IFNL2 Antibody

What is IFNL2 and how does it differ from other interferons?

IFNL2 (Interferon lambda 2), also known as IL-28A, is a member of the type III interferon family. Unlike type I interferons that bind to ubiquitously expressed receptors, IFNL2 signals through a heterodimeric receptor complex composed of IL-10 receptor β (IL-10 Rβ) and IL-28 receptor α (IL-28 Rα/IFN-λ R1) . This receptor has limited tissue distribution, making IFNL2's effects more targeted, particularly at mucosal surfaces. While sharing functional similarities with type I interferons in terms of antiviral activity and JAK-STAT signaling activation, IFNL2's restricted receptor distribution results in more localized immune responses .

What are the key structural characteristics of IFNL2 protein?

Human IFNL2 is a protein spanning from Val26-Val200 with a molecular weight of approximately 19.8 kDa . Mouse IFNL2 spans from Asp20-Val193 and shares 66% amino acid sequence identity with human IFNL2 . The protein functions as a secreted cytokine and demonstrates cross-species functionality. IFNL2 lacks N-glycosylation sites and has the following physical properties:

How does IFNL2 signaling work at the cellular level?

IFNL2 signaling begins when the cytokine binds to its heterodimeric receptor complex. This interaction triggers the JAK-STAT pathway, leading to STAT phosphorylation and formation of the IFN-stimulated regulatory factor 3 (ISGF-3) transcription factor complex . STAT proteins translocate to the nucleus where they induce interferon-stimulated genes (ISGs) expression. These ISGs mediate the biological effects of IFNL2, including antiviral activity, MHC class I antigen upregulation, and immune cell modulation . While this cascade parallels type I interferon signaling, IFNL2 typically requires higher concentrations to achieve comparable effects and targets a more limited range of cells .

What neutralizing antibodies are available for IFNL2 research?

Several validated antibodies are available for neutralizing IFNL2 activity in experimental models:

Efficacy of neutralization can be assessed using the Encephalomyocarditis Virus (EMCV) cytopathy assay in susceptible cell lines like HepG2 .

How can researchers measure IFNL2 activity in experimental settings?

Researchers can measure IFNL2 activity through several established methods:

• Cytopathic effect inhibition assay: Measuring IFNL2's ability to reduce Encephalomyocarditis Virus (EMCV)-induced cytopathy in human lung carcinoma cell line A549 or HepG2 hepatocellular carcinoma cells . This is considered the gold standard for functional assessment.

• ISG expression analysis: Quantifying induction of interferon-stimulated genes in responsive cells using RT-qPCR or RNA sequencing after IFNL2 treatment .

• STAT phosphorylation assays: Detecting STAT1 phosphorylation via Western blotting or flow cytometry following IFNL2 stimulation .

• Antiviral protection assays: Evaluating IFNL2's capacity to protect susceptible cells from viral infection, measured by reduced viral replication or viral protein expression .

• Reporter cell systems: Using cells engineered with ISG-responsive reporter genes (luciferase or fluorescent proteins) to quantify IFNL2 activity .

When conducting these assays, it's critical to include proper controls including recombinant IFNL2 standards, isotype control antibodies, and type I interferon comparisons to ensure specificity and reliable interpretation.

What technical challenges might researchers encounter when working with IFNL2 antibodies?

Researchers working with IFNL2 antibodies may encounter several technical challenges:

• Cross-reactivity issues: Due to high sequence homology between IFNL2 and IFNL3 (IL-28B), antibodies may bind both proteins unless specifically validated for IFNL2 specificity . Always verify antibody specificity through validation experiments.

• Discrepancies in molecular weight detection: Observed molecular weight (~39 kDa) often differs from calculated molecular weight (~22 kDa) in Western blot applications, potentially due to post-translational modifications or technical factors .

• Species-specific variations: Significant functional differences exist between human and mouse IFNL2, with 66% sequence identity between species . Ensure antibodies are validated for the specific species under investigation.

• Sample preparation effects: IFNL2 stability may be affected by freeze-thaw cycles; for optimal activity, store at -70°C and avoid repeated freeze-thaw cycles .

• Cell type responsiveness variations: Unlike type I interferons, not all cells express IFNL receptors, requiring careful selection of appropriate target cells for functional assays .

To address these challenges, use characterized antibodies from reliable sources, include multiple appropriate controls, and validate detection methods for your specific experimental system.

How does IFNL2 influence innate immune cell populations?

