Personal anecdote, I was looking up whether to stop occasional cannabis usage as a precaution for a while because it has been labelled an immunosuppressant and an immunomodulator. I don't understand enough of the science to decide, so I'm stopping, but what I saw in those papers suggested that it is good at preventing autoimmune diseases from getting out of hand. Any expert knowledge/opinion very welcome, as many people have access to this drug already.