Murine NKT cells can recognize alpha-galactosylceramide (alpha-GalCer) in the context of a class Ib CD1d molecule. Here we show that alpha-GalCer can selectively activate freshly isolated human Valpha24(+)Vbeta11(+) cells, functionally defining the human NKT cells. The naive human NKT cell repertoire consisted of cells expressing an invariant Valpha24JalphaQ chain and a diverse array of beta chains derived from a single Vbeta11 gene segment. Stimulation with alpha-GalCer expanded a polyclonal subset of the human NKT cell repertoire carrying a novel complementarity-determining region (CDR) 3beta consensus motif that may directly interact with the sugar moiety of alpha-GalCer. Our data suggest that certain redundancy is allowed for CDR3beta of NKT antigen receptor to interact with the ligand and provide a first clue to understand the novel protein-carbohydrate interaction mechanisms.

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Human enbryo cells were successively transformed by the Schmidt-Ruppin strain of Rous sarcoma virus (SR-RSV) and simian virus 40 (SV40) in vitro, and the double transformant HuE 13 RS was established. From this cell line the two clonal cell lines RSa and RSb were isolated. In both, presence of SV40 T antigens was demonstrated by the fluorescent antibody technique, and the presence of RSV genomes was verified in one RSb clone by focus formation after fusion with chick embryo cells. Growth of these cells was affected by dibutyryl cAMP without marked morphologic changes. Cells were extremely sensitive to the anticellular action of human leukocyte interferon.

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