Mucosal-Associated Invariant T Cells And V Delta 2(+) Gamma Delta T Cells In Community Acquired Pneumonia: Association Of Abundance In Sputum With Clinical Severity And Outcome

Mucosal-associated invariant T (MAIT) cells and V delta 2(+) gamma delta T cells are anti-bacterial innate-like lymphocytes (ILLs) that are enriched in blood and mucosa. ILLs have been implicated in control of infection. However, the role of ILLs in community-acquired pneumonia (CAP) is unknown. Using sputum samples from a well-characterized CAP cohort, MAIT cell and V delta 2(+) T cell abundance was determined by quantitative polymerase chain reaction (qPCR). Cytokine and chemokine concentrations in sputum were measured. The capacity of bacteria in sputum to produce activating ligands for MAIT cells and V delta 2(+) T cells was inferred by 16S rRNA sequencing. MAIT cell abundance in sputum was higher in patients with less severe pneumonia; duration of hospital admission was inversely correlated with both MAIT and V delta 2(+) T cell abundance. The abundance of both ILLs was higher in patients with a confirmed bacterial aetiology; however, there was no correlation with total bacterial load or the predicted capacity of bacteria to produce activating ligands. Sputum MAIT cell abundance was associated with interferon (IFN)-alpha, IFN-gamma, and sputum neutrophil abundance, while V delta 2(+) T cell abundance was associated with CXCL11 and IFN-gamma. Therefore, MAIT and V delta 2(+) T cells can be detected in sputum in CAP, where they may contribute to improved clinical outcome.