Significance of the detection of antineutrophil antibodies in children with chronic neutropenia

Chronic neutropenia in childhood: experience of a tertiary center

OBJECTIVE

To assess the prevalence of chronic neutropenia (CN) and the clinical profile of patients with CN aged up to 18 years, followed in the pediatric hematology, rheumatology, or immunology outpatient clinic of a tertiary medical center from May 1, 2018, to 30 April 2019.

METHODS

Retrospective observational study carried out by collecting data from the patient's medical charts. CN was defined as absolute neutrophil count (ANC) below 1.5 × 109/L lasting over three months. Autoimmune neutropenia (AIN) was defined by clinical criteria and an over twofold increase in ANC after glucocorticoid stimulation. AIN was considered secondary when associated with autoimmune or immunoregulatory disorders. Wilcoxon and Fisher's exact tests were used to compare variables; the significance level was 5 %.

RESULTS

A total of 1,039 patients were evaluated; 217 (20 %) presented CN. Twenty-one (2 %) had AIN, classified as primary in 57 % of the cases. The average age at the onset of symptoms was 38.6 months. During follow-up, patients had 4.2 infections on average; frequency was higher among patients with secondary AIN (p = 003). Isolated neutropenia occurred in 43 % of the patients with AIN. Neutropenia resolved in eight (38 %) of the 21 patients with AIN within 19.6 months on average. Eight patients with secondary AIN met the criteria for Inborn Errors of Immunity.

CONCLUSION

AIN prevalence was 2 %. Most cases were first evaluated by a pediatric immunologist or rheumatologist rather than a pediatric hematologist. This study highlights the need for a multidisciplinary approach involving a pediatric immunologist, rheumatologist, and hematologist.

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.

The European Guidelines on Diagnosis and Management of Neutropenia in Adults and Children: A Consensus Between the European Hematology Association and the EuNet-INNOCHRON COST Action

Neutropenia, as an isolated blood cell deficiency, is a feature of a wide spectrum of acquired or congenital, benign or premalignant disorders with a predisposition to develop myelodysplastic neoplasms/acute myeloid leukemia that may arise at any age. In recent years, advances in diagnostic methodologies, particularly in the field of genomics, have revealed novel genes and mechanisms responsible for etiology and disease evolution and opened new perspectives for tailored treatment. Despite the research and diagnostic advances in the field, real world evidence, arising from international neutropenia patient registries and scientific networks, has shown that the diagnosis and management of neutropenic patients is mostly based on the physicians' experience and local practices. Therefore, experts participating in the European Network for the Innovative Diagnosis and Treatment of Chronic Neutropenias have collaborated under the auspices of the European Hematology Association to produce recommendations for the diagnosis and management of patients across the whole spectrum of chronic neutropenias. In the present article, we describe evidence- and consensus-based guidelines for the definition and classification, diagnosis, and follow-up of patients with chronic neutropenias including special entities such as pregnancy and the neonatal period. We particularly emphasize the importance of combining the clinical findings with classical and novel laboratory testing, and advanced germline and/or somatic mutational analyses, for the characterization, risk stratification, and monitoring of the entire spectrum of neutropenia patients. We believe that the wide clinical use of these practical recommendations will be particularly beneficial for patients, families, and treating physicians.

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.

The Role of Anti-Neutrophil Antibodies in the Etiologic Classification of Childhood Neutropenia: A Cross-Sectional Study in a Tertiary Center

Infections, drugs, malignancies, immunodeficiency, and autoimmunity may cause neutropenia. In primary autoimmune neutropenia, anti-neutrophil antibodies (ANeuA) bind to membrane antigens of neutrophils, which give rise to peripheral destruction of neutrophils. However, it is not always easy to detect these antibodies. This study aims to investigate the etiology of neutropenia, and at the same time to evaluate the immune mechanisms by ANeuA testing using granulocyte indirect immunofluorescence test. In our study, 310 neutropenic patients who were between 3 months and 18 years of age were evaluated. ANeuA screening tests were performed in 108 neutropenic patients (group 1), and these patients were divided into 2 subgroups as persistent neutropenia (group 1P, n=12) and recovered neutropenia (group 1R, n=96). Besides, a control group in the same age range was formed, consisting of 39 non-neutropenic children (group 2). ANeuA serum levels were also checked in these groups, and no statistically significant difference could be found between groups 1 and 2, or between groups 1P and 1R, regarding ANeuA levels. As a conclusion, our study was the first comprehensive research in Turkey investigating the large-scale etiology of neutropenia. Moreover, while ANeuA screening tests did not provide sufficient insight for immune neutropenia, we argue that it is not necessary for routine use and that further research in the etiology of neutropenia is required.

