Increased pathogenicity and pro-inflammatory capabilities of mucosal-associated invariant T cells involved in Oral Lichen Planus.

Background: Mucosal-associated invariant T (MAIT) cells assume pivotal roles in numerous autoimmune inflammatory maladies. However, scant knowledge exists regarding their involvement in the pathological progression of oral lichen planus (OLP). The focus of our study was to explore whether MAIT cells were altered across distinct clinical types of OLP.

Methods: The frequency, phenotype, and partial functions of MAIT cells were performed by flow cytometry, using peripheral blood from 18 adults with non-erosive OLP and 22 adults with erosive OLP compared with 15 healthy adults. We also studied the changes in MAIT cells in 15 OLP patients receiving and 10 not receiving corticosteroids. Surface proteins including CD4, CD8, CD69, CD103, CD38, HLA-DR, Tim-3, Programmed Death Molecule-1 (PD-1), and related factors released by MAIT cells such as Granzyme B (GzB), interferon (IFN)-γ, tumour necrosis factor (TNF)-α, interleukin (IL)-17A, and IL-22 were detected.

Results: Within non-erosive OLP patients, MAIT cells manifested an activated phenotype, evident in an elevated frequency of CD69 CD38 MAIT cells (p < 0.01). Conversely, erosive OLP patients displayed an activation and depletion phenotype in MAIT cells, typified by elevated CD69 (p < 0.01), CD103 (p < 0.05), and PD-1 expression (p < 0.01). Additionally, MAIT cells exhibited heightened cytokine production, encompassing GzB, IFN-γ, and IL-17A in erosive OLP patients. Notably, the proportion of CD103 MAIT cells (p < 0.05) and GzB secretion (p < 0.01) by MAIT cells diminished, while the proportion of CD8 MAIT cells (p < 0.05) rose in OLP patients with corticosteroid therapy.

Conclusions: MAIT cells exhibit increased pathogenicity and pro-inflammatory capabilities in OLP. Corticosteroid therapy influences the expression of certain phenotypes and functions of MAIT cells in the peripheral blood of OLP patients.