Biomedical subjects

F T Christiansen

Publications and source records attributed to F T Christiansen.

At least 19 recordsLinked to original sources

PubMed2006

MICA, MICB, and MHC beta block matching in bone marrow transplantation: relevance to transplantation outcome.

Genetic testing of the MHC is required for selection of donors for bone marrow transplantation. The outcome of related bone marrow transplantation is usually superior to that of unrelated bone marrow transplantation. This may be the result of inaccurate or incomplete genetic testing employed for selection of donor for transplantation. Based on MHC haplotype matching, MHC block matching has been developed for selection of potential unrelated donor. Block matching has been shown previously to improve outcome when added to the conventional method of human leukocyte antigen (HLA) typing for selection of donors. In this study, we have retrospectively analyzed 44 donor recipient pairs from the Australian Bone Marrow Donor Registry Repository with respect to matching of HLA-B and HLA-Cw by sequence-based typing and MICA and MICB by polymerase chain reaction-sequence specific primer and MHC beta block matching and correlated these results with survival. Beta block matching was correlated with MIC matching (p < 0.005) and with HLA-B and HLA-Cw matching. Patients who were HLA-B and -Cw matched had significantly improved survival when they were additionally matched for MHC beta block (p(c) = 0.04) or MIC (p(c) = 0.05).

Adolescent↗

PubMed2006

The relevance of natural killer cell human leucocyte antigen epitopes and killer cell immunoglobulin-like receptors in bone marrow transplantation.

The discovery that killer cell immunoglobulin-like receptors (KIR) interact with genetically polymorphic epitopes on class I human leucocyte antigen (HLA) molecules and that the KIR receptor repertoire itself is genetically variable has led to investigation of the relevance of the KIR system to stem cell transplantation. A number of retrospective studies of transplant outcome have now demonstrated either beneficial or deleterious effects of mismatching for class I natural killer (NK) epitopes. A smaller number of studies have shown effects of the donor and/or patient KIR repertoire on outcome, irrespective of the patient and donor HLA type. The most parsimonious interpretation of the data, which are often conflicting, is that the effect of NK epitope matching is very much dependent on transplant protocols, with the extent of donor T-cell depletion possibly being the most important variable. A clearer picture of the role of matching for NK epitopes and the KIR-receptor repertoire of the donor is needed.

Bone Marrow Transplantation↗

PubMed2005

Menopausal hormone therapy and irregular endometrial bleeding: a potential role for uterine natural killer cells?

CONTEXT: Irregular bleeding affects many users of combined menopausal hormone therapy (HT) and commonly leads to invasive and expensive investigations to exclude underlying malignancy. In most cases no abnormality is found. OBJECTIVE: The main objective of this study was to explore the role of uterine natural killer (uNK) cells and their regulatory cytokine IL-15 in irregular bleeding in HT users. DESIGN: This was a prospective observational study conducted between 2002 and 2004. SETTING: The study was conducted in a tertiary referral menopause clinic at King Edward Memorial Hospital, Western Australia. PATIENTS: Patients included 117 postmenopausal women taking combined HT. INTERVENTIONS: Outpatient endometrial biopsies were taken during and outside bleeding episodes. MAIN OUTCOME MEASURES: The relationship between endometrial uNK cells (CD56+) and bleeding patterns was measured. We also addressed the impact of HT exposure on uNK cell populations, the relationship between endometrial IL-15 expression and uNK cell populations, and killer Ig like receptor genotype in subjects with irregular bleeding. RESULTS: Endometrial CD56+ uNK cells were significantly increased in biopsies obtained during bleeding episodes (P < 0.001), compared with HT users with no bleeding. The highest level of IL-15 expression was also seen in biopsies taken during bleeding. No clear relationship between killer Ig like receptor genotype and bleeding on HT was observed. CONCLUSIONS: Little is known about the mechanisms underlying irregular bleeding in HT users. This is the first report of uNK cells and their association with regulating cytokines in postmenopausal endometrium and demonstrates a possible mechanism by which HT may induce irregular bleeding.

