P6‐31: CD4+ MAIT cells in blood of patients may enhanced anti‐tuberculosis function by increasing IFN‐Γ and granzyme b production

Background and Aims: Mucosal-associated invariant T (MAIT) cells were reported to play a role in antituberculosis (TB) immunity. However, the function of CD4 MAIT cells was unclear for their low abundance. In the present study, the frequency and function of Mycobacteria tuberculosis (Mtb)-specific CD4 MAIT cells in patients with pulmonary tuberculosis (PTB) were explored. Methods: Patients with newly diagnosed active PTB and matched healthy controls (HCs) were enrolled, blood samples were collected, and then the frequency of Mtb-specific CD4 MAIT cells and CD69, CD223, IFN-γ, granzyme B expression on them were investigated by flow cytometry. Some patients were followed up after about 6 months of effective anti-TB treatment, and the changes were compared before and after the treatment. Results and Conclusions: The frequency of CD4 MAIT cells was increased in blood of PTB patients (n= 193) compared with that in HCs (n= 30) (P= 0.017), and significantly decreased after treatment (n= 13) (P= 0.041). It was also observed a significantly increased expression of CD69 and a decrease of CD223 in CD4 MAIT cells from PTB patients compared to HCs, while CD69 expression on CD4 MAIT cells decreased and CD223 expression increased in PTB patients after treatment (P< 0.05, both). Both IFN-γ and granzyme B expression on CD4 MAIT cells were increased in PTB patients compared to HCs and decreased after treatment (P< 0.05, both). Thus, increased CD4 MAIT cells in PTB patients may play a role in anti-tuberculosis immunity by increasing IFN-γ and granzyme B production.