IL21 Antibodies

Structure of IL21

Interleukin-21 (IL-21) is a cytokine mainly secreted by activated CD4+ T cells and natural killer T cells. Its molecular weight is approximately 15.4 kDa. There are certain differences in the molecular weight and structural characteristics of IL-21 among different species.

The IL-21 protein is composed of approximately 131 amino acids and its three-dimensional structure exhibits a typical short-chain four-α-helix bundle configuration. This structure is stabilized by disulfide bonds between the helix bundles, ensuring a high affinity binding with the receptor complex. The receptor binding site of IL-21 is mainly composed of specific amino acid residues on helices A and C, and these regions show high conservation among different species. The hydrophobic interactions in the core region of the helix bundle are crucial for maintaining the stability of the protein's overall structure, while the polar residues on the surface determine its specific binding to the α chain and common γ chain of the IL-21 receptor.

Fig. 1 IL-21 modulates B cell function.¹

Key structural properties of IL21:

• Typical short-chain cytokine structure consisting of four α-helical bundles
• The hydrophobic core formed by helices A and C is responsible for receptor binding
• Disulfide bonds stabilize the spatial conformation between the helices
• Cysteine residues form intramolecular disulfide bonds to maintain the stability of protein folding
• Specific glutamine and arginine residues determine the binding specificity to the IL-21 receptor α chain

Functions of IL21

The main function of IL-21 is to regulate the activity and differentiation of various immune cells. In addition, it also participates in the regulation of inflammatory responses, antibody production, and anti-tumor immunity, among other physiological processes.

IL-21 mainly binds to the IL-21 receptors expressed on the surface of target cells, activating the JAK-STAT signaling pathway, especially the phosphorylation of STAT3, thereby initiating the transcription of downstream genes.

Applications of IL21 and IL21 Antibody in Literature

1. Asao, Hironobu. "Interleukin-21 in viral infections." International Journal of Molecular Sciences 22.17 (2021): 9521. https://doi.org/10.3390/ijms22179521

The article indicates that IL-21 is mainly produced by CD4⁺ T cells (especially Tfh cells), which can regulate the function of lymphocytes and plays a crucial role in anti-viral and anti-tumor immune responses, especially in chronic viral infections where it can restore the function of exhausted CD8⁺ T cells.

2. Hao, Kangning, et al. "IL21 inhibits miR-361-5p to promote MAP3K9 and further aggravate the progression of shoulder arthritis." Aging (Albany NY) 16.9 (2024): 7915. https://doi.org/10.18632/aging.205793

The article indicates that in shoulder arthritis, IL-21 levels increase while miR-361-5p decreases. The latter targets MAP3K9 and regulates the ERK/NF-κB pathway. IL-21 inhibits miR-361-5p, leading to an increase in MAP3K9, promoting chondrocyte apoptosis and MMP expression, and facilitating the progression of arthritis.

3. Abhiraman, Gita C., et al. "A structural blueprint for interleukin-21 signal modulation." Cell reports 42.6 (2023). https://doi.org/10.1016/j.celrep.2023.112657

The article indicates that by analyzing the structure of the IL-21-receptor complex, researchers designed mutants targeting the interface between IL-21 and the γc subunit. These analogues can act as partial agonists, differently regulating the pSTAT signals in T and B cells, and regulating antibody production in human tonsil organoids, providing a new strategy for precisely regulating humoral immunity.

4. Isvoranu, Gheorghita, and Marioara Chiritoiu-Butnaru. "Therapeutic potential of interleukin-21 in cancer." Frontiers in Immunology 15 (2024): 1369743. https://doi.org/10.3389/fimmu.2024.1369743

The article indicates that IL-21 can activate T cells and NK cells, and plays a crucial role in anti-tumor immunity. Preclinical studies have shown that it is effective when used alone or in combination with monoclonal antibodies, immune checkpoint inhibitors, etc. Clinical trials have also confirmed that IL-21 has anti-tumor effects on advanced cancer patients with few side effects, making it a promising immunotherapy drug.

5. Zeng, Xiandong, et al. "The effects of interleukin-21 in the biology of transplant rejection." Frontiers in Immunology 16 (2025): 1571828. https://doi.org/10.3389/fimmu.2025.1571828

The article indicates that IL-21 is mainly secreted by Tfh cells and can regulate the functions of T and B cells. It also promotes acute and antibody-mediated chronic rejection reactions in organ transplantation. Therefore, targeting the IL-21 signaling pathway is expected to become a new therapeutic strategy for inhibiting rejection reactions and inducing immune tolerance, providing a reference for clinical immunosuppressive regimens.

Creative Biolabs: IL21 Antibodies for Research

Creative Biolabs specializes in the production of high-quality IL21 antibodies for research and industrial applications. Our portfolio includes monoclonal and polyclonal antibodies tailored for ELISA, Flow Cytometry, Western blot, immunohistochemistry, and other diagnostic methodologies.

• Custom IL21 Antibody Development: Tailor-made solutions to meet specific research requirements.
• Bulk Production: Large-scale antibody manufacturing for industry partners.
• Technical Support: Expert consultation for protocol optimization and troubleshooting.
• Aliquoting Services: Conveniently sized aliquots for long-term storage and consistent experimental outcomes.

For more details on our IL21 antibodies, custom preparations, or technical support, contact us at email.