CD56 Antigen↗

PubMed2005

Killer immunoglobulin-like receptors and HLA act both independently and synergistically to modify HIV disease progression.

Variation in the host response to infection by pathogens including HIV-1 may be conferred by polymorphic genetic factors such as HLA and killer immunoglobulin-like receptors (KIR) genes. Here, we examined KIR and HLA genotype effects on pretreatment viral load, rate of CD4(+) T-cell decline and progression to AIDS among adult HIV-1-infected patients within the Western Australian HIV Study Cohort. In this study, carriage of KIR genes within the 'B' haplotype (eg KIR2DS2) was specifically associated with a more rapid CD4(+) T-cell decline over time and progression to AIDS. In contrast, KIR gene repertoire had no effect on pretreatment viral load while selected HLA alleles (eg HLA-B*5701, HLA-B*2705) demonstrated significant protective effects on viremia. Furthermore, interactions between specific HLA and KIR genes did appear to influence HIV disease progression. The results suggest that host genetic variation within the HLA and KIR gene complexes have clinically relevant effects on the course of HIV-1/AIDS, acting independently as well as synergistically to modify disease progression at multiple levels.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Natural killer cell HLA-C epitopes and killer cell immunoglobulin-like receptors both influence outcome of mismatched unrelated donor bone marrow transplants.

Matching of donor and recipient for the class I human leukocyte antigen-C (HLA-C)-encoded natural killer (NK) epitopes has been reported to influence stem-cell (SC) graft outcome, but a consistent picture has not yet emerged. We have analyzed transplant outcome in 104 unrelated SC grafts in relation to NK epitope (C1 and C2) matching and donor killer cell immunoglobulin-like receptor (KIR) genotype. NK epitope mismatching in the rejection direction was strongly associated with an increased probability of rejection subsequent to engraftment. The prevalence of grades III-IV acute graft-vs-host disease (GVHD) was significantly higher and occurred significantly earlier when there was NK epitope mismatching in the GVH direction. Higher transplant-related mortality and lower disease-free survival rates were associated with epitope mismatching regardless of the mismatch direction. A greater number of KIR receptors, both activating and inhibitory, in the donor protected against grades III-IV GVHD and improved survival.

Adolescent↗

PubMed2004

Maternal KIR repertoire is not associated with recurrent spontaneous abortion.

BACKGROUND: In view of evidence suggesting an immunological cause of recurrent spontaneous abortions (RSA) and the large number of maternal natural killer (NK) cells present in the pregnant uterus, we investigated the genetic polymorphism of the killer cell immunoglobulin-like receptors (KIR) in women with RSA. METHODS: KIR gene repertoire and KIR2DL4 (a receptor for HLA-G) genotyping were determined by SSP and SSCP respectively, in women experiencing RSA and controls. RESULTS: The KIR repertoire did not differ between RSA patients and controls in terms of: (i) the number of inhibitory receptors; (ii) the number of activating receptors; (iii) the ratio of inhibitory to activating receptors. KIR2DL4, a receptor for HLA-G, has different transmembrane alleles, which produce functionally different phenotypes. The frequency of KIR2DL4 transmembrane genotypes differed significantly between RSA patients and controls (P=0.03). However, although homozygosity for a membrane-bound receptor was more frequent in patients (25%) than controls (10%), other genotypes that would produce the same phenotype were not more frequent in patients than controls. CONCLUSIONS: The data provide little evidence that KIR polymorphism plays a role in predisposition to RSA.

Abortion, Habitual↗

PubMed2004

The beneficial role of inhibitory KIR genes of HLA class I NK epitopes in haploidentically mismatched stem cell allografts may be masked by residual donor-alloreactive T cells causing GVHD.