Chronic Neutropenia in Children With Abscess Forming Cervical Lymphadenitis Caused by Staphylococcus aureus

BACKGROUND

Suppurative cervical lymphadenitis is rare in children with limited information about the frequency of neutropenia in any series.

METHODS

We conducted a retrospective review of pediatric patients in whom suppurative cervical lymphadenitis was diagnosed between April 2011 and March 2016 at a tertiary children's hospital in Tokyo, Japan. Microbiologically confirmed cases of cervical lymphadenitis with abscess formation were included in the analysis.

RESULTS

Twenty-five patients (median age, 1 yr old; 64% female) with abscess formation caused by Staphylococcus aureus were identified. Among these 25 patients, 5 (20%) met the criteria for chronic neutropenia and 4 (80%) received the final diagnosis of autoimmune neutropenia based on the identification of the serum anti-CD16 antibodies.

CONCLUSIONS

Chronic neutropenia and autoimmune neutropenia were relatively common among infants with suppurative cervical lymphadenitis caused by S. aureus.

Diagnostic value of cell bound and circulating neutrophil antibody detection in pediatric neutropenia

BACKGROUND

Chronic benign neutropenia of infancy includes primary autoimmune neutropenia (pAIN) and chronic idiopathic neutropenia (CIN). A diagnosis of CIN is supported by the absence of free and/or cell-bound neutrophil autoantibodies, which can be detected by flow cytometry with the indirect-granulocyte immunofluorescence test (I-GIFT) and direct-granulocyte immunofluorescence test (D-GIFT), respectively. Conclusive evidence is lacking on the diagnostic value of the D-GIFT, whose performance requires specific laboratory expertise, may be logistically difficult, and hampered by very low neutrophil count in patient samples. This study investigated whether the evaluation of D-GIFT improves the diagnostic accuracy of pediatric neutropenia.

PROCEDURE

I-GIFT and D-GIFT were performed in 174 pAIN, 162 CIN, 81 secondary AIN, 51 postinfection neutropenic, and 65 nonautoimmune neutropenic children referred to this laboratory during 2002-2014.

RESULTS

Using 90% specific median fluorescence intensity cut-off values calculated by receiver operating characteristic curves, D-GIFT was positive in 49% of CIN patients, who showed similar clinical features as those with pAIN. In 44 (27%) of 162 CIN patients, I-GIFT was repeated two to three times in a year, resulting positive in 12 and two patients at second and third screening, respectively. Interestingly, 10 of the latter 14 patients showed a positive D-GIFT at the first serological screening. False positive D-GIFT was shown by 12% and 22% of nonneutropenic and nonautoimmune neutropenic patients, respectively.

CONCLUSIONS

D-GIFT evaluation improves the diagnostic accuracy of pediatric neutropenia, but improvement of cell-bound antibody detection is needed to decrease false positive results.

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.

A Rare Case of Adult Autoimmune Neutropenia Successfully Treated with Prednisolone

Autoimmune neutropenia (AIN) is a rare disorder that may cause life-threatening infections. In adults, most cases are secondary to other pathological conditions, and primary AIN is extremely rare. We herein report a case involving a 57-year-old woman diagnosed with AIN. A granulocyte immunofluorescence test detected autoantibodies against human neutrophil antigens in her serum, while various examinations revealed no other causes of neutropenia, suggesting her AIN was primary. She was refractory to granulocyte-colony-stimulating factor but responded to prednisolone. Her neutrophil count remained normal after gradual discontinuation of prednisolone. Diagnostic procedures and optimal treatments for this disorder need to be established.

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.

Remission of autoimmune neutropenia after development of Kawasaki disease

We report the second case of the association of Kawasaki disease (KD) and autoimmune neutropenia (AIN). A 21-month-old female diagnosed as having AIN of infancy developed a complete KD when severe neutropenia continued. The patient suffered from no coronary artery lesions, and well responded to a single high-dose gamma-globulin therapy. The cytokine profile of the neutropenic infant was representative of the typical KD. Neutrophil counts notably increased during the convalescent phase of KD, and were then normalized forthwith. The prompt resolutions of KD and AIN paralleled the increase of circulating transforming growth factor (TGF)-β1 levels. The clinical course of the patient was contrasted to that of the first reported case of a patient who developed severe and refractory KD after the high dose granulocyte-colony stimulating factor (G-CSF) therapy.

