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R Blasczyk

Publications and source records attributed to R Blasczyk.

At least 37 records · Page 2Linked to original sources
PubMed2002

HLA-B*4431: a new HLA-B variant with a complex ancestral history involving HLA-B*44, B*40 and B*07 alleles.

We here describe the identification of the new allele HLA-B*4431, which was found in three members of a Turkish family. Sequencing of the new allele following haplotype-specific PCR amplification revealed that exon 2 is identical to HLA-B*4402, whereas exon 3 resembles a HLA-B*40 variant with the exception of position 572, where a single nucleotide transversion (C > G) leads to an amino acid exchange (Trp162Ser). The generation of the 3' part of B*4431 may be best explained by a separate recombination between B*40 and B*07. Although B*4431 consists of B44 in its alpha1 domain and of B60(40) in its alpha2 domain; the new allele only displayed B44 seroreactivity, which demonstrates that epitopes crucial for B60(40) specificity must be located in the alpha1 domain.

Alleles↗
PubMed2002

HLA-B*3531, a hybrid of B35 and B61, implications for diagnostic approaches to alleles with complex ancestral compositions.

The serological characterization of allelic variants that have been generated by large-scale interallelic recombination events indicates which residues may be involved in the formation of epitopes crucial for serological recognition. The allelic product of HLA-B*3531 is composed of B35 in its alpha1 domain and of B61(40) in its alpha2 domain. Both specificities are only weakly detectable with available sera. Allelic products with 'mixed' serology also represent a challenge to DNA-based HLA typing methods, as only the sequence motif of one ancestral allele may be recognized. In this case the hidden specificity would not be considered in the matching process and might not be recognized as an antigen 'unacceptable' to the recipient.

Alleles↗
PubMed2002

Sequence similarity matching: proposal of a structure-based rating system for bone marrow transplantation.

Recent advances in DNA-based typing have led to the detection of a continuously growing number of HLA alleles. For this reason, HLA matching in transplantation of hematopoietic stem cells from unrelated donors has become increasingly complicated. When there is no genotypically identical sibling and there are several alternative potential donors that all have a mismatch at a relevant HLA locus, until now no rating system has existed indicating different levels of allogenicity. In order to find a theoretical approach to this problem we propose a rating system ('dissimilarity index') based on structural data of HLA class I molecules, and on published data about frequencies of naturally occurring amino acid exchanges. For demonstration we employ our rating system for the comparison of the HLA-A*23 and A*24 groups, both of which allelic products are subdivisions of the serological HLA-A9 family. Remarkable differences between the subtypes were revealed, which were superior to a simple sequence comparison. More surprisingly, it was uncovered that some alleles of the A*24 group showed fewer differences to A*2301 than to alleles within their own subtype group. Sequence similarity matching may serve as a starting point for the clinical evaluation of acceptable mismatches within the HLA-A9 family and serve as a model for other HLA class I groups.

Bone Marrow↗
PubMed2002

Equivalent mobilization and collection of granulocytes for transfusion after administration of glycosylated G-CSF (3 microg/kg) plus dexamethasone versus glycosylated G-CSF (12 microg/kg) alone.

BACKGROUND: The aim of this study was to find a regimen for mobilization and collection of granulocytes that combines low-dose G-CSF administration with satisfactory PMN mobilization and apheresis at a low rate of donor adverse reactions. STUDY DESIGN AND METHODS: In a prospective study, 52 healthy unrelated volunteers received a single subcutaneous injection of glycosylated G-CSF (Lenograstim Chugai-Pharma, Frankfurt, Germany) at medians of 3.1 (range, 2.4-3.6) microg per kg plus dexamethasone (8 mg orally; n = 29) or at 11.8 (7.1-18.5) microg of lenograstim per kg (p < or = 0.0001) without dexamethasone (n = 23) and underwent standard apheresis using the PMN program of a cell separator (Spectra, COBE [now Gambro] BCT). WBC and PMN mobilization results and apheresis yields were compared and the severity and clinical significance of donor adverse reactions was evaluated. RESULTS: For the low-dose G-CSF plus dexamethasone versus the high-dose G-CSF alone group, similar mobilization results were observed for WBCs with 31.3 (19.1-44.9) x 10(9) per L versus 27.5 (19.2-44.0) x 10(9) per L (p = 0.21, NS) and PMNs with 29.0 (17.6-42.2) x 10(9) per L versus 25.2 (16.2-39.0) x 10(9) per L (p = 0.08, NS). The PMN apheresis yields were equal with 70 (39-139) x 10(9) per unit with low-dose G-CSF versus 68 (33-120) x 10(9) per unit in the high-dose G-CSF group (p = 0.83, NS). Regarding donor adverse reactions, 7 out of 29 (24%) and 8 out of 23 donors (35%) reported moderate or severe symptoms. The character of these reactions was different; symptoms of greater clinical significance and a higher need for analgesics were observed in the high-dose G-CSF group. CONCLUSIONS: A Lenograstim dose of 3 microg per kg plus DXM assures effective PMN mobilization and acceptable apheresis components. The combination of glycosylated G-CSF with DXM allows a significant dose reduction in G-CSF for PMN mobilization and collection as compared with higher G-CSF doses alone. In the high-dose G-CSF mobilization group, adverse reactions were more severe and required more analgesics.

