Mucosal-associated invariant T (MAIT) TCR repertoire. Homo sapiens

Mucosal-associated invariant T (MAIT) cells are a T cell subset that expresses a conserved TRAV1-2 (Vα7.2) -T cell receptor (TCR) chain and the surface marker CD161. They are involved in the defence against microbes as they recognize small organic molecules of microbial origin that are presented by the non-classical MHC molecule MR1. MAIT cells express a restricted TCR repertoire with an α chain consisting of TRAV1-2 linked to TRAJ33 (Jα33), TRAJ12 (Jα12), or TRAJ20 (Jα20) which pairs with a limited set of β chains predominated by TRBV6 (Vβ13), and TRBV20-1 (Vβ2). The TRAJ- and TRBV-usage is, however, not completely exclusive and the repertoire of the non-preferred TCR αβ chains has not been studied in great detail so far. It is in particular not known whether there is a sharp border in TCR usage between MAIT cells and classical MHC class-I restricted CD8αβ+ T cells. Here we analysed the TRAV1-2 repertoires of human CD161+TRAV1-2+ T cells TRAV1-2 and their paired β chains by pyrosequencing and the pairing preferences between α and β chains by analysing 132 single T cells. We found that the CD161+TRAV1-2+ TCR repertoire in addition to the typical MAIT TCRs further contains polyclonal elements reminiscent of classical αβ T cells. This might have consequences for antigen recognition and function in health and disease.