Management and outcome of 35 cases with foetal/neonatal alloimmune neutropenia

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.

Combined Neonatal Alloimmune Neutropenia and Thrombocytopenia in Dizygotic Twins Conceived After Oocyte Donation

Neonatal alloimmune thrombocytopenia (NAIT) and neonatal alloimmune neutropenia (NAIN) may have severe consequences in the neonatal period. We report two dizygotic twins conceived after donated oocytes, suffering NAIT and NAIN in the context of alloantibodies to human platelet antigens (anti-HPA-5b) and human leukocyte antigens (anti-HLA class I). Genotyping demonstrated paternal homozygosity for HPA-5a, while the neonates were heterozygous for HPA-5b.

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.

Neonatal Immune Neutropenia due to Isoantibodies against the Granulocyte Receptor FcγRIIIb

Introduction

Neonatal neutropenia is often secondary to sepsis, low birth weight, pregnancy-induced maternal hypertension, and other conditions.

Case Report

We report a case of asymptomatic isoimmune neutropenia in a pair of preterm twins. Genotyping confirmed that the mother was negative for HNA-1a, 1b, and 1c, consistent with an FcγRIIIb deficiency. The father was 1(a+b+c-) and the neonates were 1(a-b+c-). A strongly positive result was observed in the granulocyte immunofluorescence test against paternal neutrophils (IgG antibodies). IgG anti-CD16b isoantibodies were detected in the mother's breast milk. Neutropenia resolved after 28 days without requiring any specific treatments.

Discussion

Even though neonatal alloimmune neutropenia (NAN) is usually benign and self-limiting, some patients pre-sent with delayed separation of the umbilical cord, mild skin infections, omphalitis, or severe infections like pneumonia, sepsis, and meningitis. Thus, it is important to rule out NAN in case of neonatal neutropenia.

Targeted exome sequencing designed for blood group, platelet, and neutrophil antigen investigations: Proof-of-principle study for a customized single-test system

BACKGROUND

Immunohematology reference laboratories provide red blood cell (RBC), platelet (PLT), and neutrophil typing to resolve complex cases, using serology and commercial DNA tests that define clinically important antigens. Broad-range exome sequencing panels that include blood group targets provide accurate blood group antigen predictions beyond those defined by serology and commercial typing systems and identify rare and novel variants. The aim of this study was to design and assess a panel for targeted exome sequencing of RBC, PLT, and neutrophil antigen-associated genes to provide a comprehensive profile in a single test, excluding unrelated gene targets.

STUDY DESIGN AND METHODS

An overlapping probe panel was designed for the coding regions of 64 genes and loci involved in gene expression. Sequencing was performed on 34 RBC and 17 PLT/neutrophil reference samples. Variant call outputs were analyzed using software to predict star allele diplotypes. Results were compared with serology and previous sequence genotyping data.

RESULTS

Average coverage exceeded 250×, with more than 94% of targets at Q30 quality or greater. Increased coverage revealed a variant in the Scianna system that was previously undetected. The software correctly predicted allele diplotypes for 99.5% of RBC blood groups tested and 100% of PLT and HNA antigens excepting HNA-2. Optimal throughput was 12 to 14 samples per run.

CONCLUSION

This single-test system demonstrates high coverage and quality, allowing for the detection of previously overlooked variants and increased sample throughput. This system has the potential to integrate genomic testing across laboratories within hematologic reference settings.

Neonatal Immune Incompatibilities between Newborn and Mother

Background: Incompatibilities between the mother and unborn baby can cause complications that must be identified early to initiate the appropriate treatment. For example, neonatal alloimmune thrombocytopenia (NAIT), neonatal alloimmune neutropenia (NAIN), and morbus hemolyticus neonatorum affect children worldwide. Aim: This literature review aims to depict the similarities and differences between these three disorders from a clinical and mechanistic point of view. Material and Methods: The current literature review entailed conducting a systematic search to locate articles on the three conditions. Different electronic databases, including PsycINFO, PubMed, Web of Science, and CINAHL, were searched using the search terms "neonatal alloimmune thrombocytopenia", "neonatal alloimmune neutropenia", "morbus hemolyticus neonatorum", "NAIT", "FNAIT", "fetal", "NAIN", and "hemolytic disease of the newborn". Results: This review shows that these three diseases are caused by incompatibilities between the maternal and fetal immune systems. Furthermore, these conditions can lead to severe complications that hinder fetal development and cause death if not well managed. Discussion: The current literature review shows that NAIT, NAIN, and morbus hemolyticus neonatorum are rare conditions that occur when the mother produces antibodies against the fetal immune system. Thus, there is a need for the early detection of these conditions to initiate appropriate treatment before the child experiences adverse effects. Conclusion: The development of NAIT, NAIN, and morbus hemolyticus neonatorum is linked to the production of antibodies against the fetal immune system and fetal antigens. Further studies are required to determine potential interventions to reduce the risk of developing these three conditions.

