Recombinant Human IL-21

Recombinant Human IL-21 is widely used in research applications due to its potent immunomodulatory effects on multiple lymphocyte populations, making it valuable for studies in immunology, oncology, infectious disease, and cell therapy.

Key scientific reasons to use Recombinant Human IL-21:

• Enhances T cell and NK cell function: IL-21 promotes the proliferation, differentiation, and cytotoxic activity of CD8⁺ T cells and natural killer (NK) cells, which are crucial for antitumor and antiviral responses.
• Supports B cell biology: It regulates B cell activation, proliferation, differentiation, and immunoglobulin class switching, impacting humoral immunity and antibody production.
• Facilitates cell culture and differentiation studies: Recombinant IL-21 is used to drive the differentiation of naive CD4⁺ T cells into Th17 and T follicular helper (Tfh) cells, and to expand cytotoxic T cells for functional assays or adoptive cell therapies.
• Cancer immunotherapy research: IL-21 has demonstrated antitumor effects in preclinical and clinical studies, both alone and in combination with other immunotherapies (e.g., checkpoint inhibitors, CAR T cells, oncolytic viruses), with minimal toxicity.
• Vaccine and infectious disease models: IL-21 is important for the maintenance and function of CD8⁺ T cells during chronic infections, and can be used to study immune responses to pathogens.
• Autoimmunity and allergy studies: IL-21 is implicated in autoimmune diseases (e.g., SLE) and can suppress allergen-specific IgE production, making it relevant for research into immune regulation and hypersensitivity.

Typical research applications include:

• In vitro expansion and functional enhancement of cytotoxic lymphocytes for immunotherapy or adoptive cell transfer.
• Differentiation protocols for T cell subsets (Th17, Tfh) and B cells.
• Investigation of immune cell signaling, activation, and metabolic changes.
• Studies of humoral immunity, antibody production, and B cell apoptosis.
• Modeling immune responses in cancer, infection, and autoimmunity.

Summary:
Use of recombinant human IL-21 enables precise modulation of immune cell populations, supports advanced cell culture and differentiation protocols, and provides a robust tool for dissecting mechanisms of immunity, tolerance, and antitumor activity in both basic and translational research contexts.

Yes, recombinant human IL-21 can be used as a standard for quantification or calibration in ELISA assays, provided it is properly validated and matched to your assay system. Recombinant IL-21 is commonly used as a standard in commercial human IL-21 ELISA kits and custom sandwich ELISA protocols.

Key considerations and best practices:

• Source and Purity: The recombinant IL-21 standard should be highly purified and its concentration accurately determined, typically by protein assay or absorbance at 280 nm.
• Formulation: Standards are often supplied lyophilized and should be reconstituted according to the manufacturer’s instructions. Carrier-free formulations are preferred if BSA or other additives may interfere with your assay.
• Calibration: ELISA kits are calibrated against recombinant human IL-21, and standard curves are generated using serial dilutions of the standard protein.
• Validation: Ensure the recombinant IL-21 standard is recognized by the capture and detection antibodies in your assay. Most commercial kits and published protocols specify that their antibodies detect both natural and recombinant human IL-21.
• Matrix Effects: If quantifying IL-21 in complex biological samples (e.g., serum, plasma), consider preparing standards in a similar matrix to account for potential matrix effects.
• Documentation: Refer to the datasheet or protocol for your ELISA kit or antibody pair to confirm compatibility with recombinant IL-21 as a standard.

Typical protocol steps:

• Reconstitute recombinant IL-21 to a known concentration.
• Prepare serial dilutions to generate a standard curve (e.g., 1000, 500, 250, 125, 62.5, 31.25 pg/mL).
• Run standards alongside samples to interpolate unknown concentrations from the standard curve.

Summary Table: Use of Recombinant Human IL-21 as ELISA Standard

In conclusion, recombinant human IL-21 is widely accepted and validated as a standard for ELISA quantification, provided it is compatible with your assay antibodies and protocol.

Research Applications of Recombinant Human IL-21

Recombinant human IL-21 has been validated across a diverse range of immunological and therapeutic applications in published research.

