Human neutrophil alloantigens

Anti-HNA testing of allo-exposed COVID-19 convalescent plasma donors including genetic human neutrophil antigen screening to prevent anti-HNA antibody-mediated transfusion-related acute lung injury

BACKGROUND

Transfusion-related acute lung injury caused by antibodies against human neutrophil antigens (HNA) is a serious but rare complication associated with blood transfusion. The presence of such antibodies is most probable in donors with a transfusion/pregnancy history. During the COVID-19 pandemic period convalescent plasma (CP) containing neutralizing antibodies against SARS-CoV-2 was widely used for COVID-19 patients as a therapy in the absence of any treatment. The aim of the study was to work out a simple diagnostic algorithm of anti-HNA testing of allo-exposed CP donors including genetic HNA screening.

MATERIALS AND METHODS

A total of 457 anti-HLA-negative allo-exposed CP donors were genotyped for HNA-1a/1b, HNA-3a/3b, and HNA-2, and only donors with homozygous HNA-1a/1a; HNA-3b/3b; or HNA-2null genotypes were tested for anti-HNA antibody using LabScreenMulti (One Lambda) and homozygous HNA-1b/1b using the granulocyte immunofluorescence test (GIFT) but verified using LabScreenMulti.

RESULTS

Testing of 83 homozygous HNA-3b/3b; HNA-2null; or HNA-1a/1a donors revealed anti-HNA-3a antibody in one case. Testing of 181 HNA-1b/1b donors using GIFT gave 10 ambiguous results verified using LabScreenMulti which confirmed anti-HNA-1a antibody in one case. The frequency of FCGR3B*01 and *04 encoding HNA-1a was 0.34; FCGR3B*02, *03, and *05 encoding HNA-1b-0.66; SLC44A2*01 encoding HNA-3a-0.80; and SLC44A2*02 encoding HNA-3b-0.20. In 3.7% cases the HNA-2null genotype was revealed.

DISCUSSION

Due to applying HNA genotyping as a primary test before anti-HNA antibody testing the serological work was limited only to HNA-homozygous donors revealing two anti-HNA immunized donors. The distribution of HNA genotypes in the cohort was similar to other Caucasian populations.

Pitfalls When Determining HNA-1 Genotypes and Finding Novel Alleles

Genetic variation in the FCGR3B gene is responsible for different variants of human neutrophil antigen 1 (HNA-1). Laboratory techniques currently utilized for routine HNA-1 genotyping, predominantly PCR-sequence-specific primer (PCR-SSP) and PCR-sequence-based typing (PCR-SBT), lack specificity for FCGR3B. This study compares the capabilities and limitations of existing technologies including an in-house TaqMan PCR, a commercial PCR-SSP test, PCR-SBT and multiplex ligation-dependent probe amplification (MLPA) with those of a long-read nanopore sequencing assay. Testing was performed with both related and unrelated Danish samples with different copy numbers and/or rare alleles. Long-read nanopore sequencing was validated by blind testing of ten English samples. The results showed that FCGR3B copy numbers correlate with a dose-dependent distribution of alleles that complicates genotyping by TaqMan PCR, PCR-SSP and PCR-SBT, due to co-amplification of the homologous FCGR3A gene. MLPA can correctly quantify the dose-dependent distribution but not detect novel variants. Long-read nanopore sequencing showed high specificity for FCGR3B and was able to detect dosage-dependent distribution, and rare and novel variants that were previously not described. Current HNA-1 genotyping methods cannot produce unambiguous allele-level results, whereas long-read nanopore sequencing has shown the potential to resolve observed ambiguities, identify new HNA-1 variants and allow definitive allele assignment.

Clinical significance of human neutrophil antigen-1 antibodies in children with neutropenia

Primary autoimmune neutropenia in young children is characterized by chronic neutropenia and positivity for antibodies against human neutrophil antigens (HNAs). This study analyzed the clinical characteristics of 402 children with neutropenia to identify differences between those with and without HNA-1 antibodies (HNA1abs). HNAabs in sera were detected by granulocyte immunofluorescence testing using flow cytometry. Relative fluorescence intensity (RFI) values were used to divide patients into positive (PG, n = 302), borderline (BG, n = 34), and negative (NG, n = 66) groups. The antibodies reacted to HNA-1a alone (59%), HNA-1b alone (1%), and HNA-1a/1b (40%). The PG had a significantly lower absolute neutrophil count before definitive diagnosis and a 1.6- to 2-times greater risk of hospitalization during neutropenia than the other groups. The median duration of neutropenia was longest in the PG at 25 months, followed by 20 months in the BG and 14 months in the NG. This large-scale cohort characterizes clinically distinct groups using the RFI value for HNA1abs in young children with neutropenia. Detection of HNA1abs may aid in understanding the clinical characteristics of children with neutropenia.

Genetic landscape of human neutrophil antigen variants in India from population-scale genomes

Antibodies against human neutrophil antigens (HNAs) play a significant role in various clinical conditions such as neonatal alloimmune neutropenia, transfusion-related acute lung injury, and other nonhemolytic transfusion reactions. This study aims to identify the genotype and allele frequencies of HNAs in the healthy Indian population. Ten genetic variants in four human genes encoding alleles of HNAs class I-V approved by the International Society of Blood Transfusion-Granulocyte Immunobiology Working Party were used in the analysis. Genetic variants from whole genome sequences of 1029 healthy Indian individuals corresponding to HNA alleles were analyzed. The frequencies of the variants were compared with global population datasets using an in-house computational pipeline. In HNA class I, allele frequencies of FCGR3B*01, FCGR3B*02, and FCGR3B*03 encoding HNA-1a, HNA-1b, and HNA-1c were 0.07, 0.8, and 0.13, respectively. HNA class 3 alleles namely SLC44A2*01 (encoding HNA-3a) and SLC44A2*02 (encoding HNA-3b) were found at allele frequencies of 0.78 and 0.22, respectively. The frequencies of ITGAM*01 encoding HNA-4a and ITGAM*02 encoding HNA-4a were 0.95 and 0.05, respectively. Furthermore, allele frequencies of HNA class 5 alleles were 0.32 for ITGAL*01 (encoding HNA-5a) and 0.68 for ITGAL*02 (encoding HNA-5b). Interestingly, it was also found that rs2230433 variant deciding the HNA class 5 alleles, was highly prevalent (78.2%) in the Indian population compared with other global populations. This study presents the first comprehensive report of HNA allele and genotype frequencies in the Indian population using population genome datasets of 1029 individuals. Significant difference was observed in the prevalence of HNA5a and HNA5b in India in comparison to other global populations.

Human neutrophil antigen-1, -3, -4, and -5 allele and genotype frequencies in the Croatian blood donor population and their clinical significance

OBJECTIVES

Human neutrophil antigens (HNAs) and antibodies play an important role in allo- and autoimmunity associated with immune neutropenia and transfusion reactions. The aim of this study was to determine the HNA-1, -3, -4 and -5 allele and genotype frequencies in the Croatian blood donor population to assess the role of HNA-1, -3, -4, and -5 alleles in the development of neonatal alloimmune neutropenia and antibody-mediated transfusion-related acute lung injury.

MATERIAL AND METHODS

A total of 371 blood samples from unselected healthy blood donors were analyzed. Samples from all 371 donors were genotyped for HNA-1, samples from 160 donors were genotyped for HNA-3, and samples from 142 donors were genotyped for HNA-4 and HNA-5 using the polymerase chain reaction with sequence-specific primers (PCR-SSP) method.