Neonatal alloimmune neutropaenia: Experience from an Australian paediatric health service

AIM

To describe the presenting features and investigation findings in infants diagnosed with neonatal alloimmune neutropaenia (NAIN) within an Australian paediatric health network. The secondary aim was to describe the management and resolution of neutropaenia in infants with NAIN.

METHODS

A retrospective cohort study was conducted at Monash Children's Hospital, Melbourne, Australia. Infants referred to the Victorian Transplantation and Immunogenetics Service for evaluation of NAIN were identified and medical records were reviewed. Descriptive statistical analysis of infants' clinical outcomes, investigation findings and management was performed.

RESULTS

Nine infants were diagnosed with NAIN between December 2004 and June 2017. Overall incidence of NAIN was around 1 per 10 000 births. Median gestational age was 38 (range 35-40) weeks and birthweight was 2920 (2300-4445) g. Median age at NAIN work-up was 7 (2-33) days. Prior to investigation for NAIN, median absolute neutrophil count was 0.2 (0.01-0.6) × 10⁹ cells/L. The post-natal ward was the source of presentation in most infants (78%). All except one infant were admitted to a neonatal unit and commenced on intravenous antibiotics (89%). Six infants were asymptomatic but received antibiotics for risk of infection (75%). Granulocyte-colony stimulating factor was administered to 44% of infants due to neutropaenia with presumed or confirmed infection. NAIN resolved at median age of 32 (6-200) days.

CONCLUSIONS

Infants with NAIN frequently presented with severe, unexpected neutropaenia without major infection. Intravenous antibiotic therapy and granulocyte-colony stimulating factor use was common in this cohort.

Primary structure of human neutrophil antigens 1a and 1b

BACKGROUND

Neutrophil specific Fcγ receptor IIIb (CD16b) is a low-affinity IgG receptor. Its polymorphic variants are associated with human neutrophil antigens (HNA). HNA-1a and HNA-1b differ in four amino acids. Immunization can lead to the production of alloantibodies. The exact contribution of four amino acid exchanges for the formation of HNA-1a, -1b epitopes is currently unknown.

STUDY DESIGN AND METHODS

Permutation of each polymorphic amino acid from wild-type CD16b cDNA constructs was performed and expressed on HEK293 cells. All 16 receptor variants were produced and tested against 19 well-characterized HNA antisera in an antigen capture assay.

RESULTS

Analyzing the reaction pattern revealed that anti-HNA-1a antibodies can bind whenever asparagine (N) is present in position 65, regardless of the three other positions (CD16b *N**). Anti-HNA-1b antibodies can bind when serine (S) is present in position 36 (CD16b S***), when N is present in position 82 (CD16b **N*), or both (CD16b S*N*). CD16b variants with N65 and S36 and/or N82 (such as CD16b SNN*) bind both, anti-HNA-1a and anti-HNA-1b alloantibodies. If these specific amino acids are missing (as in CD16b RSD*), no antibodies will bind.

CONCLUSION

Whereas the primary structure of HNA-1a and HNA-1b usually differs in four amino acids, epitope composition is not "antithetical". N65 alone determines the presence of HNA-1a, and S36 and/or N82 determine the presence of HNA-1b. Amino acid 106 does not participate in epitope formation. Our findings are of specific relevance when a HNA-1 phenotype is predicted from a genotype.

Neonatal Alloimmune Neutropenia

Neonatal alloimmune neutropenia (NAIN, NAIN or NIN) is a neutrophil blood group antagonism, analogous to hemolytic disease of the fetus and newborn (HDFN) and fetal/neonatal alloimmune thrombocytopenia (FNAIT). A limited number of prospective screening studies showed that granulocyte-specific antibodies were detectable in 0.35-1.1% of random postnatal maternal samples and that the incidence of NAIN was below 0.1%. Symptoms vary from none to mild skin infections, omphalitis or more severe infections like pneumonia, sepsis, and meningitis. Treatment of neonatal infection with antibiotics and granulocyte-colony stimulating factor is advised.

