Human neutrophil antigens: Nature, clinical significance and detection

Analysis of maternal Fc gamma receptor IIIb isoantibodies using immunomagnetic negative selected neutrophils

BACKGROUND AND OBJECTIVES

The isolation of neutrophils and subsequent detection of anti-human neutrophil antigens (HNA) antibodies are crucial in clinical medicine for the diagnosis of autoimmune neutropenia, neonatal alloimmune neutropenia (NAIN) and transfusion-related acute lung injury (TRALI). This study reports two cases of maternal anti-Fc-gamma-receptor-IIIb (FcγRIIIb) isoimmunization without NAIN symptoms and compares the efficiency of immunomagnetic negative selection (IMNS) with traditional dextran/Ficoll for neutrophil isolation in HNA serological assays.

MATERIALS AND METHODS

Investigating two cases of maternal anti-FcγRIIIb isoimmunization, neutrophils from three donors were isolated from 8 mL of whole blood using IMNS and dextran/Ficoll. Serological assays included the granulocyte agglutination and immunofluorescence test, monoclonal antibody immobilization of granulocyte antigens and the LABScreen Multi (One Lambda). IMNS and dextran/Ficoll were compared in terms of cell yield, viability, time, cost and purity.

RESULTS

Maternal anti-FcγRIIIb isoantibodies with FCGR3B gene deletion were detected in both cases. Newborns and fathers exhibited specific gene combinations: FCGR3B*02/FCGR3B*02 (Case 1) and FCGR3B*02/FCGR3B*03 (Case 2). IMNS outperformed dextran/Ficoll, yielding four times more neutrophils (average neutrophil counts: 18.5 × 103/μL vs. 4.5 × 103/μL), efficiently removing non-neutrophil cells and reducing processing time (30-40 min vs. 70-90 min), although it incurred a higher cost (2.7 times).

CONCLUSION

Two cases of maternal anti-FcγRIIIb isoantibodies, unrelated to NAIN, were identified. Although neutropenia has not been described in these cases, we emphasize the importance of identifying asymptomatic cases with the potential for severe neutropenia. Additionally, IMNS is introduced as a rapid, high-yield, high-purity neutrophil isolation technique, beneficial for serological assays detecting anti-HNA antibodies.

Neutrophil antigen antibodies affect engraftment and secondary graft failure in hematopoietic progenitor cell transplantation

BACKGROUND

Research is limited on the role of antibodies against human neutrophil antigen (HNA) in hematopoietic progenitor cell (HPC) transplantation outcomes.

STUDY DESIGN AND METHODS

A retrospective review was conducted on medical records of patients at the NIH Clinical Center enrolled in six research protocols. This case-control study included 21 patients tested for HNA antibodies from January 2010 to March 2022 who underwent HPC transplantation. In addition, 42 patients following the same research protocols were randomly selected as a control group.

RESULTS

The cumulative incidence of time to neutrophil engraftment was significantly impacted by the patients' anti-HNA status (p = .042), with the patients with anti-HNA experiencing delayed engraftment. Secondary graft failure occurred in 4 out of 42 patients (9.52%; 95% confidence interval [CI]: 3.7-22.1) of the control group, while 5 out of 9 patients (55.5%; 95% CI: 26.7-81.1) with anti-HNA experienced secondary graft failure (p = .005). Furthermore, patients with anti-HNA had a lower proportion (p = .008 for full and p = .002 for partial chimerism) and cumulative incidence (p = .016 for full and p = .010 for partial chimerism) of achieving donor chimerism compared to the control group.

DISCUSSION

The study reveals a potential link between anti-HNA and HPC transplantation outcomes not previously reported. Patients with anti-HNA had a lower proportion and cumulative incidence of achieving donor chimerism. Additionally, anti-HNA status affected the time for neutrophil engraftment, with a slower rate of neutrophil engraftment and increased risk of secondary failure in patients with anti-HNA.