RESULTS

The frequencies of the FCGR3B*01, FCGR3B*02 and FCGR3B*03 HNA-1 alleles were 0.393, 0.607 and 0.022, and of the SLC44A2*01 and SLC44A2*02 HNA-3 alleles 0.781 and 0.219, respectively. The frequencies of the ITGAM*01 and ITGAM*02 HNA-4 alleles were 0.796 and 0.204, and of the ITGAL*01 and ITGAL*02 HNA-5 alleles 0.718 and 0.282, respectively.

CONCLUSION

These are the first results on the HNA allele and genotype frequencies in the Croatian blood donor population. We observed no deviations from previous reports on Caucasian populations. Determination of the HNA antigen frequencies in the population is important to estimate the risk of alloimmunization to HNA, especially the risk of fetal-maternal incompatibility and alloantibody production by transfusion of the HNA incompatible blood components.

SLC44A2 Frequency, a New TaqMan Real-Time Polymerase Chain Reaction Method for HNA-3A/3B Genotyping, and a New Application of Droplet Digital PCR

Background: Human neutrophil antigen-3A (HNA-3A) and human neutrophil antigen-3B (HNA-3B) are generated by a single-nucleotide polymorphism (rs2288904, c.461G > A) in exon 7 of the choline transporter-like protein-2 gene (CTL2, also known as SLC44A2). Antibodies to HNA-3 can be generated following blood transfusion or other factors resulting in exposure to HNA-3 antigens. These antibodies can cause transfusion-related acute lung injury (TRALI) or neonatal alloimmune neutropenia (NAIN). This study describes a sensitive and specific TaqMan real-time polymerase chain reaction (PCR) method to screen for the HNA-3 genotype using specific primers and probes designed to detect allelic polymorphisms. Considering the high sensitivity and accuracy of droplet digital PCR (ddPCR) in the identification of the rare SLC44A2*2 allele, we used this technique to identify blood donors with the rare HNA-3B antigen and calculate the allele frequency of SLC44A2 in mixed populations with different proportions.

Methods: DNA samples purified from 208 donors in northwest China were subjected to TaqMan real-time PCR to detect allelic polymorphisms in SLC44A2. The results were confirmed by Sanger sequencing. The rare HNA-3B antigen was detected by ddPCR. SLC44A2 frequency was determined by two-channel ddPCR.

Results: The genotypes of all DNA samples were detected by the TaqMan real-time PCR using specific probes for HNA-3, and the results were consistent with the Sanger sequencing results in respect to the HNA-3A and HNA-3B polymorphisms. The allele frequencies of SLC44A2*1 and SLC44A2*2 in the 208 donors in northwest China were 64.9% (95% confidence interval [CI], 59%–70.8%) and 35.1% (95% CI, 29.2%–41%), respectively. The ratio of SLC44A2*2 alleles was accurately detected in all blood pools by ddPCR but not by TaqMan real-time PCR. This allowed for the SLC44A2 frequency in the population to be accurately inferred.

Conclusion: This new method of detecting SLC44A2 alleles was highly sensitive and specific, as confirmed by Sanger sequencing. ddPCR using the designed probes resulted in successful detection of the rare HNA-3B antigen. Furthermore, we successfully detected the rare HNA-3B antigen and inferred the SLC44A2 frequency by ddPCR using the probes that we designed.

Human neutrophil antigen 2 sequence-based typing: Joining the hunt for the CD177 answer

BACKGROUND AND OBJECTIVES

Isoantibodies to human neutrophil antigen 2 (CD177) have been associated with several clinical conditions but to date the molecular basis for altered or non-expression has not been determined. Reliance on phenotyping and crossmatch to investigate these neutropenic clinical cases are inconvenient for the patients and demanding of resources within the laboratory. Therefore, a molecular approach has been introduced to address both issues.

MATERIALS AND METHODS

A DNA panel of 100 randomly selected blood donors were collected and supplemented with 18 DNA samples from blood donors previously shown to be CD177 null. All DNA samples were sequence-based typed for all exons and observed polymorphisms recorded. The DNA from two families previously investigated for neonatal alloimmune neutropenia due to CD177 isoantibodies were also analysed.

RESULTS

The incidence of CD177 null could be associated with a known exon 7 single-nucleotide polymorphism in 16/21 known CD177 null samples, which is consistent with previously published findings. Two additional mutations that may lead to null expression were also identified, of which one may be novel. In both family investigations, this same mutation could also be observed in the maternal DNA sample.

CONCLUSION

Based on these observations, introduction of CD177 genotyping into routine use would identify null expression in over 75% (16/21) of associated cases. In turn, this could significantly reduce the need for supplementary testing and associated inconvenience to patients while permitting increased efficiency of laboratory testing. An added benefit would potentially elucidate other clinically relevant mutations and associated antigenic targets.

Infant Pyogenic Liver Abscess Complicated With Autoimmune Neutropenia: Two Cases

Approximately 90% of patients with autoimmune neutropenia (AIN) suffer from mild infections although neutrophil count often decreases to <500/μL. Here, we report 2 cases of infant pyogenic liver abscess complicated with AIN. We should consider the possibility of AIN as an underlying disease when diagnosing pyogenic liver abscess during childhood.

Possible involvement of regulatory T cell abnormalities and variational usage of TCR repertoire in children with autoimmune neutropenia

Autoimmune neutropenia (AIN) in childhood is characterized by chronic neutropenia and positivity for anti-neutrophil antibodies, resulting in the excessive destruction of neutrophils. In this study, we investigated the involvement of regulatory T cells (T_regs ) in the pathogenesis of AIN in childhood. T_regs have been classified into three subpopulations based on the expressions of CD45RA and forkhead box protein 3 (FoxP3): resting T_regs , activated T_regs and non-suppressive T_regs . The frequency of activated T_regs (CD4⁺ CD25⁺ FoxP3^high CD45RA^- T cells) as well as that of total T_regs (CD4⁺ CD25⁺ FoxP3⁺ T cells) in peripheral blood was significantly decreased in patients with AIN. Analysis of the T cell receptor (TCR)-Vβ repertoire of CD4⁺ T cells revealed skewed usages in patients with AIN compared with that observed in age-matched control subjects. Regarding T cell subsets, the use of four of 24 TCR-Vβ families in T_regs and one in conventional T cells were increased in patients with AIN. The number of patients with AIN who showed skewed usages of TCR-Vβ family in conventional and T_regs was significantly higher than that reported in control subjects. When the preference between T_regs and conventional T cells in each TCR-Vβ family was individually compared, different use was prominently observed in the TCR-Vβ 9 family in patients with AIN. These results suggest that the quantitative abnormalities of T_regs and the skew of the TCR-Vβ repertoire in CD4⁺ T cells, including T_regs and conventional T cells, may be related to autoantibody production through a human neutrophil antigen-reactive T cell clone.

