Does anyone with any understanding of field believe that immune system issues just appear out of no where without an underlying trigger? The fire fighter analog

Does anyone with any understanding of field believe that immune system issues just appear out of no where without an underlying trigger? The fire fighter analogy does not match my understanding. But even if we go with the fire fighter analogy, how is it any different from say, liver disease? Usually the trigger is something else, like drinking too much, and your liver is like a firefighter, trying to fix the issue, but it's still called liver disease. In fact it's more apt because the liver won't directly attack other tissues when it fails, unlike the immune system.