IFNL2 exerts diverse effects on innate immune cells, though responses vary between human and mouse systems:

• Neutrophils:

  • Mouse neutrophils respond to IFNL2 with STAT1 phosphorylation and ISG expression

  • IFNL2 can increase ROS production in mouse neutrophils during certain infections

  • Conversely, it inhibits ROS production and degranulation during intestinal inflammation through a STAT1-independent pathway

  • In human neutrophils, IFNL2 can inhibit TNF-induced ROS production and suppress neutrophil extracellular trap formation

• Dendritic cells:

  • IFNL2 enhances migration of CD103+ DCs to draining lymph nodes

  • It promotes T helper 1 cell skewing via effects on DCs

  • IFNL2 is required for effective antigen-presenting cell migration during viral infections

• Myeloid cells:

  • In TLR7-induced inflammation models, IFNL2 promotes myeloid cell expansion

  • IFNLR1-deficient mice show reduced splenomegaly and leukocytosis in these models

These effects demonstrate IFNL2's important role in coordinating innate immune responses, particularly at mucosal surfaces where IFNL receptor expression is prominent.

What is the relationship between IFNL2 and adaptive immunity?

IFNL2 influences adaptive immunity through both direct and indirect mechanisms, with notable species-specific differences:

• B cells:

  • Human B cells express IFNLR and respond to IFNL2 by upregulating ISGs

  • IFNL2 increases TLR7-mediated and TLR8-mediated antibody production and plasmablast differentiation

  • It can inhibit influenza-induced IgG production in human PBMCs

  • Mouse B cells generally do not respond to IFNL2, representing a key species difference

• T cells:

  • Evidence for direct effects on human T cells is mixed

  • Some studies show CD8+ T cells can respond to IFNL2 by upregulating ISGs

  • Activated CD4+ T cells may upregulate IFNLR1, allowing responsiveness to IFNL2

  • Mouse T cells typically do not respond directly to IFNL2

• Indirect coordination of adaptive responses:

  • IFNL2 induces thymic stromal lymphopoietin (TSLP) production in microfold cells

  • This leads to CD103+ DC migration to draining lymph nodes

  • Subsequently promotes follicular helper T cell expansion and germinal center responses

  • IFNL2 is critical for developing effective antiviral CD8+ T cell responses during influenza infection

These findings highlight IFNL2's complex role in bridging innate and adaptive immunity, particularly at mucosal surfaces, with important implications for understanding antiviral immunity and autoimmune conditions.

How do IFN-lambda knockout models help understand IFNL2 function?

IFN-lambda knockout models provide crucial insights into IFNL2 function:

• Ifnl2−/−Ifnl3−/− mice:

  • These mice fail to control persistent murine norovirus (MNoV) replication

  • The phenotype matches that observed in Ifnlr1−/− mice (lacking the receptor for all type III IFNs)

  • This demonstrates the essential, non-redundant role of IFNL2/3 in controlling mucosal viral infections

• Receptor knockout (Ifnlr1−/−) models:

  • Show decreased antibody and CD8+ T cell responses following influenza virus infection

  • This phenotype depends on thymic stromal lymphopoietin (TSLP) production

  • IFNL induces TSLP in microfold cells, leading to DC migration and enhanced adaptive immunity

  • Reveals mechanisms by which IFNL2 coordinates both innate and adaptive responses

• Applications in disease models:

  • In TLR7-induced lupus models, IFNLR1 deficiency reduces splenomegaly and leukocytosis

  • These mice remain responsive to IFNα, demonstrating non-redundant functions

  • IFNL promotes myeloid cell expansion and T cell activation in these models

• Experimental considerations:

  • Microbiota composition can influence outcomes in viral infection models

  • Proper breeding strategies (e.g., littermate controls) are necessary to exclude microbiota effects

These models provide compelling evidence that IFNL2 plays unique roles in host defense that cannot be fully compensated by other interferon families.

How is IFNL2 transcription regulated?

The transcriptional regulation of IFNL2 involves several sophisticated mechanisms:

• Novel transcription factor ATG10S:

  • ATG10S activates IFNL2 transcription by binding to its promoter

  • It competes with IRF1 (interferon regulatory factor 1) for the same binding site

  • Functional nucleotides for ATG10S targeting are C1, A3, and C6 within the core motif

  • For IRF1, the key nucleotides are A3 and G4

  • Knockdown of endogenous IRF1 increases ATG10S activity on IFNL2 transcription

• Nuclear transport mechanisms:

  • Co-immunoprecipitation assays revealed ATG10S combination with KPNA1/importin α, KPNB1/importin β, and IRF1

  • This indicates a complex regulatory network controlling IFNL2 expression

• Promoter elements:

  • The IFNL2 promoter contains various IFN-stimulated response elements (ISREs)

  • Multiple transcription factor-binding sites regulate expression

  • IRF family transcription factors can activate the IFNL2 promoter

• Induction pathways:

  • IFNL2 expression is triggered by viral infections and double-stranded RNA

  • Pattern recognition receptors including Toll-like receptors and RIG-I family helicases play key roles

  • Antigen-presenting cells are major producers of IFNL2 in response to these stimuli

This complex regulation represents an important link between autophagy and immunity, demonstrating synergistic action between intracellular homeostasis and defense mechanisms .

