Our expanding catalog of recombinant proteins includes cytokines, chemokines, growth factors, enzymes, adhesions molecules, and more. These proteins are tested in a variety of bioassays to ensure bioactivity. For studies that are particularly sensitive to contamination with mammalian pathogens, we also offer animal-free versions of many of our recombinant proteins. Like our carrier-free formats, these proteins do not contain any carrier proteins; however, the animal-free products are produced in animal-free media with equipment that is free of all animal components. Browse our recombinant proteins groups below!


Cytokines allow cells to communicate with one another and induce a wide range of activities. They can be pro- or anti-inflammatory, promote cell growth, or influence differentiation to various cell types. To mediate these functions, cytokines bind to their respective receptors on the cell surface, initiating signaling cascades for gene transcription.

Featured Data

Recombinant Human TGF-β1(carrier-free)



Recombinant human TGF-β1 inhibits the proliferation of mouse HT-2 cell line induced by IL-4 in a dose-dependent manner. BioLegend's protein was compared side-by-side to the leading competitor's equivalent.

Th17 Polarization of Mouse CD4 Cells



Mouse CD4+ T cells were polarized with plate-bound anti-mouse CD3, soluble anti-mouse CD28, recombinant mouse IL-6, IL-23, and TGF-β, anti-mouse IFN-γ, and anti-mouse IL-4 for 4 days. After re-stimulation with PMA/ionomycin in the presence of BFA or monensin, the cells were harvested and surface stained with CD4 FITC, and intracellularly stained with IFN-γ APC and IL-17 PE.

Eager to start polarizing your own cells today? Take a look at our Activation Bundles.

Adhesion Molecules

Cell adhesion molecules (CAMs) mediate cell-to-cell and/or cell-to-extracellular matrix (ECM) interactions. In general, the CAMs belong to four different families: immunoglobulin (Ig) superfamily, integrins, cadherins, and selectins. Interactions mediated by CAMs can be either adhesive or inhibitory in nature. These interactions can also be associated with changes in downstream signaling pathways, cytoskeletal reorganization, or gene expression.

Featured Data

Recombinant Human CD6 (Carrier-Free)



Human CD6 was aliquoted in 20 mM Tris, 150 mM NaCl, pH 7.2 at 0.2 mg/ml. One aliquot was frozen and thawed four times (4x freeze/thaws) and another aliquot was kept at 37°C for one week. The proteins were tested for their ability to support the adhesion of Jurkat cells compared to a control kept at 4°C.

Recombinant Human ALCAM/CD166 (Carrier-Free)



Human ALCAM was aliquoted in 20mM Tris, 150mM NaCl, pH 7.2 at 0.2 mg/ml. One aliquot was frozen and thawed four times and another aliquot was kept at 37°C for one week. The proteins were tested for their ability to block adhesion of Jurkat cells to immobilized human CD6 compared to a control kept at 4°C.


Chemokines are relatively small cytokines which regulate cell movement, also known as chemotaxis. To mediate downstream functions, they bind to chemokine receptors which contain seven transmembrane domains. These receptors are typically promiscuous and bind to multiple chemokine ligands.

Chemokines contain several (typically four) cysteine residues in conserved positions within the protein (marked C in the image below) which provide tertiary structure through disulfide bonds. The spacing of the intervening amino acids (denoted X below) between the first two cysteine residues determine the type of chemokine.



Featured Data

Soluble Receptors

Receptors bind to their respective ligands and recognize and respond to cell signals. They are a broad group which includes signaling receptors, non-signaling decoy receptors, receptor-associated proteins, and soluble receptors. Naturally occurring soluble receptors can be generated by several mechanisms, including proteolytic cleavage of surface-bound receptor ectodomains, alternative splicing of mRNA transcripts, transcription of distinct genes, cleavage of GPI-anchored receptors, and extracellular release of membrane-bound receptors within vesicles of exosomes.

One example is soluble cytokine receptors which once bound to cytokines can act as either agonists or antagonists of cytokine signaling. Our recombinant soluble receptors are constructed to encode only the extracellular domain and do not include the transmembrane or cytoplasmic domains.

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Growth Factors

Growth factors are a broad family of proteins that regulate a number of important cellular processes including cell growth, differentiation, proliferation, and survival. Growth factors bind to transmembrane receptors typically containing a cytoplasmic tyrosine kinase domain which initiates downstream signaling pathways including MAP kinase and PI3K-mTOR pathways. Growth factors are classified into various families based on the structure of the protein, downstream function, and the ability to affect different cell types.



Featured Data

Recombinant Human FLT3L Carrier-Free)



Recombinant human FLT3L induces IL-6 production in M1 murine myeloid leukemia cell line in a dose-dependent manner in the presence of 1 ng/ml of mouse LIF recombinant protein.

Other Proteins

In addition to the groups of proteins found above, we have other recombinant proteins that can be used in a variety of bioassays. These proteins also play an important cellular roles including cell migration, survival, regulation of immune responses, apoptosis, neuroinflammation, Alzheimer’s disease, tumor cell phenotypes, and autoimmune diseases.

Featured Data

Recombinant Mouse TACI-Fc Chimera (Carrier-Free)




Recombinant mouse TACI (TNFRSF13B) inhibits the proliferation of mouse B cells induced by BAFF. The B cells were activated with an anti-IgM antibody. BioLegend’s protein was compared side-by-side to the leading competitor’s equivalent product.