Transient neutropenia in children with febrile illness and associated infectious agents: 2 years' follow-up

The aim of the study was to identify the relationship of acquired neutropenia with childhood infections and to assess its clinical course, complications, and outcome. Children admitted to two pediatric wards over a 4-year period with febrile neutropenia were prospectively investigated for underlying infections with inflammatory markers, cultures of body fluids, and serological tests. The study included 161 previously healthy children with febrile neutropenia/leukopenia aged (mean ± SD) 3.02 ± 3.86 years (range, 0.1-14). One hundred and thirty-six out of 161 patients (84.5 %) had transient neutropenia (TN), while in 25 patients, neutropenia was chronic (CN) and persisted for ≥180 days. An infectious agent was isolated in 98/161 (60.9 %) cases, in 68.4 % patients with TN, and in 20 % of those with CN (p = 0.001). Among the patients with CN, seven had positive antineutrophil antibodies (autoimmune neutropenia) and four were eventually diagnosed with hematological malignancy. In all age groups, TN was of short duration (<1 month), of mild to moderate severity, and was predominantly associated with viral infections. Two years after diagnosis, 143/161 children (88.8 %) were available for follow-up. One hundred and thirty-seven of 143 (95.8 %) had recovered completely, while the rest remained neutropenic. The latter patients had a benign course despite severe neutropenia. In conclusion, febrile neutropenia during childhood is usually transient, often following viral and common bacterial infections, without serious complications and in the majority of cases it resolves spontaneously. However, in a considerable percentage of patients, neutropenia is discovered incidentally during the course of an infection on the ground of an underlying hematological disease.

Diagnosis of autoimmune neutropenia by neutrophil-bound IgG and IgM antibodies

Autoimmune neutropenia (AIN) in infancy is caused by antineutrophil (granulocyte-specific) autoantibodies. These antibodies are rarely found in circulation because their serum levels are extremely low. We hypothesized that a direct granulocyte immunofluorescence test (D-GIFT) that enables us to detect neutrophil-bound autoantibodies consisting of both immunoglobulin (Ig) G and IgM has better diagnostic value than the detection of circulating autoantibodies. Whole blood (100 μL) was obtained from 50 infants with AIN, 12 infants with transient neutropenia, and 37 control infants. D-GIFT was performed using both fluorescein isothiocyanate-conjugated antihuman IgG Fc portion monoclonal antibodies and fluorescein isothiocyanate antihuman IgM monoclonal antibodies. Results were assessed as relative fluorescence intensity (RFI). The RFIs of antineutrophil IgG-bound and antineutrophil IgM-bound cells in patients with AIN were significantly higher than those in patients with transient neutropenia and in controls. Positive results, as assessed by RFI scores of more than 1.81 in either antineutrophil IgG-bound or antineutrophil IgM-bound cells, showed the sensitivity and specificity of D-GIFT, and the areas under the receiver operating characteristic curve (0.98, 0.98, and 0.997, respectively) in the diagnosis of AIN. D-GIFT detecting both neutrophil-bound IgG autoantibodies and IgM autoantibodies has discriminatory power for identifying patients with AIN and, therefore, can be a useful diagnostic test.

Autoimmune neutropenia in children: analysis of 116 cases

Diagnosis of autoimmune neutropenia (AIN) in infants is important, because it allows the exclusion of more severe forms of neutropenia that have an increased risk for leukemia. AIN is characterized by chronic neutropenia, which spontaneously resolves within several months to a few years, and mild infections. Diagnosis is confirmed by the presence of antibodies directed against neutrophil antigens. The human neutrophil antigen (HNA) system is a polymorphic system, which includes five antigen groups with different polymorphisms. In AIN, antibodies are mostly directed against HNA-1 (or against a specific allele of HNA-1) and HNA-4. Here, we present a series of 116 infants with AIN. We observed that anti-neutrophil antibodies were present in 60% cases; directed against HNA-1a in 73% of cases. In addition, we showed there was a bias in the HNA allele distribution in these infants because the frequency of the HNA-1a allele was greater in comparison with controls.

