Background: A role for the innate immune system in driving the autoimmune T cell cascade in psoriasis has been proposed. Toll-like receptors-(TLR)-2 and -4 play a role in inflammation, atherosclerosis, and their specific role in psoriasis remains unclear.
Objective: To evaluate TLR2 and TLR4 gene expression levels in peripheral blood mononuclear cells from psoriatic patients.
Methods: Changes in TLR2 ⁄ 4 gene expressions were evaluated using quantitative real-time reverse transcription polymerase chain reaction in peripheral blood mononuclear cells, from twenty-one patients with severe psoriasis, and analysed whether there was any correlation with cytokine plasma levels (T-helper 0-, T-helper 1-, T-helper 2- or regulatory T cells-type), or Calprotectin and with S100A8 and S100A9 gene expression levels. Eleven non-psoriatic healthy controls were analysed.
Results: A clear increase in TLR4 gene expression was observed (3.84 ± 0.93, n = 21) together with a moderate increase in TLR2 expression (1.522 ± 0.31, n = 21). Both TLR4 and TLR2 gene expressions were significantly augmented in psoriatic patients compared with controls (all P < 0.001). Correlations between TLR2 and S100A9 gene expressions (r = 0.5145, P = 0.0170, n = 21); and between TLR2 expression and plasma interleukin-2 (r = 0.5667, P = 0.0074); interleukin-4 (r = 0.4766, P = 0.0289), interleukin-10 (r = 0.4355, P = 0.0484) and interleukin-13 (r = 0.4603, P = 0.0358), were found. When patients with atheroma plaque were considered (n = 7), both TLR4 (3.47 ± 0.99, P = 0.0156) and TLR2 (1.63 ± 0.31, P = 0.0156) expressions were significantly increased vs. controls and correlated with plasma TNF-a (r = 0.8929, P = 0.0123, in both cases).
Conclusion: Differential TLR4 ⁄ 2 gene expressions on psoriatic peripheral blood mononuclear cells and correlations with regulatory and ⁄ or proinflammatory cytokines and ⁄ or damage-associated molecular pattern molecule S100A9 emphasize innate immune response role in psoriasis.