Body-wide chimerism and mosaicism are predominant causes of naturally occurring ABO discrepancies.

Routine ABO blood group typing of apparently healthy individuals sporadically uncovers unexplained mixed-field reactions. Such blood group discrepancies can either result from a haematopoiesis-confined or body-wide dispersed chimerism or mosaicism. Taking the distinct clinical consequences of these four different possibilities into account, we explored the responsible cause in nine affected individuals. Genotype analyses revealed that more than three-quarters were chimaeras (two same-sex females, four same-sex males, one sex-mismatched male), while two were mosaics. Short tandem repeat analyses of buccal swab, hair root and nail DNA suggested a body-wide involvement in all instances. Moreover, genome-wide array analyses unveiled that in both mosaic cases the causative genetic defect was a unique copy-neutral loss of heterozygosity encompassing the entire long arm of chromosome 9. The practical transfusion- or transplantation-associated consequences of such incidental discoveries are well known and therefore easily manageable. Far less appreciated is the fact that such findings also call attention to potential problems that directly ensue from their specific genetic make-up. In case of chimerism, these are the appearance of seemingly implausible family relationships and pitfalls in forensic testing. In case of mosaicism, they concern with the necessity to delineate innocuous pre-existent or age-related from disease-predisposing and disease-indicating cell clones.

Immunoglobulin Class Profiles of ABO Antibodies in Saliva and Serum of Healthy Individuals.

Introduction: The coronavirus disease (COVID-19) pandemic gave rise to studies investigating the association of ABO blood group with COVID-19 susceptibility. It is hypothesized that ABO antibodies might play a role in neutralizing SARS-CoV-2. However, ABO antibodies were exclusively analyzed in blood samples. Investigation of ABO antibodies in saliva, an easy-to-obtain surrogate for respiratory secretions, may provide novel insights into mucosal immunity crucial in early defense against respiratory pathogens. Methods: In this study, saliva and serum samples from healthy individuals with known blood groups were investigated using a flow cytometric method for separate anti-A/anti-B IgA, IgM, and IgG class antibody detection. Saliva samples were additionally tested using hemagglutination-based neutral and indirect anti-human globulin test gel cards. This method comparison was complemented by dilution experiments with a high-titer anti-A/anti-B WHO standard. Results: In saliva, IgA was the most abundant ABO antibody class, followed by IgM; IgG was detected only in low levels in all non-AB blood types. In serum, IgM was the predominant ABO antibody class in all non-AB blood types, followed by IgA and IgG, the latter mainly detected in group O individuals. Saliva and serum samples of group O individuals yielded the highest variability of ABO-specific antibody levels. Regardless of sample material and blood type, major interindividual differences in ABO antibody reactivities were recorded. Antibody levels correlated moderately between these two body fluids. There were no significant sex and age-group differences in ABO antibody levels in both serum and saliva. WHO standard dilution experiments yielded technique-specific limits of detection, illustrating the inherent differences of immunofluorescence versus agglutination. Conclusion: For the first time, salivary ABO antibodies were investigated by separate detection of the three most relevant antibody classes IgA, IgM, and IgG in a healthy cohort. This study opens new perspectives regarding mucosal ABO antibody class profiles and their potential influence on respiratory infections.

External quality assessment providers' services appear to more impact the immunohaematology performance of laboratories than national regulatory and economic conditions.

OBJECTIVES: Medical laboratories may, at their own discretion, exceed but not undercut regulatory quality requirements. Available economic resources, however, may drive or hinder eagerness to exceed minimum requirements. Depending on the respective scopes of regulatory and economic framework conditions, differing levels of quality efforts to safeguard laboratory performance can be anticipated. However, this has not yet been investigated. METHODS: Immunohaematology external quality assessment (EQA) results collected by 26 EQA providers from their participant laboratories in 73 countries from 2004 to 2019 were evaluated. Error rates were aggregated in groups according to the respective national regulatory and economic framework conditions, to whether or not expert advice was provided in case of incorrect results, and the frequency of EQA samples. RESULTS: These representative data indicate no association between national regulatory (mandatory participation in EQA, monitoring of performance of individual laboratories by authorities, financial consequences of incorrect results) and economic (level of national income, share of national health expenditure) conditions to the quality performance of medical laboratories in immunohaematology. However, EQA providers' support for laboratories in the event of incorrect results appear to be associated with lower error rates, but a high EQA sample frequency with higher error rates. CONCLUSIONS: Further research into the impact of introducing or changing services of EQA providers is needed to confirm the results found in this first of its kind study.

Quantitative PCR of INDELs to measure donor-derived cell-free DNA-a potential method to detect acute rejection in kidney transplantation: a pilot study.