Lymphoid Cell Development and Function

Recombinant IL-21 promotes differentiation of T helper 17 (TH17) and T follicular helper (Tfh) cells, expansion of CD8+ T cells, and development of B and NK cells. The cytokine regulates multiple aspects of lymphoid cell function and plays central roles in humoral immunity. Specific validated applications include in vitro differentiation of naive CD4+ T cells toward TH17 and Tfh phenotypes, in vitro expansion of CD8+ T cells with enhancement of cytotoxic T cell function, and study of NK cell development and function.

B Cell and Dendritic Cell Biology

Beyond T cell applications, IL-21 plays a critical role in B cell activation, proliferation, differentiation, and apoptosis. The cytokine is also required for migration of dendritic cells to draining lymph nodes. Additionally, IL-21 suppresses cutaneous hypersensitivity reactions by limiting allergen-specific IgE production and mast cell degranulation.

Cancer Immunotherapy

Recombinant IL-21 has been extensively validated in cancer immunotherapy applications. Early-stage clinical trials have been completed in multiple cancer types including melanoma, renal cell carcinoma, ovarian cancer, and non-Hodgkin's lymphoma, both as a single agent and in combination with immune checkpoint inhibitors. Preclinical studies demonstrated significant antitumor effects through induction of antigen-specific cytotoxic T lymphocyte responses. IL-21 has shown synergistic interactions when combined with cellular or molecularly defined vaccines, antibodies, other cytokines, and immune checkpoint blockers. Recent advances indicate IL-21 as a promising target for cancer treatment, with encouraging results in combination with monoclonal antibodies, checkpoint inhibitory molecules, oncolytic virotherapy, and adoptive cell transfer. Notably, IL-21 has been validated in engineered T cell therapy, where IL-21 receptor-armed TCR-T cells demonstrated superior antitumor function and reduced exhaustion compared to conventional TCR-T cells.

Bioassay and Functional Studies

Recombinant IL-21 has been validated for use in bioassays measuring immune cell activation. The protein enhances interferon-gamma secretion in NK cells and induces proliferation of T cell lines in a dose-dependent manner, making it suitable for quantitative functional assays.

Disease Association Studies

IL-21 has been associated with allergies, cancer, and viral infections. Research has also established links between IL-21 and systemic lupus erythematosus disease susceptibility and progression.

To reconstitute and prepare Recombinant Human IL-21 protein for cell culture experiments, dissolve the lyophilized protein in sterile PBS (phosphate-buffered saline) containing at least 0.1% carrier protein such as human or bovine serum albumin (BSA or HSA), or use sterile distilled water for carrier-free formulations.

Step-by-step protocol:

1. Briefly centrifuge the vial before opening to ensure all material is at the bottom.
2. Reconstitution concentration:
   • Commonly recommended concentrations are 100 μg/mL or 0.2 mg/mL.
   • For carrier-free formulations, reconstitute in sterile PBS or distilled water at 100 μg/mL.
   • For formulations with carrier, use PBS containing 0.1%–0.5% BSA or HSA.
3. Mix gently:
   • Swirl or tap the vial gently to dissolve. Avoid vigorous pipetting or vortexing to prevent protein denaturation.
4. Aliquot immediately:
   • Divide the solution into small working aliquots to avoid repeated freeze-thaw cycles.
5. Storage:
   • Store aliquots at –20°C to –80°C for long-term use.
   • After reconstitution, the protein is stable for 1 week at 4°C or up to 6 months at –20°C to –80°C.
6. Further dilution:
   • For cell culture, dilute the stock solution in cell culture medium containing a carrier protein (e.g., BSA or heat-inactivated FCS) to minimize adsorption and loss of activity.
   • Use low endotoxin reagents and solutions for sensitive cell types.

Additional notes:

• Always use endotoxin-free reagents for cell culture applications, especially with immune cells.
• Avoid repeated freeze-thaw cycles, as these can reduce protein activity.
• If using a carrier-free formulation, consider adding a carrier protein during dilution to working concentrations to stabilize the protein.

Example preparation for a 10 μg vial:

• Add 100 μL sterile PBS + 0.1% BSA to obtain a 0.1 mg/mL (100 μg/mL) stock solution.

This protocol ensures optimal stability and biological activity of recombinant human IL-21 for cell culture experiments.