Caracterización de los antígenos específicos del neutrófilo NA1, NA2 y SH en la población argentina / Characterization of neutrophil-specific antigens NA1, NA2 and SH in the argentinean population

Los antígenos especifícos de neutrófilos NA1 (HNA-1a), NA2 (HNA-1b) y SH (HNA-1c) son formas alotípicas del Fc gamma RIIIb y los blancos más frecuentes de los aloanticuerpos antigranulocitarios. El objetivo de este estudio fue determinar las frecuencias alélicas de los antígenos específicos de neutrófilos pertenecientes al sistema HNA-1 en donantes de sangre y amerindios de la etnia Toba de la ciudad de Rosario, Argentina. Se genotipificaron doscientos dieciocho individuos no relacionados para HNA-1a, HNA-1b y HNA-1c mediante reacción en cadena de polimerasa con cebadores secuencia específica (PCR-SSP). Las frecuencias alélicas en los donantes de sangre para HNA-1a y HNA-1b fueron 0,44 y 0,56 respectivamente y en la población amerindia Toba fueron 0,77 y 0,23 respectivamente. El alelo HNA-1c presentó una frecuencia de 0,023 en los donantes de sangre, pero no se detectó en ninguno de los individuos amerindios estudiados. Los presentes datos mostraron que las frecuencias de los alelos que codifican al sistema HNA-1 en la población mayoritaria de Rosario y en la minoritaria amerindia Toba son similares a las descriptas en europeos y otras poblaciones amerindias distantes, respectivamente.

The neutrophil-specific antigens NA1 (HNA-1a), NA2 (HNA-1b) and SH (HNA-1c) are allotypic forms of Fc gamma RIIIb and the most frequent targets of neutrophil alloantibodies. The aim of this study was to determine to gene frequencies of the neutrophil-specific antigens bolonging to the HNA-1 system in blood donors and Toba amerindians fron Rosario, Argentina. Two hundred and eighteen unrelated individual from Rosario were typed for HNA-1a, HNA-1b and HNA-1c, using polymerase chain reaction with sequence-specific primers (PCR-SSP). For the argentinean blood donors, the HNA-1a and HNA-1b gene frequencies were 0.44 and 0.56 and for the amerindians Toba were 0.77 and 0.23 respectively. The HNA-1c gene frequency in blood donors was 0.023 but the allele was absent within the amerindian individuals. The present data showed that the HNA-1 allele frequencies in the major population and the Toba amerindian from Rosario are similar to those described in European and others distant amerindians populations, respectively.

Human neutrophil alloantigens systems

Neutrophil alloantigens are involved in a variety of clinical conditions including immune neutropenias, transfusion-related acute lung injury (TRALI), refractoriness to granulocyte transfusions and febrile transfusion reactions. In the last decade, considerable progress has been made in the characterization of the implicated antigens. Currently, seven antigens are assigned to five human neutrophil antigen (HNA) systems. The HNA-1a, HNA-1b and HNA-1c antigens have been identified as polymorphic forms of the neutrophil Fcγ receptor IIIb (CD16b), encoded by three alleles. Recently, the primary structure of the HNA-2a antigen was elucidated and the HNA-2a-bearing glycoprotein was identified as a member of the Ly-6/uPAR superfamily, which has been clustered as CD177. The HNA-3a antigen is located on a 70-95 kDa glycoprotein; however, its molecular basis is still unknown. Finally, the HNA-4a and HNA-5a antigens were found to be caused by single nucleotide mutations in the αM (CD11b) and αL (CD11a) subunits of the leucocyte adhesion molecules (β2 integrins). Molecular and biochemical characterization of neutrophil antigenshave expanded our diagnostic tools by the introduction of genotyping techniques and immunoassays for antibody identification. Further studies in the field of neutrophil immunology will facilitate the prevention and management of transfusion reactions and immune diseases caused by neutrophil antibodies.

Os aloantígenos de neutrófilos estão associados a várias condições clínicas como neutropenias imunes, insuficiência pulmonar relacionada à transfusão (TRALI), refratariedade à transfusão de granulócitos, e reações transfusionais febris. Na última década, foi observado considerável progresso na caracterização dos aloantígenos envolvidos nestas condições clínicas. Atualmente sete antígenos estão incluídos em cinco sistemas de antígenos de neutrófilo humano (HNA). Os antígenos HNA-1a, HNA-1b e HNA-1c foram identificados como formas polimórficas do receptor Fcγ RIIIb (CD16b), codificados por três alelos. Recentemente, a estrutura primária do antígeno HNA-2a foi elucidada e a glicoproteína carreadora do antígeno foi identificada como um membro da superfamília Ly-6/uPARe designada como CD177. O antígeno HNA-3a está localizadoem uma glicoproteína de 70-90 kDa, entretanto sua base molecular ainda é desconhecida. Finalmente, os antígenos HNA-4ae HNA-5a são resultantes de mutações de um único nucleotídeo nas subunidades αM (CD11b) and αL (CD11a) das moléculas de adesão de leucócitos (β2 integrinas). A caracterização molecular e bioquímica dos antígenos neutrofílicos permitiu a expansão das ferramentas diagnósticas pela introdução de técnicas de genotipagem e imunoensaios para a identificação de anticorpos. Novos estudos envolvendo a imunologia de granulócitos serão de grande valor para a prevenção e tratamento de reações transfusionais e doenças imunes causadas por aloanticorpos de neutrófilos.

A Case of Neonatal Alloimmune Neutropenia Associated with Anti-Human Neutrophil Antigen-1a (HNA-1a) Antibody

Neonatal alloimmune neutropenia (NAN) is an uncommon disease of the newborn provoked by the maternal production of neutrophil-specific alloantibodies, whereby neutrophil IgG antibodies cross the placenta and induce the destruction of fetal neutrophils. Affected newborns are usually identified by the occurrence of bacterial infections. The most frequent antigens involved in NAN are the human neutrophil antigen-1a (HNA-1a), HNA-1b, and HNA-2a. We report a neonate who was delivered at 36 weeks and had a severe neutropenia but who responded well to recombinant human granulocyte colony-stimulating factor (rhG-CSF). Anti-HNA-1a antibody was identified by mixed passive hemagglutination assay in both the sera of the baby and the mother. The baby had HNA-1a and HNA-1b but the mother had only HNA-1b on granulocytes. This is the first Korean report of NAN in which the specificity of the causative antibody was identified.

Granulocyte Antibodies in Korean Neonates with Neutropenia

Neonatal alloimmune neutropenia (NAN) is a disease that can cause severe and prolonged neutropenia in neonates. However, no report is available on the incidence of granulocyte antibody in neonates, the target antigen of this antibody, and the estimated incidence of NAN in Korea. Among a total of 856 neonates admitted to a neonatal intensive care unit (NICU) over a five year period, a total of 105 neonates with neutropenia were enrolled in this study. Positive reactions were observed in the sera of six neonates (5.7%, 6/105) by mixed passive hemagglutination assay (MPHA). To confirm the presence of NAN, MPHA and granulocyte antigen typing (HNA-1a, -1b, -2a, -4a, and -5a) were performed on neonatal and maternal blood. To differentiate granulocyte antibody and HLA antibody, MPHA was also performed using HLA antibody adsorbed serum. We confirmed three cases (2.9%, 3/105) of NAN among neonates with neutropenia in which granulocyte antibody specificities (two anti-HNA-1b and one anti-HNA-1a) and fetomaternal granulocyte antigen mismatches were identified. In this study, the estimated incidence of NAN was 0.35% (3/856) among neonates admitted to NICUs in Korea.