{{ infobox .infobox-gene
| gene = IL21
| name = Interleukin 21
| chromosome = 4q27
| ncbi_gene_id = 59067
| ensembl = ENSG00000138618
| uniprot = Q9H0B4
| diseases = Autoimmune Disease, Lymphoma, Neuroinflammation
}}
IL21 (Interleukin 21) is a potent immunomodulatory cytokine belonging to the common gamma-chain receptor family, encoded by the IL21 gene located on chromosome 4q27 1. IL21 is primarily produced by activated CD4+ T cells, particularly T follicular helper (Tfh) cells and natural killer T (NKT) cells 2. This cytokine plays critical roles in regulating adaptive immune responses, including B cell differentiation, T cell proliferation, and cytotoxic NK cell function 3.
IL21 signals through a heterodimeric receptor complex consisting of IL21R (unique chain) and the common gamma chain (γc), which is shared with IL-2, IL-4, IL-7, IL-9, and IL-15 receptors 4. The widespread expression of IL21R on lymphocytes, myeloid cells, and some non-hematopoietic cells enables IL21 to exert diverse biological effects throughout the body.
Beyond its well-established roles in immunity, emerging evidence suggests important functions for IL21 in neuroinflammation and autoimmune diseases of the central nervous system, making it a therapeutic target of significant interest 5.
IL21R is expressed in multiple cell types:
IL21 signaling activates:
IL21 has profound effects on B cells:
IL21 modulates T cell responses:
IL21 enhances NK cell cytotoxicity:
IL21 plays important roles in neuroinflammation:
IL21 is implicated in several autoimmune CNS disorders:
IL21 represents a therapeutic target:
IL21 is implicated in multiple autoimmune conditions:
Dysregulated IL21 signaling contributes to:
IL21 mutations cause:
IL21 levels serve as:
IL21-targeted therapies include:
IL21 is produced by:
IL21R is expressed in: