that most T cells expressing IL-17F also express IL-17, with relatively few single-positive cells in certain contexts. IL-17F expression has been detected in CD4+ T cells isolated from the central nervous system of mice with experimental autoimmune encephalomyelitis (EAE) as well as in IL-17hi CD4+ T cells in the lamina propria and intestinal intraepithelium . Interestingly, these tissue-resident populations demonstrate different IL-17/IL-17F expression ratios, with intestinal tissues containing more IL-17 single-positive cells compared to those recovered from the CNS during inflammation .

What signaling pathways mediate IL-17F function in mice?

The signaling cascade initiated by IL-17F shares significant overlap with IL-17. Both cytokines require IL-17RA, as demonstrated by complete impairment of IL-17F and IL-17 effects in IL-17RA-deficient fibroblasts, while TNF-α and IL-1β responses remain intact . In vivo experiments further confirm this dependency, as IL-17RA-deficient mice show abolished neutrophil recruitment in response to intraperitoneal IL-17F or IL-17 administration . The signaling pathway also critically involves TRAF6 and Act1 adaptor proteins. Once activated, IL-17F induces expression of proinflammatory genes including CXCL1, IL-6, CCL2, CCL7, MMP13, and thymic stromal lymphopoietin, though typically at lower magnitudes than IL-17 .

How are IL-17F knockout mice generated and validated?

IL-17F knockout mice are generated by replacing exon 2 of the IL-17F gene with an IRES-mRFP-polyA cassette . After removal of the puromycin-resistant selection marker in the mouse germline, heterozygous IL-17F knockout mice are intercrossed to produce homozygous animals, which are then genotyped using PCR analysis of tail genomic DNA . Validation of these knockout models involves immunological challenge, such as keyhole limpet hemocyanin (KLH) immunization, followed by analysis of cytokine production after antigen restimulation. Both ELISA measurement of secreted cytokines and intracellular cytokine staining confirm the absence of IL-17F production in knockout animals . Importantly, IL-17F-deficient mice develop normally with unaltered thymic and splenic lymphocyte populations compared to wild-type mice .

What phenotypes are observed in IL-17F transgenic mouse models?

Lung-specific IL-17F transgenic mice created using the Clara cell 10 (CC10) gene promoter demonstrate several key inflammatory phenotypes. These mice show greatly increased IL-17F mRNA expression in lung tissues without affecting IL-17 expression levels . Beginning at approximately 5 months of age, they develop substantial lung pathology characterized by:

• Peribronchial and perivascular infiltration of CD4+ and B220+ lymphocytes

• Significant macrophage infiltration throughout the lung tissue

• Increased mucus production demonstrated by periodic acid Schiff (PAS) staining

• Occasional Charcot-Leyden-like crystal structures in severe cases

• Upregulation of inflammatory genes similar to those induced in lung epithelial cells by recombinant IL-17F

Notably, these pathological features closely resemble those observed in CC10-IL-17 transgenic mice, suggesting similar biological functions for both cytokines in chronic airway inflammation .

How do IL-17F knockout and IL-17 knockout mice differ in basic immunological parameters?

Comparative analysis of IL-17F-deficient and IL-17-deficient mice reveals distinct immunological differences despite both developing normally. When immunized with KLH, IL-17-deficient mice produce significantly reduced levels of IgM, total IgG, and all IgG subclasses compared to wild-type controls . In contrast, IL-17F-deficient mice show significantly increased IgG2a levels without corresponding increases in IFN-γ . These different humoral immune profiles suggest non-redundant roles for these cytokines in regulating antibody responses. Additionally, while IL-17F deficiency does not substantially affect IL-17 expression, IL-17-deficient cells show reduced IL-17F levels, suggesting IL-17 may regulate IL-17F expression but not vice versa .

What is the role of IL-17F in experimental autoimmune encephalomyelitis?

In the EAE model of multiple sclerosis, IL-17F plays a less critical role than IL-17. While IL-17-deficient mice show significantly delayed disease onset and progression, IL-17F-deficient mice exhibit only moderately improved recovery compared to wild-type controls . This indicates that IL-17, but not IL-17F, is essential for initiating neuronal inflammation. At the cellular level, both IL-17F and IL-17 knockout mice show reduced CD4+ T cell infiltration into the CNS, though CD11b+ myeloid cells are slightly increased in IL-17F-deficient animals . At the molecular level, expression of the chemokines CCL2 and CCL7 is reduced in both knockout strains but more profoundly in IL-17-deficient mice, while CXCL1 expression is severely impaired only in IL-17-deficient mice . These findings suggest that while both cytokines contribute to inflammatory cell recruitment in EAE, IL-17 plays the dominant role.

How does IL-17F contribute to allergic airway inflammation in mice?

IL-17F significantly contributes to allergic airway responses through several mechanisms. In vitro studies demonstrate that IL-17F induces multiple chemokines in the mouse lung epithelial cell line MLE12 . In allergen challenge models, IL-17F-deficient mice, but not IL-17-deficient mice, show defective airway neutrophilia . Even more strikingly, in asthma models, IL-17-deficient mice exhibit reduced T helper type 2 (Th2) responses, while IL-17F-deficient mice display enhanced type 2 cytokine production and increased eosinophil function . These findings suggest IL-17F may regulate allergic airway inflammation by suppressing certain aspects of Th2 responses, which contrasts with the generally pro-inflammatory effects observed in other contexts. The demonstration that IL-17F can induce thymic stromal lymphopoietin, a potent inducer of Th2 responses, further suggests complex cross-regulatory mechanisms between different T helper subsets mediated by this cytokine .

What are the differential effects of IL-17F versus IL-17 in intestinal inflammation models?

