Immune thrombocytopenic purpura (ITP) comprises ~1% to 4% of thrombocytopenia cases during pregnancy. Factors predicting neonatal thrombocytopenia and associated morbidities due to maternal ITP are unclear. The present study aimed to assess the neonatal outcomes of pregnant women with ITP. Fifty-five pregnant women with ITP and their babies, born between January/2013 and April/2021, were retrospectively reviewed. Maternal and neonatal thrombocytopenia cases other than ITP were excluded from the study. Physical examination, blood count, and cranial/abdominal ultrasonography findings of the newborns were recorded. Neonatal thrombocytopenia was defined as a platelet count < 150 × 109/L. Relationship between neonatal thrombocytopenia and maternal factors was investigated. Thrombocytopenia was detected in 17/55 babies (30.9%), and 8/17 (47.1%) had symptoms of bleeding, all but one being mild bleeding. There was a significant correlation between neonatal platelet counts of < 100 × 109/L and maternal splenectomy history. Incidence of moderate and severe thrombocytopenia was higher (statistically insignificant) in neonates of mothers with ITP. No significant correlation was determined between maternal and neonatal platelet counts. There was a weak insignificant correlation between platelet counts of neonates of mothers with or without thrombocytopenia. A significant correlation was found between the presence of splenectomy before delivery in the mother and a platelet count of < 100 × 109/L in the neonate. Moderate and severe thrombocytopenia was higher in neonates of mothers diagnosed with ITP before pregnancy and needed treatment during pregnancy and/or delivery, but the difference was insignificant. Close follow-up of babies born to mothers with ITP after birth is crucial since there is no significant prediction criterion for developing neonatal thrombocytopenia and associated morbidities.

BACKGROUND: Fetal and Neonatal Alloimmune Thrombocytopenia (FNAIT) results from maternal platelet alloimmunization against paternal antigens inherited by the fetus, most often due to the Human Platelet Antigen (HPA)-1 system in Caucasians. We investigated in 2023, a 30-year-old Caucasian woman Gravida 2 Para 1 who gave birth at 35 weeks of gestation to a male (body weight 2210 g) without signs of bleeding. A severe thrombocytopenia (platelet count at 3 G/L) was discovered incidentally a few hours after delivery in the context of the management of a respiratory distress. The newborn recovered after one platelet concentrate transfusion and normalized his platelet count at Day 5.
METHODS: FNAIT investigation was performed according to guideline recommendations. Platelet genotyping was carried out by multiplex PCR. Maternal serological investigation included Monoclonal Antibody-specific Immobilization of Platelet Antigens method (MAIPA) and Luminex technology.
RESULTS: Parental and newborn genotyping pointed out an HPA-4 incompatibility between the mother and the newborn and the father. Serological investigation revealed an anti-HPA-4b alloantibody confirming the diagnosis of neonatal alloimmune thrombocytopenia.
CONCLUSIONS: We described the third case of anti-HPA-4b alloantibody discovered in a Caucasian mother. This case strengthens the need for reference laboratory to genotype a panel of HPA alleles reflecting local genetic population diversity and for crossmatch of maternal serum with fresh paternal platelets in clinical suspected cases of neonatal alloimmune thrombocytopenia.

暂无摘要。

BACKGROUND: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a condition during pregnancy, which can lead to thrombocytopenia and a bleeding tendency with intracranial hemorrhage (ICH) being the most concerning complication in the fetus or neonate. An incompatibility between human platelet antigen (HPA)-1a accounts for the majority of FNAIT cases. Binding of HPA-1a-specific alloantibodies to their target on fetal platelets and endothelial cells can induce apoptosis of megakaryocytes, disrupt platelet function, and impair angiogenesis. Currently, there is no screening program to identify pregnancies at risk for severe disease. A better understanding of HPA-1a-specific antibody heterogeneity in FNAIT could aid in identifying pathogenic antibody properties linked to severe disease.
METHODS: This study aimed to isolate HPA-1a-specific B-cells from an HPA-1a-alloimmunized pregnant woman. Using fluorescently labeled HPA-1a-positive platelets, single B-cells were sorted and cultured for 10 days to stimulate antibody production. Subsequently, supernatants were tested for the presence of antibodies by enzyme-linked immunosorbent assay and their reactivity towards HPA-1a-positive platelets. Amplification and sequencing of variable regions allowed the generation of monoclonal antibodies using a HEK-Freestyle-based expression system.
RESULTS: Three platelet-specific B-cells were obtained and cloned of which two were specific for HPA-1a, named D- and M-204, while the third was specific for HLA class I, which was named L-204.
CONCLUSIONS: This study outlined an effective method for the isolation of HPA-1a-specific B-cells and the generation of monoclonal antibodies. Further characterization of these antibodies holds promise for better understanding the pathogenic nature of alloantibodies in FNAIT.

