Interleukin-15 (IL-15), also known as IL-T and MGC9721, is an immunomodulating cytokine that stimulates the proliferation of T lymphocytes and shares many biological properties with IL-2 (1). IL-15 mRNA is expressed in many cell types and tissues including adherent peripheral blood mononuclear cells, fibroblasts, and epithelial cells, monocytes, placenta and skeletal muscle. It exerts its biological activities primarily on T cells and is essential in the development, survival and activation of NK cells (2). IL-15 is also secreted by activated monocytes/macrophages following infection by virus (3). It competes for binding sites with IL-2, as both stimulate the growth of cells through the IL-2 receptor and thus negatively regulate each other's activity (4). IL-15 induces the activation of JAK kinases, as well as the phosphorylation and activation of transcription activators STAT3, STAT5, and STAT6. It can recruit and activate T lymphocytes in the synovial membrane, thereby contributing to Rheumatoid arthritis pathogenesis (5). Increased expression of IL-15 has also been implicated with inflammatory bowl disease and diseases affiliated with retroviruses HIV and HTLV-I (6). Human IL-15 is biologically active on mouse cells as measured by the dose-dependent stimulation of the proliferation of mouse CTLL cells.
Protein Details
Purity
>95% by SDS Page
Endotoxin Level
<1.0 EU/µg as determined by the LAL method
Biological Activity
The biological activity of Human IL-15 was determined in a cell proliferation assay using an IL-15 responsive human megakaryocytic leukemic cell line, MO7e. The expected ED<sub>50</sub> for this effect is typically 0.8 - 4 ng/ml. The cell number is assessed in a fluorometric assay using the redox sensitive dye, Resazurin
The predicted molecular weight of Recombinant Human IL-15 is Mr 12.9 kDa.
Predicted Molecular Mass
12.9
Formulation
This recombinant protein was 0.2 µm filtered and lyophilized from a solution containing 10 mM Sodium Bicarbonate, pH 7.2 – 8.5.
Storage and Stability
This lyophilized protein is stable for six to twelve months when stored desiccated at -20°C to -80°C. After aseptic reconstitution, this protein may be stored at 2°C to 8°C for one month or at -20°C to -80°C in a manual defrost freezer. Avoid Repeated Freeze Thaw Cycles. See Product Insert for exact lot specific storage instructions.
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Recombinant Human IL-15 is widely used in research due to its potent ability to stimulate and expand immune cell populations, particularly NK cells and CD8+ T cells, making it valuable for studies in immunology, cancer immunotherapy, infectious diseases, and cell therapy development.
Key scientific reasons to use recombinant human IL-15 in research applications:
Immune Cell Activation and Expansion: IL-15 robustly promotes the proliferation and activation of natural killer (NK) cells, CD8+ cytotoxic T lymphocytes, and to a lesser extent, B cells and NKT cells. This is critical for experiments requiring large numbers of functional effector cells, such as adoptive cell transfer or cytotoxicity assays.
Antitumor and Antiviral Research: IL-15 enhances antitumor immunity by increasing the cytotoxic activity and persistence of NK and CD8+ T cells, leading to tumor regression and improved survival in preclinical cancer models. It is also being explored as an adjunct to checkpoint inhibitors and other immunotherapies due to its ability to synergize with these agents.
Memory T Cell Homeostasis: Unlike IL-2, IL-15 is essential for the maintenance and survival of memory CD8+ T cells without inducing activation-induced cell death, making it useful for studies on long-term immune memory and vaccine development.
Ex Vivo Cell Culture and Expansion: IL-15 is commonly used to expand NK cells, CD8+ T cells, and other lymphocyte subsets in vitro for downstream applications such as cytotoxicity assays, immunophenotyping, or cell therapy manufacturing.
Metabolic and Tissue Protection Effects: Beyond immunology, IL-15 has been shown to influence lipid and glucose metabolism, protect various cell types from apoptosis, and support tissue regeneration, broadening its utility to metabolic disease and regenerative medicine research.
