Recombinant Human IL-1RL1 (ST2)-Fc Chimera (carrier-free)

Pricing & Availability
Regulatory Status
Other Names
ST2, IL-1 R4, T1, DER4, ST2L, FIT-1, IL-33Rα, IL-33R alpha, IL-33Ra, IL1RL1
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Product Citations
When recombinant human IL-33 (Cat. No. 581802) is immobilized at 2 µg/mL, recombinant human IL-1RL1 binds in a dose-dependent manner with EC50 range of 0.2 - 0.8 µg/mL.
  • 1_Human_IL-1RL1_RECOM_CF_050820
    When recombinant human IL-33 (Cat. No. 581802) is immobilized at 2 µg/mL, recombinant human IL-1RL1 binds in a dose-dependent manner with EC50 range of 0.2 - 0.8 µg/mL.
  • IL-1RL1_Human_RECOM_BA_120414
    Human IL-1R1L1 inhibits the proliferation of D10.G4.1 cells induced by IL-33 in a dose dependent manner.
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557908 500 µg 1085 CHF
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557904 25 µg 176 CHF
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557906 100 µg 382 CHF
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IL-1RL1/ST2 was initially identified in stimulated Balc3T3 cells and is encoded by the IL-1RL1 gene that produces different isoforms by alternative splicing. In humans, four isoforms have been described: a membrane attached ST2L isoform and a soluble protein (sST2/ IL1RL-a) that lacks the transmembrane and cytoplasmic domains, which acts as a natural antagonist of IL-33. The other splice variants are ST2V and ST2LV. ST2V lacks the third immunoglobulin motif and C-terminal portion of ST2 and is mainly present in the gut whereas ST2LV does not have the transmembrane domain. The membrane isoform of ST2L (IL-1RL1) associates with IL-1 receptor accessory proteins (IL-1RAcP) to form the IL-33R. The interaction of IL-33 to its receptor activates NF-kB and MAP kinases and induces Th2 cytokines from in vitro polarized Th2 cells. In vivo, IL-33 promotes the expression of IL-4, IL-5, and IL-13. IL-33 acts as an inflammatory cytokine in Th2-type immune responses during asthma and atopic dermatitis. It is host-protective against helminth infections and reduces atherosclerosis by promoting Th2-type immune responses. Human aortic, coronary artery, and heart microvascular endothelial cells express mRNA for ST2L and sST2 isoforms, acting as a source for sST2 proteins. In fact, sST2 is considered as a prognostic biomarker in myocardial infarction and heart failure. In addition, sST2 has been associated with other human diseases including asthma with acute exacerbation, eosinophilic pneumonia, sepsis and trauma, and exacerbated idiopathic pulmonary fibrosis.

Product Details
Technical Data Sheet (pdf)

Product Details

Human IL-1RL1, amino acids (Lys19 - Phe328) (Accession# D12763), with a C-terminal Fc-6His tag was expressed in 293E cells.
Molecular Mass
The 550 amino acid recombinant protein has a predicted molecular mass of approximately 62 kD. The DTT-reduced and non-reduced protein migrate approximately at 100 kD and 200 kD by SDS-PAGE. The predicted N-terminal amino acid is Lys.
>95%, as determined by Coomassie stained SDS-PAGE.
0.22 µm filtered protein solution is in 10mM NaHPO4, 0.3M NaCl, and pH 7.2.
Endotoxin Level
Less than 0.01 ng per µg cytokine as determined by the LAL method.
10 and 25 µg sizes are bottled at 200 µg/mL. 100 µg size and larger sizes are lot-specific and bottled at the concentration indicated on the vial. To obtain lot-specific concentration and expiration, please enter the lot number in our Certificate of Analysis online tool.
Storage & Handling
Unopened vial can be stored between 2°C and 8°C for up to 2 weeks, at -20°C for up to six months, or at -70°C or colder until the expiration date. For maximum results, quick spin vial prior to opening. The protein can be aliquoted and stored at -20°C or colder. Stock solutions can also be prepared at 50 - 100 µg/mL in appropriate sterile buffer, carrier protein such as 0.2 - 1% BSA or HSA can be added when preparing the stock solution. Aliquots can be stored between 2°C and 8°C for up to one week and stored at -20°C or colder for up to 3 months. Avoid repeated freeze/thaw cycles.
ED50 = 15 - 90 ng/ml, corresponding to a specific activity of 1.1 - 6.6 x 104 units/mg , as determined by inhibition of D10.G4.1 cell proliferation induced by IL-33.

