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Biomedical subjects

E Mickelson

Publications and source records attributed to E Mickelson.

At least 19 recordsLinked to original sources
PubMed2006

15q duplication associated with autism in a multiplex family with a familial cryptic translocation t(14;15)(q11.2;q13.3) detected using array-CGH.

Autism spectrum disorders (ASDs) are a group of neurodevelopmental disorders with a strong genetic aetiology. In approximately 1% of cases, duplication of the 15q11-13 region has been reported. We report the clinical, array-comparative genomic hybridization (CGH) and cytogenetic evaluation of two individuals from a multiplex family demonstrating autism due to a maternally inherited gain of 15q11-13. Our findings indicate that unlike most 15q11-13 gains, which are caused by interstitial duplication of this region or supernumerary marker chromosomes deriving from proximal 15q, the 15q gain in this family is the result of abnormal segregation of a cryptic familial translocation with breakpoints at 14q11.2 and 15q13.3. The affected members of this family were found to have a normal karyotype at >550 band resolution. This translocation was identified using the 1-Mb resolution whole genome array (Spectral Genomics). The affected individuals have a gain of seven clones from proximal 15q, a loss of two clones from proximal 14q and a gain of two clones from 6q. Fluorescent in situ hybridization (FISH) analysis with clones from chromosomes 14 and 15, combined with DAPI reverse banding, showed an abnormal karyotype with one normal chromosome 15 and the der(15) t(14;15)(q11.2.;q13.3), resulting in the gain of proximal 15q and the loss of proximal 14q in affected individuals. The duplication of two clones from 6q in the affected subjects was also found in unaffected members of the family. Our findings suggest that the gain of 15q in autism may in some cases be due to cryptic translocations with breakpoints in the pericentromic regions of chromosome 15 and a different acrocentric chromosome. Variation in the size of pericentromic regions of any acrocentric chromosome may justify karyotype and FISH studies of autistic probands and their parents using probes from the 15q proximal region to determine recurrence risk for autism in some families.

Adolescent↗
PubMed2001

Major-histocompatibility-complex class I alleles and antigens in hematopoietic-cell transplantation.

BACKGROUND: Successful engraftment of hematopoietic stem cells from unrelated donors is influenced by disparities between the donor and recipient for HLA-A, B, and C alleles. Disparities between HLA sequence polymorphisms that are serologically detectable are termed antigen mismatches, whereas those that can be identified only by DNA-based typing methods are termed allele mismatches. Whether both kinds of polymorphisms are important in transplantation is not known. We tested the hypothesis that allele mismatches that are detectable only at the DNA level are less immunogenic than those that are serologically detectable and thereby are associated with a lower risk of graft failure after hematopoietic-cell transplantation METHODS: We used DNA sequencing to define the HLA-A, B, and C alleles in 471 patients who received bone marrow from unrelated donors for the treatment of chronic myeloid leukemia after myeloablative conditioning therapy. The odds ratios for graft failure were determined for recipients of transplants from donors with a single class I allele mismatch, a single class I antigen mismatch, or two or more class I mismatches, as compared with those with no mismatch RESULTS: A single HLA allele mismatch did not increase the risk of graft failure, whereas a single antigen mismatch significantly increased the risk. The risk was also increased if the recipient was HLA homozygous at the mismatched class I locus or if the donor had two or more class I mismatches CONCLUSIONS: HLA class I antigen mismatches that are serologically detectable confer an enhanced risk of graft failure after hematopoietic-cell transplantation. Transplants from donors with a single class I allele mismatch that is not serologically detectable may be used without an increased risk of graft failure.

Genes, MHC Class I↗
PubMed2001

Genomics of unrelated-donor hematopoietic cell transplantation.

Unrelated-donor hematopoietic cell transplantation is a proven curative modality for hematologic malignancies. The success of unrelated-donor transplantation has been achieved through a better understanding of the immunobiology of the HLA system and through more precise and comprehensive matching of donors and recipients. The extensive polymorphism of HLA genes confers important biological implications affecting engraftment, graft-versus-host disease and overall survival. Although more-complete HLA identity of the donor and recipient is associated with optimal transplant outcome, new information suggests that not every HLA disparity is functionally relevant. Future advances in unrelated-donor transplantation must include the identification of tolerable HLA mismatches, so that more patients may benefit from this therapeutic modality. Furthermore, the role of cytokine-gene polymorphisms and minor histocompatibility genes in transplant outcome requires investigation. Delineation of the function of these markers as transplantation determinants may provide alternative means for optimizing the results of hematopoietic cell transplantation.