HLA allele mismatches will provoke T-cell alloreactivity after allogeneic stem cell transplantation. As donors and recipients are usually HLA matched, the public HLA epitopes that are recognized by natural killer (NK) cells (NK epitopes) are rarely mismatched, and therefore there is rarely potential for NK alloreactivity arising from the absence of ligands for inhibitory killer immunoglobulin-like receptors (KIR). Transplants using related donors sharing only one haplotype (haploidentical donors) represent a setting in which NK epitopes are often mismatched, thus resulting in the potential for NK alloreactivity. We have analyzed engraftment, acute graft vs host disease (GVHD), leukemia relapse, and survival in 62 haploidentical transplants in relationship with potential NK alloreactivity, inhibitory, and activating KIR genes of class I HLA NK epitopes. Potential NK alloreactivity in the rejection direction was not associated with any outcome variable. Potential NK alloreactivity in the GVHD direction was associated with an increased incidence of severe GVHD and poorer patient survival but not with non-engraftment nor leukemia relapse. A higher number of activating KIR receptors in the genome of the donor was associated with a higher prevalence of GVHD. These results suggest that lack of extensive T-cell depletion in haploidentical transplantation is associated with high GVHD rates and diminishes the benefits of NK-cell alloreactivity.

Adolescent↗

PubMed2004

A multicenter international evaluation of single-tube amplification protocols for sequencing-based typing of HLA-DRB1 and HLA-DRB3,4,5.

We have described previously a novel single-tube polymerase chain reaction (PCR) amplification (STAmp) protocol for the efficient sequencing-based typing (SBT) of human leukocyte antigen (HLA)-DRB1. The PCR amplification mix includes primers to each of seven allele group-sequence motifs. We have applied this principle to the simultaneous SBT of HLA-DRB3, -DRB4, and -DRB5 using locus specific primers. We report here a multicenter international evaluation of the STAmp protocols performed as a component of the 13th International Histocompatibility Workshop. Identical amplification primer mixes, sequencing primers, and DNA were sent to participating laboratories. The primer mixes contained the amplification primers and the PCR buffer. Each laboratory was requested to amplify the DNA with the primer mixes and perform SBT on the resulting PCR protocols, using their own protocols, and return the typing results for analysis. The reported results indicated that the expected sequence could be obtained with a variety of PCR amplification and sequencing platforms and protocols. There were difficulties but these seemed unrelated to STAmp reagents and suggest that optimal SBT results can be obtained if bi-directional sequencing is performed and software is used for sequence verification and editing. This indicates that SBT by STAmp can be applied in many laboratories for high-throughput HLA-DRB1 and HLA-DRB3,4,5 SBT.

Alleles↗

PubMed2004

Assign 2.0: software for the analysis of Phred quality values for quality control of HLA sequencing-based typing.

As improvements to DNA sequencing technology have resulted in increasing the throughput of DNA sequencing, the bottleneck for high throughput DNA sequencing-based typing (SBT) has shifted to sequence analysis, genotyping and quality control (QC). Consistent high-quality DNA sequence is required in order to reduce manual verification and editing of sequence electropherograms. However, identifying systematic changes in quality is difficult to achieve without the aid of sophisticated sequence analysis programs dedicated to this purpose. We describe a computer software program called Assign 2.0, which integrates sequence QC analysis and genotyping in order to facilitate high-throughput SBT. Assign 2.0 performs an analysis of Phred quality values in order to produce quality scores for a sample and a sequencing run. This enables sample-to-sample and run-to-run QC monitoring and provides a mechanism for the comparison of sequence quality between various genes, various reagents and various protocols with the aim of improving the overall quality of DNA sequence data. This, in turn, will result in reducing sequence analysis as a bottleneck for high-throughput SBT.

Alleles↗

PubMed2003

Quality assessment program for genotypic antiretroviral testing improves detection of drug resistance mutations.