Human neutrophil antigens: Nature, clinical significance and detection

Granulocytes are an essential part of both the innate and adaptive immune systems. Human neutrophil antigens (HNAs) are a family of epitopes that are located on glycoproteins that are mostly expressed on human granulocytes. Antibodies that recognize these epitopes have been associated with neutropenia, transfusion complications, haematopoietic stem cell transplant nonengraftment and renal transplant rejection. Currently, there are fourteen recognized HNA alleles across five antigen systems (HNA-1 through HNA-5), the molecular basis of which are located on the genes FCGR3B, CD177, SLC44A2, ITGAM and ITGAL, respectively. Elucidation of the associated genes has permitted the development of testing strategies for HNA typing and aided understanding of the associated epitopes. This review will outline the associated clinical conditions that require HNA investigation and how these are performed in specialized laboratories. Investigations provided are both reactive for patients with a variety of existing or suspected neutropenias and proactive in the testing of blood component donors in order to reduce the potential risk to patients who require transfusion.

Leukocyte-Reactive Antibodies in Female Blood Donors: The Austrian Experience

Introduction

Antibody-mediated transfusion-related acute lung injury (TRALI) is caused by antibodies against human leukocyte antigens (HLAs) or human neutrophil antigens (HNAs), and is one of the most serious complications associated with transfusion medicine. Prevention strategies like testing allo-exposed female blood donors have not yet been introduced nationwide in Austria. To assess the need and feasibility of routine leukocyte antibody testing, the prevalence of leukocyte-reactive antibodies in an Austrian female donor population was been determined using classical cell-based methods which were compared with a high-throughput bead-based method.

Methods

Sera from 1,022 female blood donors were screened using a granulocyte aggregation test (GAT) and a white blood cell immunofluorescence test (WIFT) after retesting and specification of positive samples by granulocyte immunofluorescence test (GIFT) and monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA). Potential HLA reactivities were confirmed using the microbeads assay LabScreen^TM Mixed. The results in 142 donor sera and 38 well-defined reference sera were investigated by the microbeads assay LabScreen^TM Multi and compared with classical cell-based methods.

Results

Reactivity with either granulocytes and/or lymphocytes was detected in 79 sera (7.7%), with the majority being HLA-specific. Antibodies against HNA were obtained in 7 samples (0.7%). The aggregating potential of the detected antibodies was observed in 9 cases (0.9%). Most of the leukocyte-reactive antibodies occurred at a donor age of between 35 and 59 years (n = 61). LabScreen Multi showed good agreement (κ = 0.767) for HNA antibody detection by cell-based assays, but double/multiple specificities (100% of 7 anti-HNA-1b sera) as well as false-negative results (40% of 15 HNA-3-specific sera) occurred.

Discussion

Leukocyte-reactive antibody screening is advised in Austrian female donors for safe blood transfusion, including single-donor convalescent plasma treatment of COVID-19 that may be implemented soon. For the introduction of LabScreen Multi, the combination with GAT should be considered to ensure correct anti-HNA-3a detection.

[Relevance of antibodies in hematopoietic stem cell transplantation: Antibodies anti-HLA, anti-platelets, anti-granulocytes, anti-erythrocytes and anti-MICA. Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

The presence of allo-antibodies in the serum of a recipient awaiting hematopoietic stem cell transplantation (HSCT) may have an impact on transfusion efficiency and/or donor choice, especially in the absence of an identical sibling donor. Prior to transplantation, donor specific anti-HLA (Human Leukocyte Antigen) antibodies (DSA) have a recognized effect on transplant outcome, correlated with the increasing MFI value and with the ability of such antibody to fix the complement fraction. Anti-platelet antibodies (anti-HLA class I and anti-HPA [Human Platelet Antigen]) are better involved in transfusion inefficiency and can be responsible for refractory status. ABO incompatibilities require a specific treatment of the graft in presence of high titer to avoid hemolytic adverse effects. Investigations of these antibodies should be carried out on a regular basis in order to establish appropriate transfusion recommendation, select an alternative donor when possible or adapt the source of cells. After transplantation, in case of delayed recovery or graft rejection, long term aplasia, persistent mixed chimerism or late release, and after elimination of the main clinical causes, a biological assessment targeted on the different type of antibodies will have to be performed in order to orient towards the cause or the appropriate therapy. Further studies should be carried out to determine the impact of anti-MICA antibodies and recipient specific anti-HLA antibodies, on the outcome of the transplantation.

A novel nonsense mutation found in the CD177 gene of Thai individuals with the HNA-2 null phenotype

OBJECTIVES

The aim of this study is to explore the molecular basis and to develop a simple sequence-specific primer polymerase chain reaction (PCR-SSP) technique for screening genotypes associated with the human neutrophil antigen-2 (HNA-2) null phenotype among Thai blood donors.

BACKGROUND

Single-nucleotide polymorphisms (SNPs) c.787A>T of the CD177 gene is well known to be primarily demonstrated as a genetic determinant for HNA-2 deficiency.

METHODS

The SNPs in the CD177 gene (exons 7 and 9) of 49 Thai blood donors with the known percentage of CD177 expression by flow cytometry including 48 HNA-2 positive and 1 HNA-2 null individuals were identified by long-range PCR amplification and sequencing. Moreover, screening for the c.1254G>A mutation was developed using an in-house PCR-SSP technique and tested among 771 unrelated donor samples.

RESULTS

A HNA-2 null sample from the first cohort was heterozygous for c.787A/T and homozygous for c.1291G/G, namely, a 787A-1291G/787T-1291G (AG/TG) genotype. Interestingly, we could identify SNP c.1254G>A (rs188387562, p. Trp418Ter) that caused a nonsense mutation of the CD177 gene in exon 9. This individual might have the 787A-1254A-1291G/787T-1254G-1291G genotype. From the second cohort (771 unrelated donors), the 1254GG homozygote was the most common (96.37%), followed by the 1254GA heterozygote (3.50%) and 1254AA homozygote (0.13%). Blood samples of two individuals with 787AT-1254GA-1291GG and 787AA-1254AA-1291GG genotypes were tested and the HNA-2 antigen expressions were 0.03% and 0.16% in rank.

CONCLUSIONS

The c.787A>T is a primary genetic hallmark to determine the HNA-2 null phenotype. Additional screening of the novel c.1254G>A in combination with c.787A>T is a suitable, convenient and effective diagnosis among Thais.

Isolated Chronic and Transient Neutropenia

Neutrophils are a critical part of the body’s defense system to prevent serious bacterial and fungal infections. Neutropenia is a term which is defined by the absolute neutrophil counts (ANC) < 1,500 cells/µL, and it becomes clinically significant when the level falls below 500 cells/µL. The risk of morbidity and mortality increases considerably when the levels fall below 200. In some ethnicities, the neutropenia is chronic and is frequently seen on routine outpatient visits. On the other hand, transient neutropenia is associated with a transient drop in the neutrophil count and many of the underlying causes are reversible. Patients and their families, as well as some clinicians, express great concern for neutropenia, leading to a multitude of tests and emergency room visits. In this review, we discuss the causes of both chronic and transient neutropenia. Also, we have given special emphasis on the mechanism of neutropenia and management of transient neutropenia.