Clinical Relevance: Recombinant human IL-15 is under investigation in clinical trials for cancer and infectious diseases, making it a translationally relevant cytokine for preclinical and mechanistic studies.
Alternative to IL-2: IL-15 shares some functions with IL-2 but does not promote regulatory T cell expansion or activation-induced cell death to the same extent, offering advantages in settings where sustained effector cell activity is desired.
In summary, recombinant human IL-15 is a versatile cytokine for research focused on immune modulation, cancer immunotherapy, infectious disease, cell therapy, and metabolic regulation, due to its unique biological properties and translational potential.
Yes, recombinant human IL-15 can be used as a standard for quantification or calibration in ELISA assays, provided that the ELISA is designed to detect human IL-15 and the recombinant standard is compatible with the assay system.
Key Points:
Standard Use: Recombinant human IL-15 is commonly used as a quantitative standard in sandwich ELISA assays to generate a standard curve, which allows for the accurate quantification of IL-15 in samples. This is supported by several manufacturers (e.g., BD Pharmingen, BioLegend, R&D Systems, Abcam).
Compatibility: Ensure that the recombinant IL-15 standard is recognized by the capture and detection antibodies used in your ELISA. Most commercial ELISA kits are calibrated against recombinant human IL-15, and the standard curves generated with recombinant IL-15 are typically parallel to those obtained with natural IL-15, allowing for reliable quantification.
Formulation: Recombinant IL-15 standards are usually provided lyophilized and should be reconstituted according to the manufacturer's instructions. They may contain stabilizers such as BSA or sodium azide, which should be considered when preparing dilutions.
Calibration: When using recombinant IL-15 as a standard, it is important to perform a serial dilution to generate a standard curve that covers the expected range of IL-15 concentrations in your samples. This curve will be used to interpolate the concentration of IL-15 in your unknown samples.
References:
BD Pharmingen: Recombinant human IL-15 (Cat. No. 560254) is provided as a quantitative standard for measuring human IL-15 protein levels using sandwich ELISA.
BioLegend: Recombinant Human IL-15 ELISA Std. is useful as a standard for a human IL-15 sandwich ELISA.
R&D Systems: The Quantikine Human IL-15 Immunoassay is calibrated against a highly purified E. coli-expressed recombinant human IL-15.
Abcam: Recombinant human IL-15 protein (Active) is available for use as a standard in ELISA assays.
By following these guidelines, you can effectively use recombinant human IL-15 as a standard for quantification or calibration in your ELISA assays.
Recombinant Human IL-15 has been validated for a broad range of applications in published research, primarily focused on immunological modulation, cancer immunotherapy, and cell-based assays.
Key validated applications include:
Activation and expansion of immune cells: IL-15 robustly stimulates proliferation and activation of natural killer (NK) cells, CD8⁺ T cells, NKT cells, and memory T cells in vitro and in vivo.
Cancer immunotherapy: Recombinant IL-15 has been used in preclinical and clinical studies to enhance anti-tumor immunity, either alone or in combination with immune checkpoint inhibitors (e.g., anti-PD-L1), showing increased infiltration and activity of cytotoxic lymphocytes in tumor models.
Cell culture and differentiation assays: IL-15 is routinely used to support the expansion and differentiation of CAR-T cells, TCR-T cells, TILs, CIK cells, and hematopoietic stem/progenitor cells for research and therapeutic development.
Functional bioassays: IL-15 is validated for use in various bioassays, including proliferation assays, cytokine release assays, and cytotoxicity assays involving NK and T cells.
Flow cytometry and immunophenotyping: IL-15 is used to modulate immune cell populations for downstream analysis by flow cytometry, particularly in studies of HIV, autoimmunity, and cancer.
Vaccine and infectious disease research: IL-15 supports the maintenance and expansion of memory T cells, contributing to vaccine efficacy and studies of viral infections such as HIV.
