Dual regulation of IRF4 function in T and B cells is required for the coordination of T-B cell interactions and the prevention of autoimmunity.
Authors: Biswas PS, Gupta S, Stirzaker RA
J. Exp. Med., 2012;209(3):581-96.
Species: Mouse
Sample Type: Whole Cells
Application: Flow
IL-21 is highly produced in Helicobacter pylori-infected gastric mucosa and promotes gelatinases synthesis.
Authors: Caruso R, Fina D, Peluso I, Fantini MC, Tosti C, Del Vecchio Blanco G, Paoluzi OA, Caprioli F, Andrei F, Stolfi C, Romano M, Ricci V, MacDonald TT, Pallone F, Monteleone G
J. Immunol., 2007;178(9):5957-65.
Species: Human
Sample Type: Whole Cells
Application: Flow

IL-21 R (interleukin-21 receptor) is a type I transmembrane glycoprotein within the class I cytokine receptor family, type 4 subfamily (1-5). Complex formation between IL-21 R and the common gamma  chain ( gamma _c), also used for IL-2, IL-4, IL-7, IL-9, IL-13 and IL-15 receptors, is required for signaling (6, 7). Mouse IL-21 R cDNA encodes 521 amino acid (aa) including a 19 aa signal peptide, a 218 aa extracellular domain (ECD) with 4 conserved cysteine residues, a fibronectin type III domain, and a WSXWS motif, a 21 aa transmembrane domain and a 271 aa cytoplasmic domain with a Box 1 motif, a kinase domain, and several sites for tyrosine phosphorylation (4, 5). One such site, pY510, mediates STAT binding (1, 2). The mouse IL-21 R ECD shares 69%, 91%, 65%, 63% and 58% aa identity with human, rat, equine, canine and bovine IL-21 R, respectively. One potential 447 aa isoform, with an alternate start site at aa 83, lacks the four conserved ECD cysteines. IL‑21 R is expressed mainly on B cells (highest on mature, activated, follicular and germinal center B cells), NK cells, and activated T cells, but is also found on dendritic cells, alternatively activated macrophages, intestinal lamina propria fibroblasts and epithelial cells, and keratinocytes (1, 3-5). Both IL-21 and IL-4 are necessary for efficient B cell IgG₁ production and normal germinal center architecture (8). B cell IL-21 R engagement induces BLIMP-1 (which mediates plasma cell differentiation), and is important for memory responses (1, 9, 10).  IL-21 R engagement on mouse NK cells enhances their cytotoxic activity and IFN-gamma production (4, 11). IL‑21 R engagement on CD8⁺ T cells aids control of viral infection and tumor growth; IL-21 R is also necessary for sufficient numbers of regulatory T cells to combat chronic inflammation (1, 12, 13). IL-21 R expression is often upregulated in allergic skin inflammation, systemic lupus erythematosus and diffuse large B cell lymphoma (DLBCL) (1, 2, 14, 15).

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