Natural killer T cells reactive to a single glycolipid exhibit a highly diverse T cell receptor β repertoire and small clone size

CD1d-restricted natural killer (NK) T cells reactive with the glycolipid a-galactosylceramide (alpha -GalCer) are a distinct lymphocyte sublineage. They express an invariant V alpha 14-J alpha 18 T cell receptor (TcR), but the role of the beta chain has been controversial. Here, we have used CD1d tetramers to identify and isolate NK T cells based on their antigen specificity. In mice lacking germline V beta8, most of the alpha -GalCer-reactive T cells express either V beta2 or V beta7, strong VP selection being revealed by the lack of an increase in other V beta regions. By contrast to the selection for complementarity determining region (CDR) 3 beta sequences in some anti-peptide responses, a-GalCer-reactive T cells have polyclonal CDR3 beta sequences. There is little CDR3 beta sequence redundancy between organs or individual mice, and, surprisingly, there also is no evidence for organ-specific CDR3 beta sequence motifs. These data argue against a T cell receptor-mediated self-reactivity for tissue-specific CD1d-bound ligands. Each NKT clone is represented by only 5-10 cells. This clone size is similar to naive conventional T cells, and much lower than that reported for memory T cells, although NK T cells have an activated/memory phenotype.