Genotypic antiretroviral testing is now widely used for the management of patients who are undergoing antiretroviral therapy for human immunodeficiency virus infection. The assays are complex, and there is considerable potential for variation between laboratories. Informative and ongoing quality assessment programs (QAPs) which address all aspects of testing are required. The panel distribution of clinical material is a critical component of QAPs. We report on the results and data from a recent panel. Four cryopreserved plasma samples from treated donors were distributed to nine laboratories. Three laboratories performed testing by commercial assays, and six laboratories used in-house assays, with one laboratory reporting results from two in-house assays. There was complete concordance between results for 95.9% of the nucleotide sequence and 94.5% of the amino acid sequence. Despite this overall high level of concordance, the degree of concordance at drug resistance mutation (DRM) sites when DRMs were present was considerably less (38% of DRM sites). Consequently, only 3 of the 10 methods reported 100% of DRMs as present. This elevated discrepancy rate is almost certainly a result of variability in the identification of mixtures of nucleotides (mixtures) at any site within the sequence. In addition, laboratories differed in the number of codons in the reverse transcriptase gene that were sequenced and their ability to amplify all samples. This panel distribution demonstrated a requirement for laboratory participation in ongoing QAPs and the optimization of assays with standards that contain mixtures.

Anti-HIV Agents↗

PubMed2002

Association between presence of HLA-B*5701, HLA-DR7, and HLA-DQ3 and hypersensitivity to HIV-1 reverse-transcriptase inhibitor abacavir.

BACKGROUND: The use of abacavir--a potent HIV-1 nucleoside-analogue reverse-transcriptase inhibitor--is complicated by a potentially life-threatening hypersensitivity syndrome in about 5% of cases. Genetic factors influencing the immune response to abacavir might confer susceptibility. We aimed to find associations between MHC alleles and abacavir hypersensitivity in HIV-1-positive individuals treated with abacavir. METHODS: MHC region typing was done in the first 200 Western Australian HIV Cohort Study participants exposed to abacavir. Definite abacavir hypersensitivity was identified in 18 cases, and was excluded in 167 individuals with more than 6 weeks' exposure to the drug (abacavir tolerant). 15 individuals experienced some symptoms but did not meet criteria for abacavir hypersensitivity. p values were corrected for comparisons of multiple HLA alleles (p(c)) by multiplication of the raw p value by the estimated number of HLA alleles present within the loci examined. FINDINGS: HLA-B*5701 was present in 14 (78%) of the 18 patients with abacavir hypersensitivity, and in four (2%) of the 167 abacavir tolerant patients (odds ratio 117 [95% CI 29-481], p(c)<0.0001), and the HLA-DR7 and HLA-DQ3 combination was found in 13 (72%) of hypersensitive and five (3%) of tolerant patients (73 [20-268], p(c)<0.0001 ). HLA-B*5701, HLA-DR7, and HLA-DQ3 were present in combination in 13 (72%) hypersensitive patients and none of the tolerant patients (822 [43-15 675], p(c)<0.0001). Other MHC markers also present on the 57.1 ancestral haplotype to which the three markers above belong confirmed the presence of haplotype-specific linkage disequilibrium, and mapped potential susceptibility loci to a region bounded by C4A6 and HLA-C. Within the entire abacavir-exposed cohort (n=200), presence of HLA-B*5701, HLA-DR7, and HLA-DQ3 had a positive predictive value for hypersensitivity of 100%, and a negative predictive value of 97%. INTERPRETATION: Genetic susceptibility to abacavir hypersensitivity is carried on the 57.1 ancestral haplotype. In our population, withholding abacavir in those with HLA-B*5701, HLA-DR7, and HLA-DQ3 should reduce the prevalence of hypersensitivity from 9% to 2.5% without inappropriately denying abacavir to any patient.

Adult↗

PubMed2001

Localization of central MHC genes influencing type I diabetes.

The contribution of MHC class II haplotypes to susceptibility to type I diabetes has been clearly established, and interest has now focused on the effects of additional genes in the MHC region. We have investigated the central MHC alleles on 8.1 ancestral haplotype (HLA-A1, B8, DR3, DQ2), as it is well conserved in Caucasian populations. The HLA-DR3-DQ2 genotype is a recognized risk factor for type I diabetes. Single nucleotide polymorphisms and microsatellites in the MHC were used to map segments of the 8.1 ancestral haplotype carried by type I diabetic and control subjects expressing either HLA-B8 or DR3, but not both these markers. In this way we controlled for the diabetogenic effect of carriage of DR3. Alleles of the 8.1 ancestral haplotype between TNFA-308/D6STNFa and HLA-B were carried with significantly greater frequency in B8(-), DR3(+) type I diabetic patients compared with B8(-), DR3(+) controls. This interval was marked by a BAT1 gene polymorphism and a MIB microsatellite allele.

