[Methods of studying T-lymphocyte repertoires].
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Biomedical subjects
N Fazilleau
Publications and source records attributed to N Fazilleau.
Most alpha/beta T cell receptor diversity is due to terminal deoxynucleotidyl transferase.
The contribution of template-independent nucleotide addition to antigen receptor diversity is unknown. We therefore determined the size of the T cell receptor (TCR)alpha/beta repertoire in mice bearing a null mutation on both alleles of the terminal deoxynucleotidyl transferase (Tdt) gene. We used a method based upon polymerase chain reaction amplification and exhaustive sequencing of various AV-AJ and BV-BJ combinations. In both wild-type and Tdt degrees / degrees mice, TCRAV diversity is one order of magnitude lower than the TCRBV diversity. In Tdt degrees / degrees animals, TCRBV chain diversity is reduced 10-fold compared with wild-type mice. In addition, in Tdt degrees / degrees mice, one BV chain can associate with three to four AV chains as in wild-type mice. The alpha/beta repertoire size in Tdt degrees / degrees mice is estimated to be 10(5) distinct receptors, approximately 5-10% of that calculated for wild-type mice. Thus, while Tdt activity is not involved in the combinatorial diversity resulting from alpha/beta pairing, it contributes to at least 90% of TCRalpha/beta diversity.
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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 alpha-galactosylceramide (alpha-GalCer) are a distinct lymphocyte sublineage. They express an invariant Valpha14-Jalpha18 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 Vbeta8, most of the alpha-GalCer-reactive T cells express either Vbeta2 or Vbeta7, strong Vbeta selection being revealed by the lack of an increase in other Vbeta regions. By contrast to the selection for complementarity determining region (CDR) 3beta sequences in some anti-peptide responses, alpha-GalCer-reactive T cells have polyclonal CDR3beta sequences. There is little CDR3beta sequence redundancy between organs or individual mice, and, surprisingly, there also is no evidence for organ-specific CDR3beta 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.
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Self peptides and the peptidic self.
Twenty years ago, antigenic and self peptides presented by MHC molecules were absent from the immunological scene. While foreign peptides could be assayed by immune reactions, self peptides, as elusive and invisible as they were at the time, were bound to have an immunological role. How self peptides are selected and presented by MHC molecules, and how self MHC-peptide complexes are seen or not seen by T cells raised multiple questions particularly related to MHC restriction, alloreactivity, positive and negative selection, the nature of tumor antigens and tolerance. These issues were addressed in the "peptiditic self model" (1986) and subsequent hypothesis. They are retrospectively and critically reviewed here in the context of our current understanding of these major immunological phenomena.
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