IL-11 (Interleukin-11): Complete Research Profile — The Pro-Fibrotic Aging Cytokine, IL-11Rα/gp130 Signaling, Oprelvekin Thrombopoiesis Biology, and Anti-IL-11 Longevity Research (2026)

# IL-11 (Interleukin-11): Complete Research Profile — The Pro-Fibrotic Aging Cytokine, IL-11Rα/gp130 Signaling, Oprelvekin Thrombopoiesis Biology, and Anti-IL-11 Longevity Research (2026)

Introduction

Interleukin-11 (IL-11) occupies a fascinating position in cytokine biology: first characterized as a thrombopoietic growth factor with clinical approval for chemotherapy-induced thrombocytopenia, it has since been repositioned as a central driver of multi-organ fibrosis and, most dramatically, as a key mediator of biological aging. A landmark 2024 study in Nature by Widjaja, Cook, and colleagues demonstrated that inhibiting IL-11 signaling extended median mouse lifespan by 22–25%, placing this cytokine at the forefront of aging and longevity research ([]()).

Far from a simple hematopoietic support factor, IL-11 now represents one of the most compelling translational targets in fibrotic disease, metabolic dysfunction, cancer biology, and age-associated pathology. This research profile covers the molecular biology, receptor pharmacology, signaling architecture, and major research applications of IL-11, with a focus on tools available for laboratory investigation.

> Research Use Only (RUO): All peptides and proteins described in this article are for laboratory and preclinical research purposes only. They are not intended for human or veterinary use, diagnosis, or treatment.

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Discovery and Molecular Biology

IL-11 was originally identified in 1990 by Paul et al., who cloned its cDNA from a bone marrow stromal cell line (SL-3) while searching for factors supporting the growth of plasmacytoma cells. The landmark paper described a stromal-derived hematopoietic cytokine with lymphopoietic and hematopoietic activity, establishing IL-11 as a pleiotropic regulator of blood cell development (PMID 2217181).

Gene and Protein Structure

The human IL11 gene is located on chromosome 19q13.3–q13.4, spanning five exons and four introns. The mature protein is 178 amino acids in length with a theoretical molecular weight of approximately 19 kDa. Structurally, IL-11 adopts a four-helix bundle topology — the hallmark fold of the IL-6 cytokine superfamily — consisting of four anti-parallel alpha helices (designated A through D) connected by crossover loops. The protein is non-glycosylated in its native form, which distinguishes it from several other gp130-signaling cytokines and explains why bacterially expressed recombinant IL-11 (oprelvekin/Neumega) retains full biological activity despite lacking post-translational glycosylation.

IL-11 belongs to the IL-6 cytokine family, which also includes IL-6, IL-27, IL-31, oncostatin M (OSM), leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF), cardiotrophin-1 (CT-1), and cardiotrophin-like cytokine (CLC). All members share the common signal-transducing receptor subunit gp130 (IL6ST/CD130), which mediates downstream JAK/STAT and MAPK signaling.

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Receptor System: IL-11Rα and gp130

Unlike IL-6, which can signal through both membrane-bound (classic signaling) and soluble (trans-signaling) receptor complexes, IL-11 signals almost exclusively through its membrane-bound, non-signaling α-receptor subunit, IL-11Rα (IL11RA/CD212). A soluble form of IL-11Rα (sIL-11Rα) exists but has limited biological impact compared to soluble IL-6R in the IL-6 trans-signaling system, making IL-11 biology highly cell-autonomous and tightly regulated by receptor expression.

Hexameric Receptor Assembly

Signal transduction begins when IL-11 binds IL-11Rα (site I interaction), followed by recruitment of two gp130 molecules to form a hexameric signaling complex: [IL-11:IL-11Rα:gp130]₂. This assembly is structurally analogous to the hexameric complex formed by IL-6/IL-6R/gp130, but with distinct kinetic and affinity parameters. The hexameric complex drives auto-phosphorylation of the intracellular domain of gp130, creating docking sites for downstream kinases and adaptor proteins.