The quantification of donor-derived cell-free DNA (ddcfDNA) in recipient's plasma is a novel, but technically challenging noninvasive method to assist the diagnosis of acute rejection (AR). A quantitative real-time PCR (qPCR) approach targeting insertion/deletion polymorphisms (INDEL) was adapted to measure ddcfNA in plasma samples from 29 kidney transplant recipients obtained at time of clinically indicated biopsies (eight patients with a histologically verified AR, nine with borderline rejection and 12 without evidence of rejection). Measured ddcfDNA levels of smaller INDEL amplicon targets differed significantly (P = 0.016, Kruskal-Wallis H test) between recipients with biopsy-proven AR (median 5.24%; range 1.00-9.03), patients without (1.50%; 0.41-6.50) and patients with borderline AR (1.91%; 0.58-5.38). Similarly, pairwise testing by Mann-Whitney U-tests revealed significant differences between recipients with AR and without AR (P = 0.012) as well as patients with AR and borderline histology (P = 0.015). Receiver operating characteristic (ROC) analysis revealed an area under the ROC curve for discriminating AR and non-AR biopsies of 0.84 (95% CI: 0.66-1.00). The determined cutoff value of 2.7% ddcfDNA showed a sensitivity of 0.88 (95% CI: 0.63-1.00) and specificity of 0.81 (95% CI: 0.64-0.98). INDEL qPCR represents a novel method to quantify ddcfDNA on standard qPCR instruments within 6-8 h with high sensitivity and specificity to detect AR.

To Win the Battle, First Know Your Enemy: Error Rates in Immunohematology External Quality Assessment Results.

BACKGROUND: As some errors in pretransfusion testing remain unrecognized, error rates and the resulting need for corrective measures are probably underestimated. External quality assessment (EQA) schemes could provide valuable input for identifying error-prone laboratory tests because they are designed to monitor test performance and errors. So far, however, there are only limited published data on error rates in such schemes. METHODS: The types and incidence of incorrect results in an EQA scheme for red cell immunohematology with 187 participating laboratories were examined. The results of 58 distributions between 1999 and 2017 were evaluated, considering also the employed determination methods. RESULTS: Out of a total of 58,726 results, 563 (0.96%) were incorrect. Error rates were 5.45% for antibody identification, 1.39% for Rh phenotyping, 0.83% for serologic cross-match, 0.60% for direct antiglobulin test, 0.20% for Kell phenotyping, 0.16% for antibody screening, and 0.14% for ABO phenotyping. During the observation period, 53 participants reported error-free results, while 37 reported one incorrect result and 97 repeatedly reported incorrect results for one or more analytes. Error rates obtained by manual methods significantly surpassed those obtained by automated methods (1.04 vs. 0.42%). The introduction of double testing with two different systems reduced error rates in Rh phenotyping from 1.55 to 0.50%. CONCLUSION: Risk assessment should consider that error rates in pretransfusion test results vary. These data delineate the error risk potential of individual laboratory tests and thus should aid in tailoring appropriate improvement measures.

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.

Evidence for the positive impact of ISO 9001 and ISO 15189 quality systems on laboratory performance - evaluation of immunohaematology external quality assessment results during 19 years in Austria.

Background ISO 9001 and ISO 15189 have been established as continuative models for quality systems beyond national laws, mandatory standards and guidelines of expert associations regarding analytical and organisational performance of medical laboratories and transfusion services. Although widely used, their impact on laboratory performance has not been investigated. Methods We retrospectively analysed the results of 167 laboratories in 59 distributions of the Austrian red cell immunohaematology external quality assessment (EQA) scheme in the years 1999-2017. The performance for each parameter and trends of individual participants were compared with respect to certification or accreditation status of participants' quality systems and to laboratory type. Results Considering more than 52,000 EQA results, the absence or presence of a laboratory quality management system showed different error rates. Laboratories with ISO 9001 or ISO 15189 certification/accreditation had 0.7% incorrect results, while this rate was doubled without such quality systems (1.4%, p=0.0002). Statistically significant error reductions were seen upon ISO 9001/ISO 15189 implementation (1.3% before vs. 0.7% after; p=0.0468). Transfusion services had fewer errors (0.9%) compared to hospital and independent laboratories (both 1.2%). Conclusions Implementation and maintenance of quality systems according to ISO 9001 or ISO 15189 as well as laboratory specialisation result in better analytical performance as can be seen in immunohaematology EQA results. The conclusion is that these results apply to other laboratory tests and perhaps to other areas of health care.

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.

Responder individuality in red blood cell alloimmunization.

