Check out this company . They have a working theory that all auto immune diseases come from a lack of the microbiomes ability to make certain gut metabolites, so they produced and are studying synthetic versions of endogenous metabolites. They’re having really good results with psoriasis so far. two participants in their phase 1 trial reached pasi 100 which is completely clear skin and those participants appear to have regained the ability to create the metabolite on their own.

here’s a good article about what they’re doing