Protection from apoptosis and dendritic cell modulation: IL-15 has been shown to protect neutrophils from apoptosis and stimulate protein expression in dendritic cells, relevant for studies of innate immunity.
Additional validated protocols include:
In vitro stimulation of NK-92 cell lines for cytotoxicity and proliferation studies.
Combination therapy studies with checkpoint inhibitors, demonstrating synergistic anti-tumor effects in animal models.
Clinical trials: Recombinant IL-15 has been administered to patients with metastatic melanoma, renal cell carcinoma, and other malignancies, resulting in increased circulating NK and CD8⁺ T cells and demonstrating safety and efficacy profiles.
These applications are supported by numerous peer-reviewed publications, clinical trial reports, and product validation data, confirming the utility of recombinant human IL-15 in both basic and translational immunology research.
To reconstitute and prepare Recombinant Human IL-15 protein for cell culture experiments, briefly centrifuge the vial to collect the contents, then reconstitute the lyophilized protein in sterile buffer—commonly sterile distilled water or sterile PBS—at a concentration suitable for your application, typically between 0.1–1.0 mg/mL.
Detailed protocol:
Centrifuge the vial briefly before opening to ensure all lyophilized material is at the bottom.
Reconstitution buffer:
For general use, sterile distilled water is acceptable.
For cell culture, sterile PBS (pH 7.4) is preferred, often supplemented with 0.1% endotoxin-free recombinant human or bovine serum albumin (HSA/BSA) to stabilize the protein and prevent adsorption to surfaces.
Concentration:
Typical reconstitution concentrations range from 50–500 μg/mL for working stocks.
For higher concentration stocks, up to 1 mg/mL may be used.
Mixing:
Gently swirl or tap the vial to dissolve the protein. Avoid vigorous pipetting or vortexing, which may denature the protein.
Aliquoting:
After reconstitution, aliquot the solution to avoid repeated freeze-thaw cycles, which can degrade IL-15.
Storage:
Store aliquots at –20°C or –80°C for long-term storage. For short-term use, 4°C is acceptable for up to one week.
Sterility:
Ensure all buffers and containers are sterile to prevent contamination in cell culture experiments.
Preparation for cell culture:
Dilute the reconstituted IL-15 to the desired working concentration in cell culture medium immediately before use.
If using serum-free media, ensure the presence of carrier protein (e.g., HSA/BSA) to maintain cytokine stability.
Avoid prolonged storage of diluted working solutions; prepare fresh dilutions for each experiment.
Summary Table:
Step
Buffer/Conditions
Concentration
Notes
Centrifuge vial
—
—
Collect lyophilized powder
Reconstitute
Sterile water or PBS + 0.1% HSA/BSA
0.1–1.0 mg/mL
Gently mix, avoid vortexing
Aliquot
—
—
Prevent freeze-thaw cycles
Store
–20°C or –80°C (long-term), 4°C (short)
—
Use manual defrost freezer
Prepare for culture
Dilute in cell culture medium
As required
Add carrier protein if serum-free
Best practices:
Always consult the specific Certificate of Analysis (CoA) for your batch for optimal reconstitution conditions.
Use endotoxin-free reagents and containers for sensitive cell types.
Validate biological activity with a dose-response assay if possible.
This protocol ensures optimal solubility, stability, and biological activity of recombinant human IL-15 for cell culture applications.
References & Citations
1. Grabstein, K. et al. (1994) Science 264:965
2. Ma, A. et al. (2006) Annu. Rev. Immunol. 24:657
3. Yoshikai, Y. et al. (1996) J. Immunol. 156:663
4. Giri, J. et al. (1994) EMBO J. 13:2822
5. Liew, F. Y. et al. (1996) Nat. Med. 4:643
6. Waldmann, T. A. et al. (1999) Annu. Rev. Immunol. 17:19
Products are for research use only. Not for use in diagnostic or therapeutic procedures.
