Neonatal alloimmune neutropenia attributed to maternal immunoglobulin G antibodies against the neutrophil alloantigen HNA-1c (SH): a report of five cases

A novel immunocomplex capture fluorescence assay (ICFA) using fluorescent beads and transfected cells for specific identification of human neutrophil antigen (HNA)-1a and -1b antibodies

BACKGROUND

To identify specific human neutrophil antigen (HNA) antibodies, assays using neutrophils such as monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA) are recommended. However, these assays are limited by labor-intensive neutrophil preparation and varying antigen expression levels.

METHODS

We evaluated a newly developed immunocomplex capture fluorescence assay (ICFA) for identifying HNA-1 antibodies and compared it to MAIGA and LABScreen Multi (LABM), which utilizes recombinant HNA-coated Luminex beads. For ICFA, HNA-1a or HNA-1b transfected cells replaced neutrophils. Cells incubated with serum were lysed, and immune complexes were captured using five CD16 monoclonal antibody-conjugated Luminex beads. Nine antisera with known specificity and 26 samples suspected of containing HNA antibodies were analyzed by ICFA and MAIGA using neutrophils or transfected cells (ICFA-N or ICFA-T, and MAIGA-N or MAIGA-T, respectively).

RESULTS

ICFA-T and MAIGA-N accurately determined the specificity of all antibodies in the nine antiserum samples. The ICFA-T detection limit was 2048-fold for anti-HNA-1a and 256-fold for anti-HNA-1b; the limits of MAIGA-T, MAIGA-N, and LABM were 32-, 4 ~ 64-, and 128-fold for anti-HNA-1a and 64-, 16 ~ 64-, and 32-fold for anti-HNA-1b, respectively. Twelve and 7 of the remaining 26 samples tested negative and positive, respectively, in both ICFA-T and MAIGA-N. Antibody specificity against HNA-1a or HNA-1b determined using ICFA-T agreed with that determined using MAIGA-N and LABM. Another seven samples tested positive in ICFA-T but negative in MAIGA-N.

CONCLUSION

The novel ICFA is highly sensitive and exhibits specificity similar to MAIGA and LABM for detecting HNA-1 antibodies.

Discerning clinicopathological features of congenital neutropenia syndromes: an approach to diagnostically challenging differential diagnoses

The congenital neutropenia syndromes are rare haematological conditions defined by impaired myeloid precursor differentiation or function. Patients are prone to severe infections with high mortality rates in early life. While some patients benefit from granulocyte colony-stimulating factor treatment, they may still face an increased risk of bone marrow failure, myelodysplastic syndrome and acute leukaemia. Accurate diagnosis is crucial for improved outcomes; however, diagnosis depends on familiarity with a heterogeneous group of rare disorders that remain incompletely characterised. The clinical and pathological overlap between reactive conditions, primary and congenital neutropenias, bone marrow failure, and myelodysplastic syndromes further clouds diagnostic clarity.We review the diagnostically useful clinicopathological and morphological features of reactive causes of neutropenia and the most common primary neutropenia disorders: constitutional/benign ethnic neutropenia, chronic idiopathic neutropenia, cyclic neutropenia, severe congenital neutropenia (due to mutations in ELANE, GFI1, HAX1, G6PC3, VPS45, JAGN1, CSF3R, SRP54, CLPB and WAS), GATA2 deficiency, Warts, hypogammaglobulinaemia, infections and myelokathexis syndrome, Shwachman-Diamond Syndrome, the lysosomal storage disorders with neutropenia: Chediak-Higashi, Hermansky-Pudlak, and Griscelli syndromes, Cohen, and Barth syndromes. We also detail characteristic cytogenetic and molecular factors at diagnosis and in progression to myelodysplastic syndrome/leukaemia.

Anti-human neutrophil antigen-1d specificity is frequently observed in anti-human neutrophil antigen-1b alloantisera

BACKGROUND

Four amino acids are involved in epitope formation of human neutrophil antigens (HNA)-1 alleles, located at positions 36, 65, 78, and 82. HNA-1a and HNA-1b alloantibody epitopes were recently characterized. The HNA-1b allele also carries the HNA-1d epitope p.78A&p.82N. The current study aimed to identify compound antibody specificities in HNA-1b alloantisera, especially the presence of anti-HNA-1d.

