External inflammatory stimulation leads to the activation of TLR4, which induces the phosphorylation of NF-κB and the release of IL-1β, IL-6, TNF-α to induce the immune response and inflammation, which may also be an important mechanism by which TLR4 is involved in the pathogenesis of PF (44, 45). Here, TNF is linked to pemphigus foliaceus.