B-lymphoblastoid cell lines as a source of reference DNA for human platelet and neutrophil antigen genotyping

DNA Reference Reagents for Genotyping RH Variants

Patients who carry Rhesus (RH) blood group variants may develop Rh alloantibodies requiring matched red blood cell transfusions. Serologic reagents for Rh variants often fail to specifically identify variant Rh antigens and are in limited supply. Therefore, red blood cell genotyping assays are essential for managing transfusions in patients with clinically relevant Rh variants. Well-characterized DNA reference reagents are needed to ensure quality and accuracy of the molecular tests. Eight lyophilized DNA reference reagents, representing 21 polymorphisms in RHD and RHCE, were produced from an existing repository of immortalized B-lymphoblastoid cell lines at the Center for Biologics Evaluation and Research/US Food and Drug Administration. The material was validated through an international collaborative study involving 17 laboratories that evaluated each DNA candidate using molecular assays to characterize RHD and RHCE alleles, including commercial platforms and laboratory-developed testing, such as Sanger sequencing, next-generation sequencing, and third-generation sequencing. The genotyping results showed 99.4% agreement with the expected results for the target RH polymorphisms and 87.9% for RH allele agreement. Most of the discordant RH alleles results were explained by a limited polymorphism coverage in some genotyping methods. Results of stability and accelerated degradation studies support the suitability of these reagents for use as reference standards. The collaborative study results demonstrate the qualification of these eight DNA reagents for use as reference standards for RH blood group genotyping assay development and analytical validation.

A nait-associated and previously unreported mutation in the ITGB3 gene with a low frequency in the local population

BACKGROUND

Neonatal alloimmune thrombocytopenia is a rare but potentially severe postnatal complication caused by maternal allo-antibodies against platelet antigens of the newborn. In relatively few cases, immunisation against low-frequency antigens has been reported.

METHODS

Platelet antigens of a newborn with severe thrombocytopenia and his family members were investigated by serological and molecular biological methods. A real-time PCR assay was developed to reliably detect this mutation in pools of DNA from up to seven individuals.

RESULTS

Serological testing showed positive reactions of maternal plasma with paternal platelets but not with conventional platelet donor panels. Sequencing of the ITGB3 gene revealed a G > A polymorphism in position c.1915 of exon 12 for the father, the newborn and three of four paternal relatives. Screening of samples from a local population of 1575 Caucasian blood donors identified only a single individual with this mutation.

CONCLUSION

This finding of a previously unreported private platelet antigen demonstrates that the identification of the target glycoprotein by MAIPA assay followed by sequencing of the affected gene can be combined with an efficient population screening by real-time PCR with pooling of DNA samples.

ACKR1 Alleles at 5.6 kb in a Well-Characterized Renewable US Food and Drug Administration (FDA) Reference Panel for Standardization of Blood Group Genotyping

The glycoprotein encoded by the ACKR1 gene expresses the Duffy blood group antigens and is a receptor for malaria parasites. We recently described 18 long-range ACKR1 alleles in an autochthonous population of a malaria endemic region. Extending this work, we sequenced the gene in a 53-sample repository established by the US Food and Drug Administration (FDA) as reference reagents for blood group genotyping. The FDA samples have been characterized for 19 genes; however, long-range haplotype information for these genes, including ACKR1, was lacking. We used a hybrid approach, novel for this type of gene, to characterize ACKR1 by combining two next-generation sequencing technologies, the short-read massively parallel sequencing and the long-read nanopore sequencing. The expedient integration of data from both next-generation sequencing systems were necessary and sufficient to allow determination of all 25 long-range ACKR1 alleles found in the 53 samples accurately. All 25 alleles identified in our current FDA cohort were novel and, unexpectedly, none had been observed among the 18 alleles in our previous study. The alleles will be useful for validation, calibration, and proficiency testing of red cell genotyping. The lack of any overlap between the ACKR1 alleles in the two studies documents differences in mutation rate and recombination frequency among populations. The exact haplotype and their interethnic or interpopulation dissimilarities can influence disease susceptibility and therapy.