STUDY DESIGN AND METHODS

For investigation of binding epitopes for HNA-1b alloantibodies, cells stably expressing different HNA-1 alleles were generated and tested against previously well-characterized HNA-1b antisera (n = 11) in an antigen capture assay. Sera with p.82N specificity or p.36S and p.82N specificity were additionally analyzed using adsorption and elution methods.

RESULTS

Three amino acids, p.36S, p.78A, and p.82N, are involved in epitope formation of HNA-1b. The following specificities were identified in 11 HNA-1b alloantisera: p.36S (6/11), p.82N (9/11), and p.78A&p.82N (8/11), of which p.36S was identified as a sole entity in 2/11, whereas 9/11 antisera contained a polyspecific mixture of anti-p.36S, p.82N (1/11), and anti-p.78A&p.82N in combination with anti p.82N (5/11) or compound specificities of anti-p.36S, p.82N, and p.78A&p82N (3/11). In seven of eight antisera with p.82N specificity, anti-p.78A&p.82N was detected.

DISCUSSION

Analysis of HNA-1b antisera indicates compound specificities for HNA-1b alloantibodies with a high variation between HNA-1b immunized individuals. Amino acids p.36S, p.82N, and p.78A&p.82N are necessary for HNA-1b epitope formation. The HNA-1d epitope is recognized by 73% (8/11) of HNA-1b immunized individuals.

Chronic neutropenia: how best to assess severity and approach management?

INTRODUCTION

Neutropenia is a relatively common finding in medical practice and the medical approach requires a gradual and pertinent diagnostic procedure as well as adapted management.

AREAS COVERED

The area of chronic neutropenia remains fragmented between diverse diseases or situations. Here physicians involved in different aspects of chronic neutropenia gather both the data from medical literature till the end of May 2021 and their experience to offer a global approach for the diagnosis of chronic neutropenia as well as their medical care.

EXPERT OPINION

In most cases, the neutropenia is transient, frequently related to a viral infection, and not harmful. However, neutropenia can be chronic (i.e. >3 months) and related to a number of etiologies, some clinically benign, such as so-called 'ethnic' neutropenia. Autoimmune neutropenia is the common form in young children, whereas idiopathic/immune neutropenia is a frequent etiology in young females. Inherited neutropenia (or congenital neutropenia) is exceptional, with approximately 30 new cases per 10⁶ births and 30 known subtypes. Such patients have a high risk of invasive bacterial infections, and oral infections. Supportive therapy, which is primarily based on daily administration of an antibiotic prophylaxis and/or treatment with granulocyte-colony stimulating factor (G-CSF), contributes to avoiding recurrent infections.

Serologic and molecular studies to identify neonatal alloimmune neutropenia in a cohort of 10,000 neonates

Neonatal alloimmune neutropenia (NAIN) is caused by maternal alloimmunisation to fetal human neutrophil antigens (HNAs). This study investigated maternal HNA/HLA alloantibodies involved with NAIN and identified the frequency of NAIN in Brazilian neonates. Neonatal neutropenia (neutrophil count < 1.5 × 10⁹ /L) was investigated in samples from 10,000 unselected neonates, resulting in 88 neutropenic newborns (NBs) and their 83 mothers. Genotyping was performed by PCR-SSP (HNA-1/-4) and PCR-RFLP (HNA-3/-5). Serologic studies were performed by GAT (granulocyte agglutination test), Flow-WIFT (white blood cells immunofluorescence test) and LABScreen-Multi-HNA-Kit (OneLambda®) (LSM). Neonatal neutropenia was identified in 88/10,000 (0·9%) NBs. Genotyping revealed 60·2% maternal-fetal HNA incompatibilities (31·8% for HNA-1; 14·8% for HNA-3; 15·9% for HNA-4; 21·6% for HNA-5). Serologic studies revealed 37·3% of mothers with positive results with at least one technique. The detected anti-HNA specificities were confirmed in eight positive cases related to HNA-1/-3 systems. In cases with maternal-fetal HNA-4/-5 incompatibility, no specific neutrophil alloantibodies were found but anti-HLA I/II were present. Anti-HNA-2 was not identified. This is a large Brazilian study which involved the investigation of antibodies against all five HNA systems in neutropenia cases and showed a frequency of NAIN in 8/10,000 neonates. Among the HNA antibodies identified, we highlight the anti-HNA-1d and anti-HNA-3b, antibodies unusual in alloimmunised women, and rarely related to NAIN cases.