IL-17F and IL-17 demonstrate notably opposing functions in intestinal inflammation. In the dextran sulfate sodium (DSS)-induced colitis model, IL-17F deficiency results in reduced disease severity, whereas IL-17 knockout mice develop more severe disease . This suggests that IL-17F promotes inflammatory pathology in the colon while IL-17 may exert protective effects in this particular tissue environment. These findings highlight the context-dependent functions of IL-17 family cytokines and underscore the importance of studying their roles in specific disease settings rather than generalizing across all inflammatory conditions . The molecular mechanisms underlying these opposing effects remain to be fully elucidated but may involve differential regulation of innate immune responses or epithelial barrier function.

How can IL-17F signaling pathways be experimentally dissected in mouse models?

Detailed experimental dissection of IL-17F signaling can be accomplished through multiple complementary approaches:

• Receptor requirement studies: Using IL-17RA-deficient cells and mice to demonstrate the essential role of this receptor subunit in mediating IL-17F responses both in vitro and in vivo

• Signaling adaptor analysis: Examining the roles of TRAF6 and Act1 through knockout approaches to delineate the proximal signaling events following receptor engagement

• Gene expression profiling: Analyzing downstream gene induction patterns in various cell types (fibroblasts, epithelial cells) after IL-17F stimulation and comparing with IL-17-induced profiles

• In vivo reconstitution experiments: Determining whether recombinant IL-17F can rescue phenotypes in IL-17F-deficient mice, particularly in acute challenge models with defined readouts like neutrophil recruitment

• Dose-response comparisons: Conducting detailed dose comparisons between IL-17F and IL-17 to quantitatively assess their relative potencies in inducing specific inflammatory mediators

What methodological approaches are optimal for studying IL-17F protein expression in mouse tissues?

The development of reliable detection methods for IL-17F protein has been crucial for understanding its expression patterns. Key methodological approaches include:

• Generation of specific reagents: Production of biologically active IL-17F-Ig fusion proteins that can be used to raise specific polyclonal antibodies against IL-17F

• Antibody validation: Rigorous validation of anti-IL-17F antibodies using transfected cells expressing IL-17F or IL-17 to confirm specificity

• Flow cytometric analysis: Intracellular cytokine staining protocols to detect IL-17F in T cells from various tissues including CNS, lamina propria, and intestinal intraepithelium

• Co-expression analysis: Simultaneous detection of IL-17F and IL-17 to determine co-expression patterns and relative expression levels in different T cell populations

• Tissue-specific analysis: Comparing expression profiles between different anatomical sites to identify tissue-specific regulation of IL-17F expression

How might findings from IL-17F mouse models translate to human inflammatory diseases?

Findings from IL-17F mouse models have significant translational implications for human inflammatory diseases:

• Genetic associations: A mutation in the IL-17F gene has been associated with human asthma and chronic obstructive pulmonary disease, suggesting functional relevance in human airway disorders

• Therapeutic targeting considerations: The differential and sometimes opposing roles of IL-17F versus IL-17 in various disease models suggest that selective targeting might be necessary for optimal therapeutic outcomes

• Biomarker development: The detection of IL-17F in the airways of allergic asthma patients upon allergen challenge provides validation of findings from mouse models and suggests potential utility as a disease biomarker

• Complex cytokine interactions: The cross-regulatory relationship between IL-17F and Th2 responses observed in mouse models may inform understanding of the complex interplay between different inflammatory pathways in human allergic diseases

What are the remaining knowledge gaps regarding IL-17F biology in mouse models?

Despite significant advances, several important questions remain regarding IL-17F biology:

• The molecular mechanisms underlying the differential functions of IL-17F versus IL-17 in various disease contexts remain incompletely understood and require further investigation

• The potential formation and functional significance of IL-17/IL-17F heterodimers in vivo needs more detailed characterization

• The precise cellular targets of IL-17F in different tissue environments and disease states require further definition

• The long-term consequences of chronic IL-17F exposure on tissue remodeling and fibrosis warrant more extensive analysis

• The interaction between IL-17F and other inflammatory or regulatory cytokines networks needs systematic mapping

What technical innovations could advance IL-17F research in mouse models?

Several technical innovations could significantly advance IL-17F research:

• Development of conditional knockout models allowing tissue-specific or temporally controlled deletion of IL-17F

• Creation of reporter mice expressing fluorescent proteins under the IL-17F promoter to enable real-time tracking of IL-17F-expressing cells

• Application of single-cell RNA sequencing to comprehensively map IL-17F-responsive cell populations in various tissues and disease states

• Development of more sensitive detection methods for measuring IL-17F protein levels in biological fluids and tissue samples

• Generation of monoclonal antibodies with differential specificity for IL-17F monomers versus IL-17F/IL-17 heterodimers

How might targeting IL-17F differ therapeutically from targeting IL-17 based on mouse model findings?

Based on mouse model findings, therapeutic targeting strategies for IL-17F may require distinct approaches from IL-17 targeting:

• In autoimmune encephalomyelitis models, IL-17 appears more critical than IL-17F for disease initiation, suggesting IL-17-selective inhibition might be sufficient for neuroinflammatory conditions

• In allergic airway inflammation, IL-17F deficiency enhances type 2 responses, suggesting that IL-17F inhibition might potentially exacerbate rather than ameliorate certain aspects of allergic asthma

• In colitis models, IL-17F and IL-17 have opposing effects, with IL-17F promoting and IL-17 protecting against inflammation, indicating that selective IL-17F inhibition might be beneficial while preserving IL-17 function

• The complex interplay between IL-17F, IL-17, and other inflammatory mediators suggests that combination therapies targeting multiple pathways might be necessary for optimal therapeutic outcomes