Characterization of MAIT TCR repertoire of gastrointestinal tract and peripheral blood MAIT cells

Mucosal-associated invariant T (MAIT) cells are an innate-like T cell that rapidly respond to infection. MAIT cells are αβ T cells that possess a Vα7.2 (TRAV1-2) TCR with mostly pairing to TRAJ33, TRAJ20 or TRAJ12 and predominantly TRBV20-1, TRBV6-1 and TRBV6-4. MAIT T cell receptors (TCR) repertoire have been previously studied in peripheral blood. However, data on MAIT TCR repertoire in gastrointestinal tract are lacking. We studied 2 individuals who are underwent esophagogastroduodenoscopy (EGD) and colonoscopy. Blood and biopsies were obtained. PBMCs were isolated from blood and LPLs were isolated from biopsies. Due to the low number of MAIT cells in each gastrointestinal tract site and being insufficient for experiments, we proliferated MAIT cells to increase MAIT cell population. Our results show that MAIT cells can proliferate in vitro. We mostly found TRAJ33 followed by TRAJ20, TRAJ12 that contained Tyr95, which necessary for interaction with antigens and TRAJ30 and TRAJ36, which contained Arg95 and Asn95 that also interact with antigens. Moreover, most TRBV gene usage in every site were TRBV6-4 and TRBV20-1. There were overlapping and non-overlapping TRBV gene usage in each site. The TRBV in ileum of both patients was the most diverse. We may concluded that MAIT TCR repertoire in mucosal was more diverse than peripheral and the result of MAIT TCR repertoire may concluded that MAIT TCR repertoire are associate with bacterial selection. However, the study of vitamin B metabolite synthesis bacteria may be help us to more understand MAIT TCR selection.