IDENTIFICATION OF A RECOMBINOGENIC MAJOR HISTOCOMPATIBILITY COMPLEX Q-GENE WITH DIVERSE ALLELES

Structural diversity enables class la molecules to present a diverse r epertoire of peptides to the T cell receptor. This diversity is though t to be generated by recombinations between class I genes. We have fou nd that two class Ib Q2 alleles exhibit extremely high sequence divers ity, even higher than class Ia alleles. Clustered nucleotide differenc es between Q2b and Q2k suggest that this sequence diversity was genera ted by microrecombinations between Q2 genes and other class I genes. T he relatively high expression of Q2b in the thymus may be significant and perhaps suggests a novel role for a Q2b product in the education a nd selection of the T cell repertoire.