<story><title>Adult immune systems ‘remember’ germs to which they’ve never been exposed (2013)</title><url>https://med.stanford.edu/news/all-news/2013/02/immune-systems-of-healthy-adults-remember-germs-to-which-theyve-never-been-exposed-stanford-study-finds.html</url></story><parent_chain><item><author>hirundo</author><text>&amp;quot;...memory CD4s proliferated and otherwise became activated in response to exposure to certain components of the influenza virus, but also to epitopes of several different bacterial and protozoan microbes. This cross-reactivity could explain why exposure to common bugs in the dirt and in our homes renders us less susceptible to dangerous infectious agents.&amp;quot;&lt;p&gt;So the CD4 is a key activated to fit a particular lock, but given the imperfections of locks it fits a random assortment of others too. As we build up a keychain of these we have a better chance to fit any random lock.&lt;p&gt;But why doesn&amp;#x27;t the larger keychain also increase the chances of auto-immune diseases when they happen to fit our own locks? Or increase inflammation from other benign microbes it fits? Seems like the metaphor needs work.</text></item></parent_chain><comment><author>nullc</author><text>&amp;gt; But why doesn&amp;#x27;t the larger keychain also increase the chances of auto-immune diseases, when they happen to fit our own locks?&lt;p&gt;The process that generates immune cells tests them for autoimmune reactivity and aggressively culls ones that are.</text></comment>
<story><title>Adult immune systems ‘remember’ germs to which they’ve never been exposed (2013)</title><url>https://med.stanford.edu/news/all-news/2013/02/immune-systems-of-healthy-adults-remember-germs-to-which-theyve-never-been-exposed-stanford-study-finds.html</url></story><parent_chain><item><author>hirundo</author><text>&amp;quot;...memory CD4s proliferated and otherwise became activated in response to exposure to certain components of the influenza virus, but also to epitopes of several different bacterial and protozoan microbes. This cross-reactivity could explain why exposure to common bugs in the dirt and in our homes renders us less susceptible to dangerous infectious agents.&amp;quot;&lt;p&gt;So the CD4 is a key activated to fit a particular lock, but given the imperfections of locks it fits a random assortment of others too. As we build up a keychain of these we have a better chance to fit any random lock.&lt;p&gt;But why doesn&amp;#x27;t the larger keychain also increase the chances of auto-immune diseases when they happen to fit our own locks? Or increase inflammation from other benign microbes it fits? Seems like the metaphor needs work.</text></item></parent_chain><comment><author>three_seagrass</author><text>You do get autoimmune diseases this way.&lt;p&gt;The thyroid does a good job of filtering out new immune cells that attack the body, but sometimes you will get an infection where the targeted protein mimics a body protein.  When that happens, you&amp;#x27;re stuck with an autoimmune disease.&lt;p&gt;Example: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Reactive_arthritis&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Reactive_arthritis&lt;/a&gt;</text></comment>