CDR3β sequence motifs regulate autoreactivity of human invariant MKT cell receptors

Invariant natural killer T (INKT) cells are a subset of T lymphocytes that recognize lipid ligands presented by monomorphic CD1d. Human iNICT T cell receptor (TCR) is largely composed of invariant V alpha 24 (V alpha 24i) TCR alpha chain and semi-variant V beta 11 TCR beta chain, where complementarity-determining region (CDR)3 beta is the sole variable region. One of the characteristic features of iNKT cells is that they retain autoreactivity even after the thymic selection. However, the molecular features of human iNKT TCR CDR3 beta sequences that regulate autoreactivity remain unknown. Since the numbers of iNKT cells with detectable autoreactivity in peripheral blood is limited, we introduced the V alpha 24i gene into peripheral T cells and generated a de novo human iNKT TCR repertoire. By stimulating the transfected T cells with artificial antigen presenting cells (aAPCs) presenting self-ligands, we enriched strongly autoreactive iNKT TCRs and isolated a large panel of human iNKT TCRs with a broad range autoreactivity. From this panel of unique iNKT TCRs, we deciphered three CDR3 beta sequence motifs frequently encoded by strongly-autoreactive iNKT TCRs: a VD region with 2 or more acidic amino acids, usage of the J beta 2-5 allele, and a CDR beta region of 13 amino acids in length. iNKT TCRs encoding 2 or 3 sequence motifs also exhibit higher autoreactivity than those encoding 0 or 1 motifs. These data facilitate our understanding of the molecular basis for human iNKT cell autoreactivity involved in immune responses associated with human disease. (C) 2015 Elsevier Ltd. All rights reserved.