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L A Baxter-Lowe

Publications and source records attributed to L A Baxter-Lowe.

51 records · Page 3Linked to original sources
PubMed1991

Detection of 14 HLA-DQB1 alleles by oligotyping.

Fourteen alleles have been identified by analysis of the nucleotide sequences encoding the HLA-DQB1 chain. This study describes the detection of these 14 alleles by selective gene amplification and sequence-specific hybridization with nonradioactive oligonucleotide probes. These techniques were employed to create an oligotyping system with two levels of resolution that provide versatility and the capacity for comprehensive detection of all polymorphic sequences. An initial low-resolution assay was employed to detect four major groups of alleles that are associated with the DQw1-w4 serological specificities. A further high-resolution assay was then employed to differentiate 14 individual DQB1 alleles. Appropriate control measures were also included to detect carry-over and to confirm hybridization specificity. This system was used to analyze the allele frequencies of DQB1-0301, -0302, and -0303 in 115 DQB1-03** Caucasian blood donors. Allele frequencies of oligotypes DQB1-05** and DQB1-06** were analyzed in 112 DQB1-01** Caucasian blood donors. This system was also utilized to identify oligotypes designated DQB1-0501 through DQB1-0503 and DQB1-0601 through DQB1-0605 in 35 Tenth International Histocompatibility Workshop DQw1 cell lines to examine the correlation with serological and cellular specificities. In one of these cell lines, an unexpected linkage was discovered between the DRB1 and DQB1 loci, suggesting a recombination event. Oligotyping is a precise and accurate method for directly defining polymorphic sequences and it promises to have a major impact on the future direction of HLA typing.

Alleles↗
PubMed1990

Successful allogeneic transplantation of T-cell-depleted bone marrow from closely HLA-matched unrelated donors.

We describe a four-year experience with bone marrow transplantation involving closely HLA-matched unrelated donors and 55 consecutive patients with hematologic disease who were seven months to 48.6 years old (median, 18 years). An intensive pretransplantation conditioning regimen and graft-versus-host disease (GVHD) prophylaxis with CD3-directed T-cell depletion and cyclosporine were employed. Durable engraftment was achieved in 50 of 53 patients who could be evaluated (94 percent; 95 percent confidence interval, 83 to 98 percent). Acute GVHD of Grade II to IV developed in 46 percent of the patients (confidence interval, 27 to 66 percent). The incidence and severity of acute GVHD were increased in recipients of HLA-mismatched marrow as compared with recipients of phenotypically matched marrow (incidence of 53 percent [confidence interval, 37 to 68 percent] vs. 17 percent [confidence interval, 5 to 45 percent]; P less than 0.05). Extensive chronic GVHD and deaths not due to relapse also tended to be more frequent when HLA-mismatched marrow was used, but not significantly so. With a median follow-up of more than 19 months (range, greater than 9 to greater than 39), the actuarial disease-free survival of transplant recipients with leukemia and a relatively good prognosis (acute leukemia in first remission and chronic myelogenous leukemia in chronic phase) was 48 percent (confidence interval, 24 to 73 percent), and that of recipients with more aggressive leukemia was 32 percent (confidence interval, 18 to 51 percent); the actuarial survival of recipients with non-neoplastic disease was 63 percent (confidence interval, 31 to 86 percent). We conclude that marrow transplantation with closely HLA-matched unrelated donors can be effective treatment for neoplastic and non-neoplastic diseases. Although transplants from phenotypically HLA-matched unrelated donors appear to be most effective, transplants with limited HLA disparity can also be successful in some patients.

Adolescent↗
PubMed1990

Bone marrow transplantation for severe aplastic anemia in children.

For young adults and children who have a bone marrow donor who is a genotypic or phenotypic sibling match, bone marrow transplantation is now the preferred treatment for severe aplastic anemia. For those who lack such a matched donor, use of matched unrelated donors and family member donors who are mismatched for a single HLA antigen have been successful and appear to be the treatment of choice. Patients lacking either of these alternatives should receive antilymphocyte globulin, either alone or combined with cyclosporine as a first step. Although the success rate of marrow transplants in our series using mismatched family donors is similar to that following treatment with antilymphocyte globulin, several caveats must be kept in mind. First, the results reported with use of alternative donors must be confirmed with study of larger numbers of patients and longer follow-up. Second, the preparative regimen given prior to bone marrow transplantation destroys the patient's residual bone marrow, whereas antilymphocyte globulin cyclosporine A and androgens do not. The sequence of immunosuppression followed by transplantation with alternative donor marrow should produce greater long-term hematopoietic improvement. Unfortunately, when marrow transplant follows one or more courses of immunosuppressive therapy, nonengraftment is then a problem because of sensitization to blood cell antigens. It should also be kept in mind that studies done in children, especially in those younger than 6 years old, show that these patients respond better to transplantation than to treatment regimens not including marrow transplantation. Therefore, for the child with severe aplastic anemia, every effort should be made to identify a suitable bone marrow donor. Finally, we need to determine the specific components of the conditioning regimen and the constitution of the donor marrow necessary for engraftment and to minimize potential long-term complications, and there should be only a tolerable degree of graft-versus-host disease. Many of the transplant-related problems that plagued us in the 1970s have still not been fully resolved, but many have shown improvement. As we enter the 1990s, increasing the pool of marrow donors for patients with severe aplastic anemia who lack an HLA-matched sibling will continue to be a top priority for research.

