IL11RA Antibody

What is the molecular structure of IL11RA and how does it interact with IL11?

IL11RA is a 45-49 kDa type I transmembrane glycoprotein belonging to the gp130 subfamily of the hematopoietic cytokine receptor family. The mature human IL11RA consists of a 347 amino acid extracellular domain containing a C2-type Ig-like domain, two fibronectin type III domains, two potential glycosylation sites, and a characteristic WSxWS motif, followed by a 21 amino acid transmembrane region and a 31 amino acid cytoplasmic domain .

IL11 signaling occurs through a two-step process: first, IL11 binds to IL11RA with low affinity; then this IL11:IL11RA complex associates with the ubiquitous gp130 receptor to form a high-affinity hexameric signaling complex (IL11:IL11RA:gp130) . This complex formation is essential for activating downstream signaling pathways. Notably, gp130 is not specific to IL11 signaling but also functions as a subunit in receptors for other cytokines including Cardiotrophin-1, CNTF, IL-6, IL-27, IL-31, LIF, and Oncostatin M .

What downstream signaling pathways are activated by IL11-IL11RA interaction?

IL11RA activation initiates both canonical and non-canonical signaling pathways:

• Canonical pathway: Upon complex formation with gp130, IL11RA primarily activates JAK/STAT signaling, particularly STAT3 phosphorylation . The importance of this pathway is demonstrated by studies showing that mutations in IL11RA dramatically reduce IL11-mediated STAT3 phosphorylation .

• Non-canonical pathways: IL11RA also activates ERK signaling and other post-transcriptional mechanisms . Importantly, many of IL11's cellular effects occur through these non-canonical pathways, making it essential to select appropriate experimental readouts that can capture both transcriptional and post-transcriptional activities .

The IL11:IL11RA:gp130 signaling complex has been implicated in controlling proliferation and differentiation of skeletogenic progenitor cells and other mesenchymal cells . Additionally, IL11 signaling plays important roles in hematopoiesis, bone development, tissue repair, and tumor development .

How is IL11RA expression regulated in different tissues?

IL11RA displays a tissue-specific expression pattern that significantly impacts experimental design considerations. The receptor is:

• Highly expressed in cells of the stromal and parenchymal niche, including hepatic stellate cells, fibroblasts, and hepatocytes

• Expressed at low levels on immune cells, highly passaged cells, and transformed cell lines

• Widely distributed in adults, embryos, and embryonic stem cells

• Specifically expressed in cranial mesenchyme, particularly around coronal suture tips and in the lambdoidal suture as demonstrated by immunofluorescence analysis

• Present in the coronal suture between overlapping frontal and parietal plates, as shown by in situ hybridization analysis of adult zebrafish

This differential expression pattern explains why primary cells better represent physiological IL11 signaling compared to immortalized cell lines. Researchers should consider tissue specificity when designing experiments, selecting appropriate positive controls, and interpreting results.

What are the optimal conditions for detecting IL11RA protein expression?

Successful detection of IL11RA requires careful consideration of several experimental parameters:

Cell selection and culturing conditions:

• Primary cells (hepatic stellate cells, fibroblasts, hepatocytes) are ideal experimental systems for studying IL11 signaling in vitro as they maintain physiological receptor expression levels

• Low passage numbers are critical as IL11RA expression decreases in highly passaged cells

• Specific culture conditions that preserve meaningful cellular states and physiological responses in conventional 2D culture systems should be employed

Recommended detection protocols:

As emphasized in the literature, "cell type, cell culture conditions, passage number, concentrations of stimuli, timing, and other factors have major implications for studies of IL11 signaling" . Therefore, researchers should optimize these conditions for their specific experimental systems.

How should researchers choose between polyclonal and monoclonal IL11RA antibodies?

