Natural killer T cells reactive to a single glycolipid exhibit a highly diverse T cell receptor beta 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. Th ey express an invariant V alpha 14-J alpha 18 T cell receptor (TcR), but th e role of the beta chain has been controversial. Here, we have used CD1d te tramers to identify and isolate NK T cells based on their antigen specifici ty. 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 sel ection for complementarity determining region (CDR) 3 beta sequences in som e anti-peptide responses, a-GalCer-reactive T cells have polyclonal CDR3 be ta 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 recep tor-mediated self-reactivity for tissue-specific CD1d-bound ligands. Each N KT clone is represented by only 5-10 cells. This clone size is similar to n aive conventional T cells, and much lower than that reported for memory T c ells, although NK T cells have an activated/memory phenotype.