Mucosal-Associated Invariant T Cells Accumulate in the Lungs during Murine Infection but Are Not Required for Clearance.

is a fungal pathogen that can cause pneumonia in immunosuppressed hosts and subclinical infection in immunocompetent hosts. Mucosal-associated invariant T (MAIT) cells are unconventional lymphocytes with a semi-invariant T-cell receptor that are activated by riboflavin metabolites that are presented by the MHC-1b molecule MR1. Although can presumably synthesize riboflavin metabolites based on whole-genome studies, the role of MAIT cells in controlling infection is unknown. We used a co-housing mouse model of infection, combined with flow cytometry and qPCR, to characterize the response of MAIT cells to infection in C57BL/6 mice, and, using MR1 mice, which lack MAIT cells, to examine their role in clearing the infection. MAIT cells accumulated in the lungs of C57BL/6 mice during infection and remained at increased levels for many weeks after clearance of infection. In MR1 mice, infection was cleared with kinetics similar to C57BL/6 mice. Thus, MAIT cells are not necessary for control of infection, but the prolonged retention of these cells in the lungs following clearance of infection may allow a more rapid future response to other pathogens.