Measuring circadian clock function in human cells

Circadian clocks are present in most cells and are essential for maintenance of daily rhythms in physiology, mood, and cognition. Thus, not only neurons of the central circadian pacemaker but also many other peripheral tissues possess the same functional and self-sustained circadian clocks. Surprisingly, however, their properties vary widely within the human population. In recent years, this clock variance has been studied extensively both in health and in disease using robust lentivirus-based reporter technologies to probe circadian function in human peripheral cells as proxies for those in neurologically and physiologically relevant but inaccessible tissues. The same procedures can be used to investigate other conserved signal transduction cascades affecting multiple aspects of human physiology, behavior, and disease. Accessing gene expression variation within human populations via these powerful in vitro cell-based technologies could provide important insights into basic phenotypic diversity or to better interpret patterns of gene expression variation in disease.

External quality assessment in molecular immunohematology: the INSTAND proficiency test program

BACKGROUND

Genotyping for red blood cell (RBC), platelet (PLT), and granulocyte antigens is a new tool for clinical pathology, transfusion medicine services, and blood banks. Proficiency in laboratory tests can be established by external quality assessments (EQAs), which are required for clinical application in many health care systems. There are few EQAs for molecular immunohematology.

STUDY DESIGN AND METHODS

We analyzed the participation and pass rates in an EQA for RBC, PLT, and granulocyte antigens. This EQA was distributed by INSTAND, a large nonprofit provider of proficiency tests, twice per year since Fall 2006 as EQA Number 235 Immunohematology A (molecular diagnostic). The coordinators defined at the outset which alleles are mandatory for detection.

RESULTS

The number of participants steadily increased from 51 to 73 per proficiency by Fall 2012. More than 60 institutions utilized this EQA at least once a year. Approximately 80% of them participated in RBC, 68% in PLT, and 22% in granulocyte systems. With the exceptions of RHD (82%) and granulocytes (85%), pass rates exceeded 93%. While the pass rate increased for granulocyte and decreased for the ABO system, the pass rates for the other systems changed little over 6½ years.

CONCLUSIONS

The INSTAND proficiency test program was regularly used for EQA by many institutions, particularly in Central Europe. While the technical standards and pass rates in the participating laboratories were high, there has been little improvement in pass rates since 2006.

Report on the 15th International Society of Blood Transfusion platelet immunology workshop

BACKGROUND AND OBJECTIVES

The aim of the 15th ISBT Platelet Immunology Workshop was to evaluate the detection of free platelet-reactive autoantibodies from ITP patients by the use of a standardized MAIPA protocol, to compare sensitivity and specificity of antibody detection for anti-HPA-1a and serologically difficult-to-assess antibodies against HPA-3, to identify whether anti-HPA-1a titration results can be compared between laboratories, and to evaluate HPA genotyping methods.

MATERIALS AND METHODS

Workshop materials were shipped from the organizing laboratory in Giessen, Germany. Thirty laboratories from 19 countries participated.

RESULTS

Results for the detection of autoantibodies differed greatly between the laboratories and no consensus was reached for one of the two sera. Detection and titration of antibodies against HPA-1a, in contrast, gave largely congruent results. Serologically difficult-to-assess antibodies recognizing HPA-3a and HPA-3b were not detected by many laboratories. For genotyping, good agreement was achieved.

CONCLUSIONS

Detection of HPA-1a antibodies, titration of anti-HPA-1a, and HPA genotyping are well performed in most participating laboratories. The workshop has identified two specific areas with room and need for improvement: the detection of autoantibodies and the detection of HPA-3 alloantibodies. Recommendations of the Working Party on techniques that can help to overcome these problems are desirable.

A new platelet alloantigen, Swi(a) , located on glycoprotein Ia identified in a family with fetal and neonatal alloimmune thrombocytopenia

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a bleeding disorder caused by transplacental passage of maternal antibodies to fetuses whose platelets (PLTs) express the corresponding human PLT antigen (HPA).