Immunologic aspects of preeclampsia

Preeclampsia is a syndrome with multiple etiologies. The diagnosis can be made without proteinuria in the presence of dysfunction of at least 1 organ associated with hypertension. The common pathophysiological pathway includes endothelial cell activation, intravascular inflammation, and syncytiotrophoblast stress. There is evidence to support, among others, immunologic causes of preeclampsia. Unlike defense immunology, reproductive immunology is not based on immunologic recognition systems of self/non-self and missing-self but on immunotolerance and maternal-fetal cellular interactions. The main mechanisms of immune escape from fetal to maternal immunity at the maternal-fetal interface are a reduction in the expression of major histocompatibility complex molecules by trophoblast cells, the presence of complement regulators, increased production of indoleamine 2,3-dioxygenase, activation of regulatory T cells, and an increase in immune checkpoints. These immune protections are more similar to the immune responses observed in tumor biology than in allograft biology. The role of immune and nonimmune decidual cells is critical for the regulation of trophoblast invasion and vascular remodeling of the uterine spiral arteries. Regulatory T cells have been found to play an important role in suppressing the effectiveness of other T cells and contributing to local immunotolerance. Decidual natural killer cells have a cytokine profile that is favored by the presence of HLA-G and HLA-E and contributes to vascular remodeling. Studies on the evolution of mammals show that HLA-E, HLA-G, and HLA-C1/C2, which are expressed by trophoblasts and their cognate receptors on decidual natural killer cells, are necessary for the development of a hemochorial placenta with vascular remodeling. The activation or inhibition of decidual natural killer cells depends on the different possible combinations between killer cell immunoglobulin-like receptors, expressed by uterine natural killer cells, and the HLA-C1/C2 antigens, expressed by trophoblasts. Polarization of decidual macrophages in phenotype 2 and decidualization of stromal cells are also essential for high-quality vascular remodeling. Knowledge of the various immunologic mechanisms required for adequate vascular remodeling and their dysfunction in case of preeclampsia opens new avenues of research to identify novel biological markers or therapeutic targets to predict or prevent the onset of preeclampsia.

Production of recombinant humanized monoclonal anti-human neutrophil antigen (HNA) antibodies with potential applicability as standard antibodies

BACKGROUND

Antibodies against human neutrophil antigen (HNA) are involved in the pathogenesis of neonatal alloimmune neutropenia, autoimmune neutropenia, and transfusion-related acute lung injury. The present methods for anti-HNA antibody identification strongly depend on the presence of standard antisera with known allo/isospecificities. Here, we aimed to produce recombinant humanized antibodies to HNA from available mouse monoclonal antibodies (MoAbs).

STUDY DESIGN AND METHODS

RNAs were extracted from available hybridoma cells producing mouse anti-HNA antibodies recognizing HNA-1a (TAG-1), -1b (TAG-2), -2 (TAG-4), and FcγRIIIb, and the cDNA was synthesized. Recombinant fragments consisting of the variable regions of the H and L chains of the mouse MoAb ligated to the constant region of human IgG were incorporated into an expression vector and transfected into CHO cells. Antibody specificity of the selected humanized monoclonal antibodies was confirmed, and tested by the participants of the ISBT Granulocyte Immunobiology Working Party (GIWP) workshop 2020.

RESULTS

GIFT results confirmed the specific reactivity of TAGH-1 to -4, except for a cross-reactivity of TAGH-2 with HNA-1a/a neutrophils, only in flow-cytometry. MAIGA results showed clear specificity of all humanized antibodies, but the selection of the appropriate capture monoclonal antibody was essential for the test. The results of the ISBT GIWP showed high concordance among the labs.

CONCLUSIONS

These are the first humanized monoclonal antibodies to HNA-1 and HNA-2 antigens produced and they will be important standard reagents for laboratories testing for neutrophil antibodies. We plan to have these humanized MoAbs available through WHO.

Kidney transplant outcomes in patients with antibodies to human neutrophil antigen 3a

BACKGROUND

Antibody mediated rejection (ABMR) of kidney transplants has been shown to occur in the absence of a known donor specific antibody to human leucocyte antigen (HLA). Antibodies to the human neutrophil antigen (HNA) system have been detected in kidney transplant recipients and linked to ABMR in the absence of an HLA donor specific antibody (DSA), but there remains limited literature regarding this.