Medicinal Uses of Hematopoietic Growth Factors in Neonatal Medicine

This review focuses on certain hematopoietic growth factors that are used as medications in clinical neonatology. It is important to note at the chapter onset that although all of the pharmacological agents mentioned in this review have been approved by the US Food and Drug administration for use in humans, none have been granted a specific FDA indication for neonates. Thus, in a sense, all of the agents mentioned in this chapter could be considered experimental, when used in neonates. However, a great many of the pharmacological agents utilized routinely in neonatology practice do not have a specific FDA indication for this population of patients. Consequently, many of the agents reviewed in this chapter are considered by some practitioners to be nonexperimental and are used when they judge such use to be "best practice" for the disorders under treatment.The medicinal uses of the agents in this chapter vary considerably, between geographic locations, and sometimes even within an institutions. "Consistent approaches" aimed at using these agents in uniform ways in the practice of neonatology are encouraged. Indeed some healthcare systems, and some individual NICUs, have developed written guidelines for using these agents within the practice group. Some such guidelines are provided in this review. It should be noted that these guidelines, or "consistent approaches," must be viewed as dynamic and changing, requiring adjustment and refinement as additional evidence accrues.

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.

Molecular Genetics of the Human Neutrophil Antigens

BACKGROUND AND OBJECTIVE

Antibodies to human neutrophil antigens (HNAs) have been implicated in transfusion-related acute lung injury and allo- and autoimmune neutropenia. To date, five HNA systems are assigned, and during the last decades enormous efforts have been undertaken to identify the underlying genes and to characterize the antigens. This review of the literature will provide the current genetic, molecular and functional information on HNAs.

RECENT FINDINGS

New information on alleles and antigens has been added to nearly each of the five HNA systems. HNA-1d has been added as the antithetical epitope to HNA-1c that is located on the glycoprotein encoded by FCGR3B*02 but not by FCGR3B. FCGR3B*04 and *05 now are included as new alleles. A CD177*787A>T substitution was demonstrated as the main reason for the HNA-2-negative phenotype on neutrophils. The target glycoprotein of HNA-3 antibodies could be identified as choline transporter-like protein 2 (CTL2) encoded by SLC44A2. The conformation sensitive epitope discriminates between arginine and glutamine at position 152 resulting in HNA-3a and HNA-3b. An additional Leu151Phe substitution can impair HNA-3a antibody binding. Recently an alloantibody against HNA-4b which discriminates from HNA-4a by an Arg61His exchange of the glycoprotein encoded by the ITGAM gene was reported in neonatal alloimmune neutropenia. An update of the current HNA nomenclature based on the new findings was provided in 2016 by the ISBT Granulocyte Immunobiology Working Party nomenclature subcommittee.

CONCLUSIONS

The molecular basis of each of the five HNA antigen systems has been decoded during the past decades. This enables reliable molecular typing strategies, antibody detection and specification as well as development of new assays based on recombinant antigens. However, research on HNA alleles, antigens, and antibodies is not finally terminated and also in the future will add new findings.

HNA-1, -3, -4, and -5 genotyping using multiplex PCR among southern Thais: Developing continual HNA-1 null detection

BACKGROUND

Antibodies against human neutrophil antigens (HNAs) are involved in various clinical conditions including transfusion-related acute lung injury and auto/alloimmune neutropenia. We aimed to determine HNA-1, -3, -4, and -5 frequencies among southern Thais using multiplex PCR and to develop HNA-1 null detection.

METHODS

Samples obtained from 427 southern Thai blood donors were genotyped HNA-1, -3, -4, and -5 using multiplex PCR and compared their allele frequencies with those previously reported in Thai populations. HNA-1 null samples were tested by newly developed PCR-SSP and PCR-RFLP and confirmed by DNA sequencing.

RESULTS

The frequencies of FCGR3B*01, FCGR3B*02, FCGR3B*03, SLC44A2*01, SLC44A2*02, ITGAL*01, and ITGAL*02 among southern Thais differed from other Thai populations, except ITGAM*01 and ITGAM*02 frequencies. Two samples without specific fragments of FCGR3B*01, FCGR3B*02, and FCGR3B*03 tested by multiplex PCR were confirmed by PCR-RFLP to identify FCGR3B deficiency (HNA-1 null). Moreover, to reduce test steps, the newly developed PCR-SSP for FCGR3B deficiency was validated and tested in all samples and the results were in agreement with DNA sequencing.

CONCLUSIONS

This was the first study to report HNA-1, -3, -4, and -5 frequencies among southern Thais. The indeterminate results of multiplex PCR for HNA-1 genotyping led to establish HNA-1 null detection using PCR-SSP, which is simple, convenient and cost-effective and can be used to identify FCGR3B deficiency.

Molecular and Functional Characterization of Fcγ Receptor IIIb-Ligand Interaction: Implications for Neutrophil-Mediated Immune Mechanisms in Malaria

The Fcγ receptor IIIb (FcγRIIIb) is a low-affinity receptor of IgG and is essential in neutrophil-mediated effector functions. Different allelic forms of FcγRIIIb carrying human neutrophil antigen (HNA-1a, -1b, -1c, and -1d) have been identified. Here, we have generated stable transfected HEK293 cell lines expressing HNA-1aa, -1bb, and -1bc. Of these, cells expressing HNA-1bc interacted significantly stronger (binding affinities, 2.277 versus 0.743) with human IgG than cells expressing the HNA-1aa or -1bb alloforms. The higher affinity of IgG toward the HNA-1c alloform was confirmed using neutrophils derived from German blood donors. Neutrophils from HNA-1abc-phenotyped individuals bound IgG significantly stronger (1.825 versus 0.903) than did neutrophils from HNA-1ab-typed individuals. These findings were confirmed by surface plasmon resonance (SPR) analysis demonstrating that recombinant HNA-1bc had a higher affinity (dissociation constant [Kd ], 7.24 × 10-6 M) than recombinant HNA-1bb (Kd , 1.15 × 10-5 M) against normal IgG. Finally, we demonstrated that Plasmodium falciparum merozoites opsonized with human IgG affinity purified against P. falciparum glutamate-rich protein (GLURP) enhanced stronger reactive oxygen species (ROS) emission in neutrophils obtained from HNA-1abc donors than in neutrophils from HNA-1ab donors. Collectively, these results indicate that the amino acid substitution Ala78Asp resulting in the HNA-1c allotype leads to higher affinity toward human IgG, enhancement of neutrophil activation, and possibly effective clearance of malaria by intracellular ROS.

HNA-3a and HNA-3b antigens among 9 ethnic populations and the Han population in Southwest China

Background

Human neutrophil antigen 3 (HNA-3) is encoded by the SLC44A2 gene. Antibodies against HNAs can cause severe, often fatal, transfusion reactions, known as transfusion-related acute lung injury, and neonatal neutropenia. We explored the 2 common HNA-3 variants in 9 ethnic populations residing in Sichuan and Yunnan provinces of China as compared to the Han population.

Methods

We genotyped for SLC44A2 (rs2288904) by polymerase chain reaction sequence-based typing among blood donors, for a total of 2206 individuals in Yunnan and 376 in Sichuan.

Results

The SLC44A2*02 allele (HNA-3b antigen) frequency varied between 0.24 and 0.33 for all 9 ethnic populations in Yunnan, including Zhuang, Derung, Hani, Lisu, Bai, Miao, Dai, Naxi, and Yi. Specifically, the Yi ethnicity did not present an unusually great SLC44A2*02 frequency at any of the 4 locations examined in Yunnan. Except of the Yi ethnicity in Sichuan (0.40), the Han ethnicity, as the majority population group, had the greatest SLC44A2*02 frequency with 0.39 in Yunnan and 0.35 in Sichuan.

