J McLean

Chromosome localization and gene synteny of the major histocompatibility complex in the owl monkey, Aotus

Rodent cells were hybridized with owl monkey (Aotus) cells of karyotypes II, III, V, and VI. Aotus-rodent somatic hybrid lines preferentially segregating Aotus chromosomes were selected to determine the chromosomal location of the major histocompatibility complex and other genes with which it is syntenic in man. Based on correlation between concordant segregation of the chromosome as visualized by G-banding and expression of the Aotus antigens or enzymes in independent Aotus-rodent hybrid clones, we have assigned Aotus gene loci for the MHC, GLO, ME1, SOD2, and PGM3 to Aotus chromosome 9 of karyotype VI (2n=49/50), chromosome 10 of karyotype V (2n=46), and chromosome 7 of karyotypes II and III (2n = 54 and 53). On the basis of banding patterns we previously postulated that these chromosomes of the different karyotypes were homologous. The gene assignments reported here provide independent evidence for that hypothesis. Aotus chromosomes 9 (K-VI), 10 (K-V), and 7 (K-II, III) are homologous to human chromosome 6 in that they all code for the MHC, GLO, ME1, SOD2, and PGM3. The structural differences between these homologous chromosomes probably resulted from a pericentric inversion.

Analysis of the DRβ chains from two DRw6 cell lines (WT46 and WT52): Recombination in vivo may have generated new haplotypes

The HLA-DRw6 haplotype of the class II major histocompatibility complex (MHC) antigens exhibits unusual complexity and cannot be uniquely typed serologically. The DRβ chains expressed by consanguineous homozygous DRw6 typing cells WT46 and WT52 were biochemically analyzed using three monoclonal antibodies (mAb) that recognize denatured DRβ chains. The results of isoelectric focusing and N-terminal sequencing demonstrate that each DRw6 B-cell line expresses two DRβ chains. Evidence of an exchange of mAb epitopes involving the two DRβ chains of one of these cell lines was obtained and may be explained by a recombinational mechanism involving reciprocal exchange of genetic segments of the DRβ chains, one of which may encode the putative DRw6 chain and the other the chain carrying the MT2 allotypic determinant. Since a recombinational hot spot has been shown to occur uniquely in the mouse MHC within the Eβ gene, the occurrence of a recombination within the human homolog, DR(MT2)β, could reflect some specific feature of this MHC region. Comparison of the DRβ chains of the WT46 and WT52 cell lines with those of a third DRw6 cell line, LB, suggests that two alleles of MT2 occur.

Human T Cell Receptor γδ Structure

A subpopulation of peripheral blood T-lymphocytes exists that is distinct from T cells that express the T cell receptor (TCR) αβ. This population of T cells expresses a receptor composed of TCR γ and TCR δ polypeptides that are associated with CD3 (Brenner et al., 1986). The TCR γ gene (Saito et al., 1984; Quertermous et al., 1986) has been extensively examined and is composed of variable (V), joining (J), and constant (C) region gene segments that undergo somatic rearrangement during development (Hayday et al., 1985).