When recombinant human IL-33 (Cat. No. 581802) is immobilized at 2 µg/mL, recombinant human IL-1RL1 binds in a dose-dependent manner with EC50 range of 0.2 - 0.8 µg/mL.


Application Notes

BioLegend carrier-free recombinant proteins provided in liquid format are shipped on blue-ice. Our comparison testing data indicates that when handled and stored as recommended, the liquid format has equal or better stability and shelf-life compared to commercially available lyophilized proteins after reconstitution. Our liquid proteins are verified in-house to maintain activity after shipping on blue ice and are backed by our 100% satisfaction guarantee. If you have any concerns, contact us at

Antigen Details

Cytokine receptor.

Membrane-ST2 is expressed by Th2 lymphocytes, CD8+ T cells, mast cells, macrophages, dendritic cells (DCs), eosinophils, basophils, endothelial, and epithelial cells. Aortic, coronary artery, and heart microvascular endothelial cells are sources of sST2.

Acts as a decoy receptor for IL-33 and prevents its signaling through ST2L.
Biology Area
Molecular Family
Cytokine/Chemokine Receptors, Soluble Receptors
Antigen References

1. Schmitz et al. 2007. Immunity 23:479.
2. Chakerian EA, et al. 2007. J. Immunol. 179:2551.
3. Hayakawa H, et al. 2007. J. Biol. Chem. 282:26369.
4. Pulmori SK, et al. 2012. J. Immunol. 189:50.
5. Demyanets S, et al. 2013. J. Mol. Cell Cardiol. 60:16.
6. Lin J, et al. 2013. PLoS One 8(4):e60963.

Gene ID
9173 View all products for this Gene ID
View information about IL-1RL1 on

Related FAQs

Why choose BioLegend recombinant proteins?

     • Each lot of product is quality-tested for bioactivity as indicated on the data sheet.
     • Greater than 95% Purity or higher, tested on every lot of product.
     • 100% Satisfaction Guarantee for quality performance, stability, and consistency.
     • Ready-to-use liquid format saves time and reduces challenges associated with reconstitution.
     • Bulk and customization available. Contact us.
     • Learn more about our Recombinant Proteins.

How does the activity of your recombinant proteins compare to competitors?

We quality control each and every lot of recombinant protein. Not only do we check its bioactivity, but we also compare it against other commercially available recombinant proteins. We make sure each recombinant protein’s activity is at least as good as or better than the competition’s. In order to provide you with the best possible product, we ensure that our testing process is rigorous and thorough. If you’re curious and eager to make the switch to BioLegend recombinants, contact your sales representative today!

What is the specific activity or ED50 of my recombinant protein?

The specific activity range of the protein is indicated on the product datasheets. Because the exact activity values on a per unit basis can largely fluctuate depending on a number of factors, including the nature of the assay, cell density, age of cells/passage number, culture media used, and end user technique, the specific activity is best defined as a range and we guarantee the specific activity of all our lots will be within the range indicated on the datasheet. Please note this only applies to recombinants labeled for use in bioassays. ELISA standard recombinant proteins are not recommended for bioassay usage as they are not tested for these applications.

Have your recombinants been tested for stability?

Our testing shows that the recombinant proteins are able to withstand room temperature for a week without losing activity. In addition the recombinant proteins were also found to withstand four cycles of freeze and thaw without losing activity.

Does specific activity of a recombinant protein vary between lots?

Specific activity will vary for each lot and for the type of experiment that is done to validate it, but all passed lots will have activity within the established ED50 range for the product and we guarantee that our products will have lot-to-lot consistency. Please conduct an experiment-specific validation to find the optimal ED50 for your system.

How do you convert activity as an ED50 in ng/ml to a specific activity in Units/mg?

Use formula Specific activity (Units/mg) = 10^6/ ED50 (ng/mL)

Go To Top Version: 3    Revision Date: 05.08.2020

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*These products may be covered by one or more Limited Use Label Licenses (see the BioLegend Catalog or our website, BioLegend products may not be transferred to third parties, resold, modified for resale, or used to manufacture commercial products, reverse engineer functionally similar materials, or to provide a service to third parties without written approval of BioLegend. By use of these products you accept the terms and conditions of all applicable Limited Use Label Licenses. Unless otherwise indicated, these products are for research use only and are not intended for human or animal diagnostic, therapeutic or commercial use.


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