METHODS

Case series analysis was carried out examining three cases of HNA-3a antibody positive flow cytometry cross match (FC-XM) from two transplant centres in Scotland.

RESULTS

All patients included were female and had been sensitised as a result of pregnancy. One live donor recipient with HNA-3a antibodies identified prior to transplant received ATG induction and has had a good outcome. The remaining two patients received deceased donor transplants. HNA-3a antibodies were indicated following a retrospective flow cytometry crossmatch. Both patients received Basiliximab induction and both have experienced ABMR requiring supplementary immunosuppression.

CONCLUSIONS

The predicted rate of HNA-3a antibodies amongst patients awaiting kidney transplant in the UK is <1%. However, with increasing evidence to support a role for HNA-3a antibodies in the development of ABMR there may be value in screening at risk groups to allow for augmented immunosuppression to be considered at the time of kidney transplant.

World human neutrophil antigens investigation survey

BACKGROUND AND OBJECTIVES

Human neutrophil antigens (HNAs) are categorized into five systems: HNA-1 to HNA-5. Given the importance of neutrophils in immunity, we sought to create awareness of the role of HNA diagnostic services in managing immune neutropenia and transfusion-related acute lung injury. To provide health communities all around the world with access to these services, we conducted a survey to create a directory of these HNA diagnostic services.

MATERIALS AND METHODS

An Excel table-based survey was created to capture information on the laboratory's location and was emailed to 55 individuals with known or possible HNA investigation activity. The collected data were then summarized and analysed.

RESULTS

Of contacted laboratories, the surveys were returned from 23 (38.2%) laboratories; 17 have already established HNA diagnostic (of them 12 were regular participants of the International Granulocyte Immunobiology Workshop [ISBT-IGIW]), 4 laboratories were in the process of establishing their HNA investigation and the remaining 2 responder laboratories, did not conduct HNA investigations. In established laboratories, investigation for autoimmune neutropenia (infancies and adults) was the most frequently requested, and antibodies against HNA-1a and HNA-1b were the most commonly detected.

CONCLUSION

The directory of survey respondents provides a resource for health professionals wanting to access HNA diagnostic services. The present study offers a comprehensive picture of HNA diagnostics (typing and serology), identifying weak points and areas for improvement for the first time. Identifying more laboratories involved in HNA diagnostics with limited access to international societies in the field will globally improve HNA diagnostics.

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.

An adult case of refractory autoimmune neutropenia after liver transplantation

Autoimmune neutropenia (AIN) is an exceptionally rare condition that occurs after liver transplantation. Here, we report an adult case of refractory AIN 3.5 years after liver transplantation. A 59-year-old man who underwent brain-dead donor liver transplantation in August 2018 developed rapid neutropenia (0.07 × 10⁹/L) in December 2021. The patient was diagnosed with AIN based on positivity for anti-human neutrophil antigen-1a antibody. There was no response to granulocyte colony-stimulating factor (G-CSF), prednisolone, or rituximab, and intravenous immunoglobulin (IVIg) therapy induced only a temporary recovery in neutrophil count. The patient continued to have a low neutrophil count for several months. However, the response to IVIg and G-CSF improved after the post-transplant immunosuppressant was changed from tacrolimus to cyclosporine. Post-transplant AIN has many unknown aspects. Tacrolimus-induced immunomodulation and graft-associated alloimmunity may be involved in its pathogenesis. Further studies are needed to elucidate the underlying mechanisms and explore new treatment options.

Genetic epidemiology of human neutrophil antigen variants suggests significant global variability

Human neutrophil antigens possess significant clinical implications especially in the fields of transfusion and transplantation medicine. Efforts to estimate the prevalence of genetic variations underpinning the antigenic expression are emerging. However, there lacks a precise capture of the global frequency profiles. Our article emphasizes the potential utility of maintaining an organized online repository of evidence on neutrophil antigen-associated genetic variants from published literature and reports. This, in our opinion, is an emerging area and would significantly benefit from the awareness and understanding of population-level diversities.

