E.M. Dauber

Tetragametic chimerism detected in a healthy woman with mixed-field agglutination reactions in ABO blood grouping

BACKGROUND: The case of a healthy woman with serologic blood group AB and her biologic father showing blood group O was investigated. Further analysis, including blood, buccal swabs, and nail clippings, revealed a tetragametic chimerism.

Germline mutations of STR-alleles include multi-step mutations as defined by sequencing of repeat and flanking regions

Well defined estimates of mutation rates are a prerequisite for the use of short tandem repeat (STR-) loci in relationship testing. We investigated 65 isolated genetic inconsistencies, which were observed within 50,796 allelic transfers at 23 STR-loci (ACTBP2 (SE33), CD4, CSF1PO, F13A1, F13B, FES, FGA, vWA, TH01, TPOX, D2S1338, D3S1358, D5S818, D7S820, D8S1132, D8S1179, D12S391, D13S317, D16S539, D17S976, D18S51, D19S433, D21S11) in Caucasoid families residing in Austria and Switzerland. Sequencing data of repeat and flanking regions and the median of all theoretically possible mutational steps showed valuable information to characterise the mutational events with regard to parental origin, change of repeat number (mutational step size) and direction of mutation (losses and gains of repeats). Apart from predominant single-step mutations including one case with a double genetic inconsistency, two double-step and two apparent four-step mutations could be identified. More losses than gains of repeats and more mutations originating from the paternal than the maternal lineage were observed (31 losses, 22 gains, 12 losses or gains and 47 paternal, 11 maternal mutations and 7 unclear of parental origin). The mutation in the paternal germline was 3.3 times higher than in the maternal germline. The results of our study show, that apart from the vast majority of single-step mutations rare multi-step mutations can be observed. Therefore, the interpretation of mutational events should not rigidly be restricted to the shortest possible mutational step, because rare but true multi-step mutations can easily be overlooked, if haplotype analysis is not possible.

Detection of granulocyte-reactive antibodies: a comparison of different methods.

Granulocyte‐reactive antibodies can cause autoimmune and neonatal immune neutropenias as well as transfusion‐related acute lung injury. The classical antibody‐detection methods granulocyte aggregation test (GAT), granulocyte immunofluorescence test (GIFT) and monoclonal antibody‐specific immobilization of granulocyte antigens (MAIGA) are time‐consuming and technically challenging. In recent years, flow cytometric white blood cell immunofluorescence test (Flow‐WIFT) and the microbeads assay LabScreen® Multi have emerged and are still subject of evaluation. These serological tests were compared on a screening and specification level.

Granulocyte-reactive antibodies are associated with red blood cell alloimmunization

Granulocyte‐reactive antibodies may cause transfusion‐related acute lung injury (TRALI) and immune neutropenias. Risk factors for their acquisition other than previous alloexposition are largely unknown. In addition to the known association between human leucocyte antigen alloantibodies and red blood cell alloimmunization in selected cohorts of transfused patients, this study investigated a possible extension of this association to granulocyte‐reactive antibodies in women with a history of pregnancy. The overall prevalence of granulocyte‐reactive antibodies in 333 samples from women with a history of pregnancy (143 samples containing red cell alloantibodies) was 23·1%. The prevalence in the red cell‐alloimmunized group (32·9%) was significantly higher than in controls (15·8%, P < 0·001). This could suggest that some individuals may be strong immunological responders, forming alloantibodies more readily than others.

Further sequence and length variation at the STR loci HumFES/FPS, HumVWA, HumFGA and D12S391

This paper reports population data and statistics for the HumFES/FPS, HumVWA, HumFGA and D12S391 loci in Austria. The sequences of some rare and new variant alleles which have been identified in the course of the present population study and other investigations are described. Sequence variation occurred in a HumFES/FPS allele revealing an (ATTT)9 structure and an A to C transversion in the 5′ flanking region. At the HumVWA locus the structural type of the common allele 14 has been found in one allele 13 and in three examples of allele 15. Additionally the TCTA (TCTG)3(TCTA)n structure has been observed in three examples of allele 13 and one allele 14, which is very uncommon. Another allele 14 showed a C to T transition in the third of nine TCTA repeats. The sequences of three length variations at the HumFGA locus, namely the alleles 16, 19.2 and 21.2 are reported. At the D12S391 locus a novel 19.1 allele was found in this study. An extended nomenclature is proposed for the HumVWA locus to denominate sequence variants in a precise but simple way.

Sequence-based definition of eight short tandem repeat loci located within the HLA-region in an Austrian population

Sequenced allelic ladders are a prerequisite for reliable genotyping of short tandem repeat (STR) polymorphisms and consistent results across instrument platforms. For eight STR-loci located on the short arm of chromosome 6 (6p21.3), a sequenced based nomenclature was established according to international recommendations. Publicly available reference DNA samples were sequenced enabling interested laboratories to construct their own allelic ladders. Three tetrameric (D6S2691, D6S2678, DQIV), one trimeric (D6S2906) and four dimeric repeat loci (D6S2972, D6S2792, D6S2789, D6S273) were investigated. Apart from the very complex sequence structure at the DQIV locus, three loci showed a compound and four loci a simple repeat pattern. In the flanking regions of some loci additional single nucleotide and insertion/deletion polymorphisms occurred as well as sequence polymorphisms within the repeat region of alleles with the same length. In an Austrian Caucasoid population sample (n=293) between eight and 22 alleles were found. No significant deviation from Hardy-Weinberg expectations was observed, the power of discrimination ranged from 0.826 to 0.978. The loci cover the HLA-coding region from HLA-A to HLA-DQB1 and can be used for a better definition of HLA haplotypes for population and disease association studies, recombination point mapping, haematopoietic stem cell transplantation as well as for identity and relationship testing.

