PD-1-expressing MAIT cells from patients with tuberculosis exhibit elevated production of CXCL13

To understand functional role of PD-1-expressing MAIT cells during tuberculosis infection in humans, sorted PD-1(+) and PD-1(-) MAIT cells from pleural effusions of patients with pleural tuberculosis were subjected to transcriptome sequencing. PD-1-expressing MAIT cells were analysed by flow cytometry and their phenotypic and functional features were investigated. Transcriptome sequencing identified 144 genes that were differentially expressed between PD-1(+) and PD-1(-) MAIT cells from tuberculous pleural effusions and CXCL13 was the gene with highest fold difference. The level of PD-1-expressing MAIT cells was associated with extent of TB infection in humans. PD-1-expressing MAIT cells had increased production of CXCL13 and IL-21 as determined by flow cytometry. PD-1(high)CXCR5(-) MAIT cells were significantly expanded in pleural effusions from patients with pleural tuberculosis as compared with those from peripheral blood of both patients with tuberculosis and healthy controls. Although PD-1(high)CXCR5(-) MAIT cells from tuberculous pleural effusions had reduced IFN-gamma level and increased expression of Tim-3 and GITR, they showed activated phenotype and had higher glucose uptake and lipid content. It is concluded that PD-1-expressing MAIT cells had reduced IFN-gamma level but increased production of both CXCL13 and IL-21.