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Biomedical subjects

M Ellexson

Publications and source records attributed to M Ellexson.

7 recordsLinked to original sources
PubMed1997

Polymorphism at codons 114, 116, 145, and 163 muddle the typing of HLA-B*1304.

Genetic exchanges often muddle the typing of HLA class I molecules, this is also the case for HLA-B*1304. Serologic and molecular DNA class I typing report a B15/B55 type for cell 847, whereas DNA sequencing finds B*5501/B*1304. HLA-B*1304 differs by no more than four amino acids from other HLA-B13 molecules, a comparative analysis of the B13 and B15 families was therefore performed to determine why serologic and molecular DNA approaches report a B15 type for B*1304. Comparisons demonstrate that limited differences individuate the B15 and B13 molecules such that the genetic recombination of codons 145 and 163 in the class I heavy chain's alpha 2 alpha helix prompt B*1304 to exhibit a B15X21 pattern of serologic cross-reactivity. Molecular DNA class I typing approaches are also swayed by genetic recombinations to type B*1304 as a B15 molecule: B15-like nucleotide sequences encoding residues 114, 116, and 145, lead B*1304 to exhibit a B15 PCR amplification pattern. Thus, genetic exchanges encoding key amino acids in the class I heavy chain lead molecular and serologic typing approaches to categorize HLA-B*1304 as a member of the B15 family.

Alleles↗
PubMed1996

Characterization of baboon class I major histocompatibility molecules. Implications for baboon-to-human xenotransplantation.

Increasingly strong medical and political pressures are stimulating consideration of the transplantation of baboon organs and cells into humans. Critical to the success of these xenotransplants is management of the immune system such that graft rejection and, in the case of bone marrow transplantation, graft-versus-host disease do not result in transplant failure. The polymorphic products of the major histocompatibility complex (MHC) are the primary barrier to successful allotransplantation, and here we describe class I MHC molecules from baboon (Papio anubis) to gain an understanding of how similarities and differences between baboon and human MHC molecules might affect xenograft survival and function. Comparative analyses of our five novel baboon class I molecules with defined HLA class I molecules demonstrate that the baboon class I molecule are up to 90% identical. Disparity between baboon class I proteins and their human homologues lies predominately at positions in the antigen-binding groove, while C-terminal portions of the class I heavy chain are more conserved between the two species. Such concentration of cross-species differences within the alpha1 and alpha2 domains involves a majority of substitutions at positions demonstrating polymorphism in human alleles; the location of substitutions distinguishing baboon and human molecules thus resembles the positioning of human class I allopolymorphisms. Because this preliminary characterization indicates that both baboon and human T cells with be restricted by xenogeneic class I molecules, immune responses triggered during baboon-to-human transplantation should mimic those arising during MHC mismatched human allotransplantation.

Amino Acid Sequence↗
PubMed1996

Novel alleles HLA-B*7802 and B*51022: evidence for convergency in the HLA-B5 family.

We have characterized two novel HLA-B alleles, B*7802 and B*51022. The Caucasian-derived variant B*7802 most resembles the African-derived variant B*7801, from which B*7802 differs by two nucleotides. Only one of these modifications, however, is translated: a tyrosine for aspartate substitution occurs at residue 74 in B*7802, while the second nucleotide difference reflects a proximal synonymous substitution in codon 23. A second variant, B*51022, differs synonymously only at codon 23 from B*51021. Comparative analysis of the B5 CREG demonstrates that other pairs of B5 alleles differ synonymously only at codon 23 or synonymously at codon 23 and non-synonymously at a second more distal location. Contrary to the genesis of like pairs of B5 alleles via introduction of coordinate yet distant mutagenic events onto a single B5 progenitor, we postulate that synonymously different B5 progenitor molecules, B5ATT and B5ATC, are evolving in convergence to generate homologous B5 allele pairs differing silently at codon 23. Our finding that B*7802 is a single amino acid away from complete convergence with B*7801 and that B*51022 and B*51021 are in complete convergence is exemplary of such evolution.

Alleles↗
PubMed1991

Occupational therapy work-hardening programs: a demographic study.

A survey was conducted of 192 work-hardening and work-adjustment programs to gain an overview of practice patterns. The questionnaire covered program affiliation, services offered, staffing, program scheduling, average length of treatment per client, equipment used, physical settings, program status, number of clients seen each week, and types of functional outcome studies and research. The results demonstrate the tremendous growth of the involvement of occupational therapy in work hardening. This demographic study provides baseline information that can assist in the examination of trends and the development of new programs.

Demography↗