Genotyping of human neutrophil antigens 1, 3, 4 and 5 using a novel multiplex polymerase chain reaction

OBJECTIVES

Our study aimed to establish a novel multiplex polymerase chain reaction (PCR) for rapid simultaneous detection of all relevant human neutrophil antigen (HNA)-1, -3, -4 and -5 alleles.

BACKGROUND

Granulocyte-reactive antibodies are involved in several diseases, such as neonatal alloimmune neutropenia, autoimmune neutropenia and transfusion-related acute lung injury. A panel of well-defined test granulocytes is required for diagnostic antibody detection and prospective blood donor screening. Several genotyping methods for the detection of HNA alleles have been described, but most approaches require separate amplification of each HNA allele or at least a separate amplification of the HNA-1 alleles.

METHODS

The new method is based on simultaneous detection in one reaction tube, where each HNA-1 allele is amplified by two allele-specific primers, one primer of which is labelled with a fluorescent dye (HEX, FAM). Allelic polymorphisms for HNA-3, -4 and -5 were amplified with one common unlabelled primer and two fluorescence-labelled (HEX, FAM) allele-specific primers. DNA fragments of HNA alleles are analysed on a Genetic Analyser 3130xl by amplicon size and fluorescent dye. A total of 110 blood donors with known genotypes were studied.

RESULTS

In the 110 DNA samples studied, all HNA-1, -3, -4 and -5 alleles could be detected precisely. All results matched perfectly with those from reference typing by PCR-sequence-specific primer. Amplification performed well even at low DNA concentrations (10 ng μL^-1 ).

CONCLUSION

Our method enables fast and easy genotyping of all relevant HNA-alleles in one PCR reaction. Results are easy to analyse due to different amplicon sizes and fluorescent dyes. Furthermore, the method is suitable for high sample throughput.

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.

How to differentiate congenital from noncongenital chronic neutropenia at the first medical examination? Proposal of score: A pilot study from the French Severe Chronic Neutropenia registry

OBJECTIVES

We developed a diagnostic score to differentiate congenital from noncongenital neutropenia at the time of diagnosis using reliable data collected at the first visit of a patients with neutropenia.

STUDY DESIGN

In a pilot retrospective study, we included 120 patients diagnosed with chronic neutropenia; 61 had congenital and 59 had noncongenital neutropenia. We reviewed patient medical charts and collected the initial complete blood count (CBC) and other reliable data. We used logistic regression to determine the probability that the neutropenia was congenital.

RESULTS

On the initial CBC, the degree of neutropenia had no predictive value; only monocytosis >1.5 × 10⁹ /l, hemoglobin <90 g/l, or mild thrombocytopenia <150 × 10⁹ /l suggested congenital neutropenia. The most predictive factors for congenital neutropenia were a medical history (consanguinity and patient history of neutropenia), severe infections, and oral stomatitis or gingivitis at the time of diagnosis. The age at diagnosis had limited predictive value.

CONCLUSION

A diagnosis of congenital neutropenia may be reliably suspected based only on information from the CBC, some basic information from patient and parent interviews, and a clinical examination. A pilot score with six factors that could be readily, reliably collected, should facilitate the diagnosis of congenital neutropenia.

Congenital neutropenia in the era of genomics: classification, diagnosis, and natural history

This review focuses on the classification, diagnosis and natural history of congenital neutropenia (CN). CN encompasses a number of genetic disorders with chronic neutropenia and, for some, affecting other organ systems, such as the pancreas, central nervous system, heart, bone and skin. To date, 24 distinct genes have been associated with CN. The number of genes involved makes gene screening difficult. This can be solved by next-generation sequencing (NGS) of targeted gene panels. One of the major complications of CN is spontaneous leukaemia, which is preceded by clonal somatic evolution, and can be screened by a targeted NGS panel focused on somatic events.

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.

Immune neutropenias of infancy and childhood

BACKGROUND

Anti-neutrophil antibodies are a well-recognized cause of neutropenia, producing a potential increase in risk of infection: in the majority of patients antibodies react against antigens located on the IgG Fc receptor type 3b (FcRIIIb), but other target antigens have been identified.

DATA SOURCES

In this review the most important papers of auto and alloimmune neutropenias of infancy and childhood were analyzed. PubMed, Google Scholar and Thompson ISI Web of Knowledge were searched for identifying relevant papers.

RESULTS

Primary autoimmune neutropenia of infancy is mostly a benign condition with self-limited course, whereas isolated alloimmune neonatal neutropenia or secondary autoimmune neutropenia may be occasionally complicated by severe infections.