The Diagnostic and Predictive Significance of Immune-Related Genes and Immune Characteristics in the Occurrence and Progression of IgA Nephropathy

Objective

To investigate the potential diagnostic and predictive significance of immune-related genes in IgA nephropathy (IgAN) and discover the abnormal glomerular inflammation in IgAN.

Methods

GSE116626 was used as a training set to identify different immune-related genes (DIRGs) and establish machine learning models for the diagnosis of IgAN; then, a nomogram model was generated based on GSE116626, and GSE115857 was used as a test set to evaluate its clinical value. Short Time-Series Expression Miner (STEM) analysis was also performed to explore the changing trend of DIRGs with the progression of IgAN lesions. GSE141344 was used with DIRGs to establish the ceRNA network associated with IgAN progression. Finally, ssGSEA analysis was performed on the GSE141295 dataset to discover the abnormal inflammation in IgAN.

Results

Machine learning (ML) performed excellently in diagnosing IgAN using six DIRGs. A nomogram model was constructed to predict IgAN based on the six DIRGs. Three trends related to IgAN lesions were identified using STEM analysis. A ceRNA network associated with IgAN progression which contained 8 miRNAs, 14 lncRNAs, and 3 mRNAs was established. A higher macrophage ratio and lower CD4+ T cell ratio in IgAN compared to controls were observed, and the correlation between macrophages and monocytes in the glomeruli of IgAN patients was inverse compared to controls.

Conclusion

This study reveals the diagnostic and predictive significance of DIRGs in IgAN and finds that the imbalance between macrophages and CD4+ immune cells may be an important pathomechanism of IgAN. These results provide potential directions for the treatment and prevention of IgAN.

Human Neutrophil Antigen Genotype and Allele Frequencies in Iranian Blood Donors

Objective

Human neutrophil antigens (HNAs) can be targeted by HNA-allo antibodies and cause a variety of clinical conditions such as transfusion-related acute lung injury (TRALI) and neonatal alloimmune neutropenia (NAIN). The current study is aimed at identifying the genotype and allele frequencies of HNAs in Iranian blood donors.

Methods

A total of 150 blood samples were obtained from healthy blood donors. HNA-1, HNA-3, HNA-4, and HNA-5 were genotyped, using the polymerase chain reaction sequence-specific primer (PCR-SSP) technique. The expression of the HNA-2 antigen on the neutrophil surface was evaluated by flow cytometry.

Results

The allele frequencies of FCGR3B∗1 (encoding HNA-1a), FCGR3B∗2 (encoding HNA-1b), and FCGR3B∗3 (encoding HNA-1c) were 0.34, 0.63, and 0.03, respectively. For HNA-3, the allele frequencies for SLC44A2∗1 (encoding HNA-3a) and SLC44A2∗2 (encoding HNA-3b) were 0.63 and 0.37, respectively. The frequencies of ITGAM∗1 (encoding HNA-4a) and ITGAM∗2 (encoding HNA-4b) alleles were 0.85 and 0.15, respectively. Furthermore, the frequencies of ITGAL∗1 (encoding HNA-5a) and ITGAL∗2 (encoding HNA-5b) alleles were 0.72 and 0.28, respectively. In the studied population, HNA-2 antigen was present on the neutrophil surface in 97.3% of the individuals, while no detectable HNA-2 expression was observed in 2.7% of the individuals. However, no significant difference in HNA-2 expression between different age groups was found.

Conclusion

The present study provides the first report of the HNA allele and genotype frequencies among the Iranian population. All HNAs (HNA-1 to HNA-5) were typed using the PCR-SSP and flow cytometer. In the current cohort study, the determined HNA allele frequencies were similar to the previous reports from British, German, and Danish populations. Considering the presence of different Iranian ethnic groups, further studies with a larger sample size are needed to draw a total picture for HNA allele frequencies.

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.