Animals↗
PubMed2001

The biological significance of HLA-DP gene variation in haematopoietic cell transplantation.

Although it has been over 25 years since HLA-DP was mapped to the major histocompatibility complex (MHC), its biological functions remain ill-defined. We sought to test the hypothesis that HLA-DP functions in a manner similar to that of other class II genes by measuring the risk of clinically severe grades III-IV acute graft-vs.-host disease (GVHD) associated with recipient HLA-DP disparity after haematopoietic cell transplantation. HLA-DPB1 exon 2 was sequenced in 205 patients who underwent transplantation from HLA-A, -B, -C, -DRB1 and -DQB1 allele-matched unrelated donors. HLA-DPB1 mismatched recipients experienced a significantly increased risk of acute GVHD compared with HLA-DP-identical transplants. Patients who were mismatched for a single HLA-DPB1 allele had an odds ratio (OR) of 1.0 (0.5, 2.2; P = 0.99) and patients who were mismatched for two alleles had an OR of 2.2 (1.0, 4.9; P = 0.06) for developing acute GVHD. Compared with matched and single-allele mismatched transplants, patients who were mismatched for two DPB1 alleles had an OR of 2.2 (1.2, 4.1; P = 0.01). HLA-DP plays an important role in the alloimmune response. A threshold effect of multiple HLA-DP disparities is evident in determining the risk of acute GVHD after haematopoietic cell transplantation from unrelated donors.

Adolescent↗
PubMed1997

A comparative study of HLA-DRB typing by transcription-mediated amplification with the hybridization protection assay (TMA/HPA) versus PCR/SSOP.

To evaluate alternative human leukocyte antigen (HLA)-DNA typing methods, we used a system of transcription-mediated amplification (TMA) with a probe hybridization protection assay (HPA) in a microtiter plate format developed by Chugai Pharmaceutics Ltd. (Tokyo, Japan) to perform intermediate-level DRB typing for 502 individual samples. Two hundred fifty-two samples submitted to our Clinical Immunogenetics Laboratory were prospectively tested concurrently with a locally developed intermediate-level DRB polymerase chain reaction/sequence-specific oligonucleotide probe (PCR/SSOP) assay in a double-blind fashion. In addition, 250 retrospective samples of archived frozen cells or DNA from clinical and research panels, previously typed by allele-level DRB1 PCR/SSOP, were chosen to include 66 distinct DRB1 alleles representing Caucasian, American Black, Asian, and Native American ethnic groups. Among the prospectively typed samples, except for four samples with a TMA/HPA microplate handling problem, a single TMA/HPA allele assignment (1/462 alleles = 0.2%) was discordant with PCR/SSOP. Among the 250 retrospective samples, a single HPA probe for codon 57 aspartic acid consistently cross-reacted with the codon 57 valine sequence of DRB1*0807. However, TMA/HPA identified six samples with previous PCR/SSOP typing errors, all of which involved identification of sequences at codons 67-71 in samples heterozygous for two DR52-associated DRB1 alleles. Assay turnaround time from sample preparation to results was 11 h for 24 samples or 6-7 h for 1-4 samples. In summary, we found the TMA/HPA DRB typing system to provide rapid, reliable, and accurate HLA-DRB typing results. The current TMA/HPA methodology could be improved by use of a molded plastic cold block to provide more consistent and secure microtiter plate cooling than the current water/ice slurry. Nevertheless, this methodology, based on a microtiter plate format but without the usual plate washing steps of the traditional ELISA, has superior potential for microplate handling and reagent distribution with a robotics system and a work surface incorporating microplate heating and cooling units.

Alleles↗
PubMed1997

Evaluation of pretransplant donor anti-recipient cytotoxic and helper T lymphocyte responses as correlates of acute graft-vs.-host disease and survival after unrelated marrow transplantation.

