Elucidating the Characteristics and Functionality of the Mouse Mucosal-Associated Mucosal Invariant T (MAIT) Cell Receptor

Abstract

Mucosal-associated invariant T cells (MAIT) are a subset of invariant, innate-like T-cells that are abundant in the gut lamina propria, kidney, lungs, and peripheral blood. MAIT cells are stimulated by the recognition of microbial vitamin B-derived metabolites by the MHC class I-like molecule, MR1. Recent studies have implicated MAIT cells in several autoimmune diseases, various cancers, and CNS disorders, making it essential to design animal models that replicate the human disease state. The relatively small population of MAIT cells in mice makes it difficult to isolate and characterize them. The MAIT cell receptor (TCR) is comprised of a Vα7.2-Jα33 rearrangement in humans and TRAV1-TRAJ33 in mice. This project aimed to create a tool to study mouse MAIT cells in detail by generating lentiviral plasmid constructs expressing cDNAs encoding the MAIT cell TCR α and β chains that will be ectopically expressed in TCR-deficient mouse T cells. A bulk TCR analysis of the mouse MR1-restricted MAIT hybridomas 6C2 and 8D12 was performed to confirm variable and joining regions in the TCR α and β chains. This analysis confirmed the proper MAIT cell TCR usage in the MAIT cell hybridomas. As both MAIT cell hybridomas can be stimulated by MR1-presented antigens, we obtained synthetic cDNAs that were generated for the TRAV1-TRAJ33 α chain and TRBV8.2 (TRBV13-2) β chain. These were subcloned into GFP- and mCherry-expressing plasmids and packaged into lentiviruses that will be used for transduction of TCR-deficient mouse T cells. Flow cytometry and ELISAs will ultimately be performed to confirm the functional expression of the MAIT cell TCR. These tools will greatly facilitate the investigation of MAIT cell function in vitro and the ultimate generation of retrogenic mice for the tracking of MAIT cells in vivo.