Immunohistochemical study of toll-like receptors 2, 4, and 9 expressions in pemphigus and bullous pemphigoid lesions.

Pemphigus and bullous pemphigoid (BP) are severe autoimmune skin diseases. Whether innate immunity could be a trigger or a part of the pathogeneses is unknown. Toll-like receptors (TLRs) are important components of the innate immune system, with no previous evaluation of TLRs in autoimmune bullous diseases. This work aims to investigate TLRs 2, 4, and 9 expressions in pemphigus and bullous pemphigoid. Thirty-six patients with pemphigus vulgaris (PV), pemphigus foliaceus (PF), bullous pemphigoid (BP), and six healthy controls were studied. Skin biopsies from the patients and the controls were examined immunohistochemically for TLR2, 4, and 9 expressions. The TLR4 expressed mainly at the basal layer of epidermis in controls, but in the cases with autoimmune bullous diseases, TLR4 staining located at basal layer and suprabasal layer, even superficial layer of epidermis. The immunostaining-intensity-distribution (IID) index of TLR4 in patients with PF (13.83, P = 0.001), PV (13.08, P = 0.003), and BP (11.42, P = 0.042) were significantly higher than that of the controls (6.17). TLR2 and TLR9 showed no significantly changes at epidermal expression (P > 0.05) compared with controls. There was no correlation found between the expressions of these TLRs. This work, thus, shows a re-localization of TLR4 expression sites with increased expression in pemphigus and bullous pemphigoid lesions. Targeting TLR4 signaling is expected to be a novel treatment strategy for autoimmune bullous diseases.