IL-11Rα expression is widespread but particularly prominent in fibroblasts, megakaryocytes, epithelial cells, and hepatocytes — a distribution that explains IL-11's diverse tissue effects. Research tools targeting IL-11Rα (neutralizing antibodies, soluble decoy receptors) are well-established reagents for dissecting IL-11-specific versus shared gp130 biology in vitro and in vivo.

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Signal Transduction Pathways

JAK/STAT3 Canonical Pathway

Phosphorylation of gp130 creates SH2-domain docking sites that recruit JAK1, JAK2, and TYK2. Activated JAKs phosphorylate STAT3 at Tyr705, driving STAT3 homodimerization, nuclear translocation, and transcription of target genes including SOCS3, BCL2, MYC, and pro-inflammatory cytokine genes. In hematopoietic contexts, JAK/STAT3 activation by IL-11 drives megakaryocyte maturation and platelet production. In cancer epithelial cells, the JAK/STAT3 axis drives tumor cell survival, proliferation, and EMT.

MEK/ERK Pro-Fibrotic Axis

A critical insight from Cook laboratory research is that STAT3 activation is largely dispensable for IL-11-driven fibrogenesis. In mesenchymal cells (fibroblasts, stellate cells, pericytes), IL-11 signals through MEK1/2 to activate ERK1/2 in a sustained manner. This sustained ERK activation drives fibroblast-to-myofibroblast transition at the translational level — meaning IL-11 promotes fibrosis gene expression through post-transcriptional protein synthesis pathways rather than transcriptional activation. Pharmacological STAT3 inhibition does not prevent fibroblast activation, whereas ERK inhibition completely blocks it.

Nintedanib, a clinically approved tyrosine kinase inhibitor for idiopathic pulmonary fibrosis (IPF), inhibits fibroblast activation partly through blockade of this ERK-translation axis downstream of IL-11 signaling, linking IL-11 biology mechanistically to established anti-fibrotic pharmacology.

ERK–AMPK–mTORC1 Aging Axis

The 2024 Nature study ([]()) identified a broader ERK–AMPK–mTORC1 signaling axis by which IL-11 regulates organismal aging. As mice age, IL-11 expression increases across multiple cell types and tissues. Elevated IL-11 activates ERK, which phosphorylates and inhibits AMPK (a master energy sensor and longevity regulator), leading to mTORC1 hyperactivation. This ERK→AMPK↓→mTORC1↑ axis suppresses autophagy, promotes cellular senescence, and drives the metabolic dysfunction characteristic of aging tissues. Genetic deletion of Il11 or pharmacological blockade with anti-IL-11 antibody reversed this cascade, restoring AMPK activity and reducing mTORC1 signaling in aged mice.

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Classic Research Application: Thrombopoiesis and Hematopoiesis

Prior to the fibrosis era, IL-11 was established as a key driver of megakaryocyte differentiation and platelet production. IL-11 directly stimulates the proliferation of hematopoietic stem cells (HSCs) and megakaryocyte progenitor cells, promoting megakaryocyte maturation, ploidy increase, and proplatelet formation. This thrombopoietic activity led to the clinical development of recombinant human IL-11 (rhIL-11) as oprelvekin.

Oprelvekin (Neumega) — FDA-Approved rhIL-11

Oprelvekin (trade name: Neumega; Wyeth/Pfizer) received FDA approval in 1997 for prevention of severe chemotherapy-induced thrombocytopenia (CIT) in adults receiving myelosuppressive chemotherapy for non-myeloid malignancies. It remains the only FDA-approved recombinant IL-11 product and serves as the gold-standard reference agonist for IL-11Rα/gp130 activation in hematopoiesis research.

