Editing Autoimmunity (section)

==== Infectious diseases and parasites ====
An interesting inverse relationship exists between infectious diseases and autoimmune diseases. In areas where multiple infectious diseases are endemic, autoimmune diseases are quite rarely seen. The reverse, to some extent, seems to hold true. The [[hygiene hypothesis]] attributes these correlations to the immune-manipulating strategies of pathogens. While such an observation has been variously termed as spurious and ineffective, according to some studies, parasite infection is associated with reduced activity of autoimmune disease.<ref>{{cite journal | vauthors = Saunders KA, Raine T, Cooke A, Lawrence CE | title = Inhibition of autoimmune type 1 diabetes by gastrointestinal helminth infection | journal = Infection and Immunity | volume = 75 | issue = 1 | pages = 397–407 | date = January 2007 | pmid = 17043101 | pmc = 1828378 | doi = 10.1128/IAI.00664-06 }}</ref><ref>{{cite web|url=https://www.sciencedaily.com/releases/2007/01/070117091058.htm|title=Parasite Infection May Benefit Multiple Sclerosis Patients<!-- Bot generated title -->|work=sciencedaily.com}}</ref><ref>{{cite journal | vauthors = Wållberg M, Harris RA | title = Co-infection with Trypanosoma brucei brucei prevents experimental autoimmune encephalomyelitis in DBA/1 mice through induction of suppressor APCs | journal = International Immunology | volume = 17 | issue = 6 | pages = 721–728 | date = June 2005 | pmid = 15899926 | doi = 10.1093/intimm/dxh253 | doi-access = free }}</ref>

The putative mechanism is that the parasite attenuates the host immune response in order to protect itself.  This may provide a serendipitous benefit to a host that also has autoimmune disease. The  details of parasite immune modulation are not yet known, but may include secretion of anti-inflammatory agents or interference with the host immune signaling.

A paradoxical observation has been the strong association of certain microbial organisms with autoimmune diseases.
For example, ''[[Klebsiella pneumoniae]]'' and [[Coxsackie B|coxsackievirus B]] have been strongly correlated with [[ankylosing spondylitis]] and [[diabetes mellitus type 1]], respectively. This has been explained by the tendency of the infecting organism to produce [[super-antigens]] that are capable of [[Polyclonal antibodies|polyclonal]] activation of [[B-lymphocytes]], and production of large amounts of antibodies of varying specificities, some of which may be self-reactive (see below).