CONCLUSION

Granulocyte colony stimulating factor is an effective therapy for patients affected by all types of autoimmune and alloimmune neutropenia, even though most of them do not need any therapy.

Diagnosis and management of primary autoimmune neutropenia in children: insights for clinicians

Autoimmune neutropenia of infancy (AIN), also called primary autoimmune neutropenia, is a disease in which antibodies recognize membrane antigens of neutrophils, mostly located on immunoglobulin G (IgG) Fc receptor type 3b (FcγIIIb receptor), causing their peripheral destruction. It is the most frequent type of neutropenia in children under 3-4 years of age and in most cases shows a benign, self-limited course. The diagnosis is based on evidence of indirect antineutrophil antibodies, whose detection frequently remains difficult. In this review we have analyzed the literature regarding AIN and present our personal experience in diagnosis and management.

Diagnostic assays for chronic granulomatous disease and other neutrophil disorders

Inasmuch as neutrophils are the primary cellular defense against bacterial and fungal infections, disorders that affect these white cells typically predispose individuals to severe and recurrent infections. Therefore, diagnosis of such disorders is an important first step in directing long-term treatment/care for the patient. Herein, we describe methods to identify chronic granulomatous disease, leukocyte adhesion deficiency, and neutropenia. The assays are relatively simple to perform and cost effective and can be performed with equipment available in most laboratories.

Chronic chorioamnionitis is the most common placental lesion in late preterm birth

OBJECTIVES

The pathogenesis of late preterm birth remains elusive for the mechanisms of disease responsible. Placental examination can often provide important clues for the pathogenesis of pregnancy complications. This study was conducted to determine placental pathologic findings according to the gestational age and the clinical circumstances of preterm birth.

STUDY DESIGN

Placental pathologic findings and obstetrical and neonatal outcomes were reviewed in a consecutive preterm birth cohort from a single tertiary center (N = 1206). Placentas of term births (N = 300) were used as normal controls.

RESULTS

Acute chorioamnionitis (22.7% vs. 16.7%), maternal vascular underperfusion (6.4% vs. 0.5%), and chronic chorioamnionitis (20.8% vs. 10.5%) were significantly more frequent in preterm births than in term births (P < 0.05, for each). Among preterm births, chronic chorioamnionitis was the most common pathology of late preterm birth (gestational age <37 and ≥34 weeks), while acute chorioamnionitis was the most common lesion of extremely preterm birth (gestational age <28 weeks). While the frequency of acute chorioamnionitis decreased with advancing gestation, that of chronic chorioamnionitis increased (P < 0.001, for each). The upward trend of the frequency of chronic chorioamnionitis was related to advancing gestation in both spontaneous and indicated preterm births (P < 0.001, for each).

CONCLUSIONS

Chronic chorioamnionitis is a common pathology of late preterm birth. It is suggested that chronic chorioamnionitis, a feature of maternal anti-fetal rejection, is an important etiology of preterm birth, especially of late preterm birth.

Neonatal alloimmune neutropenia: still a diagnostic and therapeutical challenge

OBJECTIVE

To describe a case of neonatal alloimmune neutropenia (NAN), a very rare disease of the newborn and the first ever reported in our neonatal intensive care unit, with emphasis in its management and outcome.

DESCRIPTION

We report a case of NAN due to anti-human neutrophil antigen-1b alloimmunization in a 29-week preterm admitted to our neonatal intensive care unit. In this case, the neutropenia was severe and persisted for almost 2 months. There was a good response to the administration of intravenous immunoglobulin.

COMMENTS

NAN is caused by maternal production of neutrophil-specific alloantibodies in response to antigens from paternal heritage present on the newborn neutrophiles. The course of the disease is usually mild and self-limiting. The optimal therapy is yet a debate, with some authors finding the use of intravenous immunoglobulin effective, prophylactic antibiotic therapy or recombinant human granulocyte colony-stimulating factor.

Rapid enzyme-linked immunosorbent assay for the detection of antibodies against human neutrophil antigens -1a, -1b, and -1c

BACKGROUND

Several methods exist for the detection of neutrophil antibodies; most of them, however, require fresh neutrophils. In this study, an enzyme-linked immunosorbent assay (ELISA) using recombinant HNA-1 antigens (rHNAs) was developed to detect HNA-1a, -1b, and -1c alloantibodies in serum samples.

