Recombinant Human Interleukin 15 Receptor, Alpha (IL-15Rα)

Using Recombinant Human Interleukin 15 Receptor, Alpha (IL-15Rα) in your research applications is critical for maximizing the biological activity and stability of IL-15, particularly in studies focused on immunology, cancer immunotherapy, and cell-based assays. IL-15Rα enables the formation of IL-15/IL-15Rα complexes, which more closely mimic the natural trans-presentation mechanism and significantly enhance the potency of IL-15 in stimulating immune cells.

Key scientific reasons to use recombinant IL-15Rα:

• Enhanced IL-15 Activity: The IL-15/IL-15Rα complex increases the affinity of IL-15 for the IL-2Rβγc receptor on effector cells by up to 150-fold compared to IL-15 alone, resulting in much stronger stimulation of CD8⁺ T cells and NK cells.
• Improved Stability and Half-life: Recombinant IL-15Rα, when complexed with IL-15, increases the serum half-life and intracellular stability of IL-15, overcoming the rapid clearance and degradation issues associated with free IL-15.
• Augmented Antitumor Efficacy: IL-15/IL-15Rα complexes and superagonists have demonstrated superior antitumor activity in preclinical models, promoting proliferation and activation of NK, NKT, and memory CD8⁺ T cells, and leading to tumor regression and improved survival.
• Trans-presentation Mechanism: IL-15Rα is essential for the trans-presentation of IL-15, a physiological process where IL-15 bound to IL-15Rα on one cell is presented to neighboring cells expressing the IL-2Rβγc receptor, thereby efficiently activating immune responses.
• Versatile Research Applications: Recombinant IL-15Rα is used in designing superagonists, cell-based vaccines, and fusion proteins for immunotherapy, as well as in basic research to dissect IL-15 signaling pathways and immune cell biology.

Typical applications include:

• Cancer immunotherapy studies (e.g., evaluating antitumor immune responses, developing IL-15-based therapeutics).
• Immunological assays (e.g., stimulating and expanding NK and CD8⁺ T cells for functional studies).
• Cell-based vaccine platforms (e.g., engineering cells to secrete IL-15/IL-15Rα complexes for enhanced immunogenicity).

In summary, recombinant IL-15Rα is indispensable for research aiming to harness or study the full immunostimulatory potential of IL-15, especially where robust activation, stability, and physiological relevance are required.

Recombinant Human IL-15Rα can be used as a standard for quantification or calibration in ELISA assays, but only in assays specifically designed to detect IL-15Rα or IL-15/IL-15Rα complexes, not for quantifying IL-15 alone.

For ELISA assays targeting IL-15Rα (the receptor subunit), recombinant IL-15Rα is suitable as a standard, provided the assay is validated for this purpose. Such assays typically use anti-IL-15Rα antibodies for capture and detection, and the recombinant protein standard allows for accurate quantification of IL-15Rα concentrations in samples.

For assays measuring IL-15/IL-15Rα heterodimeric complexes, the standard should be a purified IL-15/IL-15Rα complex, not the receptor alone. Studies have shown that ELISAs specific for the heterodimer use serial dilutions of purified human IL-15/IL-15Rα complexes as the reference standard, which closely mimics the physiological form found in serum. Using only recombinant IL-15Rα as a standard in these assays would not accurately reflect the analyte being measured.

For IL-15 quantification, recombinant IL-15 is used as the standard, not IL-15Rα. ELISA kits for IL-15 are calibrated against recombinant IL-15, and the standard curve is generated using this protein.

Key considerations:

• Use recombinant IL-15Rα as a standard only in ELISAs designed to quantify IL-15Rα.
• For heterodimeric IL-15/IL-15Rα detection, use a purified complex as the standard.
• For IL-15 quantification, use recombinant IL-15 as the standard.
• Always verify that your ELISA protocol is validated for the specific analyte and standard you intend to use.

If your goal is to quantify soluble IL-15Rα in biological samples, recombinant IL-15Rα is appropriate as a standard. If you wish to quantify IL-15/IL-15Rα complexes, you must use a standard that reflects the complexed form. Using the wrong standard can lead to inaccurate quantification and misinterpretation of results.