What are the species-specific differences in IFNL2 function?

Understanding species-specific differences in IFNL2 function is crucial for translating research findings:

How do ATG10S and IRF1 competitively regulate IFNL2 expression?

The competitive regulation of IFNL2 expression by ATG10S and IRF1 reveals a sophisticated control mechanism:

• Binding site competition:

  • ATG10S and IRF1 compete for the same binding site on the IFNL2 promoter

  • Both factors can drive IFNL2 transcription through this site

• Functional nucleotide mapping:

  • Individual nucleotide substitution showed that ATG10S targeting depends on C1, A3, and C6 nucleotides

  • IRF1 function depends on A3 and G4 nucleotides within the core motif

  • This partial overlap explains the competitive nature of their binding

• Expression regulation:

  • Overexpression of either ATG10S or IRF1 significantly raises endogenous IFNL2 levels

  • IRF1-siRNA transfection decreases endogenous IFNL2 levels

  • Knockdown of endogenous IRF1 increases ATG10S activity on IFNL2 transcription

  • This suggests a balance between these factors controls IFNL2 expression

• Protein interactions:

  • Co-immunoprecipitation assays revealed ATG10S interaction with nuclear transport proteins (KPNA1/importin α, KPNB1/importin β)

  • ATG10S also interacts with IRF1 itself, suggesting complex regulatory mechanisms beyond simple promoter competition

This competitive regulation represents an important control point for IFNL2 expression and highlights the link between autophagy (ATG10S) and immune regulation (IRF1, IFNL2), providing potential novel targets for antiviral therapeutic strategies .

What is IFNL2's role in viral infections?

IFNL2 plays critical roles in viral infections, particularly at mucosal surfaces:

• Murine norovirus (MNoV) control:

  • Mice lacking both Ifnl2 and Ifnl3 (Ifnl2−/−Ifnl3−/− mice) fail to control persistent MNoV replication

  • This phenotype mirrors that of Ifnlr1−/− mice lacking the IFNL receptor

  • These findings establish IFNL2/3 as essential factors for controlling norovirus at mucosal surfaces

• Influenza virus defense:

  • IFNL2 coordinates both innate and adaptive immune responses

  • It induces TSLP production in microfold cells of the upper airway

  • This leads to CD103+ DC migration to draining lymph nodes

  • Subsequently promotes follicular helper T cell expansion and germinal center responses

  • IFNL2 is crucial for effective antiviral CD8+ T cell responses during influenza infection

• Encephalomyocarditis virus (EMCV) protection:

  • Recombinant IFNL2 reduces EMCV-induced cytopathy in cell lines like HepG2

  • This protection is dose-dependent and can be neutralized by specific anti-IFNL2 antibodies

  • This model provides a reliable bioassay for IFNL2 activity assessment

• Mechanism of action:

  • IFNL2 induces ISG expression in target cells via JAK-STAT signaling

  • It enhances antiviral state in epithelial cells at mucosal surfaces

  • It coordinates recruitment and activation of immune cells to infection sites

  • IFNL2 helps shape subsequent adaptive immune responses

These findings highlight IFNL2's essential role in host defense against diverse viral pathogens, with particular importance at mucosal interfaces.

What is IFNL2's involvement in autoimmune conditions?

IFNL2 demonstrates complex involvement in autoimmune conditions, particularly lupus:

• Systemic lupus erythematosus (SLE) associations:

  • Increased concentrations of IFNL2 correlate with higher autoantibody levels in human SLE

  • In TLR7-induced lupus mouse models, serum IFNL2 and IFNL3 levels are elevated

  • IFNLR1 deficiency substantially reduces splenomegaly and leukocytosis in these models

• Species-specific considerations:

  • Human B cells express IFNLR and respond to IFNL2 by increasing antibody production

  • Mouse B cells generally do not respond to IFNL2

  • In mouse models, IFNLR1 deficiency did not affect autoantibody levels

  • This presents a key translational challenge when interpreting mouse models of human lupus

• Mechanisms in autoimmunity:

  • IFNL2 promotes myeloid cell expansion following TLR7 stimulation

  • It contributes to T cell activation in inflammatory settings

  • In humans, it may directly enhance B cell function including TLR7-mediated antibody production

  • These effects could contribute to autoantibody production and immune complex formation

• Therapeutic implications:

  • Targeting the IFNL2 pathway might offer selective approaches for modulating autoimmune inflammation

  • Its more restricted receptor distribution compared to type I IFNs could mean fewer side effects

  • Understanding the precise mechanisms in different contexts remains crucial for therapeutic development

The distinct role of IFNL2 in autoimmunity highlights its potential as both a biomarker and therapeutic target, though species differences must be carefully considered when translating findings to human applications.