STUDY DESIGNS AND METHODS

We observed a fetus with FNAIT who died from a severe intracranial hemorrhage. Analysis of maternal serum in antigen capture assay with paternal PLTs showed reactivity with PLT glycoprotein (GP)IIb/IIIa (α(IIb) β(3) ) and GPIa/IIa (α(2) β(1) integrin), indicating the presence of anti-HPA-1a and an additional alloantibody against GPIa (termed anti-Swi(a) ).

RESULTS

By immunochemical studies, the localization of the Swi(a) antigen on GPIa/IIa could be confirmed. Analysis of paternal GPIa full-length cDNA showed a single-nucleotide substitution C(3347) T in Exon 28 resulting in a Thr(1087) Met amino acid substitution. Testing of family members by polymerase chain reaction-restriction fragment length polymorphism using MslI endonuclease showed perfect correlation with phenotyping. Extended family and population studies showed that 4 of 10 members of the paternal family but none of 500 unrelated blood donors were Swi(a) carriers. Expression studies on allele-specific transfected Chinese hamster ovary (CHO) cells confirmed that the single-amino-acid substitution Thr(1087) Met was responsible for the formation of the Swi(a) epitope. Adhesion of CHO cells expressing the Swi(a) alloantigen to immobilized collagens was not impaired compared to the wild-type control and was not inhibited by anti-Swi(a) alloantibodies.

CONCLUSION

In this study we defined a new PLT alloantigen Swi(a) that was involved in a case of additional immunization against HPA-1a. Our observations demonstrate that combinations of PLT-specific alloantibodies may comprise low-frequency alloantigens.

The effects of EBV transformation on gene expression levels and methylation profiles

Epstein-Barr virus (EBV) transformed lymphoblastoid cell lines (LCLs) provide a conveniently accessible and renewable resource for functional genomic studies in humans. The ability to accumulate multidimensional data pertaining to the same individual cell lines, from complete genomic sequences to detailed gene regulatory profiles, further enhances the utility of LCLs as a model system. A lingering concern, however, is that the changes associated with EBV transformation of B cells reduce the usefulness of LCLs as a surrogate model for primary tissues. To evaluate the validity of this concern, we compared global gene expression and methylation profiles between CD20+ primary B cells sampled from six individuals and six independent replicates of transformed LCLs derived from each sample. These data allowed us to obtain a detailed catalog of the genes and pathways whose regulation is affected by EBV transformation. We found that the expression levels and promoter methylation profiles of more than half of the studied genes were affected by the EBV transformation, including enrichments of genes involved in transcription regulation, cell cycle and immune response. However, we show that most of the differences in gene expression levels between LCLs and B cells are of small magnitude, and that LCLs can often recapitulate the naturally occurring gene expression variation in primary B cells. Thus, our observations suggest that inference of the genetic architecture that underlies regulatory variation in LCLs can typically be generalized to primary B cells. In contrast, inference based on functional studies in LCLs may be more limited to the cell lines.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for genotyping of human platelet-specific antigens

BACKGROUND

Genotyping of single-nucleotide polymorphisms (SNPs) using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an emerging technique, where finally tools for end users have become available to design primers and analyze SNPs of their own interest. This study investigated the potential of this technique in platelet (PLT) genotyping and developed a validated method for genotyping of clinical relevant human PLT antigens (HPAs).

STUDY DESIGN AND METHODS

A multiplex assay using MALDI-TOF MS to analyze six HPA loci (HPA-1, HPA-2, HPA-3, HPA-4, HPA-5, and HPA-15) simultaneously in a single reaction was applied for the genotyping of 100 DNA samples from a cohort of plateletpheresis donors and a patient population (n = 20) enriched for rare alleles. The genotyping results using MALDI-TOF MS were validated by the comparison with the results from typing by polymerase chain reaction with sequence-specific primers and conventional DNA sequencing.

RESULTS

Both homozygous and heterozygous genotypes of HPA-1 to -5 and -15 of the 120 individuals were easily identified by a six-plexed assay on MALDI-TOF MS. The three approaches achieved a 100 percent concordance for the genotyping results of the six HPA loci.