Adult↗
PubMed2001

Second German consensus on immunogenetic donor search for allotransplantation of hematopoietic stem cells.

The present paper summarizes the results of the second German consensus meeting on immunogenetic donor search for allotransplantation of hematopoietic stem cells held in Essen in November 1999 under the auspices of the German Society for Immunogenetics (DGI) and the German Working Party for Blood and Marrow Transplantation (DAG-KBT). Immunogeneticists and transplant physicians from all over the country agreed to update the national standards for: (1) search strategy including the role of unrelated and extended family donor search after unsuccessful core family donor search, (2) histocompatibility loci to be typed, (3) histocompatibility typing techniques to be used (HLA serology vs DNA-based HLA typing, cellular tests, serum cross-match), and (4) acceptable HLA mismatches in the context of a defined underlying disease, donor type, and conditioning regimen.

Aging↗
PubMed2001

Glatiramer acetate (GA) induces IL-13/IL-5 secretion in naive T cells.

In order to define possible mechanisms of immunomodulation by glatiramer acetate (GA), we investigated the primary in vitro cytokine response of peripheral blood mononuclear cells (PBMCs) and T-cell subpopulations. In PBMCs from healthy subjects and untreated patients with multiple sclerosis (MS) GA-induced T-cell proliferation and mRNA expression/cytokine, secretion of IL-13 and IL-5 but not of IL-10, TGF-beta or IL-12, IL-4 was detected at the mRNA level only. IFN-gamma was induced in a few subjects at very low concentrations. The response to GA was driven by the CD4(+)/CD45RA(+) T-cell subpopulation and was mediated by T-cell receptor (TCR) engagement as determined by anti-TCR blocking antibodies. The findings are compatible with the hypothesis that GA functions as partial or weak TCR-agonist activating naive T cells to produce the Th2 cytokines IL-13 and IL-5.

Adjuvants, Immunologic↗
PubMed2001

Non-expression of HLA-B*5111N is caused by an insertion into the cytosine island at exon 4 creating a frameshift stop codon.

The identification of the "blank" allele HLA-B*5111N, which was detected in German and Czech individuals, is described. In the pedigree analysis this new allele segregates with the serological haplotype HLA-A2; B-; DR4 which is frequent in Czech population. The non-expression of B*5111N is caused by the insertion of an additional cytosine molecule at the cytosine island between the nucleotides 621-626 (codons 183-185, first three codons of exon 4) leading to a frame shift that creates a stop codon at codon 196. This insertion may be explained either by conversion with the pseudogene HLA-J or by slipped-strand mispairing. In order not to overlook the presence of alleles with altered expression in case of hematopoietic stem cell transplantation, both serological and DNA-based typing should be performed (Note).

Alleles↗
PubMed2001

Comparative association analysis reveals that corneodesmosin is more closely associated with psoriasis than HLA-Cw*0602-B*5701 in German families.

HLA antigens are associated with psoriasis vulgaris across populations with different ethnic background. We have previously shown that in Caucasians this association is primarily based on the class I alleles of the extended HLA haplotype 57.1 (EH57.1/I), HLA-Cw6-HLA-B57. However, it remained unclear whether HLA-Cw6 itself or a closely linked locus predisposes to the disease. An interesting candidate for this presumed locus is corneodesmosin, which is exclusively synthesized in keratinocytes. The corneodesmosin gene locus (CDSN) is only 160 kb telomeric to HLA-C and tightly associated with psoriasis. In order to find out whether EH57.1/I or a corneodesmosin variant are the susceptibility determinants on 6p, HLA class I alleles and single-nucleotide polymorphisms (SNPs) of corneodesmosin were investigated at the sequence level and analyzed by comparative association tests. Transmission disequilibrium tests (TDT) were performed in 52 nuclear families, of which 36 were fully informative for a joint comparison of HLA and CDSN with regard to association to psoriasis. The extended TDT according to Wilson was employed to test for locus interaction. Using the HLA haplotype EH57.1/I and the CDSN haplotype formed by three intragenic variant sites at nt=619 (T), 1236 (T), and 1243 (C), we obtained the best resolution of parental transmission to index cases in the trio families. On direct comparison of the contributions of the HLA and the CDSN haplotypes, there was a markedly stronger association of the corneodesmosin TTC haplotype, which is not apparent in single locus analysis. We show furthermore that there is no higher order interaction between psoriasis, HLA, and CDSN. This lack of three-locus interaction is suggestive of two independent genetic contributions to psoriasis within the major histocompatibility complex (MHC).

