Editing Cytokine (section)

=== Structural ===
Structural homogeneity has been able to partially distinguish between cytokines that do not demonstrate a considerable degree of redundancy so that they can be classified into four types:

*The four-[[Helix bundle|α-helix bundle]] family ({{InterPro|IPR009079}}): member cytokines have three-dimensional structures with a bundle of four [[alpha helix|α-helices]]. This family, in turn, is divided into three sub-families:
# the [[interleukin 2|IL-2]] subfamily. This is the largest family. It contains several non-immunological cytokines including [[erythropoietin]] (EPO) and [[thrombopoietin]] (TPO).<ref>{{cite journal | vauthors = Leonard WJ | title = Cytokines and immunodeficiency diseases | journal = Nature Reviews. Immunology | volume = 1 | issue = 3 | pages = 200–208 | date = December 2001 | pmid = 11905829 | doi = 10.1038/35105066 | url = https://zenodo.org/record/1233113 | s2cid = 5466985 | doi-access = free }}</ref> They can be grouped into ''long-chain'' and ''short-chain'' cytokines by topology.<ref>{{cite journal | vauthors = Rozwarski DA, Gronenborn AM, Clore GM, Bazan JF, Bohm A, Wlodawer A, Hatada M, Karplus PA | title = Structural comparisons among the short-chain helical cytokines | journal = Structure | volume = 2 | issue = 3 | pages = 159–173 | date = March 1994 | pmid = 8069631 | doi = 10.1016/s0969-2126(00)00018-6 | doi-access = free }}</ref> Some members share the [[common gamma chain]] as part of their receptor.<ref>{{cite journal | vauthors = Reche PA | title = The tertiary structure of γc cytokines dictates receptor sharing | journal = Cytokine | volume = 116 | pages = 161–168 | date = April 2019 | pmid = 30716660 | doi = 10.1016/j.cyto.2019.01.007 | s2cid = 73449371 }}</ref>
# the [[interferon|interferon (IFN)]] subfamily.
# the [[interleukin 10|IL-10]] subfamily.
*The [[interleukin 1|IL-1]] family, which primarily includes IL-1 and [[interleukin|IL-18]].
* The [[cysteine knot]] cytokines ({{UniProt|IPR029034}}) include members of the [[transforming growth factor beta superfamily]], including [[TGF beta 1|TGF-β1]], [[TGF beta 2|TGF-β2]] and [[TGF beta 3|TGF-β3]].
* The [[interleukin 17|IL-17]] family, which has yet to be completely characterized, though member cytokines have a specific effect in promoting proliferation of T-cells that have cytotoxic effects.