Interleukin-2 (IL-2) is a member of a cytokine family, each member of which has a four alpha helix bundle; the family also includes IL-4, IL-7, IL-9, IL-15 and IL-21. IL-2 signals through the IL-2 receptor, a complex consisting of three chains, termed alpha (CD25), beta (CD122) and gamma (CD132), which are expressed by lymphocytes. The gamma chain is shared by all family members. It is a 15.5–16 kDa protein that regulates the activities of white blood cells (leukocytes, often lymphocytes) that are responsible for immunity. IL-2 is part of the body’s natural response to microbial infection, and in discriminating between foreign (“non-self”) and “self. IL-2 has essential roles in key functions of the immune system, tolerance and immunity, primarily via its direct effects on T cells. In the thymus, where T cells mature, it prevents autoimmune diseases by promoting the differentiation of certain immature T cells into regulatory T cells, which suppress other T cells that are otherwise primed to attack normal healthy cells in the body. IL-2 enhances activation-induced cell death (AICD). IL-2 also promotes the differentiation of T cells into effector T cells and into memory T cells when the initial T cell is also stimulated by an antigen, thus helping the body fight off infections. Together with other polarizing cytokines, IL-2 stimulates naive CD4+ T cell differentiation into Th1 and Th2 lymphocytes while it impedes differentiation into Th17 and folicular Th lymphocytes.
Protein expression analysis
Strain specific IL2 expression analysis in homozygous B-hIL2 mice by ELISA.
Serum were collected from WT and heterozygous B-hIL2 (H/+) mice stimulated with anti-CD3ε and anti-CD28 in vivo, and analyzed by ELISA with species-specific IL2 ELISA kit. Mouse IL2 was detectable in WT and heterozygous B-hIL2 mice. Human IL2 was exclusively detectable in heterozygous B-hIL2 but not WT mice.