STUDY DESIGN AND METHODS

Soluble rHNA-1a, -1b, and -1c were isolated from culture supernatant of transfected insect cells. Purified rHNA antigens were immobilized on microtiter wells using antibody against V5-Tag protein. Sera were added, and bound antibodies were detected by enzyme-labeled secondary antibodies. In parallel, monoclonal antibody-immobilized granulocyte antigen (MAIGA) was performed with two different monoclonal antibodies (MoAbs) against FcγRIIIb (3G8 and BW209).

RESULTS

Fifteen MAIGA-positive sera containing HNA-1a alloantibodies were tested in ELISA. Thirteen of 15 (86.7%) MAIGA-positive sera captured by MoAbs 3G8 and/or BW209 reacted specifically with rHNA-1a. Four (26.7%) HNA-1a sera showed additional reaction with rHNA-1c. When anti-HNA-1b alloantibodies were analyzed in ELISA, 13 of 15 (86.7%) showed specific positive reaction with rHNA-1b, and 12 of 15 (80.0%) cross-reacted with rHNA-1c. Two HNA-1c sera reacted specifically with rHNA-1c. Immunoprecipitation analysis of all ELISA-negative HNA-1a and -1b sera did not show any specific band indicating false-positive reaction of these sera in MAIGA assay.

CONCLUSIONS

These results suggested that rapid ELISA using recombinant neutrophil antigens may provide a valuable method for rapid screening of human alloantibodies against HNA-1a, -1b, and -1c in patients with neutropenia and in blood donors.

Maternal HLA panel-reactive antibodies in early gestation positively correlate with chronic chorioamnionitis: evidence in support of the chronic nature of maternal anti-fetal rejection

PROBLEM

Maternal tolerance of the fetus is essential for viviparity, yet anti-fetal rejection occurs in several pregnancy complications. Chronic chorioamnionitis is a feature of anti-fetal cellular rejection. There is a robust association between chronic chorioamnionitis and maternal seropositivity for anti-human leukocyte antigen (HLA) panel-reactive antibodies (PRA) at the time of delivery. This longitudinal study was performed to assess maternal HLA PRA status in early gestation and the temporal evolution of maternal HLA PRA in the context of chronic chorioamnionitis and, thereby, to determine whether HLA PRA during the course of pregnancy is useful for the detection of anti-fetal rejection.

METHOD OF STUDY

Maternal sera obtained before 16 weeks of gestation and at delivery were analyzed for HLA PRA in cases with (N = 100) and without (N = 150) chronic chorioamnionitis.

RESULTS

IgG (but not IgM) HLA class I and II PRA positivity at delivery was higher in cases with chronic chorioamnionitis than in those without chronic chorioamnionitis. IgG HLA class I PRA positivity before 16 weeks of gestation was higher in cases with chronic chorioamnionitis than in those without (30.3 versus 13.3%; P = 0.001). Positive conversion (negative HLA PRA before 16 weeks of gestation but positive at delivery) of IgG HLA class I and II PRA was significantly associated with chronic chorioamnionitis. Fetal HLA class I antigen-specific antibodies were confirmed in 12 of 16 mothers tested who were sensitized to HLA class I antigens before 16 weeks of gestation.

CONCLUSION

Positive maternal HLA PRA before 16 weeks of gestation and the temporal evolution of maternal HLA PRA are associated with the presence of chronic chorioamnionitis at the time of delivery. Maternal IgG HLA PRA has the potential to be a monitoring tool of anti-fetal rejection. Furthermore, the findings herein indicate that subsets of fetuses are exposed to alloimmune HLA antibodies for months, especially in cases with chronic chorioamnionitis.

Detection of granulocyte antibodies using simultaneous analysis of specific granulocyte antibodies assay (SASGA)

OBJECTIVE

Granulocyte-associated antibodies can cause several clinical granulocytopenic disorders. The monoclonal-antibody-specific immobilization of granulocyte antigens (MAIGA) is currently used as the standard assay to specify these antibodies. Here we describe an assay for specific analysis of granulocyte antibodies (SASGA) which is able to simultaneously detect and specify granulocyte IgG- and IgM-antibodies using flow cytometry.

METHODS

Bead populations with distinct fluorescence intensities were used as solid phase for immobilization of mAb. Typed granulocytes were incubated with human sera and a mix of three distinct mouse monoclonal antibodies against specific granulocyte antigens (for example CD16, CD11a, HLA class I). After cell lysis and incubation of lysate with beads, goat antibodies against human IgG and IgM antibodies were added. Seventy-one frozen sera of donors and patients previously implicated in transfusion reactions and various underlying disorders were analysed for specific granulocyte-binding antibodies using MAIGA and SASGA.