Autoimmune neutropenia due to antineutrophil antibodies in a patient with primary sclerosing cholangitis

Autoimmune neutropenia (AIN) is defined as a decrease in the circulating absolute neutrophil count (ANC) to less than 1500/μl caused by serum antineutrophil antibodies. Secondary AIN is associated with various autoimmune diseases. Herein we present the case of a patient with primary sclerosing cholangitis (PSC) who developed secondary AIN. A 19-year-old man was admitted due to liver injury, and a diagnosis of PSC was established by cholangiogram and liver biopsy. Severe neutropenia, with the ANC down to 130/μl, developed during his hospital course. No medications had been given at that time and bone marrow aspiration revealed no abnormality. Therefore we suspected secondary AIN as a causative etiology and examined whether antineutrophil antibodies were detectable in the patient's sera by flow cytometric analysis of the granulocyte indirect immunofluorescence test. We found that antineutrophil antibody was strongly positive on admission, and the titer decreased along with recovery from neutropenia. This is the first reported case of a patient with PSC who developed AIN, with detection of serum antineutrophil antibodies.

Primary autoimmune neutropenia in children in Taiwan

BACKGROUND

Autoimmune neutropenia in children is caused by granulocyte-specific autoantibodies. These antibodies react to the patient's own neutrophils but disappear when the neutropenia spontaneously remits. This study reviewed our experience with autoimmune neutropenia in children and investigated possible associations with HLA-DR and HLA-DQ alleles.

STUDY DESIGN AND METHODS

From 1993 to 2006, our laboratory received 155 blood samples from children with neutropenia. Of these samples, 55 had granulocyte-specific autoantibodies on the indirect granulocyte immunofluorescence test. As the children had no other disorders associated with neutropenia, they were diagnosed with primary autoimmune neutropenia. HLA-DRB1 and -DQB1 allele typing was performed in 31 cases, and the results were compared with those of 190 normal healthy unrelated Taiwanese controls.

RESULTS

The mean ages of onset and resolution of neutropenia were 9.8 months (median, 9.0 months; range, 4-28 months) and 22.5 months (median, 20.0 months; range, 13-44 months), respectively. The male-to-female ratio was 1.2:1. The mean absolute neutrophil count was 190 per microL (standard deviation, 213/microL). Most patients (74%) had antibodies against HNA-1a. Autoimmune neutropenia in children in Taiwan was significantly associated with HLA-DQB1*0503 (odds ratio, 6.48; p = 0.0002; p(c) = 0.003) allele.

CONCLUSION

In Taiwan, autoimmune neutropenia in children is associated with HLA-DQB1*0503. The autoantibody in autoimmune neutropenia is most commonly anti-HNA-1a.

Idiopathic neutropenia of childhood is associated with Fas/FasL expression

Idiopathic neutropenia (IN) in children is characterized by decreased neutrophil counts (<1500/microl), can be acute or chronic (greater than 6 months duration). The pathophysiology is not well understood; therefore, potential mechanisms of pediatric IN were investigated. An increase in Fas transcripts in neutrophils of IN patients compared to age-matched healthy control (HC) neutrophils was observed (p<0.005). Increased expression of Fas protein was found in IN neutrophils, while Fas surface expression on other immune cells was similar. Plasma from acute IN patients had higher protein levels of soluble FasL than chronic IN patients. When HC neutrophils were incubated in plasma from IN patients, greater rates of apoptosis were observed. Biochemical studies suggest the apoptotic factor(s) in plasma is heat-sensitive, non-IgG, and 12-50 kD protein. Addition of anti-sFasL blocking antibodies to patient plasma caused a statistically significant decrease in neutrophil apoptosis. These studies show that the Fas/FasL pathway could be associated with neutrophil apoptosis in childhood IN.

