Editing Interleukin 2 (section)

== Function ==

IL-2 has essential roles in key functions of the immune system, [[Central tolerance|tolerance]] and [[Immunity (medical)|immunity]], primarily via its direct effects on [[T cells]]. In the [[thymus]], where T cells mature, it prevents [[autoimmune diseases]] by promoting the [[Cellular differentiation|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|activation-induced cell death (AICD)]].<ref name=":0" /> 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.<ref name="Liao_2011"/> Together with other polarizing cytokines, IL-2 stimulates naive CD4<sup>+</sup> T cell differentiation into [[Th1 cell|T<sub>h</sub>1]] and [[Th2 cell|T<sub>h</sub>2]] lymphocytes while it impedes differentiation into [[T helper 17 cell|T<sub>h</sub>17]] and folicular T<sub>h</sub> lymphocytes.<ref>{{cite journal | vauthors = Liao W, Lin JX, Leonard WJ | title = Interleukin-2 at the crossroads of effector responses, tolerance, and immunotherapy | journal = Immunity | volume = 38 | issue = 1 | pages = 13–25 | date = January 2013 | pmid = 23352221 | doi = 10.1016/j.immuni.2013.01.004 | pmc = 3610532 }}</ref><ref name="pmid30089912">{{cite journal | vauthors = Spolski R, Li P, Leonard WJ | title = Biology and regulation of IL-2: from molecular mechanisms to human therapy | journal = [[Nature Reviews Immunology]] | volume = 18 | issue=10 | pages = 648–659 |date=2018 | doi = 10.1038/s41577-018-0046-y | pmid = 30089912| s2cid = 51939991 }}</ref>

IL-2 increases the cell killing activity of both [[natural killer cell]]s and [[cytotoxic T cell]]s.<ref name="pmid30089912" />

Its expression and secretion is tightly regulated and functions as part of both transient positive and negative [[Feedback#Biology|feedback loops]] in mounting and dampening immune responses. Through its role in the development of T cell immunologic memory, which depends upon the expansion of the number and function of antigen-selected T cell clones, it plays a key role in enduring [[cell-mediated immunity]].<ref name="Liao_2011" /><ref name="Malek_2010">{{cite journal | vauthors = Malek TR, Castro I | title = Interleukin-2 receptor signaling: at the interface between tolerance and immunity | journal = Immunity | volume = 33 | issue = 2 | pages = 153–65 | date = August 2010 | pmid = 20732639 | pmc = 2946796 | doi = 10.1016/j.immuni.2010.08.004 }}</ref>