I know, which seems to outrule any direct benefit to the immune system, except as you pointed out through improving gut health which I can only find a rat study on.
I'll leave it at that, I more or less copypasta'd the section from aragon's work to give a complete review, I'm interested in jacked fibahs as opposed to general health. If you want to argue that the two are related we may as well suggest a fibre supplement for muscle gain while we're at it.