We analyzed pretransplant donor anti-recipient cytotoxic and helper T lymphocyte (CTL and HTL) responses separately in two cohorts of unrelated marrow transplant recipients. Donors and recipients were typed for HLA-A and -B antigens by serologic methods, and for HLA-DRB1 by molecular methods. A single mismatch for a cross-reactive HLA-A or -B antigen or the -DRB1 allele was accepted in patients younger than 36 years if an HLA-A, -B, or -DRB1-matched donor could not be identified. The combination of methotrexate and cyclosporine was used for graft-vs.-host disease (GVHD) prophylaxis, and marrows were not T cell depleted. Donor anti-recipient CTL precursor frequencies showed no correlation with the severity of acute GVHD or with survival after transplantation. HTL responses were detected in the presence of HLA-class II disparity and showed weak correlations with the severity of acute GVHD (p = 0.054) and with survival after transplantation (p = 0.08). These results suggest that testing donor anti-recipient CTL responses before unmodified marrow transplantation does not predict clinically important events and is not likely to help select unrelated donors. With the current availability of molecular genetic methods for assessing HLA-class II compatibility, testing donor anti-recipient HTL responses is not likely to add information that would help select unrelated donors.

Acute Disease↗
PubMed1995

Marrow transplants from unrelated donors.

Unrelated-donor transplants have been a realistic option for an increasing number of patients, and the results of these transplants are favorable for patients with good prognostic features. Timing of the transplant early in the course of disease, before malignant clones become resistant to therapy and while the patient remains in good clinical condition, is a critical variable. Further improvements in the safety and efficacy of unrelated-donor transplants will require new approaches to GVHD prevention, better supportive care, acceleration of immune reconstitution and facilitation of tolerance induction without loss of the graft-versus-leukemia effect.

Adult↗
PubMed1993

Inhibition of allostimulated HLA-DQ and DP-specific T cells by staphylococcal enterotoxin A.

Bacterial superantigens have two immunologically important features. They bind MHC class II molecules and stimulate T cells bearing certain V beta TCR phenotypes. Superantigens such as SEA, SEB, and TSST bind to each of the three HLA class II isotypes (DR, DQ, and DP). Allotypic variation seems to play an important role in superantigen binding to class II molecules, but the functional implications of these differences remain largely unknown. In the present investigation, we studied the effects of SEA, SEB, and TSST on allostimulation of HLA-DR-, DQ-, and DP-allospecific T-cell clones. To avoid direct stimulation of T-cell responses by the superantigens, SEA and/or SEB nonresponsive T-cell clones were selected. We show that SEA strongly inhibited DQ- and DP-specific T-cell responses. In contrast, SEB and TSST had only weak inhibitory effects. DR-specific T-cell responses were unaffected or only weakly inhibited by the superantigens tested. The inhibition appeared not to be due to induction of cytotoxicity or suppression of either T cells or EBV-LCLs by SEA. In conclusion, the bacterial superantigen SEA can block alloantigen-specific stimulation of T clones in vitro. These results suggest that SEA binds to certain MHC class II molecules in a way that prevents MHC-TCR interactions.

Antigens, Bacterial↗
PubMed1993

A comparative study of HLA-DRB1 typing by standard serology and hybridization of non-radioactive sequence-specific oligonucleotide probes to PCR-amplified DNA.

A double-blind study was carried out to evaluate the relative performance and reliability of the PCR/SSOP assay compared to conventional serological typing in identifying HLA-DR alleles. A total of 268 consecutive samples were entered into the study. In 14 (5.2%) of the cases, HLA-DR serology could not be performed due to poor cell viability, while in seven (2.6%) of the cases, PCR/SSOP typing could not be performed due to poor amplification or to contamination with exogenous DNA. Among samples that were successfully typed by both methods, serologic typing correctly identified 455/465 (97.9%) DR antigens, while PCR/SSOP correctly identified 464/465 (99.8%) DR alleles (p = 0.0117, McNemar's test). The majority of discrepancies in serologic typing resulted from a lack of discriminative alloantisera to identify DR6 or DR103. For the overall sample set (N = 268), serology provided accurate results in 244 (91.0%) cases, while PCR/SSOP provided accurate results in 260 (97.0%) cases (p = 0.0037). The results of this study demonstrate that PCR/SSOP typing for HLA-DRB1 alleles provides results that are equal to or surpass serological typing for HLA-DR antigens. In addition, the PCR/SSOP approach offers the advantages of better reagent availability, lower cost, more rapid turn-around time, and greater accuracy, all of which would warrant its use as an HLA typing method of choice.

