Background: Toll-like receptors (TLRs) have been found to be important pattern recognition receptors that are involved in recognizing components of microbial pathogens and initiating and instructing cutaneous immune responses. Human keratinocytes express a large repertoire of TLRs and functional TLR2, 3, and 4.
Objective: To evaluate the expression of TLR2 in psoriasis.
Patients and methods: The study was carried out on 20 patients with psoriasis vulgaris and 20 healthy controls. One 4-mm punch skin biopsy specimen was taken from every patient and control. Immunohistochemical staining for TLR2 expression was carried out for all the specimens.
Results: TLR2 expression in psoriatic skin was significantly higher in all layers of the epidermis compared with the controls (P<0.01), and their expression in the upper epidermal layers was significantly higher in psoriatic skin compared with that in normal controls (P<0.01). The expression of TLR2 in basal/suprabasal layers was significantly higher in normal skin compared with psoriatic skin (P<0.01). The expression of TLR2 in the dermis of psoriatic skin was significantly higher compared with normal skin (P<0.01).
Conclusion: TLR2 overexpression in psoriatic skin provides new insights into the role of TLR in the pathogenesis of psoriasis, through inappropriate stimulation by infectious or endogenous ligands. Furthermore, TLR2 targeted by specific pharmacologic TLR2 antagonists may offer new therapeutic modalities and preventive approaches for psoriatic patients.