Recombinant Mouse CD25/IL-2R alpha Protein, CF

IL-2 receptor alpha (IL-2 R alpha), also known as CD25, is a 55 kDa type I membrane glycoprotein that belongs to the family of cytokine receptors that utilize the common gamma chain subunit ( gamma_c). IL-2 R alpha is primarily expressed on activated T cells and on regulatory T cells (Treg) (1-3). The mouse IL-2 R alpha cDNA encodes a 268 amino acid (aa) precursor that includes a 21 aa signal peptide, a 215 aa extracellular domain (ECD) with two Sushi domains, a 21 aa transmembrane segment, and an 11 aa cytoplasmic domain (4, 5). Within the ECD, mouse IL-2 R alpha shares 81% and 58% aa sequence identity with rat and human IL-2 R alpha, respectively. It shares approximately 15% aa sequence identity with IL-4, -7, -9, -15, and -21 receptor subunits that also complex with gamma_c. IL-2 R beta (CD122) and gamma_c (IL-2 R gamma/CD132) dimerize to form a constitutively expressed intermediate affinity IL-2 receptor (6, 7). By itself, IL-2 R alpha binds IL-2 with low affinity. It associates with IL-2 R beta and gamma_c to generate a ternary high affinity IL-2 receptor complex (8). A soluble form of IL-2 R alpha can be generated by proteolytic cleavage of the cell surface receptor, rendering the T cell unresponsive to IL-2 (9, 10). Increased serum levels of soluble IL-2 R alpha are found in some cancers and immune disorders (11). IL-2 R alpha is required for activation induced cell death (AICD) of naive T cells, a mechanism responsible for deleting autoreactive T cell clones (12, 13). IL-2 R alpha is also required for the development of CD4⁺CD25⁺ Treg which suppress autoreactive CD4⁺ T cells, thereby contributing to peripheral T cell homeostasis (12-14).