Recombinant Human IL-18 Rβ

I need to clarify an important distinction regarding your query. The search results and scientific literature focus on recombinant human IL-18 as a complete cytokine protein, not specifically on IL-18 Rβ (the beta chain of the IL-18 receptor) as a standalone research reagent.

Understanding the Distinction

Recombinant human IL-18 is the mature cytokine itself—a pro-inflammatory protein that functions as a signaling molecule. In contrast, IL-18 Rβ refers to the beta subunit of the IL-18 receptor complex, which is part of the cellular machinery that receives the IL-18 signal rather than being the active cytokine itself.

Applications of Recombinant Human IL-18

If you're considering recombinant human IL-18 for your research, the scientific rationale is well-established:

Immunological Research: Recombinant human IL-18 is a powerful inducer of type 1 immune responses, enhancing interferon-gamma (IFN-γ) production by natural killer cells, Th1 cells, and CD8+ cytotoxic T cells. It acts synergistically with IL-12 to stimulate Th1 immune responses and promotes myeloid dendritic cell maturation.

Cancer Immunotherapy Studies: IL-18 exhibits diverse antitumor activities, including enhancement of anti-tumor immunity, modulation of angiogenesis, and augmentation of antibody-dependent cellular cytotoxicity (ADCC) by NK cells and monocytes. Clinical studies have demonstrated that recombinant human IL-18 can be administered in biologically active doses to cancer patients, with objective tumor responses observed.

Bioassay Development: Recombinant human IL-18 serves as a standard for IL-18 detection and quantification assays, and is useful for screening antibodies that block IL-18 signaling or for validating engineered IL-18 variants.

Disease Research: Abnormal IL-18 serum concentrations are associated with immune-mediated inflammatory diseases, making recombinant IL-18 valuable for studying conditions like cryopyrin-associated periodic syndrome and multiple sclerosis.

If you specifically need the IL-18 receptor beta chain for receptor binding studies or structural research, you would need to clarify that distinction with your supplier, as this represents a different research application than the cytokine itself.

Recombinant Human IL-18 Rβ should not be used as a standard for quantification or calibration in ELISA assays designed to measure IL-18. ELISA standards must match the analyte being quantified in terms of molecular identity and immunoreactivity.

Supporting details:

• ELISA standards are typically recombinant or purified forms of the specific analyte (e.g., human IL-18 protein) that the assay is designed to detect. The standard curve generated from these standards allows for accurate quantification of the target analyte in unknown samples.
• IL-18 Rβ (Interleukin-18 receptor beta) is a receptor protein, not the cytokine IL-18 itself. Its structure, epitopes, and immunoreactivity are different from IL-18, so it will not be recognized by antibodies specific for IL-18 in standard ELISA kits.
• ELISA kits for IL-18 quantification use recombinant human IL-18 as the standard, not IL-18 Rβ or other related proteins.
• Using a non-matching standard (such as IL-18 Rβ for IL-18 quantification) will result in inaccurate calibration, unreliable quantification, and potentially invalid assay results.

Best practice:

• Always use a standard that is identical to the analyte being measured. For human IL-18 ELISA, use recombinant human IL-18 protein as the standard.
• Recombinant human IL-18 Rβ may be used as a standard only in assays specifically designed to quantify IL-18 Rβ, such as an IL-18 Rβ ELISA.

Summary Table:

Conclusion:
For quantification or calibration in IL-18 ELISA assays, use recombinant human IL-18 as the standard. Recombinant human IL-18 Rβ is not suitable for this purpose.

Recombinant Human IL-18 Rβ has been validated for several key applications in published research, primarily in studies of cytokine signaling, immune cell activation, and antibody screening.

Validated Applications:

• Binding and Activation Assays: Recombinant IL-18 Rβ is used to study the interaction between IL-18 and its receptor complex (IL-18Rα/IL-18Rβ), which is essential for downstream signaling and induction of inflammatory cytokines such as IFN-γ. These assays often employ recombinant IL-18 Rβ to reconstitute the receptor complex in vitro and measure functional responses, such as NFκB activation or cytokine release.

• Antibody Screening: Recombinant IL-18 Rβ is utilized in screening assays to identify and characterize antibodies or antibody fragments (e.g., single domain antibodies, bispecifics) that bind specifically to IL-18 Rβ. These studies assess binding affinity, specificity, and the ability of antibodies to modulate receptor function.

• ELISA and Western Blot: Recombinant IL-18 Rβ serves as a standard or target antigen in direct ELISA and Western blot assays to detect and quantify IL-18 Rβ protein, as well as to validate antibody specificity.

• Structural and Mechanistic Studies: Recombinant IL-18 Rβ is used in structural biology research to elucidate the molecular basis of IL-18 recognition and signaling. These studies often involve recombinant protein for crystallization, binding kinetics, and mutational analyses.

Supporting Details:

• Functional Validation: Studies have shown that recombinant IL-18 Rβ, when combined with IL-18 and IL-18Rα, reconstitutes the signaling complex necessary for immune cell activation, including NK cells and T cells. This is critical for research into cytokine signaling pathways and immune modulation.

• Antibody Engineering: Recombinant IL-18 Rβ is a key reagent in the development and validation of engineered antibodies or cytokine mimetics that target the IL-18 receptor complex, with applications in immunotherapy and cancer research.

• Assay Development: The protein is used as a control or standard in immunoassays to ensure specificity and sensitivity in the detection of IL-18 Rβ, supporting both basic research and clinical assay development.

If you require protocols or technical details for a specific application (e.g., ELISA setup, binding kinetics, or cell-based assays), please specify the intended use.

To reconstitute and prepare Recombinant Human IL-18 Rβ protein for cell culture experiments, follow these general best practices based on standard recombinant protein handling and available protocols:

Reconstitution

1. Centrifuge the Vial: Briefly centrifuge the lyophilized protein vial before opening to ensure all contents are at the bottom.
2. Reconstitution Buffer: Reconstitute the protein in sterile, ice-cold, distilled water or the buffer specified in the product datasheet (often PBS or a similar physiological buffer). For most recombinant proteins, sterile distilled water is suitable unless otherwise indicated.
3. Concentration: Reconstitute to a concentration recommended by the manufacturer (commonly 0.1–0.5 mg/mL or as specified). For example, some protocols suggest reconstituting at 200 μg/mL in PBS.
4. Gentle Mixing: Gently swirl or pipette up and down to dissolve the protein. Avoid vortexing or vigorous pipetting to prevent denaturation or foaming.

Preparation for Cell Culture

1. Aliquot and Store: If not using immediately, aliquot the reconstituted protein and store at ≤ -20°C. Avoid repeated freeze-thaw cycles.
2. Working Dilutions: Dilute the protein in cell culture medium (e.g., RPMI 1640 with 10% fetal bovine serum) to the desired working concentration just before use.
3. Sterility: Ensure all steps are performed under sterile conditions to prevent contamination.

Additional Tips

• Stability: Reconstituted protein can typically be stored at 2–8°C for up to one week, or at ≤ -20°C for longer-term storage (up to 3 months).
• Avoid Foaming: Always avoid foaming during reconstitution and dilution to maintain protein activity.
• Check Datasheet: Always refer to the specific product datasheet for any unique requirements or recommendations.

By following these steps, you can ensure the proper reconstitution and preparation of Recombinant Human IL-18 Rβ protein for your cell culture experiments.