Anemia, Aplastic↗
PubMed1989

Third-party-mediated graft rejection and graft-versus-host disease after T-cell-depleted bone marrow transplantation, as demonstrated by hypervariable DNA probes and HLA-DR polymorphism.

Graft rejection after marrow transplantation is generally thought to be mediated by alloreactive immune effector cells of host origin. Transfused blood products also contain immune cells capable of alloreactivity against both donor graft and host. To reduce the risk of transfusion-associated graft-versus-host disease (GVHD) and graft rejection, standard procedure is to irradiate all blood products with at least 1,500 rad before transfusion. We report a patient with chronic myelogenous leukemia who developed graft rejection and GVHD after receiving a T-cell-depleted transplant from a serologically HLA-A, B, DR/DQ matched and mixed lymphocyte culture (MLC) nonreactive unrelated donor. Cytogenetic analysis of marrow cells collected at the time of graft rejection revealed a PH1-negative female karyotype that was not consistent with donor cells. Use of specific minisatellite DNA probes (YNH 24, H-RAS, and 3' HVR) revealed the exclusive presence of third-party (neither donor nor recipient) restriction-fragment-length polymorphisms (RFLP) in both peripheral blood and marrow. Repeat RFLP analysis 3 days later showed persistence of this unique third-party banding pattern. DNA-based HLA-typing, using polymerase chain reaction (PCR) and oligonucleotide probe hybridization, also showed these cells to be derived from an individual whose HLA-DR type was distinct from donor and recipient. Together, these findings suggested the presence of a proliferating population of transfused cells possessing alloreactivity against both donor graft and host, despite prior irradiation of all blood products with 2,000 rad. Limiting dilution analysis to assess the frequency of irradiated lymphocytes able to respond to mitogen revealed an approximate 5- to 6-log reduction at 1,500 to 2,000 rad as compared with unirradiated controls. These data indicate that a small percentage of lymphocytes can survive irradiation at these doses and suggest that existing blood-product irradiation guidelines may require reassessment, especially in T-cell-depleted transplant recipients.

Bone Marrow Transplantation↗
PubMed1989

Molecular cloning of the Na,K-ATPase alpha-subunit in developing brine shrimp and sequence comparison with higher organisms.

We report here the molecular cloning, nucleotide sequence, and predicted amino acid sequence of an alpha-subunit of the developmentally useful model, Artemia. The amino acid sequence shows divergence from that of mammals, birds, Torpedo, and Drosophila. However, regions in the putative ATP binding and transmembrane domains show absolute or high levels of conservation. Major differences occur in the amino-terminal domain and several other hypervariable regions. These differences are consistent with the suggestion that the brine shrimp is a 'fast clock' organism which diverged from the precursors of vertebrates 0.5-1 billion years ago.

Amino Acid Sequence↗
PubMed1989

HLA gene amplification and hybridization analysis of polymorphism. HLA matching for bone marrow transplantation of a patient with HLA-deficient severe combined immunodeficiency syndrome.

The treatment of choice for certain immunodeficiency syndromes and hematological disorders is bone marrow transplantation (BMT). The success of BMT is influenced by the degree of HLA compatibility between recipient and donor. However, aberrant expression of HLA sometimes makes it difficult, if not impossible, to determine the patient's HLA type by standard serological and cellular techniques. We describe here the application of new molecular biological techniques to perform high resolution HLA typing independent of HLA expression. A patient with HLA-deficient severe combined deficiency was HLA typed using in vitro amplification of the HLA genes and sequence-specific oligonucleotide probe hybridization (SSOPH). Two major advances provided by this technology are:detection of HLA polymorphism at the level of single amino acid differences; and elimination of a requirement for HLA expression. Although the patient's lymphocytes lacked class II HLA proteins, polymorphism associated with DR7,w53;DQw2;DRw11a (a split of DR5), w52b (a split of DRw52);DQw7 were identified. The patient's class I expression was partially defective, and typing was accomplished by a combination of serological (HLA-A and -C) and SSOPH analysis (HLA-B). Complete patient haplotypes were predicted after typing of family members [A2;B35(w6); Cw4; DRw11a(w52b);DQw7 and A2;B13(w4); Cw6;DR7(w53); DQw2]. Potential unrelated donors were typed and a donor was selected for BMT.

Alleles↗
PubMed1988

In vitro biosynthesis of the beta-subunit of the Na+/K+-ATPase in developing brine shrimp: glycosylation and membrane insertion.