Key characteristics of oprelvekin relevant to research:

• •Structure: Non-glycosylated 177-amino acid protein produced in Escherichia coli via recombinant DNA technology (lacks the N-terminal proline of native IL-11)
• •Mechanism: Stimulates megakaryocyte progenitor proliferation and maturation → increased platelet production
• •Concurrent hematopoietic effects: Also stimulates erythropoiesis and myelopoiesis, consistent with IL-11's role as a multi-lineage hematopoietic regulator
• •Research utility: Oprelvekin serves as a validated positive control for IL-11Rα/gp130 activation assays in megakaryocyte, HSC, and thrombopoiesis research contexts

IL-11 research in hematopoiesis spans bone marrow niche biology, platelet function, and the intersection of cytokine signaling with hematopoietic malignancies, including the rationale for anti-CD123 (IL-3Rα) approaches in blastic plasmacytoid dendritic cell neoplasm (BPDCN) research, where IL-11-related IL-3 signaling is relevant context.

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Multi-Organ Fibrosis: IL-11 as a Master Fibrotic Cytokine

The reframing of IL-11 as a pro-fibrotic cytokine began with a landmark 2017 Nature study demonstrating that IL-11 is a crucial determinant of cardiovascular fibrosis (PMID 29160304). What followed was a systematic demonstration that the same IL-11→ERK→myofibroblast activation axis operates across virtually every organ susceptible to fibrotic disease.

Cardiac Fibrosis

In cardiac fibroblasts, IL-11 is robustly induced by TGF-β1, angiotensin II (AngII), and other pro-fibrotic stimuli. IL-11 signaling through IL-11Rα→ERK drives fibroblast-to-myofibroblast transition, characterized by αSMA expression, collagen I/III deposition, and pathological ECM remodeling. Critically, overexpression of IL-11 selectively in cardiac fibroblasts (using a periostin promoter-driven transgene) is sufficient to cause cardiac fibrosis and dysfunction in mice, while deletion of Il11ra1 (encoding IL-11Rα) protects against pressure overload-induced cardiac fibrosis. This genetic gain-of-function/loss-of-function symmetry establishes IL-11 as a causal driver, not merely a marker, of cardiac fibrosis.

Hepatic Fibrosis

Liver fibrosis research has identified IL-11 as a key mediator of hepatic stellate cell (HSC) activation. IL-11 produced by injured hepatocytes and portal fibroblasts drives HSC-to-myofibroblast transition through ERK-dependent mechanisms. Genetic or pharmacological blockade of IL-11 attenuates CCl₄-induced and NASH-associated liver fibrosis in mouse models, with transcriptomic datasets showing IL11 upregulation as one of the most conserved fibrosis signatures across liver, kidney, and colon ([]()).

Pulmonary Fibrosis (IPF)

Idiopathic pulmonary fibrosis (IPF) research has increasingly focused on IL-11 as a central mediator of lung fibroblast activation. IL-11 expression is elevated in IPF lung tissue compared to normal lung, and both the JAK2/STAT3 and MEK/ERK1/2 cascades are activated in IPF-associated IL-11 signaling, though ERK dominates the fibrogenic response. Recent research with inhaled lipid nanoparticles and siRNA delivery systems targeting IL-11 in IPF models represent emerging research tools for exploring cytokine-targeted pulmonary delivery.

Renal Fibrosis

The kidneys show conserved IL-11 pro-fibrotic biology. IL-11 drives tubular epithelial cell EMT and interstitial fibroblast activation in the renal cortex. A 2025 review established IL-11 as a bidirectional pathobiology factor in kidney disease — operating through both epithelial autocrine loops and fibroblast paracrine signaling (PMC12179510). Anti-IL-11Rα antibodies have demonstrated protection in unilateral ureteral obstruction (UUO) and ischemia-reperfusion kidney injury mouse models.

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IL-11 and Biological Aging

The most consequential recent advance in IL-11 research is its identification as a central regulator of biological aging — transforming this previously niche cytokine into one of the most discussed longevity targets of the 2020s.