Conclusion

The ethnic populations in Southwest China are not at an increased risk for anti-HNA3a compared to the Han population, with the possible exception of Yi in Sichuan. Our data, however, corroborated the known high prevalence of SLC44A2*02 in Han populations. Hence, the Han populations in Yunnan, Sichuan and elsewhere in China are at a comparatively great risk for developing HNA-3a antibodies.

Genotype frequencies of human neutrophil antigen-3 in the Chinese Zhuang and Dong populations

Individuals with the human neutrophil antigen (HNA)-3b/3b type can produce HNA-3a antibodies, which have been reported to cause severe, sometimes fatal transfusion-related acute lung injury (TRALI). Our study aimed to determine the genotype frequency of HNA-3a/3b which will be helpful to estimate the potential risk for forming anti-HNA-3a, the clinically relevant antibody linked to TRALI in two different ethnic groups of southern China. Five hundred unrelated and healthy blood donors (284 male, 216 female; 300 Zhuangs, 200 Dongs) from the Guangxi Zhuang Autonomous Region were simultaneously typed for the HNA-3 allele using a polymerase chain reaction sequence-based typing (PCR-SBT) method. Genotype frequencies of HNA-3a/3a, HNA-3a/3b and HNA-3b/3b were 51.7%, 39.7% and 8.6% in the Zhuang population, and 44.0%, 49.0% and 7.0% in the Dong population, respectively. Homozygous HNA-3b/3b genotype frequency among the Zhuang population (8.6%) was significantly higher than previously reported in African Americans (0.4%), Brazilians (3.6%) and English Caucasians (2.9%) (p < .05). And the HNA-3b/3b genotype frequency among the Dong population was higher than African Americans (0.4%) (p < .05). This study showed Chinese Zhuang and Dong populations possessed a higher frequency of HNA-3b/3b genotype, suggesting that they may be at greater risk for developing anti-HNA-3a alloantibodies that may cause severe cases of TRALI. A molecular-based identification of the HNA-3b/3b genotype in all multiparous female blood donors was suggested to reduce the risk of TRALI following plasma and whole blood allogeneic transfusions.

Anti-human neutrophil antigen-1a, -1b, and -2 antibodies in neonates and children with immune neutropenias analyzed by extracted granulocyte antigen immunofluorescence assay

BACKGROUND

Anti-human neutrophil antigen (HNA) antibodies have been implicated in the development of neonatal alloimmune neutropenia (NAN) and autoimmune neutropenia (AIN). There are many conventional assay methods that detect anti-HNA antibodies. However, a method to measure multiple samples and detect several anti-HNA antibodies simultaneously is needed.

STUDY DESIGN AND METHODS

We developed a new method, the extracted granulocyte antigen immunofluorescence assay (EGIFA), to analyze anti-HNA-1a, -1b, and -2 antibodies in sera. The results obtained by EGIFA were evaluated in comparison with those from several standard assay methods. Anti-HNA antibodies in serum samples from nine familial cases with suspected NAN (n = 19) and children with suspected AIN (n = 88) were also measured by EGIFA.

RESULTS

The evaluation of nine serum samples with anti-HNA antibodies suggested that EGIFA demonstrated equivalent specificity and superior sensitivity to monoclonal antibody-specific immobilization of granulocyte antigens and had comparable sensitivity to the granulocyte indirect immunofluorescence test. EGIFA successfully detected anti-HNA-1a or -1b antibodies in seven of nine familial cases with suspected NAN. EGIFA detected anti-HNA antibodies in 40.9% of children with suspected AIN. Among them, isolated anti-HNA-1a or -1b antibody was detected in 4.5 or 12.5% of children, respectively, and anti-HNA-2 antibody was identified in 3.4% of children. The 30.8% (16 of 52) of children negative for anti-HNA antibody by EGIFA were positive for anti-HLA antibody.

CONCLUSION

EGIFA facilitated the measurement of anti-HNA-1a, -1b, and/or -2 antibodies in sera. The prompt measurement of anti-HNA antibodies will improve the diagnosis and clinical management of patients with suspected NAN or AIN.

The role of endothelium in the onset of antibody-mediated TRALI

Transfusion Related Acute Lung Injury (TRALI) is one of the leading causes of mortality and morbidity following blood transfusion. The mechanisms behind the disease are not yet fully understood but seem to involve many different activating pathways and donor factors, in synergy with patient susceptibility. Studies have focused mostly on neutrophil activation, as aggregates of neutrophils and edema in lungs are found in post-mortem histological sections. This review aims to highlight the role of the endothelium in TRALI, as activated endothelium is the main promoter of leukocyte transmigration, and creates the barrier between blood and tissue. Since recent evidence suggests that a strong endothelial barrier prevents leukocyte transmigration and vascular leakage, we suggest that strengthening this barrier may be key to TRALI prevention.

Prolonged neutropenia due to antihuman neutrophil antigen 2 (CD177) antibody after bone marrow transplantation

We describe a patient who presented with prolonged neutropenia due to anti-human neutrophil antigen (HNA)-2 (CD177) antibody after allogeneic bone marrow transplantation. A granulocyte immunofluorescence test showed bimodal expression of antineutrophil antibody that resulted from specific binding of anti-HNA-2 to CD177⁺ neutrophils from healthy donors. The patient did not respond to granulocyte colony stimulating factor, which is able to upregulate CD177 expression on neutrophils. The low percentage of CD177⁺ cells in the few remaining neutrophils supports the possibility of elimination of CD177-upregulated neutrophils. These findings might explain an inferior response to neutrophil growth factors in neutropenia secondary to anti-HNA-2 antibody.

Assessment of HNA alloimmunisation risk in Northeastern Thais, Burmese and Karen

OBJECTIVES

This study aimed to determine human neutrophil antigen (HNA) frequency, estimate possible HNA incompatibilities and predict the risk of HNA alloimmunisation in the Northeastern Thai, Burmese and Karen populations.

BACKGROUND

Alloantibodies against HNA are implicated in a number of clinical conditions, including immune-mediated neutropenia and transfusion reactions.

METHODS

A total of 400 unrelated healthy Thais, 261 Burmese and 249 Karen was included in this study. DNA samples were typed for HNA-1, -3, -4 and -5 systems using polymerase chain reactions with sequence-specific primers (PCR-SSP).

RESULTS

In this cohort, HNA-1a was more prevalent than HNA-1b. Accordingly, the possible risk of HNA-1a alloimmunisation against HNA-1a is lower than HNA-1b (0·0802-0·1351 vs 0·2293-0·2497). This is in contrast to the situation reported in Caucasian and African populations. The predicted risk of HNA-3 incompatibility in Thais, Burmese and Karen were 28·09%, 30·66% and 22·77%, respectively. The possible risks of HNA-3a alloimmunisation were 0·0493 in Thais, 0·0608 in Burmese and 0·0196 in Karen, respectively. No individuals were found to be homozygous for HNA-4bb. The probability of developing alloantibodies against HNA-4a was low in these populations and every population in Asia. In contrast, the overall frequency of HNA-5bb homozygous individuals was high in this study, peaking at 0·192.

CONCLUSIONS

This is the first study that reported the allele frequencies of HNA-1, -3, -4, and -5 in a large sample of healthy unrelated individuals from ethnic Thais, Burmese and Karen. Our results indicated the high possible risk of HNA-1, -3 and -5 alloimmunisation in these populations.