Alleles↗
PubMed2001

Identification of the novel allele HLA-DRB1*1137 which probably originated from DRB1*11011: implications for mismatch with its ancestor allele at bone marrow transplantation.

The identification of the new allele HLA-DRB1*1137, which was found in a Caucasian individual, is described. In the sequence analysis the new allele differs from DRB1*11011 by position 227 (T>A) which is located in exon 2. At the protein level, the new allele has one amino acid difference compared to DRB1*1101 (Phe47Tyr). Residue 47 is likely to contribute to the peptide binding site of HLA-DR11 and thus to be important for peptide binding. However, as phenylalanine and tyrosine have very similar physical and chemical features allogenicity in case of mismatch at bone marrow transplantation may be weak.

Alleles↗
PubMed2001

HLA-DRB fluorotyping by dark quenching and automated analysis.

In fluorescence-based sequence-specific primed polymerase chain reaction (PCR), referred to as fluorotyping for HLA typing, a major problem is the overlap of the emission spectra of the single dyes. In order to increase the robustness of the previously described HLA-DRB1,3,4,5 low-resolution fluorotyping method, we have constructed two probes quenched by the non-fluorescent acceptor dye DABCYL. The HLA-DRB-specific probe was labeled with FAM, and the internal control probe with TAMRA, respectively, as reporter fluorescent dyes. TAMRA was replaced by DABCYL as a quencher, which led to increased robustness and better discrimination between negative and positive amplification results. ROX was used as a reference to normalize the fluorescence of the reporter dyes. Moreover, as FAM and TAMRA differ strongly by their emission maxima, HLA-DRB-specific and internal control amplification could be clearly distinguished. To further automate data analysis, the software of the TaqMan system 7700 was supplemented by an EXCEL-based calculation table, which directly took over the data. Using modified fluorotyping chemistry and automated data analysis, a total of 201 DNA samples was typed correctly. In summary, HLA-DRB fluorotyping by dark quenching and automated analysis proved to be a robust and reliable tool for research and routine purposes.

Electronic Data Processing↗
PubMed2001

The nucleotide diversity of MICA and MICB suggests the effect of overdominant selection.

The major histocompatibility complex (MHC) class I-related molecules A and B (MICA and MICB) are stress-inducible cell surface antigens that are recognized by immunocytes bearing the receptor NKG2D. In our study we estimated the average number of synonymous (pis) and nonsynonymous nucleotide substitutions (pia) per site in exons 2-4 of MICA and MICB. In exons 2 and 3 of MICB only nonsynonymous substitutions were found, and in exon 3 of MICA pia clearly exceeded pis. This finding is in contrast to the evolutionary parameters found in most other genes, and is reminiscent of the elevated pia values caused by overdominant selection in the peptide-binding region of conventional MHC class I molecules. It may be explained by the hypothetical interaction with nonpeptide antigens, or by resistance against pathogens.

Evolution, Molecular↗
PubMed2000

The noncoding regions of HLA-DRB uncover interlineage recombinations as a mechanism of HLA diversification.

The mechanisms generating new alleles at the MHC loci are still unknown in detail, and several proposals have been made to explain the extent of polymorphism. The patchwork pattern of polymorphism in the 2nd exon of HLA-DRB1 recommends this locus as a model for the study of the potential of interallelic gene conversion. In general, the inference of gene conversion-like events based exclusively on exon sequence comparisons may be misleading because the identity of the putative donor allele remains unknown. In this study, we describe five alleles of the HLA-DRB1 gene, which intron regions give evidence for interlineage recombination events either strictly located at the 2nd exon or involving the adjacent introns. Furthermore, we show that the noncoding regions provide important clues to the mechanisms of the generation of new alleles, and our results indicate that interlineage recombinations may be hidden and are perhaps more frequent than currently expected.