Somatic mosaicisms of chromosome 1 at two different stages of ontogenetic development detected by Rh blood group discrepancies

Spontaneous Rh blood group changes are a striking sign, reported to occur mainly in patients with hematologic disorders. Upon routine blood grouping, 2 unrelated individuals showed unexplained mixed red cell phenotype regarding the highly immunogenic c antigen (RH4), clinically relevant for blood transfusion and fetomaternal incompatibility. About half of their red cells were c-positive, whereas the other half were c-negative. These apparently hematologically healthy females had no history of transfusion or transplantation, and they tested negative for chimerism. Genotyping of flanking chromosome 1 microsatellites in blood, finger nails, hair, leukocyte subpopulations, and erythroid progenitor cells showed partial loss of heterozygosity encompassing the RHD/RHCE loci, spanning a 1p region of 26.7 or 42.4 Mb, respectively. Remarkably, in one case this was detected in all investigated tissues, whereas in the other, exclusively myeloid cells showed loss of heterozygosity. Both carried the RhD-positive haplotypes CDe and the RhD-negative haplotype cde. RHD/RHCE genotypes of single erythroid colonies and dual-color fluorescent in situ hybridization analyses indicated loss of the cde haplotype and duplication of the CDe haplotype in the altered cell line. Accordingly, red cell C antigen (RH2) levels of both propositae were higher than those of heterozygous controls. Taken together, the Rhc phenotype splitting appeared to be caused by deletion of a part of 1p followed by duplication of homologous stretches of the sister chromosome. In one case, this phenomenon was confined to myeloid stem cells, while in the other, a pluripotent stem cell line was affected, demonstrating somatic mosaicism at different stages of ontogenesis.

Allograft and patient survival after sequential HSCT and kidney transplantation from the same donor-A multicenter analysis

Tolerance induction through simultaneous hematopoietic stem cell and renal transplantation has shown promising results, but it is hampered by the toxicity of preconditioning therapies and graft‐versus‐host disease (GVHD). Moreover, renal function has never been compared to conventionally transplanted patients, thus, whether donor‐specific tolerance results in improved outcomes remains unanswered. We collected follow‐up data of published cases of renal transplantations after hematopoietic stem cell transplantation from the same donor and compared patient and transplant kidney survival as well as function with caliper‐matched living‐donor renal transplantations from the Austrian dialysis and transplant registry. Overall, 22 tolerant and 20 control patients were included (median observation period 10 years [range 11 months to 26 years]). In the tolerant group, no renal allograft loss was reported, whereas 3 were lost in the control group. Median creatinine levels were 85 μmol/l (interquartile range [IQR] 72‐99) in the tolerant cohort and 118 μmol/l (IQR 99‐143) in the control group. Mixed linear‐model showed around 29% lower average creatinine levels throughout follow‐up in the tolerant group (P < .01). Our data clearly show stable renal graft function without long‐term immunosuppression for many years, suggesting permanent donor‐specific tolerance. Thus sequential transplantation might be an alternative approach for future studies targeting tolerance induction in renal allograft recipients.

Standardized genotyping of HLA STR by CE as surrogate for HLA class I and II markers and for identification of HLA identical siblings.

Linkage disequilibria (LD) between alleles and haplotypes of human leucocyte antigen, locus A (HLA) and STR loci located in the human major histocompatibility complex were analyzed in order to investigate whether or not HLA alleles and haplotypes are predictable by alleles or haplotypes of HLA STRs. Standardized genotyping of eight STR loci (D6S2972, D6S2906, D6S2691, D6S2678, D6S2792, D6S2789, D6S273, and DQIV) was performed by CE on 600 individuals from 150 Austrian Caucasoid families with known HLA‐A,‐B,‐C and –DRB1 typing. From those, 576 full haplotypes of four HLA and eight STR loci were obtained. Haplotypes of two flanking STRs predicted HLA alleles and two‐locus HLA haplotypes better than single STR alleles, except HLA‐DRB1 alleles (92% were in LD with DQIV alleles only). A percentage of 65–86% of three and four‐locus HLA haplotypes were in LD with haplotypes of three, four, and eight of their flanking STR loci including numerous clear‐cut predictions (20–61%). All eight and a set of the four most informative STR loci D6S2972, D6S2678, D6S2792, and DQIV could identify all HLA identical and nonidentical siblings in 138 pairs of siblings. The results of this proof of concept study in Austrian Caucasoids show, that HLA STRs can aid the definition of HLA‐A,‐B,‐C,‐DRB1 haplotypes and the selection of sibling donors for stem cell transplantation.