[Advances in research on childhood neutropenia]

Neutrophils, an important type of human immune cells, are involved in host defense against infections. Neutropenia refers to a group of diseases manifesting as a reduction in the absolute value of mature neutrophils and is often accompanied by an increased risk of bacterial infection. According to etiology and pathogenesis, neutropenia is classified into congenital and acquired neutropenia. This article reviews the current research status and advances in the etiology of neutropenia in children. A deep understanding of the etiology of neutropenia helps to improve the diagnosis and treatment of this disease.

Late onset cytopenias following haematopoietic stem cell transplant associated with viral infection and cell specific antibodies

This report describes a patient who received an allogeneic haematopoietic stem cell transplant and who, following a viral infection, developed late onset cytopenias associated with antibodies against red cells, platelets and granulocytes. Investigation of these cytopenias revealed the presence of lineage specific auto- and allo-antibodies, which were not present in either the donor or in the recipient prior to the viral infection. This case provides further evidence for the concept that viral challenges following HSCT can result in the production of cell specific antibodies that can have significant implications for patient management.

Autoimmune and other acquired neutropenias

This educational review addresses the diagnostic evaluation of patients for autoimmune and other forms of acquired neutropenia, including the futility of deconstructing the overlap of chronic "autoimmune," "benign," and "idiopathic" categories. Isolated neutropenias caused by infection, drugs, and immunologic disorders are also addressed. Discussion of management options emphasizes a conservative approach, with largely supportive care for these mostly benign and self-limited disorders.

Evaluation of a new microbeads assay for granulocyte antibody detection

BACKGROUND

To reduce the risk of transfusion-associated acute lung injury (TRALI), a high number of plasma donors were tested for human leukocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies. For HNA antibody detection, the gold standard is a combination of the granulocyte immunofluorescence test (GIFT) and the granulocyte agglutination test (GAT). However, these tests are not suitable for a high-throughput of samples.

STUDY DESIGN AND METHODS

To evaluate the new generation of the LABScreen MULTI assay (One Lambda, Inc.), which has special new beads for all the known HNA specificities, including HNA-3a, 97 sera samples containing well-defined HNA antibodies were used. For background testing, we used 91 samples from plasma donors previously identified by GAT, GIFT, and the monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA) assay.

RESULTS

Compared with previous tests, the new LABScreen MULTI assay was highly specific for the HNA-1a, HNA-1b, HNA-2, and HNA-3a antibody specificities required to prevent TRALI. Ninety-eight percent of the HNA-1a, HNA-1b, and HNA-2 antibodies could be detected as true positive; and 90% of the HNA-3a antibodies were recognized correctly as positive. False-positive reactions were identified in 5.5% of samples that previously tested negative.

CONCLUSION

The detection of HNA-3a antibody specificities could be integrated into the new LABScreen MULTI assay; however, we detected only 90%. In addition, we detected further HNA antibodies, such as HNA-1c, HNA-1d, and some HNA-3b and HNA-4a antibodies. The new generation of LABScreen MULTI is a great step toward feasible high-throughput testing for HNA antibodies. Nevertheless, GIFT and GAT remain the gold-standard methods for the differentiation of rare and currently unknown HNA specificities.

Heterogeneity of Human Neutrophil CD177 Expression Results from CD177P1 Pseudogene Conversion

Most humans harbor both CD177neg and CD177pos neutrophils but 1-10% of people are CD177null, placing them at risk for formation of anti-neutrophil antibodies that can cause transfusion-related acute lung injury and neonatal alloimmune neutropenia. By deep sequencing the CD177 locus, we catalogued CD177 single nucleotide variants and identified a novel stop codon in CD177null individuals arising from a single base substitution in exon 7. This is not a mutation in CD177 itself, rather the CD177null phenotype arises when exon 7 of CD177 is supplied entirely by the CD177 pseudogene (CD177P1), which appears to have resulted from allelic gene conversion. In CD177 expressing individuals the CD177 locus contains both CD177P1 and CD177 sequences. The proportion of CD177hi neutrophils in the blood is a heritable trait. Abundance of CD177hi neutrophils correlates with homozygosity for CD177 reference allele, while heterozygosity for ectopic CD177P1 gene conversion correlates with increased CD177neg neutrophils, in which both CD177P1 partially incorporated allele and paired intact CD177 allele are transcribed. Human neutrophil heterogeneity for CD177 expression arises by ectopic allelic conversion. Resolution of the genetic basis of CD177null phenotype identifies a method for screening for individuals at risk of CD177 isoimmunisation.

Genotype frequency of human neutrophil antigen-3 polymorphisms in the Yi, Han, and Tibetan populations of China

BACKGROUND

Human neutrophil antigen-3 (HNA-3) alloantibodies can cause fatal transfusion-related acute lung injury (TRALI). Most frequencies of SLC44A2 alleles encoding the HNA-3a/b antigens have been established in Han individuals by polymerase chain reaction with sequence-specific priming (PCR-SSP). We sequenced SLC44A2 gene fragments and determined allele frequencies in three ethnicities of China.

STUDY DESIGN AND METHODS

Genomic DNA was extracted from 448 samples of 100 blood donors of Yi ethnicity in Xichang, Liangshan; 248 Han in Nanjing, Jiangsu; and 100 Tibetan in Lhasa, Tibet. A PCR-SSP was applied to determine the phase of two single-nucleotide polymorphisms (SNPs); SLC44A2 haplotypes were constructed.

RESULTS

In the 567 nucleotides of the SLC44A2 gene covered by our sequencing approach in Han individuals, we detected the known 331-44G>A (rs12972963) and 461G>A (rs2288904) polymorphisms. In the 243 nucleotides sequenced in Yi and Tibetan populations, we detected the known 461G>A and 503-15T>C (rs1560711) polymorphisms. A PCR-SSP for the common HNA-3a/b SNP was 100% concordant. The frequencies of the HNA-3a allele were 0.58, 0.66, and 0.69 in Yi, Han (Nanjing), and Tibetan, respectively (0.42, 0.34, and 0.31 for HNA-3b).

CONCLUSIONS

The Yi population of China had the highest frequency of blood donors at risk of harboring anti-HNA-3a compared to any population studied so far. We confirmed that the underlying SLC44A2*2 allele is more common in China than in any European or African populations.

Allelic Discrimination by TaqMan-PCR for Genotyping of Human Neutrophil Antigens

Neutrophil antigens are implicated in a variety of clinical conditions, including neonatal immune neutropenia, transfusion-related acute lung injury, refractoriness to granulocyte transfusions, febrile transfusion reactions, and autoimmune neutropenia. In this report, we describe simultaneous genotyping of human neutrophil antigens (HNA)-1, -3, -4, and -5 using PCR with allele-specific TaqMan probes and end-point fluorescence detection, which is a robust, rapid, and reproducible method, allowing for high-throughput genotyping.

Frequencies of human neutrophil antigen-4 and human neutrophil antigen-5 among Thai blood donors

Context:

Antibodies against human neutrophil antigens (HNAs) are implicated in immune-mediated neutropenia, transfusion-related acute lung injury and febrile transfusion reactions.

Aims:

This study aimed to determine HNA gene frequencies of the HNA-4 and HNA-5 systems among Thai populations and compare these frequencies with those previously reported for other populations.

Materials and Methods:

800 DNA samples obtained from 500 unrelated healthy blood donors from Bangkok and 300 samples from Chiang Mai, Thailand were included. Samples were typed for each HNA allele including HNA-4a, HNA-4b, HNA-5a, and HNA-5b using an in-house polymerase chain reaction with sequence-specific primer technique.