Alleles↗
PubMed2000

Identification of the novel allele HLA-B*0809 in a Caucasian individual: estimation of allogeneic potential between B*08 variants.

The identification of the new allele HLA-B*0809, which was found in a Caucasian individual, is described. In the sequence analysis the new allele differs from B*0801 by six nucleotides located in exon 3. As the structure is identical to a variety of other HLA-B alleles, it is likely that the new allele originated by gene conversion. At the protein level, the new allele has two amino acid differences compared to B*0801. Comparing the residues of the alpha1 and alpha2 domains of the B*08 variants to each other, a high degree of polymorphism was found. Three alleles differ from B*0801 by only one amino acid residue whereas the other comparisons revealed at least two disparities. B*0809 differs from the other B*08 variants by at least two amino acid residues, suggesting that mismatching may provoke alloreactivity and thus impair clinical outcome of bone marrow transplantation. Among the B*08 alleles with a single amino acid difference, the mismatch combinations B*0801 vs. B*0805 and B*0801 vs. B*0807 appear to be the most compatible based on structural data.

Alleles↗
PubMed2000

Identification of the novel allele HLA-B*1545: assessment of alloreactivity in case of mismatch with other B*15 alleles.

The novel allele HLA-B*1545, which has been serologically typed as B62, was identified in a male Caucasian. In the sequence analysis the new allele differs from B*1507 by nucleotide 419 which is located in exon 3. Its structure suggests that it may have originated by a point mutation or by gene conversion with a variety of HLA-B alleles. At the protein level, the nucleotide substitution results in an amino add exchange compared to B*1507 (Tyr116Ser). Due to probably substantial differences to B*1507 and the other B*15 variants with regard to peptide binding, a mismatch is likely to impair clinical outcome of bone marrow transplantation.

Alleles↗
PubMed2000

Identification of the novel allele HLA-B*1546 which belongs to the serological B72 type: implications for bone marrow transplantation.

The identification of the novel allele HLA-B*1546, which has serological B50 and B72 reactivity, was found in two members of a family of Turkish origin. In the sequence analysis the new allele differs from B*1501 by four nucleotides in exon 2. Its structure suggests that it may have originated by gene conversion with B*40, B*41, B*44, B*4501, B*47, B*4901 or B*50. At the protein level, the new allele has three amino acid differences compared to B*1501. Sequence alignment demonstrates that amino acid residue 46 is crucial for serological B72 reactivity. Due to substantial differences with other B*15 variants a possible mismatch may impair clinical outcome of bone marrow transplantation.

Alleles↗
PubMed2000

HLA-A*2416: a new allele of the HLA-A19 lineage.

We here report on a new HLA-A19 allele (A*2416) found in a German kidney recipient. Serological class I typing revealed HLA-A11,19 without clear definition of the A19 split antigen. As with serology, polymerase chain reaction (PCR)-based typing also revealed inconclusive results. We therefore sequenced the gene from the 5' flanking region through the 3'-end of exon 4 of this allele after haplotype-specific PCR amplification. The sequence analysis revealed a new HLA-A allele which is identical to A*3101 with the exception of the 3' half of exon 2 which is identical to the common A9 alleles. The phylogenetic analysis constructed with the nearest-neighbor algorithm and based on exons 1-4 or introns 1-3 clearly indicated, that A*2416 belongs unequivocally to the A19 lineage.

Alleles↗
PubMed2000

Identification of the novel allele HLA-A*6813 in two members of a family of Syrian origin: implications for bone marrow transplantation.

The identification of the new allele HLA-A*6813, which was found in a woman of Syrian origin and her son, is described. In the sequence analysis the new allele differs from A*68011 by positions 259 (A>G) and 261 (C>G) in exon 2. As the structure is thus identical to the HLA-A consensus sequence it is likely that the new allele originated by gene conversion. At the protein level, the new allele has one amino acid difference from A*6801 (Asn63Glu), which results in a distinct banding pattern in one dimensional-isoelectric focusing. Amino acid residue 63 contributes to the formation of pocket A and B and is thus important for peptide binding. A*6813 was serologically detectable only by two of six polyclonal, but by three monoclonal antisera. The restricted serological A68 activity may be explained by altered peptide binding as presented peptides can affect the serological recognition of major histocompatibility complex (MHC) class I molecules. Moreover, our findings suggest that a possible mismatch with the other known A*68 variants may impair clinical outcome of bone marrow transplantation.

Alleles↗