CONCLUSION

Compared to conventional methods, the MALDI-TOF MS showed several advantages, such as a high velocity, the ability to perform multiplexed assays in a single reaction, and automated high-throughput analysis of samples. This enables cost-efficient large-scale PLT genotyping for clinical applications.

Multicolor real-time polymerase chain reaction genotyping of six human platelet antigens using displacing probes

BACKGROUND

Several genotyping methods for six clinically relevant human platelet antigens (HPAs) have been reported. A four-color real-time polymerase chain reaction (PCR) method using displacing probes for genotyping of the six HPAs is described.

STUDY DESIGN AND METHODS

Primers and four differently fluorophor-labeled displacing probes were designed and synthesized to detect single-nucleotide polymorphisms responsible for each of the HPA-1, -2, -3, -4, -5, and -15 genotypes. Two HPA systems were analyzed in a single PCR procedure. After validation with samples of known genotypes, a total of 150 blood samples from healthy donors were genotyped. The results were compared with PCR with sequence-specific primers (SSP), PCR-restriction fragment length polymorphism (RFLP), and/or direct DNA sequencing. The frequencies of each HPA allele were calculated.

RESULTS

Unequivocal real-time PCR genotyping results were obtained with minimal manual manipulation and carryover contamination. All 150 blood samples were correctly genotyped as confirmed by PCR-SSP, PCR-RFLP, and/or direct DNA sequencing. The allelic frequencies of HPA-1 through -5 and -15 among the Chinese population in Xiamen were comparable with those previously reported with Chinese living in other territories. For each specimen, genotyping of all six HPA biallelic systems was achieved in three tubes of PCR within 90 minutes and with material cost of no more than $1.

CONCLUSION

Genotyping of HPA with real-time PCR using displacing probes is more rapid and reliable compared with PCR-SSP and PCR-RFLP methods and is more affordable than existing real-time PCR-based HPA genotyping assays. Thus, our approach is more suitable for routine HPA analysis and ideal for both urgent clinical testing and high-throughput screening.

HPA-13bw neonatal alloimmune thrombocytopenia and low frequency alloantigens: case report and review of the literature

BACKGROUND

Fetal-neonatal alloimmune thrombocytopenia (FNAIT) linked to rare or private antigens is not a rare event.

STUDY DESIGN AND METHODS

Such a case discovered during the follow-up of a second child with jaundice with mild thrombocytopenia is reported here. Platelet (PLT) genotyping was performed by polymerase chain reaction (PCR)-sequence-specific primers method and PCR-restriction fragment length polymorphism (RFLP) analysis. Serologic investigation was done with the monoclonal antibody-specific immobilization of PLT antigens technique. Glycoprotein Ia-specific amplification and sequencing were performed for the polymorphism 807 (exon 7).

RESULTS

The mother was found to be HPA-13aaw, and the father HPA-13abw. A maternal alloantibody directed against HPA-13bw has been characterized, leading to the diagnosis of neonatal alloimmune thrombocytopenia.

CONCLUSION

This report provides further evidence that NAIT associated with low-frequency antigens is not restricted to single families. Therefore, laboratory investigation of a suspected case should be carried out in a specialist laboratory well experienced in optimal testing to propose appropriate management for the index case and subsequent pregnancies.

White blood cell-reactive antibodies are undetectable in solvent/detergent plasma

BACKGROUND

Transfusion-related acute lung injury (TRALI) is a life-threatening complication of transfusion. Although all types of blood products have been associated with TRALI, fresh-frozen plasma (FFP) is the most commonly implicated component. It has been postulated that TRALI is an immune-mediated event, because white blood cell (WBC)-reactive antibodies in the donor's plasma are frequently associated with the syndrome. In contrast to single donor-derived FFP, solvent/detergent (S/D) plasma is produced from multiple donations, leading to an at least 500-fold dilution of a single plasma unit. It was hypothesized that WBC-reactive antibodies are undetectable in S/D FFP.

STUDY DESIGN AND METHODS

Twenty batches of S/D FFP (5 of each ABH group) were analyzed with well-established routine techniques to detect WBC antibodies.

RESULTS

All samples tested negative for granulocyte-specific as well as HLA Class I and Class II antibodies.