Rising Expression with Age

IL11 expression increases with age across multiple tissues in both mice and humans, consistent with IL-11 functioning as an "inflammaging" cytokine: a driver of the low-grade, sterile inflammation characteristic of aged tissues. Unlike acute-phase cytokines (IL-6, TNF-α) that spike with infection, IL-11 rises gradually and persistently, making it a chronic tissue-remodeling signal rather than an acute immune effector.

The 2024 Nature Lifespan Study

Widjaja AA, Lim WW, Cook SA et al. published "Inhibition of IL-11 signalling extends mammalian healthspan and lifespan" in Nature (August 2024; DOI: 10.1038/s41586-024-07701-9; []()):

Genetic deletion results:

• •Il11-knockout mice of both sexes showed extended median lifespan by an average of 24.9%
• •Reduced adiposity, improved lean mass, lower senescence biomarkers in aged Il11-KO vs. wildtype

Antibody treatment results (X203 anti-IL-11):

• •X203 administered to 75-week-old mice (equivalent to late middle-age in humans) once every three weeks for 25 weeks
• •Extended median lifespan by 22.5% (males) and 25% (females)
• •Treated mice showed reduced fat mass, improved lean mass and grip strength, lower frailty scores, improved metabolic parameters, and reduced circulating aging biomarkers
• •Autopsy analysis revealed lower tumor incidence in anti-IL-11-treated mice, suggesting a link between IL-11 suppression and reduced age-associated cancer susceptibility

Mechanistic basis:

The ERK→AMPK↓→mTORC1↑ signaling axis was confirmed as the dominant pathway linking elevated IL-11 to aging hallmarks, including suppressed autophagy, accelerated mTORC1 activity, and metabolic inflexibility.

These findings position anti-IL-11 interventions alongside rapamycin and metformin as pharmacological approaches that robustly extend mouse lifespan, with anti-IL-11 notably effective when initiated in middle age — a practical advantage over lifelong treatments.

IL-11 and Inflammaging: The IL-33 Link

IL-11 has also been shown to stimulate IL-33 expression in fibroblasts across multiple tissue types, creating a paracrine amplification loop: IL-11 activates fibroblasts → IL-33 release → ILC2/mast cell/T cell activation → further cytokine release → tissue inflammation and remodeling. This IL-11→IL-33 cascade may explain why aged tissues accumulate both fibrosis and heightened type 2 innate immune activity, integrating inflammaging across different cytokine families.

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IL-11 in Cancer Biology

IL-11 was identified as a tumor-promoting cytokine in gastrointestinal malignancies in landmark studies by Putoczki, Ernst, and colleagues showing IL-11 is the dominant IL-6 family cytokine during gastric and colorectal tumorigenesis (PMID 23948300).

STAT3-Driven Tumor Promotion

In cancer epithelial cells, IL-11 engages the canonical JAK/STAT3 pathway to promote:

• •Tumor cell survival: STAT3→BCL-2, MCL-1 upregulation
• •EMT and invasion: STAT3→Snail, Twist activation
• •Angiogenesis: STAT3→VEGF transcription
• •Immune evasion: STAT3-mediated suppression of antigen presentation and T cell recruitment

Cancer-Associated Fibroblasts (CAFs)

IL-11-expressing cancer-associated fibroblasts (CAFs) constitute a distinct fibroblast subset in the colorectal cancer tumor microenvironment (TME). IL-11⁺ fibroblasts activate tumor cells through a feed-forward IL-11 secretion loop, and the gene signature of IL-11⁺ fibroblasts correlates with reduced recurrence-free survival in colorectal cancer patients. This CAF-tumor IL-11 axis represents an active area of research using single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics tools.

Bone Metastasis

IL-11 produced by breast cancer cells promotes osteoclastogenesis and osteolytic bone metastasis through RANKL induction in osteoblasts — a research paradigm that predates the fibrosis-centric work by over two decades and remains an active area in bone metastasis biology.

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Research Tools for IL-11 Biology

Recombinant IL-11 Proteins

Species-matched recombinant proteins are generally preferred given the partial cross-reactivity of human and murine IL-11 on their respective receptors.