RESULTS

The SASGA assay was able to simultaneously detect granulocyte-specific antibodies for different glycoproteins. Overall, the results of MAIGA and SASGA were concordant in 92·9%. 5 sera containing anti-HNA-1b (n=2) and -HLA class I (n=3) were not detected by MAIGA, but were recognized by the SASGA. In serial dilution tests with sera containing anti-HNA-1a, -1b, -2a and HLA class I, the SASGA assay detected the antibodies at higher dilutions than MAIGA.

CONCLUSION

The SASGA assay permits reliable detection of specific granulocyte antibodies. Six distinct antibodies can be simultaneously determined. This method will potentially open the way to investigations on additional specific antibodies as it facilitates laboratory diagnosis.

HNA-3a-specific antibodies recognize choline transporter-like protein-2 peptides containing arginine, but not glutamine at Position 154

BACKGROUND

Antibodies specific for the neutrophil antigen HNA-3a cause severe, sometimes fatal transfusion-related acute lung disease (TRALI) when transfused, but it has not been possible to screen blood donors for anti-HNA-3a because using neutrophils as targets was impractical and molecular properties of the antigen were unknown. Recently it was shown that HNA-3a is carried on choline transporter-like protein-2 (CTL2) and that the HNA-3a/b phenotype is closely correlated with an R154Q amino acid polymorphism in CTL2. However, it has not been shown by direct experiment that R154 is essential for the HNA-3a epitope.

STUDY DESIGN AND METHODS

Preliminary attempts to express recombinant full-length CTL2 (R154) recognized by anti-HNA-3a were unsuccessful. We therefore tested HNA-3a-specific antibodies from donors implicated in TRALI reactions for reactivity against chemically synthesized linear and cyclic CTL2 peptides containing R154 or Q154.

RESULTS

Nine of 20 HNA-3a antibodies recognized the R154, but not the Q154 version of a cyclic 36-residue CTL2 peptide (D131-K166). However, 11 others failed to distinguish between the two versions of this peptide.

CONCLUSION

The findings provide direct evidence that R154 in the context of CTL2 D131-K166 is necessary to create the HNA-3a epitope but, in the context of cyclic CTL2 peptide D131-K166, is sufficient to detect only about one-half of the HNA-3a-specific antibodies implicated in TRALI. It is likely that fragments of CTL2 longer than can be made on a large scale with an automated synthesizer will be needed to produce a target capable of detecting all examples of anti-HNA-3a in donated blood.

[The immunological conflict in the transfusion-related acute lung injury or TRALI]

Despite its underrated incidence, transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related morbidity and mortality worldwide. The pulmonary edema in TRALI occurs in the course of the transfusion of apheresis products or erythrocyte concentrates. Its pathogenesis is attributed to the infusion of donor antibodies that recognize leucocyte antigens in the transfused host, with subsequent sequestration of leucocytes in the pulmonary vessels. It is also associated with the passive transfer of lipids and other biological response modifiers that accumulate during the storage or processing of blood components. The innate immunity and inflammatory kinins are key components. The knowledge of its etiopathogenesis must come into play for improving prevention and diagnosis and for application of adapted care of the patient.

The frequency and specificity of human neutrophil antigen antibodies in a blood donor population

BACKGROUND

Transfusion-related acute lung injury (TRALI) has been associated with both human leukocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies. HNA antibody frequency, specificity, and demographic associations have not been well defined in the blood donor population.

STUDY DESIGN AND METHODS

A subset of 1171 donors (388 nontransfused males, 390 HLA antibody-negative females with three or more pregnancies, and 393 HLA antibody-positive females with three or more pregnancies) from a larger Leukocyte Antibody Prevalence Study was tested for immunoglobulin (Ig)G and IgM HNA antibody using a granulocyte immunofluorescence flow cytometry assay. Additional testing on selected samples included monoclonal antibody immobilization of granulocyte antigen-flow cytometry and granulocyte genotyping.