Results:

The frequencies of HNA-4a and HNA-4b alleles in central Thais were 0.975 and 0.025, respectively and for Northern Thais, their frequencies were 0.965 and 0.035, respectively. For HNA-5a and HNA-5b alleles, their frequencies were 0.771 and 0.229; 0.748, and 0.252 in central and Northern Thais, respectively. The frequencies of HNA-4 and HNA-5 systems in central Thais are closely related to those in Northern Thais (P > 0.05). However, their frequencies were different from other populations (P < 0.001), except HNA-5a and HNA-5b gene frequencies in Thais were similar to Caucasians (P > 0.05).

Conclusion:

This study could contribute to predict the risk of alloimmunization to HNA-4 and HNA-5 systems, especially in feto-maternal incompatibility in Thais.

Transfusion-related alloimmune neutropenia with no pulmonary complications: one donor-five cases

BACKGROUND

Neutrophil alloantibodies are well-known triggers of transfusion-related acute lung injury (TRALI) and also cause immune neutropenia. Alloimmune neutropenia due to transfusion is an isolated phenomenon that is only rarely identified. Its incidence is specified in the literature as being less than one in 10,000 transfused plasma-containing units. We expect that this phenomenon is underreported.

STUDY DESIGN AND METHODS

We observed five cases of alloimmune neutropenia with no respiratory complications with only one case initially reported as a suspected transfusion reaction. The other four cases were detected in the course of the subsequent lookback investigation.

RESULTS

The first case was reported as a potential transfusion reaction when a female patient showed a decrease in the white blood cell count after a platelet (PLT) transfusion. Examinations of the donor blood revealed an antibody against the human neutrophil antigen HNA-1b; the recipient was typed HNA-1b positive and HNA-1a negative. After examining the blood counts of other patients who previously received PLT concentrates from the same donor, we identified four other patients with an unreported decrease in the leukocyte and/or granulocyte count of more than approximately 50% after transfusion.

CONCLUSION

HNA antibodies are generally regarded as potential triggers of TRALI. Here we describe an HNA antibody that reproducibly caused transfusion-related neutropenia only without pulmonary complications. Factors predisposing patients to TRALI development are widely discussed. Our case suggests that antibody characteristics are also relevant in the development of TRALI. Current measures to prevent TRALI should also prevent transfusion-related alloimmune neutropenia.

Human neutrophil antigen profiles in Banjar, Bugis, Champa, Jawa and Kelantan Malays in Peninsular Malaysia

BACKGROUND

Human neutrophil antigens (HNA) are polymorphic and immunogenic proteins involved in the pathogenesis of neonatal alloimmune neutropenia, transfusion-related acute lung injury (TRALI) and transfusion-related alloimmune neutropenia. The characterisation of HNA at a population level is important for predicting the risk of alloimmunisation associated with blood transfusion and gestation and for anthropological studies.

MATERIALS AND METHODS

Blood samples from 192 healthy, unrelated Malays were collected and genotyped using polymerase chain reaction-sequence specific primers (HNA-1, -3, -4) and polymerase chain reaction-restriction fragment length polymorphisms (HNA-5). The group comprised 30 Banjar, 37 Bugis, 51 Champa, 39 Jawa and 35 Kelantan Malays.

RESULTS

The most common HNA alleles in the Malays studied were HNA-1a (0.641-0.765), -3a (0.676-0.867), -4a (0.943-1.000) and -5a (0.529-0.910). According to principal coordinate plots constructed using HNA allele frequencies, the Malay sub-ethnic groups are closely related and grouped together with other Asian populations. The risks of TRALI or neonatal neutropenia were not increased for subjects with HNA-1, -3 and -4 loci even for donor and recipient or pairs from different Malay sub-ethnic groups. Nonetheless, our estimates showed significantly higher risks of HNA alloimmunisation during pregnancy and transfusion between Malays and other genetically differentiated populations such as Africans and Europeans.

DISCUSSION

This study reports HNA allele and genotype frequencies for the five Malay sub-ethnic groups living in Peninsular Malaysia for the first time. These Malay sub-ethnic groups show closer genetic relationships with other Asian populations than with Europeans and Africans. The distributions of HNA alleles in other lineages of people living in Malaysia (e.g. Chinese, Indian and Orang Asli) would be an interesting subject for future study.

High Frequency of Thyroid Disorders in Patients Presenting With Neutropenia to an Outpatient Hematology Clinic STROBE-Compliant Article

Granulopoiesis abnormalities have been described in association with thyroid disorders (TD). However, data regarding systematic evaluation of adult neutropenia and concurrent or prior TD are scarce. To investigate the frequency of TD among patients presenting with neutropenia, and the immunophenotypic and immunologic profile of neutropenic patients with concomitant thyroidopathy. Two hundred eighteen consecutive neutropenic patients were prospectively evaluated in our outpatient Hematology Clinic, with a detailed laboratory screen, including thyroid function tests, antineutrophil antibodies, blood lymphocytes immunophenotyping, and detection of T-cell clonality by PCR. Among 218 patients with neutropenia, 95 (43.6%) had TD, 65 chronic immunologic neutropenia, 20 clonal proliferation of T-large granular lymphocytes (T-LGL), 5 autoimmune disorders, and 33 other diagnoses. TD-patients had an increased frequency of recurrent infections compared with other patients (P = 0.045). The following correlations were found: negative correlation between FT3 and absolute neutrophil count (ANC) (r² = -0.274, P = 0.007), negative correlation between TPO-Abs/TG-Abs and C4 (r² = -0.16, P = 0.045; r² = -0.266, P = 0.001), and CD4⁺ counts were inversely correlated to T4 and positively to TSH (r² = -0.274, P = 0.024; r² = 0.16, P = 0.045). In addition, TD-patients had significantly higher percentages of CD4⁺ lymphocytes (P = 0.003). Among TD-patients, 23.4% had Hashimoto thyroiditis (HT), 4.1%, Graves disease (GD), 8.2% nontoxic multinodular goiter (NTMG), 5% subclinical hypothyroidism, and 2.8% had undergone total thyroidectomy associated with nodules (TTM). Thirteen TD-patients displayed T-LGL. Patients with autoimmune thyroidopathy had an increased frequency of concomitant autoimmune manifestations (P = 0.03). Significant differences between the different thyroidopathies included: HT-patients had higher percentages of B-lymphocytes, while the opposite was evident for the TTM-subgroup (P = 0.009, 0.02); GD-patients showed an increase of the proportion of NK cells and a decrease in the percentage of TCRγδ+ lymphocytes (P = 0.001, 0.045); and NTMG-patients had significantly higher ANC (P = 0.004) compared to other thyroidopathies. Antineutrophil antibodies were found in 37.2% of TD-patients tested. Anti-TPO titers were significantly higher in patients with positive antineutrophil antibodies (P = 0.04). The frequency of TD among neutropenic patients may be higher than previously reported. The existence of antineutrophil antibodies, as well as the different distribution of lymphocyte subsets among patients with different TD, suggests both humoral and cellular mechanisms in the pathophysiology of thyroid disease-associated neutropenia.