Characterization of the bone marrow immunofluorescence test in childhood autoimmune neutropenia

The bone marrow immunofluorescenece test (BMIFT) demonstrates autoantibodies to granulocytes and their precursors on fresh-frozen bone marrow slides. It may be used to differentiate childhood autoimmune neutropenia (AIN) from other causes of childhood neutropenia, even when circulating neutrophil counts are low. We sought to characterize the diagnostic utility of the BMIFT in childhood AIN. All BMIFT requests for investigation of children with neutropenia between January 1998 and May 2007 were reviewed. Patients were classified as AIN or nonautoimmune causes. Baseline demographic data, results of BMIFT, granulocyte immunofluorescence testing and bone marrow findings were collected from clinical records and the institutional laboratory database. Seventy-six children had BMIFT performed for investigation of neutropenia. There were 45 patients diagnosed with AIN, 28 with nonimmune neutropenia and three failed tests. The median age of children with AIN was 1.2 years (range 0.3-15.3), compared with 3.6 years (range 0.1-15.7) in the nonautoimmune group. The median neutrophil count in AIN was 0.3 x 10(9)/l (0.9 x 10(9)/l in nonautoimmune). BMIFT was positive in 24 of 45 patients with AIN and 0 of 28 with nonautoimmune neutropenia (sensitivity 53%, specificity 100%, positive predictive value (PPV) 100%, negative predictive value 57%). Ten patients had other autoimmune diatheses at diagnosis. The BMIFT is a simple, highly specific test with excellent PPV and thus is a clinically useful test to confirm AIN in children.

A pediatric case of transfusion-related acute lung injury following bone marrow infusion

TRALI is a rare but serious complication associated with transfusion, and known to occur following infusion of all types of plasma-containing blood products. However, only one adult case of TRALI after allogenic marrow graft has been reported. In this study, we present a pediatric case possibly associated with allogenic marrow infusion. A 10-yr-old girl was referred to our hospital for the treatment of acute myeloid leukemia. She underwent allogenic bone marrow transplantation from her HLA-2-loci-mismatched mother. During conditioning, she suffered from bacterial sepsis, but it had improved with antibiotics until day 0 of transplantation. Two h after starting the marrow infusion, she developed severe hypoxia. We discontinued the infusion and started steroids, which improved her respiratory condition. However, she developed respiratory failure again after resuming infusion of the graft. Despite intensive care with mechanical ventilation, the patient died of endotoxin shock five days after transplantation. Although we could not identify the antibody which might have been involved in the respiratory distress, the clear temporal relationship between marrow infusion and respiratory distress suggested that similar acute lung injury to TRALI might have occurred following allogenic marrow infusion in the present case.

Severe neutropenia in children: a single institutional experience

Severe neutropenia (SN) is a rare disorder in childhood. This study aimed to document the approach to diagnosis and treatment of children with SN in a single university-based children's hospital, determine the types of SN seen in a 4-year period, and determine outcomes of the subtypes of SN. Forty-five children with SN were identified between 2000 and 2004. Two patients had autoimmune, 3 congenital, 3 familial, 6 cyclic, and 31 idiopathic SN. The median age of the patients with idiopathic SN was 15 months (3 mo to 17 y). Thirteen patients with idiopathic SN received filgrastim and 18 were observed. The history of severe infection and hospitalization at presentation was significantly more common among the patients who received filgrastim than those observed, but was not different between the 2 groups during the follow-up period. SN resolved in 16 patients and persisted in 14 patients. One patient with idiopathic SN did not respond to filgrastim and died of sepsis while she was still neutropenic. In summary, the majority of patients with SN had idiopathic SN, the infection risk was variable, treatment was based on clinical judgment rather than absolute neutrophil count, and approximately half of the patients had complete recovery.

Establishment of cell lines stably expressing HNA-1a, -1b, and -2a antigen with low background reactivity in flow cytometric analysis

BACKGROUND

Antibodies to neutrophil antigens have been implicated in neonatal alloimmune neutropenia, autoimmune neutropenia, and transfusion-related acute lung injury. Most often, neutrophil-specific antibodies are directed toward human neutrophil antigen (HNA)-1 (Fcgamma receptor 3b) and HNA-2a (CD177) in these disorders.

STUDY DESIGN AND METHODS

To detect the alloantibodies in the serum samples, a panel of cell lines was established in which the HNA-1a, HNA-1b (polymorphisms of HNA-1), or HNA-2a gene was transduced with a retrovirus vector to confer stable transgene expression in K562 cells that exhibited low background reactivity to human serum samples obtained from healthy donors in flow cytometric analysis.

RESULTS

It was shown that several well-characterized human serum samples containing antibodies against HNA-1a, -1b, and -2a were unambiguously identified by the established panel cell lines and observed a lower background reactivity and longer shelf life of the K562 panel cell lines compared with isolated neutrophils, which have been used for the cell panel to identify antibodies against HNA in human serum samples.