RESULTS

Eight samples were HNA antibody positive (prevalence, 0.7%; 95% confidence interval [CI], 0.3%-1.3%]). Three HNA antibodies (one IgG and two IgM) were found in nontransfused males (prevalence, 0.8%; 95% CI, 0.2%-2.2%); all were panreactive or nonspecific. One HLA antibody-negative previously pregnant female had an IgG HNA antibody with HNA-1a specificity (prevalence, 0.3%; 95% CI, 0.01%-1.4%). Four HLA antibody-positive previously pregnant females demonstrated HNA antibodies, three IgG and one IgM (prevalence, 1%; 95% CI, 0.3%-2.6%). Two of these were HNA-1a specific, one HNA-4a specific, and one nonspecific.

CONCLUSIONS

HNA antibodies occur with low frequency in the donor population and are present in both male and female donors. Despite the implementation of TRALI reduction strategies, HNA antibodies are still present in donor blood products. Although our data do not create a case for urgent implementation of donor HNA antibody testing, future new developments for high-throughput HNA antibody screening, including for HNA-3a, may warrant reconsideration.

Granulocyte colony stimulating factor in neonatal alloimmune neutropenia: a possible association with induced thrombocytopenia

Neonatal alloimmune neutropenia (NAIN) is a rare cause of congenital neutropenia seen in <1% of births. Significant morbidity, usually infections, may result from this disease. The pathophysiology of NAIN, mediated by maternal antibodies crossing the placenta to destroy fetal cells expressing paternal antigens, is similar to that of neonatal alloimmune thrombocytopenia, as well as Rh/ABO hemolytic disease of the newborn. The use of high-dose granulocyte colony stimulating factor in patients with NAIN may cause a reversible thrombocytopenia in some patients.

Clinicopathologic features of agranulocytosis in the setting of levamisole-tainted cocaine

Levamisole is a known contaminant of cocaine and, via this route, has been associated with otherwise unexplained agranulocytosis. Levamisole is currently present in the majority of cocaine samples seized by the US Drug Enforcement Agency. We identified 20 cases of unexplained agranulocytosis in our practice locations of Albuquerque, NM, and Vancouver, Canada. Epidemiologic investigation revealed recent or ongoing cocaine use in 14 cases (70%). Certain morphologic features, including circulating plasmacytoid lymphocytes, increased bone marrow plasma cells, and mild megakaryocytic hyperplasia, were associated with the cocaine-exposed group. Of 5 patients tested, 3 (60%) were HLA-B27+ and showed antineutrophil antibodies, consistent with known associations of levamisole-induced agranulocytosis. One patient, who was positive for cocaine and levamisole by toxicology testing, died of infectious complications. Inadvertent consumption of levamisole via cocaine is a severely under-appreciated risk factor for agranulocytosis, and specific laboratory features are suggestive of this etiology.

The neutrophil alloantigen HNA-3a (5b) is located on choline transporter-like protein 2 and appears to be encoded by an R>Q154 amino acid substitution

The molecular basis of the HNA-3a/b (5b/a) leukocyte antigen system has not yet been defined despite evidence that HNA-3a-specific antibodies are particularly prone to cause severe, often fatal, transfusion-related lung injury. We used genome-wide single nucleotide polymorphism scanning and sequencing of DNA from persons of different HNA-3a/b phenotypes to identify a single single nucleotide polymorphism in exon 7 of the CLT2 gene (SLC44A2) that predicts an amino acid substitution in the first extracellular loop of choline transporter-like protein 2, a member of the choline transporter-like protein family of membrane glycoproteins, and correlates perfectly with HNA-3a/b phenotypes (R154 encodes HNA-3a; Q154 encodes HNA-3b). Mass spectrometric analysis of proteins immunoprecipitated from leukocytes by anti-HNA-3a provided direct evidence that anti-HNA-3a recognizes choline transporter-like protein 2. These findings will enable large-scale genotyping for HNA-3a/b to identify blood donors at risk to have HNA-3a-specific antibodies and should facilitate development of practical methods to detect such antibodies and prevent transfusion-related lung injury.

Rapid screening of granulocyte antibodies with a novel assay: flow cytometric granulocyte immunofluorescence test

BACKGROUND

White blood cell (WBC)-associated antibodies can lead to severe pulmonary transfusion reactions (transfusion-related acute lung injury [TRALI]). Investigation of a large number of blood donor samples using the standard granulocyte immunofluorescence test (GIFT) and granulocyte agglutination test (GAT) proved to be difficult to perform due to the time-consuming process and the large quantity of test cells required. This study describes the novel flow cytometric GIFT (Flow-GIFT) method for a rapid detection of granulocyte antibodies by flow cytometric analysis.