OBJECTIVE: Polymorphic molecules expressed on the surface of certain blood cells are traditionally categorized as blood groups and human platelet or neutrophil antigens. CD36 is widely considered a platelet antigen (Naka) and anti-CD36 can cause foetal/neonatal alloimmune thrombocytopenia (FNAIT) in CD36-negative pregnant women. CD36 is used as a marker of differentiation in early erythroid culture. During the experimental culture of CD34+ cells from random blood donors, we observed that one individual lacked CD36. We sought to investigate this observation further and determine if CD36 fulfils the International Society of Blood Transfusion criteria for becoming a blood group.
METHODS: Surface markers were monitored by flow cytometry on developing cells during the erythroid culture of CD34+ cells. Genetic and flow cytometric analyses on peripheral blood cells were performed. Proteomic datasets were analysed, and clinical case reports involving anti-CD36 and foetal anaemia were scrutinized.
RESULTS: Sequencing of CD36-cDNA identified homozygosity for c.1133G>T/p.Gly378Val in the CD36-negative donor. The minor allele frequency of rs146027667:T is 0.1% globally and results in abolished CD36 expression. CD36 has been considered absent from mature red blood cells (RBCs); however, we detected CD36 expression on RBCs and reticulocytes from 20 blood donors. By mining reticulocyte and RBC datasets, we found evidence for CD36-derived peptides enriched in the membrane fractions. Finally, our literature review revealed severe cases of foetal anaemia attributed to anti-CD36.
CONCLUSIONS: Based on these findings, we conclude that CD36 fulfils the criteria for becoming a new blood group system and that anti-CD36 is implicated not only in FNAIT but also foetal anaemia.

BACKGROUND: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) ensues from parental incompatibility for platelet alloantigens with maternal sensitization. HPA-1a/1b incompatibility is the most common cause of FNAIT in Caucasians. Placental villitis and lower birthweight in FNAIT suggest anti-HPA-1a may have effects beyond inducing thrombocytopenia.
OBJECTIVE: Does FNAIT secondary to anti-HPA-1a result in smaller newborns and, the corollary, does antenatal management of FNAIT increase birthweight?
METHODS: Birthweights of 270 FNAIT-affected newborns from a randomized clinical trial and a NAITbabies.org survey (135 paired siblings) were compared with those of published controls and treated to untreated FNAIT-affected siblings. Birthweights were converted to percentiles to account for gestational age, sex, and role of birth order in birth weight. Body weights of FNAIT-affected and -unaffected pups in a mouse FNAIT model were analyzed.
RESULTS: Untreated siblings in both the clinical trial and NAITbabies.org cohorts were not small, compared with normal controls. However, treated siblings in both cohorts had significantly higher birthweight percentiles compared with their previous untreated affected sibling. After accounting for gestational age, sex, and birth order, increased birthweight percentile in treated compared with the untreated siblings remained significant in both cohorts. FNAIT-affected neonatal mice had lower bodyweights than FNAIT-unaffected pups.
CONCLUSIONS: Untreated FNAIT-affected newborns were not small; however, treatment of FNAIT-affected pregnancies increased newborn birthweights despite corrections to account for other factors that might have influenced the results. High dose IVIG is believed to \"block\" FcRn and lower maternal anti-HPA-1a levels, and thus increase birthweights by reducing levels of maternal anti-HPA-1a and reducing placental villitis.

