The H2-T23 locus of the Major Histocompatibility Complex encodes the class Ib Qa-1 antigen. The T23 locus is oligomorphic, with two main families, Qa-1a and Qa-1b. Sequencing of H2-T23 (encoding Qa-1d) indicates that it is more similar to Qa-1b. Unlike class Ia genes, exons 2 and 3 of H2-T23 are not under positive evolutionary selection, implying that Qa-1 is specialized to present a limited class of ligands. The predominant ligand of Qa-1 is a peptide called Qdm, which derives from the leader sequences of the class la H2-D and -L molecules. Anti-Qa-1 CTL are oligoclonal in T cell receptor (TCR) usage. TCRβ chain genes are predominated by Vb5.1, Vb5.2, and Vb8.2. One third of the clones contain Jb2.6 gene segments, and overall, more Jb2 segments are seen than Jb1 segments. TCRa chain genes preferentially use Va1 and Va8. CDR3 lengths of TCRβ chains are approximately twice that for TCRα chains, and Qa-1-restricted CTL have TCRβ CDR3 regions which contain at least one acidic, basic or Gly residue. No preferences were observed in TCRβ gene usage in clones recognizing different Qa-1 alleles or Qa-1 restricted peptides. In contrast, a majority of Qdm-independent CTL use Va1 and Va8, while Qdm-dependent CTL tend to use Va3 and Va4.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Molecular Biology