Many different factors influence the propensity of transfusion recipients and pregnant women to form red blood cell alloantibodies (RBCA). RBCA may cause hemolytic transfusion reactions, hemolytic disease of the fetus and newborn and may be a complication in transplantation medicine. Antigenic differences between responder and foreign erythrocytes may lead to such an immune answer, in part with suspected specific HLA class II associations. Biochemical and conformational characteristics of red blood cell (RBC) antigens, their dose (number of transfusions and pregnancies, absolute number of antigens per RBC) and the mode of exposure impact on RBCA rates. In addition, individual circumstances determine the risk to form RBCA. Responder individuality in terms of age, sex, severity of underlying disease, disease- or therapy-induced immunosuppression and inflammation are discussed with respect to influencing RBC alloimmunization. For particular high-risk patients, extended phenotype matching of transfusion and recipient efficiently decreases RBCA induction and associated clinical risks.

Frequency and prognostic value of D alloantibodies after D-mismatched allogeneic hematopoietic stem cell transplantation after reduced-intensity conditioning.

BACKGROUND: Due to the fact that the ABO and D system is inherited independently from the HLA system, approximately 40% of allogeneic hematopoietic stem cell transplants (HSCT) are performed across the blood group barrier. Reports on the development of de novo anti-D in patients undergoing reduced-intensity conditioning (RIC) followed by D-mismatched allogeneic HSCT are rare. The objective of this study was to evaluate the frequency of anti-D alloimmunization after D-mismatched HSCT following RIC and its prognostic impact on transplant outcome. STUDY DESIGN AND METHODS: Forty patients with hematologic diseases who underwent D-mismatched HSCT were retrospectively analyzed: 19 D- patients with a D+ donor and 21 D+ patients with a D- donor. Routine serologic testing for blood group typing and antibody screening was performed by a column agglutination method every time when transfusion of red blood cell units was requested and in the posttransplantation course to demonstrate establishment of donor ABO type and to detect alloimmunization. RESULTS: After a median serologic follow-up of 21 (range, 0 to 73) months after HSCT, anti-D was identified in 2 of 21 (10%) D+ patients receiving a D- transplant, 23 and 34 months after HSCT. None of the 19 D- patients with a D+ donor developed an anti-D. CONCLUSION: We observed an infrequent de novo anti-D formation that is more likely in D+ recipients of D- grafts. However, the development of anti-D does not normally impair the transplant outcome and is not of clinical relevance in the posttransplant course.

Characterization of the novel alleles: HLA-A*01:305, HLA-B*58:120, HLA-C*04:428Q and HLA-C*05:01:56.

Four new HLA class I alleles were characterized by next-generation sequencing and haplotypes determined.

Lower Levels of ABO Anti-A and Anti-B of IgM, IgG and IgA Isotypes in the Serum but Not the Saliva of COVID-19 Convalescents.

Individuals with ABO type O, naturally possessing anti-A and anti-B antibodies in their serum, are underrepresented among patients infected with SARS-CoV-2 compared with healthy controls. The ABO antibodies might play a role in the viral transmission. Therefore, we aimed to quantify anti-A/anti-B, including their subclasses IgM, IgG and IgA, in the serum and saliva of Caucasians (n = 187) after mild COVID-19 to compare them with individuals who had never been infected with SARS-CoV-2. Two samples were collected within two months after the diagnosis (median days: 44) and two months later. ABO antibodies were determined by flow cytometry. Additionally, total IgA in saliva and antibodies specific to SARS-CoV-2 were tested by ELISA. COVID-19 convalescents had significantly lower levels of anti-A/anti-B IgM, IgG and IgA in their serum than control subjects (p < 0.001). Interestingly, no significant differences were observed in saliva. ABO antibody levels remained stable over the period considered. No relation of ABO to the level of SARS-CoV-2-specific antibodies was observed. Total IgA was lower in convalescents than in controls (p = 0.038). Whereas ABO antibodies in the saliva may not contribute to the pathogenesis of COVID-19, individual pre-existing high serum concentrations of anti-A/anti-B may have a protective effect against SARS-CoV-2 infection.

Haemovigilance: are there significant differences among plasma products?

An analysis of adverse reactions caused by single-donor fresh frozen plasma (FFP) and pooled (solvent/detergent) S/D-treated plasma reveals that these plasma products are significantly different. We are unaware of any reports associating pooled S/D-treated plasma with transfusion-associated acute lung injury, or post-transfusion-thrombocytopenia. In contrast, each of these transfusion reactions is a well-recognized adverse effect of single-donor FFP. Pooled S/D-treated plasma also has a more favorable clinical profile with reference to common acute reactions, such as fever, chills, and allergic reactions, which occur less frequently compared to single-donor FFP.