Alleles↗
PubMed1992

HLA antigens in Tlingit Indians with rheumatoid arthritis.

HLA-DR4 has been described in association with rheumatoid arthritis (RA) in multiple populations. We have studied HLA antigens in Alaskan Tlingit Indians. HLA-DR4 was decreased in the RA group (n = 32) compared with controls (n = 62) (6% vs 21% p = 0.07). The predominant DR4 allele observed was DRB1*0403 (Dw13.1). The most striking observation in these studies was a marked predominance of the DRB1*1402 allele encoding Dw16 (DRw14). This allele was present in 91% of RA cases, but was also highly prevalent in controls (80%, OR = 2.4 p = 0.20). DRB1*1402 only was observed in 47% of cases and 31% of controls. The DRB3*0101 (DRw52), and the DQA*0501 and DQB*0301 alleles encoding a subset of DQw3 were associated with DRB1*1402 in cases and in controls. HLA-Bw62 was increased in RA cases (28%) compared with controls (8%) (OR = 4.5, p = 0.01, corrected p = ns).

Adult↗
PubMed1992

Donor alloreactivity may predict acute graft-versus-host disease in patients receiving marrow transplants from HLA identical siblings.

In a study of 27 patients receiving marrow grafts from HLA-identical donors, the immune response capacity of donor T cells measured pretransplant was compared with the incidence and severity of post-transplant acute graft-versus-host disease (GVHD). Donors were categorized as either high responders or low responders based on their responsiveness to monocyte-dependent soluble antigens and to alloantigens expressed on a B-lymphoblastoid cell line. The high or low responder status of donor cells as defined by response to soluble antigen did not correlate with the incidence of acute GVHD in patients receiving transplants from these donors. The responder status of donor cells as defined by response to alloantigen, however, did correlate with incidence of post-transplant GVHD. Of nine patients receiving marrow from low responder donors, only two developed GVHD (Grades I-II). Conversely, of 18 patients receiving marrow from high responder donors, 13 developed GVHD (Grade I-IV) (chi 2 = 3.71; d.f. = 1, p = 0.05), with nine of the 13 developing moderate to severe Grade II-IV GVHD (chi 2 = 2.60; d.f. = 1, p = 0.10). These results indicate that pretransplant testing of donor T cells for response to alloantigen may identify those patients who will be at increased risk of developing clinically significant acute GVHD following marrow transplantation. Since there was only a trend toward statistical significance, however, these data require confirmation in a prospective study with larger number of patients.

Acute Disease↗
PubMed1991

DRw8 microvariation: a new DRB1 allele identified in association with DQw7 in American blacks.

In the American black population, DRw8 is commonly found in association with DQw7 and an undefined HLA-D specificity. Polymerase chain reaction amplification was used to obtain DRB1 cDNA clones from two unrelated individuals expressing this haplotype. The DRB1 sequence is most similar to a sequence found in cells expressing DRw8, DQw4, Dw8.2 differing at the protein level by a single amino acid substitution at position 86.

Alleles↗
PubMed1991

Dw14(DRB1*0404) is a Dw4-dependent risk factor for rheumatoid arthritis. Rethinking the "shared epitope" hypothesis.

