Editing Macrophage (section)

===== Alternative =====
T<sub>H</sub>2 cells play an important role in alternative macrophage activation as part of type 2 immune response against large extracellular pathogens like [[Parasitic worm|helminths]].<ref name="Murphy-2022" /><ref name="Rolot-2018">{{cite journal | vauthors = Rolot M, Dewals BG | title = Macrophage Activation and Functions during Helminth Infection: Recent Advances from the Laboratory Mouse | journal = Journal of Immunology Research | volume = 2018 | pages = 2790627 | date = 2018-07-02 | pmid = 30057915 | pmc = 6051086 | doi = 10.1155/2018/2790627 | doi-access = free }}</ref> T<sub>H</sub>2 cells secrete IL-4 and IL-13, which activate macrophages to become M2 macrophages, also known as alternatively activated macrophages.<ref name="Rolot-2018" /><ref>{{cite journal | vauthors = Gordon S | title = Alternative activation of macrophages | journal = Nature Reviews. Immunology | volume = 3 | issue = 1 | pages = 23–35 | date = January 2003 | pmid = 12511873 | doi = 10.1038/nri978 | s2cid = 23185583 }}</ref> M2 macrophages express [[Arginase|arginase-1]], an enzyme that converts [[arginine]] to [[ornithine]] and [[urea]].<ref name="Rolot-2018" /> Ornithine help increase smooth muscle contraction to expel the worm and also participates in tissue and wound repair. Ornithine can be further metabolized to [[proline]], which is essential for synthesizing [[collagen]].<ref name="Rolot-2018" /> M2 macrophages can also decrease inflammation by producing IL-1 receptor antagonist (IL-1RA) and IL-1 receptors that do not lead to downstream inflammatory signaling (IL-1RII).<ref name="Murphy-2022" /><ref>{{cite journal | vauthors = Peters VA, Joesting JJ, Freund GG | title = IL-1 receptor 2 (IL-1R2) and its role in immune regulation | journal = Brain, Behavior, and Immunity | volume = 32 | pages = 1–8 | date = August 2013 | pmid = 23195532 | pmc = 3610842 | doi = 10.1016/j.bbi.2012.11.006 }}</ref>