We demonstrate here translation, glycosylation, and membrane insertion of the beta-subunit of the Na+/K+-ATPase of the developing brine shrimp, Artemia, in a reticulocyte lysate translation system. The apparent molecular weight of the primary translation product as determined by SDS-PAGE is 33,000 +/- 1000 (n = 7). When microsomal membranes are present during the entire translation period, a new band with an apparent molecular weight of 37,000 +/- 1000 (n = 7) appears. This change in apparent molecular weight is due to the addition of about two N-linked oligosaccharides. The temporal relationship between protein synthesis and glycosylation have also been examined. Glycosylation and membrane insertion could be achieved if membranes were added after completion of about 70% of the peptide chain. However, glycosylation did not occur if membranes were added after the completion of translation of the beta-subunit. The beta-subunit was synthesized on membrane-bound polysomes, where about two N-linked oligosaccharides were added to the growing polypeptide chain. These studies demonstrate that in vitro translation systems will be useful for studying the biosynthesis of the beta-subunit of the brine shrimp, which is a good model system to examine the developmental regulation of the Na+/K+-ATPase.

Animals↗
PubMed1986

Regulation of Na,K-ATPase biosynthesis in developing Artemia salina.

Regulation of the biosynthesis of the sodium- and potassium-activated adenosine triphosphatase (Na,K-ATPase) (EC 3.6.1.3) was studied in the developing brine shrimp, Artemia salina. Measurement of levels of the subunits of the Na,K-ATPase by radioimmunoassay indicated the presence of both alpha and beta subunits in undeveloped cysts and developing embryos prior to the appearance of enzymatic activity. The quantity of each subunit increased dramatically between 8 and 24 h of development and then reached a plateau at about 32 h. The quantities of translationally active mRNA alpha and mRNA beta were also determined. Undeveloped cysts contained mRNA alpha and mRNA beta, and the amounts increased 9- and 3-fold, respectively, during the first 24 h of development. The data suggest that the increase in Na,K-ATPase activity was at least in part due to increases in protein synthesis related to changes in mRNA levels. The data also suggest involvement of additional regulatory mechanisms. The alpha-subunit has been detected as two molecular weight forms (alpha 1 and alpha 2) which demonstrate changes in relative amounts during development (Peterson, G. L., Churchill, L., Fisher, J. A., and Hokin, L. E. (1982) J. Exp. Zool. 221, 295-308). We show here that this was not due to changes in mRNA alpha 1 and mRNA alpha 2.

Animals↗
PubMed1984

Site of synthesis of the alpha and beta subunits of the Na,K-ATPase in brine shrimp nauplii.

Developing nauplii (embryos) of the brine shrimp Artemia salina are an excellent model system for studying the biogenesis of the sodium- and potassium-activated adenosine triphosphatase (Na,K-ATPase). The nauplii exhibit a burst of Na,K-ATPase synthesis between 6 and 32 h of development (Peterson, G. L., Churchill, L., Fisher, J. A., and Hokin, L. E. (1982) J. Exp. Zool. 221, 295-308). We have now determined the sites of synthesis of the alpha and beta subunits of the Na,K-ATPase in developing A. salina nauplii. Membrane-bound and free polysomes were isolated from nauplii, and RNA was extracted from the polysomes. The polysomal RNA was translated in vitro in a rabbit reticulocyte lysate, and the translation products were immunoprecipitated by anti-subunit antisera. The immunoprecipitated proteins were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and visualized by fluorography. Our data show that the alpha subunit precursor is synthesized on membrane-bound polysomes and the beta subunit precursor is synthesized on free polysomes. In addition, the alpha subunit precursor appears as two separate peptides on sodium dodecyl sulfate-polyacrylamide gels, which suggests that the two alpha subunit forms seen in mature brine shrimp Na,K-ATPase are products of two distinct messenger RNAs. The beta subunit precursor appears as a single discrete band, unlike the mature beta subunit, which appears as a diffuse band.

Animals↗
PubMedDate not supplied

Automated nucleotide sequencing reveals substantial disparity between the HLA-A2 genes of bone marrow transplant recipients and donors.

HLA disparity is associated with immunological complications after bone marrow transplant and it has been demonstrated that a single amino acid substitution can dramatically alter the function or allorecognition of an HLA molecule. Current serological methods for typing Class I HLA do not distinguish between most HLA-A2 variants which can differ by 1-8 amino acid residues. HLA-A2 disparity between bone marrow transplant patients and donors was investigated using automated nucleotide sequencing of the entire coding region of HLA-A2 genes. A total of 122 HLA-A2 alleles were sequenced from 47 patient-donor pairs (94 individuals). HLA-A2 disparity was observed in 10 of 47 pairs (21.3%) and consisted of HLA-A*0201 mismatched with 0202 (n = 2), 0205 (n = 3), 0206 (n = 3), 0217 (n = 1) or 0221 (n = 1). Four of 6 (66.7%) non-Caucasian or mixed race pairs were HLA-A2 disparate, while 6 of 36 (16.7%). Caucasian pairs were HLA-A2 disparate (p = 0.008). Among all individuals HLA-A*0201 was the most frequently observed allele (90.0%) while 0202 (1.6%), 0205 (2.5%), 0206 (4.1%), 0217 (0.8%) and 0221 (0.8%) were also observed. This study illustrates the diversity of HLA-A2 in non-Caucasian individuals and suggests that HLA-A2 subtyping for applications such as bone marrow transplantation, especially in non-Caucasian or mixed-race donor-recipient pairs, may be important.

Alleles↗