Mucosal Associated (semi)-invariant T cells (MAIT) are a subset of innate lymphocytes that recognize riboflavin metabolites derived from bacteria and fungi presented on MHC-related protein, MR1. After recognizing MR1-bound ligand, MAIT are activated, secrete Interferon γ (IFNγ), IL-17 and granzyme, and kill bacterially infected cells. Among the many microbes that synthesize riboflavin is Mycobacterium tuberculosis (M. tb), the leading global cause of death due to a bacterial infection.
M. tb infection induces MAIT cell depletion in peripheral blood and enrichment in the lung in experimental mouse models as well as in humans with active Tuberculosis. We hypothesize that the diversity of MAIT cell quantity or function among humans contributes to innate immunity to M. tb infection and can determine progression to microbial clearance, persistence or progression to active disease.
We developed a MAIT assay using A549 lung epithelial adenocarcinoma cell-line incubated with Mycobacterium smegmatis (M. smeg) whole bacteria, supernatant, lysates, as well as a recently characterized MR1 ligand derived from a condensation reaction of riboflavin intermediate, 5-amino-6-(D-ribitylamino)uracil (5-ARU), with the pyruvate derivative, methylglyoxal, in healthy donor peripheral blood mononuclear cells (PBMCs) with no reported exposure to M. tb. MAIT quantity and function was assessed by flow cytometry.
There was inter-individual variability in MAIT number and function among donors. A549 cells incubated with M. smeg whole bacteria, supernatant or lysates produced inefficient activation of MAIT when compared to A549 incubated with 5-ARU/methylglyoxal.
This is a novel MAIT assay that can be used to investigate MAIT cell quantity and function in PBMCs from patients with M. tb. This tool will be used to interrogate the role of MAIT in innate immunity to M. tb in a cohort of healthy Haitian volunteers with varying degrees of M. tb exposure and patients with active disease.
C. K. Vorkas,
J. Aubé, None
D. Fitzgerald, None
M. Glickman, None