CONCLUSIONS

Different strategies to reduce the risk of TRALI are currently discussed. These include screening of all potentially immunized donors for WBC-reactive antibodies and exclusion of multiparous or all women from donating FFP. Here, it is demonstrated that neither granulocyte- nor lymphocyte-reactive antibodies are detectable in S/D FFP. Thus, S/D FFP may represent a potential alternative to reduce the risk of TRALI associated with the transfusion of FFP.

Relevance of the HPA-15 (Gov) polymorphism on CD109 in alloimmune thrombocytopenic syndromes

BACKGROUND

Alloantibodies against the human platelet (PLT) alloantigen (HPA)-15 system residing on CD109 can cause fetal and neonatal alloimmune thrombocytopenia (FNAIT), posttransfusion purpura, and PLT transfusion refractoriness. The detection of antibodies against HPA-15, however, is hampered by the variable low expression and instability of the CD109 molecule during preparation and storage.

STUDY DESIGN AND METHODS

This study analyzed the occurrence of HPA-15 alloantibodies in 1403 patients: 930 FNAIT and 473 polytransfused (PT) patients by modified monoclonal antibody specific immobilization of PLT antigens (MAIPA) assay with well-defined phenotyped PLTs. A DNA typing technique was developed to confirm the phenotypes of PLT donors. B-cell lines were established as sources of reference DNA.

RESULTS

Genotyping of 407 unrelated blood donors revealed the gene frequencies 0.512 and 0.488 for HPA-15a and -15b, respectively. Based on the selection of PLTs expressing high amounts of CD109 on the surface (mean fluorescence intensity ratio 4-5 on expression peak on Days 2-4 after apheresis) antibody screening by the MAIPA assay was performed. In total, 16 (1.1%) HPA-15 alloantibodies were found comprising four anti-HPA-15a and 12 anti-HPA-15b. Anti-HPA-15b without other PLT-reactive antibodies were detectable in three serum samples of PT patients. The incidence of HPA-15 alloimmunization in PT patients was significantly higher than in mothers with FNAIT (3.0% vs. 0.22%). In relation to all detected HPA-specific antibodies, HPA-15 is responsible for 6.2 percent of alloimmunizations.

CONCLUSION

These observations indicate that alloimmunization against HPA-15 should be considered as a cause for immune thrombocytopenia, particularly in patients receiving multiple PLT transfusions.

Immunization against a low-frequency human platelet alloantigen in fetal alloimmune thrombocytopenia is not a single event: characterization by the combined use of reference DNA and novel allele-specific cell lines expressing recombinant antigens

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is caused by maternal immunization against a fetal platelet (PLT) alloantigen. In cases of FNAIT attributed to low-frequency PLT alloantigens, the laboratory diagnosis is often hampered by the lack of adequate PLTs.

STUDY DESIGN AND METHODS

Three families with maternal immunization against fetal PLT antigens were analyzed. In Family 1, previous immunization of another female or woman has been observed. In Families 2 and 3, newborns presented with the typical clinical picture of FNAIT. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism and direct sequencing with reference to DNA from Epstein-Barr virus-transformed B-lymphoblastoid cell lines. Antibodies were characterized by glycoprotein (GP)-specific immunoassay with a panel of stable Chinese hamster ovary cell lines expressing low-frequency alloantigens.

RESULTS

In three families, maternal immunization associated with the low-frequency alloantigens human PLT antigen (HPA)-8bw (Sra), HPA-11bw (Groa), and HPA-13bw (Sita) was identified. Maternal serum samples showed positive reactions in an antigen capture assay with cell lines carrying recombinant GP IIb/IIIa (HPA-8bw and -11bw) or GPIa/IIa (HPA-13bw), respectively. These results could be confirmed by genotyping analysis of fathers and newborns.

CONCLUSION

This study demonstrates that cases of FNAIT attributed to low-frequency PLT alloantigens cannot be regarded as single events. The availability of reference DNA and cell lines expressing recombinant PLT alloantigens can facilitate their identification.

