However, it is not known whether tannic acid (TA), a verified PDI inhibitor with outstanding anti-inflammatory effects, could alleviate autoimmune diseases.<h4>Objective</h4>We set out to explore the anti-inflammatory mechanism of TA and whether it could be used to treat the classical autoimmune disease, psoriasis.<h4>Methods</h4>Molecular interactions were assessed using insulin reduction assays with full-length PDI and its domain fragments to identify TA binding sites. Here, P4HB is linked to autoimmune disease.