Alleles↗

PubMed2001

Can MHC class II genes mediate resistance to type 1 diabetes?

Numerous studies have associated carriage of HLA-DRB1*1501, DQA1*0102 and DQB1*0602 (DR15, DQ6) with dominant resistance to type 1 diabetes and have concluded that one or more of the component HLA class II molecules mediate this effect. Mechanisms for MHC class II-mediated resistance to diabetes have been proposed from studies of transgenic mice, usually using the diabetes-prone non-obese diabetic (NOD) strain. However, these studies have not reached any consensus on a plausible mechanism. In this study we question why the role of central MHC genes in resistance to diabetes has not been addressed, as the central MHC carries markers of susceptibility to diabetes in linkage disequilibrium with several genes with known or putative immunoregulatory functions. To illustrate the type of studies required to address this issue, we selected diabetes patients and control subjects for carriage of HLA-DR15 and the C allele at position +738 in the inhibitor of kappa B-like gene (IKBL). These alleles mark the 7.1 haplotype (HLA-A3, B7, IKBL738*C, DR15, DQ6). HLA-DR15 was the most effective marker of resistance, but an effect may be evident with IKBL738*C in a larger study. Moreover, carriage of the entire haplotype was particularly rare in patients. The best explanation for this is that the critical gene lies between IKBL and HLA-DRB1, and is more closely linked to HLA-DRB1. Candidate genes at the centromeric end of the central MHC are reviewed, highlighting the need for further study.

Adult↗

PubMed2000

Duplication and diversification of the apolipoprotein CI (APOCI) genomic segment in association with retroelements.

We have previously shown that several multicopy gene families within the major histocompatibility complex (MHC) arose from a process of segmental duplication. It has also been observed that retroelements play a role in generating diversity within these duplicated segments. The objective of this study was to compare the genomic organization of a gene duplication within another multicopy gene family outside the MHC. Using new continuous genomic sequence encompassing the APOE-CII gene cluster, we show that APOCI and its pseudogene, APOCI', are contained within large duplicated segments which include sequences from the hepatic control region (HCR). Flanking Alu sequences are observed at both ends of the duplicated unit, suggesting a possible role in the integration of these segments. As observed previously within the MHC, the major differences between the segments are the insertion of sequences (approximately 200-1000 bp in length), consisting predominantly of Alu sequences. Ancestral retroelements also contribute to the generation of sequence diversity between the segments, especially within the 3' poly(A) tract of Alu sequences. The exonic and regulatory sequences of the APOCI and HCR loci show limited sequence diversity, with exon 3 being an exception. Finally, the typing of pre- and postduplication Alus from both segments indicates an estimated time of duplication of approximately 37 million years ago (mya), some time prior to the separation of Old and New World monkeys.

Alu Elements↗

PubMed2000

The genomic organization and evolution of the natural killer immunoglobulin-like receptor (KIR) gene cluster.

Natural killer (NK) immunoglobulin-like receptors (KIRs) are a family of polymorphic receptors which interact with specific motifs on HLA class I molecules and modulate NK cytolytic activity. In this study, we analyzed a recently sequenced subgenomic region on chromosome 19q13.4 containing eight members of the KIR receptor repertoire. Six members are clustered within a 100-kb continuous sequence. These genes include a previously unpublished member of the KIR gene family 2DS6, as well as 2DL1, 2DL4, 3DL1, 2DS4, 3DL2, from centromere to telomere. Two additional KIR genes, KIRCI and 2DL3, which may be located centromeric of this cluster were also analyzed. We show that the KIR genes have undergone repeated gene duplications. Diversification between the genes has occurred postduplication primarily as a result of retroelement indels and gene truncation. Using pre- and postduplication Alu sequences identified within these genes as evolutionary molecular clocks, the evolution and duplication of this gene cluster is estimated to have occurred 30-45 million years ago, during primate evolution. A proposed model of the duplication history of the KIR gene family leading to their present organization is presented.