Evaluation of DXS9902, DXS7132, DXS6809, DXS7133, and DXS7423 in humans and chimpanzees: sequence variation, repeat structure, and nomenclature.

Sequencing data obtained in this study provide information on the short tandem repeat allele structures of DXS9902, DXS7132, DXS6809, DXS7133, and DXS7423. Data were obtained from the three human major population groups, namely Africans, Caucasians, and Asians as well as from chimpanzees (Pan troglodytes). DXS7133 was found to be the most stable locus and DXS6809 seemed to have evolved from a simple array of CTAT units but currently reveals a highly complex and compound structure within and between humans and chimpanzees. DXS9902 results support a TAGA allele nomenclature, which increases in one repeat unit previously reported allele distributions at this locus. For DXS7132, human/chimpanzee comparisons performed in this study provided important evidence that the CTAT allele structure should be considered for allele nomenclature purposes. Also, possible population-specific intermediate type alleles (with Native American origin) were detected at this locus that could be useful for ethnic group differentiation. DXS7423 results revealed two different sequence structures and one of these structures seems to be restricted to a single allele class in just one population group (Africans).

X-chromosome STR sequence variation, repeat structure, and nomenclature in humans and chimpanzees.

Qualitative information on the sequence composition of the allele and locus structure of the X-STRs DXS8378, DXS9898, DXS6789, GATA31E08, and GATA172D05 was generated in this study. Sequence data were obtained from chimpanzees (Pan troglodytes) and diverse human population groups including Africans, Caucasians, Asians, African-Americans, and Hispanics. Results revealed DXS8378 as the most stable locus. On the other hand, DXS9898 and GATA172D05 showed unstable regions identified through chimpanzee-human sequence comparison. At DXS6789, intra-allelic variation was found in all human populations, i.e., alleles with same fragment sizes showed structural differences only detected by sequencing. At the GATA31E08 locus, a previously unreported variation between humans and chimpanzees was identified in an adjacent region upstream from the repeat. This resulted in the addition of two repeat units and the proposal of a new allele nomenclature at this locus. Also, the sequence analyses did not detect ethnic differences between the studied population samples that would justify the use of these markers to help identify ethnic origin in an anthropological context.

Time from venipuncture to cell isolation: Impact on granulocyte-reactive antibody testing.

BACKGROUND AND OBJECTIVES: Classical neutrophil-reactive antibody testing depends on the quick isolation of neutrophils from freshly taken whole blood. To allow a better logistic preparation before testing, the influence of time interval between venipuncture and cell isolation has been evaluated in this study. MATERIALS AND METHODS: Neutrophils and whole leukocytes were isolated from EDTA whole blood immediately (T0) as well as 4, 8 and 24 h after blood donation (T4, T8 and T24). These cells were tested against reference sera containing antibodies against HNA-1b, -2, -3a and HLA class I using granulocyte aggregation test (GAT), microscopic granulocyte immunofluorescence test (GIFT) and flow-cytometric white blood cell immunofluorescence test (Flow-GIFT/WIFT). RESULTS: GAT was the most error-prone test displaying overall weaker aggregation strengths already at T4 (overall accuracy OA = 0.72, κ = 0.58). GIFT results showed good agreement at T4 (OA = 0.86, κ = 0.79) and remained stable until T8, while test results were slightly impaired at T24 (OA = 0.71, κ = 0.55). Flow-GIFT/WIFT was identified as the most robust screening method, remaining stable even at T24. Calculated ratios (sample/negative control) decreased non-significantly and remained highly above the cut-off in all samples. CONCLUSION: Acceptable time limits for cell isolation are different for each screening method investigated. For GAT, cell isolation should be performed within 4 h, while GIFT tolerates a neutrophil isolation delay of 8 h. Flow-GIFT/WIFT isolation can be performed even after 24 h without impairment of the results. Using the latter test as a stand-alone pre-screening test, whole blood can be used from donors who are not directly accessible.

Milestones in immunohematology.

The milestones in immunohematology, as seen by immunogeneticists, are described.

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.

The tetranucleotide repeat polymorphism C2_4_4: population data and linkage disequilibria with HLA class I.

The tetranucleotide repeat locus C2_4_4 situated in the HLA class I region (6p21.3) and the HLA-ABC specificities were investigated in an Austrian population sample of 240 unrelated Caucasoid individuals. The analysis of the linkage disequilibrium between C2_4_4 and HLA class I showed several significant values, especially when factors coded for by so-called "superhaplotypes" were considered; such linkage disequilibria are of importance for the practical use of HLA coded short tandem repeats.