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Oral lichen planus (OLP) is a T cell-mediated immune disorder, and we have indicated a Th1-dominated immune response in OLP. MicroRNA-155 (miR-155) could promote Th1 cells polarization. The present study aims to determine the role of miR-155 in immune response of OLP. The expression of miR-155 and the target mRNA was tested by Real-Time PCR. The serum levels of IL-2, 4, 10 and IFN-γ were examined with ELISA. Furthermore, in vitro study was built to observe the function of miR-155 in erosive-type OLP (EOLP). Finally, we determined the expression and correlation of miR-155 and SOCS1 in EOLP CD4(+) T cells. The results showed miR-155 was high related with the disease severities. Besides, serum IFN-γ was specifically increased in EOLP group, while IL-4 was decreased. In vitro studies showed miR-155 could reinforce IFN-γ signal transducer, and the induction of IFN-γ could also promote miR-155 expression in EOLP CD4(+) T cells. In addition, miR-155 levels were negatively related with SOCS1 mRNA expression in EOLP CD4(+) T cells. Our study revealed a positive miR-155- IFN-γ feedback loop in EOLP CD4(+) T cell, which might contribute to the Th1-dominated immune response. Furthermore, miR-155 could be used for the evaluation and treatment of OLP.

Our previous salivary study had demonstrated an apparent T helper 2 (Th2)-predominance in saliva of oral lichen planus (OLP) patients and suggested a potential of salivary interleukin-4 (IL-4) as a biomarker for monitoring disease severity. To further determine the consistency of Th1/Th2 bias of OLP, this study investigated the expression profile of interferon-γ (IFN-γ) and IL-4 in serum and the relationship of the serum levels of these cytokines with their saliva partners. Sixty ethnic Chinese patients with OLP (40 of the erythematous/ulcerative form and 20 of the reticular form) were recruited for this study, with 40 age-sex-matched healthy volunteers as control group. IFN-γ and IL-4 levels in serum and paired saliva samples were screened by enzyme-linked immunosorbent assay. OLP patient showed a low-level IFN-γ but high-level IL-4 expression profile in both serum and saliva, with a lower IFN-γ/IL-4 ratio. Serum IL-4 level in the erythematous/ulcerative group was significantly higher than that in the reticular group. Serum levels of IFN-γ and IL-4 were significantly and positively correlated with their saliva partners. These results provided more evidence for Th2 cytokine-predominant immune imbalance in OLP, as well as the potential of IL-4 as the biomarker for monitoring severity of OLP.