Both polyclonal and monoclonal antibodies against IL11RA have distinct advantages depending on the research application:

Polyclonal antibodies:

• Recognize multiple epitopes, potentially providing stronger signal for low-abundance proteins

• Example: Proteintech's polyclonal antibody (10264-1-AP) shows reactivity with human, mouse, and rat samples across multiple applications (WB, IHC, IF/ICC, ELISA)

Monoclonal antibodies:

• Offer higher specificity for particular epitopes and typically show less batch-to-batch variation

• Available options target distinct epitopes on IL11RA, with some recognizing highly conserved regions between species (like E27 antibody targeting the N-terminus) and others binding to less conserved regions (like antibodies targeting amino acids 319-363 in the membrane-proximal domain)

• Specific monoclonal antibodies like EPR5446 (ab125015) are validated for multiple applications including IHC-P, ICC/IF, I-ELISA, WB, and Flow Cytometry

Selection criteria should include:

• Research question: Is epitope-specific recognition required or is detection of the whole protein sufficient?

• Application: Different antibodies may perform better in specific applications

• Species cross-reactivity requirements: Consider whether cross-species recognition is beneficial or problematic

• Function-blocking needs: For mechanistic studies, antibodies targeting specific functional domains may be preferred

For comprehensive IL11RA studies, researchers might benefit from using multiple antibodies targeting different epitopes to validate findings and gain deeper mechanistic insights.

What controls should be included when validating IL11RA antibody specificity?

Rigorous antibody validation is essential for reliable IL11RA research. The following controls should be considered:

Positive controls:

• Mouse colon tissue for Western blot applications

• Human prostate cancer tissue and mouse colon tissue for immunohistochemistry

• N2a cells for immunofluorescence/immunocytochemistry

Negative controls:

• Samples with IL11RA knockdown/knockout

• Secondary antibody-only controls

• Isotype controls for monoclonal antibodies

Specificity validation approaches:

• Testing antibody recognition of both native and denatured receptor forms

• Evaluating performance on membrane-bound IL11RA expressed in transfected cell systems (e.g., gp130/hIL-11Ralpha-co-transfected Ba/F3 cells)

• Confirming expected molecular weight (45-49 kDa) by Western blot under reducing conditions

• Functional validation through IL11-mediated STAT3 phosphorylation assays in appropriate cell systems

By incorporating these controls, researchers can ensure specificity and reliability of their IL11RA detection methods, minimizing the risk of experimental artifacts that have historically complicated IL11 signaling research.

What role does IL11RA play in liver pathophysiology and how can it be targeted therapeutically?

IL11RA has emerged as a significant player in liver pathophysiology, particularly in the context of drug-induced liver injury:

Pathophysiological role:

• In acetaminophen (APAP)-induced liver injury (AILI) mouse models, IL11 expression is upregulated, suggesting involvement of IL11 signaling in this common form of drug-induced liver damage

• IL11 signaling contributes to hepatocyte death and centrilobular necrosis in this context

Therapeutic targeting approaches:

• Researchers have developed a human IL11RA knock-in mouse model (B-hIL11RA) where human IL11RA replaces murine Il11ra to evaluate anti-human IL11RA antibodies

• Anti-human IL11RA antibody treatment in this model inhibited multiple aspects of AILI:

  • Reduced hepatocyte death (as measured by ALT, AST, and TUNEL biomarkers)

  • Decreased centrilobular necrosis

This represents a paradigm shift in understanding IL11's role in liver pathophysiology. Historical studies using recombinant human IL11 (rhIL11) in mouse models incorrectly suggested protective effects of IL11, while recent research with species-matched reagents and receptor-specific antibodies demonstrates that inhibiting IL11 signaling is actually beneficial .

These findings highlight IL11RA as a promising therapeutic target for liver injury, with the B-hIL11RA mouse model providing a valuable tool for preclinical evaluation of human-specific IL11RA-targeting therapies.

How do mutations in IL11RA lead to craniosynostosis and other developmental disorders?

