Does the toll-like receptor 2 (TLR2) play a role in oral mucosal lichen planus (OMLP)?

Abstract

<h3>Aims</h3> To correlate TLR2 expression with the immunological microcellular environment of oral mucosal lichen planus (OMLP), immune cell surface identification markers (CD3, CD4, CD8, CD19 and CD83) were also studied. <h3>Methodology</h3> 50 FFPE tissue specimens [control group (<i>n</i>=10) and OMLP group (<i>n</i>=40)] were examined for TLR2, CD3, CD4, CD8 CD19 and CD83 expression by immunohistochemistry. In addition, the expression level of 84 human TLR signalling pathway genes in both groups [control group (<i>n</i>=6) and OMLP group (<i>n</i>=6)] was determined in parallel. <h3>Results</h3> CD3⁺, CD4⁺, CD8⁺, CD19⁺and CD83⁺ showed a significantly higher expression of positive cells in OMLP than in the control group (<i>p</i> < 0.05). No TLR2 immunostaining was observed in either group. Twenty TLR signalling pathway genes were expressed significantly in the OMLP group compared to the control group (<i>p</i> < 0.05). Genes that were up-regulated included CXCL10, LTA and IFNG; those down-regulated included HSPD1 and TLR2. <h3>Discussion</h3> Negative TLR2 immunostaining and down-regulation of the TLR2 genes suggests that there was a deactivation of TLR2 receptor. This indicates that OMLP is not associated with host response to pathogens or heat shock protein <i>via</i> TLR2 stimulation of the NF-kβ or JNK/p38 pathways. CD3, CD4 and CD8 positive T cells were the predominant inflammatory cell type in OMLP. High levels of CXCL10, IFNG and LTA cytokines are known to be associated with T cell migration into the developing lesion suggesting that these cytokines play an important role determining the immunological microcellular environment in OMLP.