STUDY DESIGN AND METHODS

A total of 141 sera were analyzed for the presence of granulocyte antibodies that were previously associated with suspected TRALI. As test cells whole blood samples from human neutrophil antigen (HNA)-typed donors were isolated using cell sedimentation in a ficoll density gradient. WBCs were incubated with the respective serum and binding of antibodies to the test cells was detected using fluorescein isothiocyanate-conjugated anti-human antibody. Standard GIFT and GAT were performed as reference methods.

RESULTS

Seven sera containing anti-HNA-3a, CD16, and HLA Class I were negative in the standard GIFT and eight sera containing anti-HNA-2a, anti-CD16, and anti-HLA Class I were not detected in the GAT. The novel Flow-GIFT was able to detect all granulocyte antibodies, which were only detectable in a combination of standard GIFT and GAT. In serial dilution tests, the Flow-GIFT detected the antibodies at higher dilutions than the reference methods GIFT and GAT.

CONCLUSION

The Flow-GIFT method permits rapid detection of granulocyte antibodies requiring fewer donor test cells. This method is ideal for automation and will potentially open the way for screening of granulocyte antibodies in a large donor population.

Alloimmune neonatal neutropenia due to anti-HNA-2a alloimmunization with severe and prolonged neutropenia but mild clinical course: two case reports

Alloimmunization to granulocyte-specific antigens can occur during pregnancy. Maternal IgG can cross the placenta and result in neonatal neutropenia. The clinical course of alloimmune neonatal neutropenia is usually self-limiting with only mild infection. However, in severe cases complicated with bacterial sepsis it is a potentially life-threatening disorder. The effect of intravenous (IV) immunoglobulin, prophylactic antibiotic therapy, and recombinant human granulocyte-colony stimulating factor is variable and may prove useful in some cases. Two cases of alloimmune neonatal neutropenia due to anti HNA-2a alloimmunization in two siblings are reported. The first neonate was administered IV gammaglobulins to increase the blood neutrophil count, at a standard dosage (0.4 g/kg body weight) for 5 days without response. The second neonate did not receive specific therapy for blood neutrophil count increase. Neutropenia persisted for 2 and 6 months, respectively. The choice and efficacy of specific therapy for neutrophil count increase in the management of alloimmune neonatal neutropenia have not yet been fully defined and require additional evaluation in the majority of cases.

Diagnostic assays for chronic granulomatous disease and other neutrophil disorders

Inasmuch as neutrophils are the primary cellular defense against bacterial and fungal infections, disorders that affect these white cells typically predispose individuals to severe and recurrent infections. Therefore, diagnosis of such disorders is an important first step in directing long-term treatment/care for the patient. Herein, we describe methods to identify chronic granulomatous disease (CGD), leukocyte adhesion deficiency (LAD), and neutropenia. The assays are relatively simple to perform, cost-effective, and can be performed with equipment available in most laboratories.

Mechanisms of transfusion-related acute lung injury (TRALI): anti-leukocyte antibodies

There is abundant evidence that leukocyte antibodies in blood donor products are somehow involved in transfusion-related acute lung injury (TRALI). Human leukocyte antigen (HLA) class I, HLA class II, and neutrophil-specific antibodies in the plasma of both blood donors and recipients have been implicated in the pathogenesis of TRALI. The case for a relationship between leukocyte antibodies and TRALI is more compelling if concordance between the antigen specificity of the leukocyte antibodies in the donor plasma and the corresponding antigen on the cells of the affected recipient is demonstrated. Such antibody-antigen concordance can be investigated by typing the recipient for the cognate leukocyte antigens or by cross-matching the donor plasma against the recipient's leukocytes. Two proposed pathophysiologic mechanisms for TRALI have received the most attention: the antibody hypothesis and the two-event hypothesis. The final common pathway in all of the proposed pathogenic mechanisms of TRALI is increased pulmonary capillary permeability, which results in movement of plasma into the alveolar space causing pulmonary edema. A typical TRALI serologic workup consists of tests for HLA class I and II and neutrophil-specific antibodies. The use of flow cytometry and HLA-coated microbeads is recommended for detection of HLA antibodies in plasma of implicated blood donors and a combination of the granulocyte agglutination test and granulocyte immunofluorescence test for detection of neutrophil-specific antibodies. Genotyping for class I and II HLA and for a limited number of neutrophil antigens may also be helpful in establishing antibody-antigen concordance.