IL11RA plays a critical role in craniofacial development, with mutations causing distinctive developmental abnormalities:

Genetic basis:

• Mutations in the IL11RA gene cause an autosomal recessive Crouzon-like craniosynostosis

• These mutations result in dramatically reduced IL11-mediated STAT3 phosphorylation, indicating impaired signaling function

Developmental expression pattern:

• Immunofluorescence analysis shows specific Il11ra expression in cranial mesenchyme, localized around coronal suture tips and in the lambdoidal suture in mice

• In situ hybridization in adult zebrafish demonstrates zfil11ra expression in the coronal suture between overlapping frontal and parietal plates

Functional significance:

• IL11RA is essential for normal development of craniofacial bones and teeth

• It restricts suture fusion and regulates tooth number, with mutations associated with supernumerary teeth

• Loss of normal IL11RA function leads to premature fusion of cranial sutures (craniosynostosis)

These findings establish IL11RA as a critical regulator of craniofacial development, with mutations leading to a recognizable syndrome of craniosynostosis and dental abnormalities. This provides important insights into both the molecular mechanisms of craniofacial development and the pathogenesis of craniosynostosis syndromes.

What strategies can be used to therapeutically target the IL11-IL11RA axis?

Therapeutic targeting of the IL11-IL11RA axis represents a promising approach for various pathologies, with several strategies under investigation:

Anti-IL11RA antibodies:

• Monoclonal antibodies against human IL11RA have been developed and tested in humanized mouse models

• These antibodies block IL11 binding to its receptor, preventing formation of the signaling complex

• Efficacy has been demonstrated in models of acetaminophen-induced liver injury, with inhibition of hepatocyte death and centrilobular necrosis

Anti-IL11 antibodies:

• An alternative approach involves directly neutralizing the IL11 cytokine

• Search results mention mice administered neutralizing IL11 antibodies, suggesting this approach is also being explored

Epitope considerations:

• Different epitopes have been identified on the extracellular part of IL11RA:

  • One epitope at the N-terminus (defined by E27 antibody)

  • Three epitopes clustered in the membrane-proximal, C-terminal region

• Targeting specific epitopes may offer advantages for particular therapeutic applications

Humanized models for preclinical testing:

• The development of human IL11RA knock-in mouse models (B-hIL11RA) provides a valuable tool for preclinical evaluation of human-specific IL11RA antibodies

• These models express human IL11RA mRNA and protein, enabling accurate assessment of human-targeted therapies

An important near-term question in the field is "is anti-IL11/IL11RA therapy safe in humans?" Clinical translation of these approaches will require careful safety evaluation, particularly given the revised understanding of IL11 biology that has emerged in recent years.

How do species-specific differences in IL11-IL11RA signaling impact translational research?

A critical revelation in IL11 research concerns species-specific differences that led to fundamental misinterpretations of IL11 biology:

Key species differences:

• Recombinant human IL11 (rhIL11) binds strongly to mouse Il11ra1 but incompletely activates the resulting signaling complex

• This causes rhIL11 to act as a partial/incomplete agonist that actually blocks endogenous mouse Il11 signaling

• Consequently, many historical studies using rhIL11 in mouse models were inadvertently demonstrating IL11 loss-of-function rather than gain-of-function effects

Impact on research interpretation:

• The early literature (1995-2015) correctly reported rhIL11 as protective in mouse models of disease, but misattributed this to IL11 agonism rather than antagonism

• This led to multiple unsuccessful clinical trials of rhIL11 for conditions including myocardial infarction, colitis, liver disease, hepatitis, and rheumatoid arthritis

Solutions for translational research:

• Use species-matched recombinant proteins (mouse IL11 for mouse studies, human IL11 for human studies)

• Employ humanized mouse models like the B-hIL11RA knock-in mouse for testing human-specific antibodies

• Consider crystal structure studies to better understand complex interactions between human IL11 and mouse Il11ra1

This case represents a compelling example of how cross-species incompatibilities can lead to fundamental misunderstandings about cytokine biology and misguided therapeutic development efforts. Researchers must carefully consider species-specific differences when designing experiments and interpreting results from animal models.

What approaches can be used to study IL11RA signaling while avoiding experimental artifacts?