Alleles↗

PubMed2000

A quality control program for crossmatching procedures for solid organ transplantation. The participating laboratories of the Australasian and South Asian Tissue Typing Association.

The National Kidney Matching Scheme (NKMS) allows matching and allocation of donor organs throughout Australia. Sera from potential recipients are distributed to each interstate tissue typing laboratory on a monthly basis for crossmatching in the event of a cadaver donor. Therefore, it is essential there is consensus for results between these laboratories in order for donated organs to be allocated appropriately. A quality control program conducted under the auspices of ASEATTA was undertaken for (1) panel reactive antibody characterization; (2) routine T lymphocyte crossmatching; and (3) characterization of antibody isotype by DTT treatment. These aims were achieved by distribution of (1) six sera for the determination of PRA activity; (2) 20 scrambled trays including replicate dilutions of a strongly positive lymphocytotoxic serum, high titer monoclonal antibody and negative sera and; (3) 20 trays containing sera with IgG and/or IgM antibodies. These were then evaluated by each laboratory on a panel of T cells. There was concordance between laboratories for PRA levels and antibody characterization. However, there was considerable variation in crossmatch sensitivity and reproducibility, several laboratories had carryover and others could not detect weak IgM antibodies. These results demonstrate the utility and need for ongoing crossmatch exchange programs, particularly for laboratories participating in organ exchange programs.

Dithiothreitol↗

PubMed2000

Detection of KIR2DL4 alleles by sequencing and SSCP reveals a common allele with a shortened cytoplasmic tail.

Single-stranded conformation polymorphism (SSCP) by capillary electrophoresis was assessed as a screening and typing method for alleles of KIR2DL4. Exon 6 was investigated as this exon was reported to include three polymorphic nucleotides. Exon 6, intron 6 and exon 7 were amplified as a single polymerase chain reaction (PCR) product of 650 bp from genomic DNA. The PCR product was sequenced and analysed by SSCP. Exon 7 was found to be invariant. Only two nucleotides were found to be polymorphic in exon 6 and another three were found in intron 6. Strong linkage disequilibrium was found between the polymorphic nucleotides resulting in the presence of three alleles in a panel of 20 cell lines. Two alleles differed within intron 6 while the third allele differed at two nucleotides in exon 6. All six possible genotypes were distinguishable by SSCP providing information from both the forward and reverse primers was used. Exon 6 of one allele was one nucleotide shorter than that of the other alleles and the resulting frame shift is predicted to produce a truncated cytoplasmic tail due to a premature stop codon four codons into exon 7. SSCP was found to be an efficient method of typing exons 6 and 7 in a panel of 46 bone marrow donors. All three alleles were found to be common and one was in strong linkage disequilibrium with the presence of another KIR sequence KIR3DS1.

Alleles↗

PubMed2000

A novel locus affecting serum levels of IgG2a maps to the murine H2 region.

The effects of genes in the murine H2 region on basal immunoglobulin levels were investigated and ratios of IgG1/IgG2a were calculated, as low ratios indicate a Th1 cytokine mileu. H2b mice with B10 or BALB genetic backgrounds had higher levels of IgG2a than H2k and H2d congenic strains, and hence had low IgG1/IgG2a ratios. B10 (H2b) mice generally had high levels of IgG2b, IgG3, IgA and IgM, but this outcome was more variable. The high IgG2a phenotype was denoted Igis1 (Immunoglobulin isotype-1) and mapped telomeric of IEbeta using B10.A(4R) mice (high IgG2a) and B10.A(3R) and B10.A(5R) mice (low IgG2a). Further mapping in B10.A(2R), B10.A(1R) and B10.A(18R) mice placed Igis1 in the 27kb region between G7c and G7e.

Animals↗