Anti-IL-11 Neutralizing Antibodies

• •X203 (anti-IL-11): Monoclonal antibody used in the landmark 2024 aging study; binds human and murine IL-11 with high affinity and blocks IL-11Rα engagement
• •Polyclonal anti-IL-11 IgG: Available from multiple commercial sources for Western blot, ELISA, IHC, and in vitro neutralization
• •Anti-IL-11Rα antibodies: Block ligand-receptor interaction at the receptor level; useful for distinguishing IL-11-specific from other gp130 ligand effects

Genetic Models

• •Il11 knockout mice: C57BL/6 background; validated for fibrosis protection, longevity, and metabolic studies
• •Il11ra1 knockout mice: Protect against organ-specific fibrosis in TGF-β1, AngII, CCl₄, and UUO challenge models
• •Il11 fibroblast-specific transgenic mice: Periostin-Cre driven IL-11 overexpression for gain-of-function fibrosis induction

Detection and Measurement

Human and murine IL-11 ELISA kits enable quantification in conditioned medium, serum, plasma, and tissue lysates. Measurement of IL-11 in aged vs. young tissue lysates is a standard readout for aging research experiments, and ELISA-based IL-11 quantification in fibroblast conditioned medium is the primary in vitro readout for fibroblast activation studies.

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IL-11 in the Context of the IL-6 Cytokine Family

Researchers working across the IL-6 superfamily should distinguish IL-11 from its closest functional relatives:

Cross-reactivity between IL-11 and other gp130 ligands can complicate interpretation of gp130-targeted pharmacological interventions. IL-11-specific tools (anti-IL-11Rα antibodies, IL-11-specific ELISAs, IL-11Rα knockout cells) are preferred for attributing phenotypes unambiguously to IL-11.

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Clinical Research Context

While this profile is limited to laboratory research applications, it is worth noting that IL-11-targeted therapies are in early clinical development for fibrotic diseases. Antibodies blocking IL-11 or IL-11Rα have entered or are approaching Phase I/II clinical trials, making IL-11 one of the most commercially significant cytokine research targets of the mid-2020s. This translational trajectory makes the tools and models described above relevant for both basic science and drug discovery research contexts.

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Summary

IL-11 is a 178-amino acid, four-helix bundle cytokine of the IL-6 family that signals via hexameric IL-11Rα/gp130 complexes to activate JAK/STAT3 (in hematopoietic and cancer contexts) and MEK/ERK (in mesenchymal and aging contexts). Its dual biology as a thrombopoietic growth factor (oprelvekin/Neumega) and as a master driver of multi-organ fibrosis and biological aging makes it uniquely positioned at the intersection of hematology, fibrosis, oncology, and longevity research. The 2024 Nature discovery that anti-IL-11 extends mouse lifespan by >22% has dramatically elevated research interest and is driving rapid expansion of the IL-11 reagent and model ecosystem. For laboratory researchers, validated recombinant proteins, neutralizing antibodies, and genetic models are now widely available to dissect IL-11's roles across these biology areas.

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References

1. Paul SR, Bennett F, Calvetti JA, et al. Molecular cloning of a cDNA encoding interleukin 11, a stromal cell-derived lymphopoietic and hematopoietic cytokine. Proc Natl Acad Sci USA. 1990;87(19):7512–7516. PMID 2217181

2. Schafer S, Viswanathan S, Widjaja AA, et al. IL-11 is a crucial determinant of cardiovascular fibrosis. Nature. 2017;552(7683):110–115. PMID 29160304

4. Putoczki TL, Thiem S, Loving A, et al. Interleukin-11 is the dominant IL-6 family cytokine during gastrointestinal tumorigenesis and can be targeted therapeutically. Cancer Cell. 2013;24(2):257–271. PMID 23948300

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For research use only. Not intended for diagnostic, therapeutic, or clinical applications.