Monthly 3-4 day fasts - combined with a healthy diet in between (Mediterranean for ex) do wonders for autoimmune issues as well.

It was found fasting kills off old immune cells and activates stem cells to make new ones.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7474734/

https://pubmed.ncbi.nlm.nih.gov/31442401/

https://www.nejm.org/doi/10.1056/NEJMra1905136

http://www.cell.com/cell-stem-cell/abstract/S1934-5909(14)00...

In plain English

https://www.forbes.com/sites/stevensalzberg/2014/12/30/can-a...

https://www.medicalnewstoday.com/articles/277860#In-mice,-pr...