Enzymes and Regulators

Enzymes act as biological catalysts to regulate chemical reactions and are highly specific to the substrates with which they react. Through these reactions, enzymes and their regulators (such as inhibitors) modulate cell fate, localization, and activity of many proteins. Additionally, enzymes can regulate protein-protein interactions, create new bioactive molecules, and contribute to signal transduction. Through these actions, enzymes influence cellular functions such as proliferation, differentiation, DNA replication, inflammation, and apoptosis.



Featured Data

Recombinant Human Elafin (carrier-free)




The activity of hElafin was measured by its ability to inhibit human neutrophil elastase. The potency of inhibition was measured by monitoring the cleavage of a fluorogenic substrate MeO-Suc-AAPV-AMC (100 μM) in the presence of human neutrophil elastase (100 ng/mL). The IC50 value of hElafin is less than 3.0 nM (34 ng/mL).


Recombinant Human MMP-10 (carrier-free)




The activity of human MMP-10 was measured with 10 μM of fluorogenic MMP substrate, Mca-RPKPVE-Nval-WRK(Dnp)-NH2, in the presence of 6.25, 12.5, 25, 50, 100 ng of activated hMMP-10. The activity of activated hMMP-10 is >200 pmole/min/μg.


How are BioLegend's carrier-free recombinant proteins shipped?


Our carrier-free recombinant proteins are shipped on blue ice.  These products have been validated to maintain activity after shipping using blue ice.  


What is a carrier protein?


Carrier proteins, such as BSA, improve the stability of the reconstituted protein, and helps prevent the product from sticking to the wall of the vial.


What is the difference between the carrier-free and the non carrier-free recombinant proteins?


All our carrier-free and animal-free formats of recombinant proteins do not have any additional carrier proteins such as BSA in the formulation. Typically our ELISA standard recombinants have carrier proteins added to the formulation for added stability and to avoid the product from sticking to the wall of the vial. When the presence of carrier is not desirable (e.g., in-vivo applications), carrier-free proteins can be used directly. When carrier proteins do not affect the outcome in a study, the customer can decide what type of carrier protein they would like to use and whether it is necessary to add it to their stock.


Can I use different recombinant proteins from different companies for my ELISA?


Antibodies used are different in different kits. The specificity of the antibodies partially dictate how much signal is being detected. Recombinant standards used are different. First of all, different kits may use recombinant proteins expressed and purified using different method. Second, recombinant proteins expressed from E. coli from the same source can show greater than 10 fold difference in term of immunoreactivity from lot to lot, primarily due to refolding inconsistency. Third, different kit standards can be produced and calibrated against different references. So far there is no universally accepted standardization for cytokine immunoreactivities. Each BioLgend ELISA product was developed and validated with reagent concentrations and protocols optimized for best analytical robustness. Any changes to the reagents (standards, antibodies, matching matrices) and protocols etc all affect the final assay performance.


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.


What should I reconstitute the protein with? What do you recommend for its long-term storage?


Most of our carrier-free recombinants are shipped in liquid form, so there is no need for reconstitution. Our animal-free recombinant proteins are shipped in lyophilized form and protein reconstitution information is indicated on the respective datasheets. If you need to make dilutions, refer to the formulation on the product data sheet. Stock solutions should be prepared at 50-100 μg/mL in buffer containing carrier protein such as 1% BSA or HSA or 10% FBS (for chemokines, use either BSA or HSA). For long-term storage, aliquot into polypropylene vials and store in a manual defrost freezer. Avoid repeated freeze/thaw cycles.

For reconstitution of our lyophilized recombinant proteins (ELISA Std, animal-free, and some carrier-free) please refer to the Certificate of Analysis and/or Technical Datasheet included with the product and follow the instructions. 


Are BioLegend’s recombinant proteins suitable for in vitro and in vivo bioassays?


BioLegend’s recombinant protein solutions are 0.2 μm-filtered prior to bottling by membrane filtration method. In addition, our recombinants are endotoxin-tested and are guaranteed to have levels less than 0.1 ng per μg protein. All our recombinants can be safely used for both in vitro and in vivo bioassays.


Do you test the bioactivity of your recombinant proteins with in vivo assays?


We typically validate the activity of the proteins with in-vitro assays as described on the data sheet and not with in-vivo testing. However, all our carrier-free and animal-free formats can be used for in vivo applications as is evident from many customers who have successfully used it for this purpose.


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.


What is the difference between laboratory (observed) units and international units?


There is no direct relationship between International Units and the units that are calculated using the inverse of the specific activity because we do not use the International Standard provided by WHO (National Institute for Biological Standards and control). The best way to compare the activity of two sources of recombinants is by doing the bioassay side by side using the same system.


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


Use the formula Specific activity (Units/mg) = 106/ ED50 (ng/mL)


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.


What is the difference between carrier-free and animal-free categories of recombinant proteins?


Our animal-free products are proteins that go through the entire production process without touching any animal containing components. This includes using animal-free media and purification equipment that are animal component-free. Some studies which are particularly sensitive to contamination by mammalian pathogens may require the use of animal-free products. Our carrier-free products do not contain any carrier protein in the solution, as expected, but they are produced using animal-containing components. Both versions are expected to have similar activity and function, though specific activity is lot-dependent.