HLA-DR4 has been shown to be associated with risk for developing rheumatoid arthritis (RA) in multiple populations and racial groups. The allelic variants of DR4 share the DR4 serologic specificity but differ by 1 to 3 amino acids in the third hypervariable region (positions 67 to 74) and at positions 57 and 86 of the DR beta 1 chain. We have examined DR4 variants in 61 DR4+ RA cases and 55 DR4+ healthy controls. Dw14 was not associated with RA risk in DR4 heterozygous (DR4,X) cases. Only 15% of DR4,X cases had the Dw14 allele compared with 28% of DR4,X controls. In homozygous (DR4,4) individuals who also expressed Dw4, however, Dw14 was associated with increased RA risk. Moreover, the relative risk for Dw4,Dw14 (16.1, p = 0.001) actually exceeded that of Dw4,Dw4 (2.2, p = ns). Thus Dw14 is not an independent risk factor for RA but is a synergistic risk factor for individuals who also have the Dw4 allele.

Alleles↗
PubMed1990

Polymorphic DQ alpha and DQ beta interactions dictate HLA class II determinants of allo-recognition.

18 transfected cell lines were generated that expressed distinct DQ molecules related to the serologically defined HLA-DQw3 specificity. These transfectants were constructed using site-directed mutagenesis to introduce nucleotide substitutions into DQ3.2 beta cDNA, followed by retrovirus-mediated gene expression of the mutagenized genes in human B cell lines with different endogenous DQ alpha chains. The capacity of particular class II dimers to stimulate alloreactive T cell clones was investigated. T cell activation was found to be dependent on both DQ alpha and DQ beta chains. In some cases, single amino acid substitutions at codons 13, 26, 45, or 57 of the DQ beta chain were sufficient to dramatically alter T cell reactivity; T cell recognition of these substitutions, however, was strongly influenced by the alpha chain polymorphisms present in the stimulatory class II dimer. Both gain and loss of major serologic and cellular specificities associated with specific DQw3+ alleles were observed with a limited array of site-directed substitutions.

Amino Acid Sequence↗
PubMed1990

Suppressed antidonor MLC responses in renal transplant candidates conditioned with donor-specific transfusions that carry the recipient's noninherited maternal HLA haplotype.

Forty-seven patients with end-stage renal disease were entered into a donor-specific transfusion protocol consisting of three infusions of whole blood every two weeks prior to transplantation. Fourteen of the patients became sensitized following transfusion and were not transplanted. Thirty-one patients received a transplant from the DST donor and have an estimated two-year graft survival of 97%, three-year survival of 88%, and four-year survival of 69%. Cells of eleven of the 36 recipients tested in one-way MLC before and two weeks after completion of DST exhibited a significantly decreased antidonor MLC response. Deletion of CD8+ positive lymphocytes from suppressed MLCs resulted in restoration of antidonor MLC reactivity in four of six patients. An analysis of the family HLA profile in patients exhibiting a decreased donor-directed MLC response revealed a significant (P less than 0.02) association between decreased MLC reactivity following DST and the expression of noninherited maternal HLA antigens by cells of the transfusion donor. These alterations in cellular immune responses noted in some patients following DST are consistent with the appearance of specific antidonor T suppressor cells as a result of donor-specific transfusion.

Blood Transfusion↗
PubMed1990

The HLA system in clinical marrow transplantation.

The HLA system is comprised of more than 30 class I and class II genes that encode a polymorphic array of cell-surface glycoprotein molecules that function to restrict or direct the specificity of T-cell responses. Class I alloantigens, encoded by HLA-A, -B, and -C genes, historically have been identified and characterized by the use of alloantisera. Three additional class I genes, HLA-E, -F, and -G, have been identified recently, but it is not known yet if these are relevant to transplantation. The demonstration of further polymorphism among class I alleles, however, has been made possible by the use of cytotoxic lymphocytes and by isoelectric focusing gel electrophoresis. Class II alloantigens, encoded by DR, DQ, and DP genes residing in the HLA-D region, can be defined both serologically and by the use of cellular reagents. Recent advances in DNA typing methods, including restriction fragment length polymorphism and sequence-specific oligonucleotide probe analysis, provide tools which more completely define the extent of HLA polymorphism within given populations. The diversity of allelic variation within the HLA system, coupled with the fundamental role of class I and class II molecules in the triggering of allograft reactions, necessitates the continuing improvement of techniques for characterizing distinct HLA molecules and providing for the better matching of donor and recipient prior to allotransplantation.

Bone Marrow Transplantation↗