The aryl hydrocarbon receptor (AhR), which is key to this discovery, appears to be super relevant to psoriasis, another autoimmune disease.
AhR has been known for a long time, but it seems it's been somewhat mysterious until a series of recent breakthroughs. In 2022, an AhR inhibitor called tapinarof, sold as VTAMA, was launched, and has shown itself to be one of the most effective treatments for psoriasis to date. It's also unique in that it appears to have the ability to bring lasting remission. In the main clinical trial, patients who used VTAMA for one year and then stopped had a mean remission duration of 4 months until their psoriasis returned. That is unheard of for any topical medication used on psoriasis.
Blocking AhR has also shown promise in treating MS [1].
I haven't read the lupus paper, but often with papers like these, the "cause" turns out not to be the actual origin, but some cytokine or other protein that is more disease-specific than current drug targets. This lupus discovery appears to identify an imbalance that may be compensated for, but we still don't know what triggers the imbalance in the first place.
In some cases diseases turn out to be a genetic fault, but my money is on pathogens acting as the initial triggering event, which then spins the immune system into a vicious cycle of autoimmunity. In psoriasis we see this with strep bacteria, for example, but the exact mechanisms are not well understood. However, the mechanism that makes psoriasis chronic has been identified, a type of T-cell called a tissue-resident memory (TRM) T-cell. This type of cell acts as a kind of biological memory for infections.
[1] https://newsroom.uvahealth.com/2023/02/15/multiple-sclerosis...