Not at all off-topic,
@Mithriel.
I thought the general view was the opposite - that stress compromises the immune system, leaving one more vulnerable to infections. If we are responding to a major threat to our body or life, it would make sense to divert resources from the immune system to the central and autonomic nervous systems to gear up for that "fight or flight". A few people here have talked about how a large acute physical stressor, like moving house or taking a long haul flight, relieves their symptoms. I have experienced this myself following sleep loss related to long haul flights, and my condition is definitely immune-related (I've been diagnosed with an autoinflammatory disease).
I also worry about the word "stress", because it is such a general word. It can slide from grief and despair from the loss of a relationship or loved one, to the experience of being under intense performance pressure, to physical "stressors" such as contracting an infection, incurring an injury, undergoing surgery, etc. These things may challenge - or enhance - the immune system in the same way, but it is also very possible that they do so in very different - and possibly even opposite - ways.
It makes me particularly uncomfortable when people cite evidence from the effects of physical stressors (like surgery, shock therapy, injury, acute overexertion or infection) to argue for a role of psychological stress in illness. There's really no reason to think those two categories are anything the same.