New monogenic disorders identify more pathways to neutropenia: from the clinic to next-generation sequencing

Neutrophils are the most common type of leukocyte in human circulating blood and constitute one of the chief mediators for innate immunity. Defined as a reduction from a normal distribution of values, neutropenia results from a number of congenital and acquired conditions. Neutropenia may be insignificant, temporary, or associated with a chronic condition with or without a vulnerability to life-threatening infections. As an inherited bone marrow failure syndrome, neutropenia may be associated with transformation to myeloid malignancy. Recognition of an inherited bone marrow failure syndrome may be delayed into adulthood. The list of monogenic neutropenia disorders is growing, heterogeneous, and bewildering. Furthermore, greater knowledge of immune-mediated and drug-related causes makes the diagnosis and management of neutropenia challenging. Recognition of syndromic presentations and especially the introduction of next-generation sequencing are improving the accuracy and expediency of diagnosis as well as their clinical management. Furthermore, identification of monogenic neutropenia disorders is shedding light on the molecular mechanisms of granulopoiesis and myeloid malignancies.

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.

How I manage children with neutropenia

Neutropenia, usually defined as a blood neutrophil count <1·5 × 10⁹ /l, is a common medical problem for children and adults. There are many causes for neutropenia, and at each stage in life the clinical pattern of causes and consequences differs significantly. I recommend utilizing the age of the child and clinical observations for the preliminary diagnosis and primary management. In premature infants, neutropenia is quite common and contributes to the risk of sepsis with necrotizing enterocolitis. At birth and for the first few months of life, neutropenia is often attributable to isoimmune or alloimmune mechanisms and predisposes to the risk of severe bacterial infections. Thereafter when a child is discovered to have neutropenia, often associated with relatively minor symptoms, it is usually attributed to autoimmune disorder or viral infection. The congenital neutropenia syndromes are usually recognized when there are recurrent infections, the neutropenia is severe and there are congenital anomalies suggesting a genetic disorder. This review focuses on the key clinical finding and laboratory tests for diagnosis with commentaries on treatment, particularly the use of granulocyte colony-stimulating factor to treat childhood neutropenia.

Prevalence of granulocyte antibodies in never allo-exposed female and male donors

BACKGROUND

Foetal/neonatal allo-immune neutropenia (FNAIN) is a serious condition usually resulting from immunisation of the mother to paternally inherited neutrophil antigens of the foetus. Understanding the biology of female immunisation against neutrophils could help predict or prevent FNAIN.

OBJECTIVES

To quantify differences in the prevalence of specific and pan-reactive granulocyte antibodies, between allo-exposed and never allo-exposed male and female blood donors.

METHODS/MATERIALS

We previously reported the prevalence of granulocyte antibodies in healthy male and female blood donors. Here, we compare specific vs. pan-reactive antibodies.

RESULTS

The prevalence of specific granulocyte antibodies was similar in male [1.0%; 95% confidence interval (CI): 0.70-1.4] and female nulliparous blood donors (0.87%; CI: 0.029-1.7) and doubled after pregnancies (1.8%; CI: 0.52-3.0). In contrast, pan-reactive antibodies were almost three times less common in male (0.81%; CI: 0.50-1.1) compared to female nulliparous blood donors (2.3%; CI: 0.91-3.8) and were half as high after pregnancies (1.1%; CI: 0.58-1.7).

CONCLUSION

We found unexpected differences between male and female blood donors. Determining the clinical relevance of the pan-reactive antibodies requires further research, but none of the tested blood donors experienced any symptoms of neutropenia.

How we diagnose and treat neutropenia in adults

Neutropenias (NPs), being acute and often transient, or chronic, range from life-threatening conditions with very low absolute neutrophil blood counts (ANC) to disorders characterized by only mild NP and of no obvious significance for health. Many are caused by genetic variations/mutations, e.g. the benign familial NP and the chronic severe NPs (e.g. Kostmann disease). Some of the latter are associated with various bodily malformations. Many of the mild-to-moderate NPs are signs of underlying disorders that need specialized treatments (e.g. HIV, hepatitis, autoimmune disorders, the large granular lymphocyte syndrome). We provide here means for the evaluation of a previously unknown NP, suggest a triage and treatments.