Serologic analysis of three cases of neonatal alloimmune thrombocytopenia associated with HLA antibodies

BACKGROUND

Neonatal alloimmune thrombocytopenia (NAIT) is caused when maternal alloantibodies react with paternally inherited antigens present on the fetal PLTs, a reaction mainly due to antibodies against human PLT antigens. Cases in which NAIT has been caused by HLA antibodies are relatively rare. In this study, three cases of NAIT associated with HLA antibodies that occurred in a 1-year period are reported.

STUDY DESIGN AND METHODS

The presence of HLA antibodies in these three NAIT case studies was elucidated by examining reactions of the neonatal and maternal sera with lymphocytes, PLTs, and beads from an HLA antibody screening test (FlowPRA, One Lambda Inc.). Absorption and elution tests with paternal cells were also conducted. In addition, the influence of titer and specificity of HLA antibodies on NAIT was analyzed in light of 24 other documented cases in Japan.

RESULTS

In the three case studies presented herein, antibodies against human PLT antigens were found in neither the maternal nor neonatal sera, while specific HLA antibodies were identified in both sera. Absorption of maternal serum with paternal PLTs eliminated the reactivity against paternal PLTs and lymphocytes.

CONCLUSION

Transplacental passage of maternal HLA antibodies was observed in the three neonates cited in the present study.

PCR with sequence-specific primer-based simultaneous genotyping of human platelet antigen-1 to -13w

BACKGROUND

Accurate human platelet antigen (HPA) typing is important for patients with diagnosis of alloimmune thrombocytopenic syndromes and provision of HPA-matched blood components for these patients.

STUDY DESIGN AND METHODS

Thirteen sequence-specific primers (SSPs) designed on the basis of known published polymorphisms for HPA-1 to HPA-13w, respectively, were employed for simultaneous HPA genotyping. All PCR amplifications were carried out with identical cycling conditions in 96-well plates containing primer mixtures. A total of 300 blood samples from unrelated volunteer donors in Taiwan were included in the study.

RESULTS

All primers had specific amplification products. The typing results were available within 4 hours each time for up to four blood samples tested. Among the 13 HPAs, HPA-3 had the greatest heterozygosity with a gene frequency of 0.3267, 0.4967, and 0.1767 for HPA-3a/HPA-3a, HPA-3a/HPA-3b, and HPA-3b/HPA3-b, respectively. For the remaining 12 HPAs, the predominance of a/a homozygosity was noted for HPA-1, -2, -4, -5, and -6, with a frequency ranging from 0.9200 to 0.9967. The frequency of a/a homozygosity was 1.0000 for HPA-7w to -13w, except for HPA-10w, for which one case was observed to be HPA-10aw/HPA-10bw heterozygous. Excluding HPA-3, b/b homozygosity was noted in only one case (HPA-6b/HPA-6b). The prevalence rates of HPA-1 to -13w in this study were consistent with previous reports using different methods.

CONCLUSION

An extended, streamlined PCR-SSP protocol for simultaneous genotyping of HPA-1 to HPA-13w was established. This allows fast and reliable diagnosis of alloimmune thrombocytopenia, and is readily applicable to large-scale genetic population studies.

A functional platelet fibrinogen receptor with a deletion in the cysteine-rich repeat region of the beta(3) integrin: the Oe(a) alloantigen in neonatal alloimmune thrombocytopenia