Antibody-mediated transfusion-related acute lung injury; from discovery to prevention

Transfusion-related acute lung injury (TRALI), a syndrome of respiratory distress caused by blood transfusion, is the leading cause of transfusion-related mortality. The majority of TRALI cases have been related to passive infusion of human leucocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies in donor blood. In vitro, ex vivo and in vivo animal models have provided insight in TRALI pathogenesis. The various classes of antibodies implicated in TRALI appear to have different pathophysiological mechanisms for the induction of TRALI involving endothelial cells, neutrophils, monocytes and, as very recently has been discovered, lymphocytes. The HLA and HNA-antibodies are found mainly in blood from multiparous women as they have become sensitized during pregnancy. The incidence of TRALI has decreased rapidly following the introduction of a male-only strategy for plasma donation. This review focuses on pre-clinical and clinical studies investigating the pathophysiology of antibody-mediated TRALI.

FCGR3B gene frequencies among ethnic Thai blood donors from a regional hospital in Eastern Thailand

The FCGR3B gene encodes three human neutrophil antigens which consist of HNA-1a, HNA-1b, and HNA-1c. These antigens are encoded by three alleles in the FCGR3B locus: FCGR3B*01, FCGR3B*02, and FCGR3B*03 alleles, respectively. The frequencies of FCGR3B alleles have been reported in different ethnic populations. This study compared the FCGR3B gene frequencies among 230 unrelated healthy Eastern Thai blood donors in Rayong hospital with the previously published studies. The polymerase chain reaction-sequence-specific primers method was performed to determine FCGR3B genotypes. The results showed that the allele frequencies of FCGR3B*01, FCGR3B*02, and FCGR3B*03 were 0.722, 0.274, and 0.009, respectively. The FCGR3B*01 and FCGR3B*02 frequencies found in the Eastern Thais were similar to the previous reports investigating in Northern Thais, Chinese Han, Taiwanese, and Japanese populations. Interestingly, our data showed statistically significant difference (P < 0.05) to Central Thais, Korean, Indian, Turkish, Australian, Tunisian, American, German, and Italian populations. In addition, one FCGR3Bnull , which represents a gene deletion, was also found in this study. This information is important not only for the assessment of neutrophil antibody-mediated clinical conditions and for disease association studies but also for anthropological studies.

Risk estimation of HNA-3 incompatibility and alloimmunization in Thai populations

Severe transfusion-related acute lung injury (TRALI) is often due to antibodies in blood components directed against human neutrophil antigen (HNA)-3a. This study aimed to report the genotype frequencies of the HNA-3 system and to estimate the potential risk of HNA-3 incompatibility and alloimmunization in two Thai populations. Eight hundred DNA samples obtained from 500 unrelated healthy blood donors at the National Blood Centre, Thai Red Cross Society, Bangkok and 300 samples from the Blood Bank, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand were included. HNA-3 genotyping was performed using an in-house polymerase chain reaction with sequence-specific primer (PCR-SSP) technique. The observed frequencies of the HNA-3a/3a, HNA-3a/3b, and HNA-3b/3b genotypes were 0.528, 0.380, and 0.092 in central Thais and 0.600, 0.350, and 0.050 in northern Thais, respectively. The frequencies were used to estimate HNA-3 incompatibility and risk of HNA-3a alloimmunization. The HNA-3 incompatibility in central Thais (33.28%) was higher than northern Thais (28.75%), corresponding to a significantly higher probability of HNA-3a alloimmunization (P<0.05) similar to Japanese and Chinese populations. This study showed the high risk of HNA-3 incompatibility and alloimmunization, especially in central Thai blood donors. A molecular-based identification of the HNA-3 genotype of female donors is suggested to reduce the risk of TRALI following plasma and whole blood allogeneic transfusion.

A comparison of assays for accurate copy number measurement of the low-affinity Fc gamma receptor genes FCGR3A and FCGR3B

The FCGR3 locus encoding the low affinity activating receptor FcγRIII, plays a vital role in immunity triggered by cellular effector and regulatory functions. Copy number of the genes FCGR3A and FCGR3B has previously been reported to affect susceptibility to several autoimmune diseases and chronic inflammatory conditions. However, such genetic association studies often yield inconsistent results; hence require assays that are robust with low error rate. We investigated the accuracy and efficiency in estimating FCGR3 CNV by comparing Sequenom MassARRAY and paralogue ratio test-restriction enzyme digest variant ratio (PRT-REDVR). In addition, since many genetic association studies of FCGR3B CNV were carried out using real-time quantitative PCR, we have also included the evaluation of that method’s performance in estimating the multi-allelic CNV of FCGR3B. The qPCR assay exhibited a considerably broader distribution of signal intensity, potentially introducing error in estimation of copy number and higher false positive rates. Both Sequenom and PRT-REDVR showed lesser systematic bias, but Sequenom skewed towards copy number normal (CN = 2). The discrepancy between Sequenom and PRT-REDVR might be attributed either to batch effects noise in individual measurements. Our study suggests that PRT-REDVR is more robust and accurate in genotyping the CNV of FCGR3, but highlights the needs of multiple independent assays for extensive validation when performing a genetic association study with multi-allelic CNVs.

Olfactomedin-4 autoantibodies give unusual c-ANCA staining patterns with reactivity to a subpopulation of neutrophils

Testing for the presence of ANCAs in circulation is part of the clinical examinations routinely performed upon suspected autoimmune disorders, mainly vasculitis. The autoantibodies are typically directed toward neutrophil MPO or PR3. These are major granule-localized proteins, and similar to all hitherto-described ANCA antigens, they are expressed by all neutrophils, and ANCA-containing sera thus give rise to uniform reactivity toward all neutrophils in a sample. In this paper, we describe sera from 2 unrelated patients with diffuse inflammatory symptoms that gave rise to peculiar c-ANCA patterns, only reacting with a subpopulation (roughly 30%) of human neutrophils. By immunoblotting, both sera reacted to the same antigen, which was expressed in intracellular granules. The antigen could be released to the extracellular milieu through secretion but also through the formation of NETs. Neutrophils have long been considered a homogenous cell population, but it is becoming increasingly clear that distinct subpopulations, defined by the presence or absence of certain proteins, exist. One such marker that defines a neutrophil subset is the granule protein OLFM4. The unusual, subset-restricted c-ANCA sera reacted only with OLFM4-positive neutrophils, and MS analysis revealed that the autoantigen was, in fact, OLFM4. These data describe for the first time a c-ANCA pattern reactive to only a subpopulation of neutrophils and identify the granule protein OLFM4 as a novel autoantigen.

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

BACKGROUND AND OBJECTIVES

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.

MATERIALS AND METHODS

For screening, the combination of GAT/GIFT was compared to Flow-WIFT testing 333 samples. Positive samples were further analysed with MAIGA and LabScreen® Multi.

RESULTS

Granulocyte aggregation test/GIFT detected 77 positive samples, Flow-WIFT found 108 granulocyte-reactive samples. Six Samples were only positive in GAT/GIFT, and 37 samples were only positive in Flow-WIFT (κ = 0.682). Antibody specification with MAIGA and the microbeads assay confirmed granulocyte-reactivity in 83 cases with 70 matching results (κ = 0.742). However, out of six detected human neutrophil antigen (HNA) reactivities only two specificities matched in both assays.

CONCLUSION

Flow-WIFT may be a valuable addition to GIFT for granulocyte-reactive antibody screening. MAIGA remains the most reliable laboratory method for antibody specification.