Studying IL11RA signaling requires careful experimental design to avoid artifacts that have historically led to misinterpretations:

Cell and culture considerations:

• Use primary cells rather than immortalized cell lines for physiologically relevant responses

• Primary hepatic stellate cells, fibroblasts, and hepatocytes represent ideal experimental systems

• Maintain low passage numbers, as IL11RA expression decreases in highly passaged cells

• Follow specific culturing conditions that preserve meaningful cellular states and physiological responses ex vivo

Experimental design strategies:

• Select appropriate readouts to capture both canonical (JAK/STAT) and non-canonical (ERK, post-transcriptional) activities of IL11 signaling

• Carefully control concentrations of stimuli and timing of measurements

• Use species-matched recombinant proteins to avoid cross-species incompatibilities

Methodological recommendations:

As emphasized in the literature, "In vitro experiments with primary cell material need to be planned and executed with great caution. Otherwise, physiologically relevant mechanisms may become dysfunctional and reproducible experimental artefacts can obscure our view of true cytokine biology."

How do membrane-bound and soluble forms of IL11RA differ in function?

IL11RA exists in both membrane-bound and soluble forms, with distinct functional implications:

Membrane-bound IL11RA:

• Standard transmembrane receptor form with extracellular, transmembrane, and cytoplasmic domains

• Mediates classic IL11 signaling on cells expressing the receptor

• Forms a complex with IL11 and gp130 to activate intracellular signaling cascades

Soluble IL11RA (sIL11RA):

• Acts as an agonist of IL11 activity rather than an antagonist

• The IL11:sIL11RA complex binds to IL6ST/gp130 on cell surfaces

• Induces signaling even on cells that do not express membrane-bound IL11RA

• This process, called IL11 trans-signaling, extends the range of IL11-responsive cells

Sources of soluble IL11RA:

• General soluble form that may result from proteolytic cleavage of membrane-bound receptor

• Specific isoform called HCR2 that functions as a soluble receptor

The existence of these different forms adds complexity to IL11 biology and has important implications for both physiological understanding and therapeutic targeting. Trans-signaling may be particularly relevant in pathological conditions where expanding the range of IL11-responsive cells could amplify IL11's effects in tissues.

How can researchers reconcile contradictory findings regarding IL11's role in hematopoiesis versus fibrosis?

A major paradigm shift in IL11 biology concerns its role in hematopoiesis versus fibrosis:

Historical view of IL11 in hematopoiesis:

• IL11 was first identified in 1990 as a factor supporting growth of an IL6-dependent plasmacytoma

• Studies showed recombinant human IL11 (rhIL11) increased platelet counts in mice, monkeys, and humans

• This led to FDA approval of rhIL11 (Neumega; Oprelvekin) in 1998 for treating thrombocytopenia

Evidence challenging this view:

• IL11 receptor knockout mice (Il11ra1 deleted), IL11 knockout mice, and animals administered neutralizing IL11/IL11RA antibodies show no effects on blood counts

• Human IL11RA knockouts similarly show no hematopoietic phenotype

• This suggests that while pharmacological doses of rhIL11 can increase platelet counts, endogenous IL11 may not be critical for normal hematopoiesis

Current understanding of IL11 in fibrosis:

• Recent evidence indicates IL11 is actually "toxic, pro-fibrotic and pro-inflammatory," contrary to earlier understanding

• The apparent protective effects of rhIL11 in mouse models were due to its partial antagonism of endogenous mouse Il11

• Species-matched studies (using mouse IL11 in mouse cells) reveal the true pro-fibrotic nature of IL11 signaling

Reconciliation approach:

• Distinguish between pharmacological effects of high-dose rhIL11 and physiological functions of endogenous IL11

• Use species-matched recombinant proteins for accurate biological assessment

• Recognize that earlier literature using rhIL11 in mice was demonstrating IL11 loss-of-function rather than gain-of-function

• Consider that acute pharmacological effects may differ from chronic physiological roles

This revised understanding of IL11 biology highlights the importance of rigorous experimental design and careful interpretation in cytokine research.