CONCLUSION

These results indicate that the K562 panel cell lines provide a good panel for detecting HNA-reactive neutrophil antibodies in human serum samples.

Primary autoimmune neutropenia in children: a study of neutrophil antibodies and clinical course

BACKGROUND AND OBJECTIVES

Primary autoimmune neutropenia (AIN) in children is characterized by severe neutropenia, but mild bacterial infections and a spontaneous resolution. Neutrophil autoantibodies are involved in the disease. The precise relationship between the specificity and level of reactivity of the antibodies with the absolute neutrophil count and frequency of infections is not known. To obtain a better insight into this relationship, we performed a follow-up study in 15 patients with primary AIN. In addition, we performed two different neutrophil antibody tests to evaluate their sensitivity and specificity.

MATERIALS AND METHODS

Blood samples from 15 children were tested for neutrophil antibodies, at different time-points during the disease, by using the indirect granulocyte immunofluorescence test (GIFT) and the monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA) assay. Clinical data related to the occurrence of bacterial infections and treatment, and neutrophil counts were collected.

RESULTS

Early in the disease, antibodies with pan-FcRIIIb specificity were detected, and HNA-1a or HNA-1b specificity of the antibodies developed over time. The sensitivity and specificity of neutrophil antibody detection tests were higher in the GIFT than in the MAIGA assay. Variables predicting time of recovery from neutropenia were not found. Prophylactic antibiotics led to the almost complete disappearance of infections.

CONCLUSIONS

In patients with primary neutropenia, neutrophil antibody specificity changes over time. Prophylactic antibiotics do benefit the patients.

Congenital and Acquired Neutropenia

Our understanding of the pathogenesis of congenital and acquired neutropenia is rapidly evolving. New ground-breaking observations have identified the genes responsible for many of the congenital neutropenia syndromes and are also providing new insights into normal neutrophil commitment and differentiation. Acquired neutropenia remains a poorly understood syndrome, although new insights into its pathogenesis are also emerging, especially with regard to subsets of immune neutropenia.

In Section I, Dr. Marshall Horwitz reviews the current understanding of the genetic basis, molecular pathology, and approaches to treatment of congenital neutropenia and cyclic hematopoiesis. Mutations in the ELA2 gene, which encodes for neutrophil elastase, cause cyclic hematopoiesis. ELA2 mutations are also the most common cause of congenital neutropenia, where their presence may equate with a more severe clinical course and higher frequency of leukemic progression. Emerging evidence indicates interrelatedness with Hermansky Pudlak syndrome and other disorders of neutrophil and platelet granules.

In Section II, Dr. Nancy Berliner presents an overview of the clinical approach to the evaluation and treatment of acquired neutropenia. This includes a review of the pathogenesis of primary and secondary immune neutropenia, drug-induced neutropenia, and non-immune chronic idiopathic neutropenia of adults. Studies used to evaluate patients for potential immune neutropenia are reviewed. Management issues, especially the use of granulocyte colony-stimulating factor (G-CSF), are discussed.

In Section III, Dr. Thomas Loughran, Jr., reviews the pathogenesis and clinical manifestations of large granular lymphocyte (LGL) leukemia. Possible mechanisms of neutropenia are discussed. In particular, discussion focuses on the relationship between LGL leukemia, rheumatoid disease, and Felty’s syndrome, and the complex interplay of defects in neutrophil production, distribution, destruction, and apoptosis that underly the development of neutropenia in those syndromes.

Efficacy of prophylactic use of trimethoprim-sulfamethoxazole in autoimmune neutropenia in infancy

PURPOSE

Most children with autoimmune neutropenia (AIN) have a benign clinical course because of the spontaneous resolution of neutropenia. The authors observed the clinical course of AIN in infancy accompanied by the prophylactic use of trimethoprim-sulfamethoxazole (TMP-SMX) during neutropenia.

PATIENTS AND METHODS

Eight infants with AIN were followed by serial tests for antineutrophil antibodies and management of infectious complications.

RESULTS

The spontaneous disappearance of antineutrophil antibodies that preceded the normalization of the neutrophil count was found in all patients. Until the resolution of neutropenia, TMP-SMX was administered in five patients, resulting in a reduction in the incidence of infection with no adverse effects.

CONCLUSIONS

These observations demonstrate the possibility of the safety and usefulness of TMP-SMX treatment in patients with AIN.