This report describes a new low-frequency alloantigen, Oe(a), responsible for a case of neonatal alloimmune thrombocytopenia (NAIT). In a population study none of 600 unrelated blood donors was an Oe(a) carrier. By immunochemical studies the Oe(a) antigen could be assigned to platelet glycoprotein (GP) IIIa. Sequencing of GPIIIa complementary DNA from an Oe(a) (+) individual showed deletion of a lysine residue at position 611 (DeltaLys(611)). Analysis of 20 Oe(a) (-) and 3 Oe(a) (+) individuals showed that the DeltaLys(611) form of GPIIIa was related to the phenotype. Anti-Oe(a) reacted with the DeltaLys(611), but not with the wild-type isoforms on stable transfectants expressing GPIIIa, indicating that DeltaLys(611) directly induces the expression of Oe(a) epitopes. Under nonreducing conditions the Pro(33)DeltaLys(611) variant migrated with a slightly decreased molecular weight compared to the Pro(33)Lys(611) isoform suggesting that DeltaLys(611) has an influence on the disulfide bonds of GPIIIa. The Pro(33)DeltaLys(611) GPIIIa could undergo conformational changes and bind to fibrinogen in a similar manner as the Pro(33)Lys(611) isoform. No difference was found in the tyrosine phosphorylation of pp125(FAK), suggesting that DeltaLys(611) has no effect on integrin function. In contrast to all other low-frequency antigens, the DeltaLys(611) isoform was associated with the HPA-1b, but not with the high frequency HPA-1a allele. Comparison with GPIIIa DNA from nonhuman primates indicated that the HPA-1a allele represents the ancestral form of GPIIIa. It can be assumed that the Oe(a) form did arise as a result of a mutational event from an already mutated GPIIIa allele.

Acute and chronic neutropenias. What is new?

Recently, some of the mechanisms and consequences in the severe chronic neutropenias (e.g. the neutrophil elastase gene mutations and the risk to progress to myelodysplasia and acute leukaemia) and in drug-induced agranulocytosis (e.g. the apoptosis-inducing ability of metabolites of clozapine) have been elucidated, and new aspects of autoimmune and the large granular lymphocyte syndrome were described (e.g. aberrant elaboration of Fas-ligand causing neutrophil apoptosis). Investigations of the mild to moderate chronic neutropenias have shown the significance of interactions between the myeloid development and the immune network (e.g. relations to immunoglobulin aberrations). Granulocyte-colony stimulation factor (G-CSF) is widely used in patients with severe chronic neutropenia, however, its use in other conditions is mostly based on anecdotal evidence. In addition, immune modulating regimens, such as metothrexate, ciclosporine and monoclonal antibodies, are increasingly employed for the autoimmune neutropenias.

Report on the Tenth International Platelet Genotyping and Serology Workshop on behalf of the International Society of Blood Transfusion

BACKGROUND AND OBJECTIVES

The aims of the 10th International Platelet Serology and Genotyping Workshop were to evaluate the proficiency of platelet immunology determinations.

MATERIALS AND METHODS

There were 40 participants from 25 countries of four continents. Thirty-eight institutions reported results for genotyping, and 38 institutions reported their serological results. For genotyping, EDTA-anticoagulated whole-blood samples were provided (to allow the inclusion of DNA-separation methodology in the analysis) as well as separated DNA of a and b alleles for human platelet antigen (HPA)-1 to -6. For serological evaluations, sera contained allo- and autoantibodies, and for sensitivity testing a standard freeze-dried sample of HPA-5 antibody.

RESULTS

All participants reported HPA-1, -2, -3 and -5 genotyping results; HPA-4 was determined in 29 laboratories and HPA-6 in 21. Results from 16 laboratories were concordant with the majority vote for all allotypes, eight institutions reported one deviation, five laboratories two, and nine laboratories three or more deviations. Twelve institutions had no deviation from the majority vote for HPA antibodies, nine had one, three had two, and 14 had three or more deviations. Most laboratories reported a reactivity of the standard anti-HPA-5b sample with HPA-5b platelets at a dilution of 1:4-1:8. Four laboratories detected anti-Gova in one sample. Seventeen laboratories reported no deviation from the majority vote for pan-reactive platelet antibodies, 12 had one deviation, two had two, and seven had three or more deviations. In addition, seven participants reported antibodies against glycoprotein IV (GPIV), three against glycoprotein V (GPV) and three against CD 109. These results were discussed at a meeting organized jointly with the International Society of Blood Transfusion (ISBT) 2000 Congress.

CONCLUSION

The results for pan-reactive antibodies were heterogeneous with most discrepancies from the majority vote. The provision of sufficient samples for many participants is difficult. Based on the results and discussion it is clear that frequent workshops are needed in the future. Therefore, workshops shall be organized regionally, and each region shall participate with one institution in international workshops. The latter are needed to assure international exchange of experience and quality.