Recombinant Human Interleukin 15 Receptor, Alpha (IL-15Rα) has been validated in published research primarily for applications in cancer immunotherapy, immune cell activation assays, and mechanistic studies of cytokine transpresentation.

Key validated applications include:

• Cancer Immunotherapy Models: IL-15Rα, especially as part of IL-15/IL-15Rα complexes, has been used to enhance the antitumor activity of immune cells such as NK cells and CD8^+^ T cells in both in vitro and in vivo models. These complexes prolong IL-15 half-life and boost its biological activity, resulting in improved tumor growth inhibition and increased survival in mouse xenograft models.

• Transpresentation and Immune Cell Activation: IL-15Rα enables the transpresentation of IL-15 to neighboring NK cells and CD8^+^ T cells, leading to superior activation, proliferation, and cytotoxicity compared to IL-15 alone. This has been validated in protocols using dendritic cells engineered to express IL-15Rα, which stimulate NK cell activation and tumor cell killing.

• Combination Immunotherapy: Recombinant IL-15Rα complexes have been tested in combination with immune checkpoint inhibitors (e.g., PD-1 antibodies), showing synergistic effects in suppressing tumor growth in preclinical models.

• Pharmacokinetic Enhancement: Fusion proteins comprising IL-15 and the extracellular domain of IL-15Rα (sometimes linked to Fc domains) have been validated for their ability to significantly extend the half-life of IL-15 in circulation, thereby maximizing its therapeutic potential.

• Cellular and Molecular Mechanism Studies: IL-15Rα has been used to dissect the mechanisms of IL-15 transpresentation, receptor shedding, and downstream signaling pathways relevant to immune cell function and antitumor responses.

• CAR-NK Cell Engineering: IL-15Rα has been incorporated into chimeric antigen receptor (CAR) constructs to enhance NK cell proliferation, cytokine secretion, and cytotoxicity against hematologic malignancies.

Summary Table of Validated Applications

These applications are supported by multiple peer-reviewed studies, demonstrating the utility of recombinant human IL-15Rα in both basic and translational immunology research.

To reconstitute and prepare Recombinant Human Interleukin 15 Receptor, Alpha (IL-15Rα) protein for cell culture experiments, follow these general steps, which are based on best practices for recombinant protein handling and specific protocols for similar cytokine receptors:

1. Centrifuge the vial briefly before opening to ensure all lyophilized material is at the bottom.

2. Reconstitution:

   • Use sterile, endotoxin-free PBS (phosphate-buffered saline) or sterile water for reconstitution, depending on the protein's formulation and your experimental requirements.
   • A typical starting concentration is 100 μg/mL in sterile PBS. If your application requires a different concentration, adjust accordingly by diluting with the same buffer.

3. Carrier Protein Addition (optional but recommended for stability):

   • Add a carrier protein such as 0.1–1% BSA (bovine serum albumin) or 5% trehalose to the buffer to enhance protein stability, especially if the protein will be stored for more than a few days or at low concentrations.

4. Mixing:

   • Gently swirl or invert the vial to dissolve the protein completely. Avoid vigorous vortexing, which can denature the protein.

5. Sterile Filtration (if required for cell culture):

   • If sterility is critical and the protein solution is not already sterile, filter the reconstituted protein through a 0.2 μm sterile filter.

6. Aliquoting and Storage:

   • Aliquot the reconstituted protein to avoid repeated freeze-thaw cycles, which can degrade the protein.
   • Store aliquots at 2–8°C for up to one month or at –20°C to –70°C for long-term storage.
   • Avoid multiple freeze-thaw cycles.

7. Preparation for Cell Culture:

   • Before use, thaw an aliquot on ice and dilute to the desired working concentration in your cell culture medium, ideally containing serum or additional carrier protein to minimize adsorption to plasticware.

Additional Notes:

• If using a specific IL-15Rα variant (e.g., Fc chimera, sushi domain), confirm the recommended buffer and concentration with the product datasheet, as some constructs may have unique requirements.
• For experiments involving IL-15/IL-15Rα complexes, pre-incubate the receptor with IL-15 at the desired molar ratio before adding to cells, as this can enhance biological activity and stability.

Summary Table: Reconstitution Steps

These steps will help ensure protein integrity and reproducibility in your cell culture experiments. Always consult the specific product datasheet for any unique instructions.