system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does Sjogren's (an autoimmune disease) cause damage?

Sjogren's is an autoimmune disease.  The body attacks the saliva and tear glands, resulting in reduced secretions.

How does the damage happen?
gpt
The immune system is really very violent. All it is capable of doing is killing things, and it won't hesitate to kill other cells of the body if doing so will fight a perceived threat. In fact, its basic response to viral infections is just to kill every host cell that's been infected, which is the body's equivalent of treating a plague by nuking the city its in. The immune system causes damage to the body when it finds something that it incorrectly identifies as being hostile. Unfortunately, it's not currently known exactly what causes the immune cells to do that in Sjogren's disease. It seems to be thought so far that it happens when something about the glands prompts an inflammation response it shouldn't normally have, so a mutated protein somewhere in that extremely complicated chain of activity that breaks the message in some way, recruiting immune cells to the glands when they're not necessary or keeping them around long after an infection is over.