Activation and increased production of interleukin‐17 and tumour necrosis factor‐α of mucosal‐associated invariant T cells in patients with periodontitis

Abstract Aim Mucosal‐associated invariant T (MAIT) cells are known to be resident in oral mucosal tissue, but their roles in periodontitis are unknown. This study aimed to examine the level and function of MAIT cells in periodontitis patients. Materials and Methods Frequency, activation, and function of MAIT cells from 28 periodontitis patients and 28 healthy controls (HCs) were measured by flow cytometry. Results Circulating MAIT cells were numerically reduced in periodontitis patients. Moreover, they exhibited higher expression of CD69 and annexin V, together with more increased production of interleukin (IL)‐17 and tumour necrosis factor (TNF)‐α, in periodontitis patients than in HCs. Interestingly, periodontitis patients had higher frequencies of MAIT cells in gingival tissue than in peripheral blood. In addition, circulating MAIT cells had elevated expression of tissue‐homing chemokine receptors such as CCR6 and CXCR6, and the corresponding chemokines (i.e., CCL20 and CXCL16) were more strongly expressed in inflamed gingiva than in healthy gingiva. Conclusions This study demonstrates that circulating MAIT cells are numerically deficient with an activated profile toward the production of IL‐17 and TNF‐α in periodontitis patients. Furthermore, circulating MAIT cells have the potential to migrate to inflamed gingival tissues.