暂无摘要。

The etiologies of thrombocytopenia are highly diverse; however, early neonatal thrombocytopenia might be more common among extremely low-weight neonates. Therefore, in this study, we aimed to examine the current neonatal platelet (PLT) transfusion practices in Saudi Arabia. This is a cross-sectional online survey study that was conducted between October and December 2022. Convenience sampling was used to recruit the participants. In this study, we developed a questionnaire based on an extensive literature review to examine current neonatal PLT transfusion practices. A total of 81 neonatologists participated. The vast majority of them (85.2%) were practicing in a level 3 neonatal intensive care unit, with 60.0% of them reporting that they transfuse PLTs over 1 hour. Around 53% reported that they typically order 10 mL/kg per PLT transfusion. Up to 34.6% of the study participants reported that they use pooled whole-blood-derived PLT products in their practicing unit. Almost half (48.0%) of the study participants reported that they have written guidelines for PLT transfusion in their practicing unit, with 81.1% reporting that the PLT transfusion threshold was stated in the guidelines. Neonatal thrombocytopenia is typically treated with PLT transfusions. PLT transfusion criteria should be lowered in light of recent evidence suggesting that doing so may be counterproductive. However, there is some disagreement about whether a PLT count constitutes a medical emergency requiring a transfusion for a newborn baby. Furthermore, there is a great deal of variation in the administration of PLT infusions in Saudi Arabia because of the absence of clear protocols. Strict neonatal PLT transfusion standards and carefully planned clinical research are needed to address the risks and/or benefits of these diverse methods.

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Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a serious bleeding condition mostly caused by the reaction between maternal anti-HPA-1a antibodies and fetal platelets. This reaction leads to Fc-dependent platelet phagocytosis. Although several serological methods have been developed to identify maternal antibodies, a reliable laboratory parameter as a prognostic tool for FNAIT severity is still lacking. In this study, we developed whole blood platelet phagocytosis assay (WHOPPA), a flow cytometry-based phagocytosis assay that uses a pH-sensitive fluorescent dye (pHrodo-SE) to analyze anti-HPA-1a-dependent platelet phagocytosis in whole blood. WHOPPA revealed a high phagocytosis rate for the anti-HPA-1a opsonized platelets by monocytes but not by neutrophils. Analysis of different monocyte populations showed that all monocyte subsets, including classical (CD14++CD16-), intermediate (CD14++CD16+), and nonclassical (CD14+CD16++) monocytes, were able to engulf opsonized platelets. A unique monocyte subset, termed shifted monocytes (CD14+CD16-), showed the highest phagocytosis rate and was detected after platelet engulfment. FcγR inhibition tests revealed that except for FcγRIIa, FcγRI and FcγRIII on monocytes were responsible for the phagocytosis of anti-HPA-1a opsonized platelets. Analysis of anti-HPA-1a antibodies from FNAIT cases (n = 7) showed the phagocytosis of HPA-1aa but not of HPA-1bb platelets by monocytes. The phagocytosis rate was highly correlated with bound antibodies measured by flow cytometry (p < 0001; r = 0.9214) and MAIPA assay (p < 0.001; r = 0.7692). The phagocytosis rates were equal for type I and II anti-HPA-1a antibodies recognizing the plexin-semaphoring-integrin (PSI) domain and PSI/epidermal growth factor 1 domain of β3 integrin, respectively. By contrast, type III anti-HPA-1a antibodies reacting with αvβ3 integrin did not induce platelet phagocytosis. Furthermore, effector-silenced mAbs against HPA-1a inhibited the phagocytosis of anti-HPA-1a opsonized platelets. In conclusion, WHOPPA is a reliable in vitro platelet phagocytosis assay that mimics the phagocytosis of anti-HPA-1a opsonized platelets in whole blood. This assay allows to prove platelet phagocytosis ex vivo and evaluate the inhibitory capacity of different inhibitors as therapeutically strategies for the prevention of fetal thrombocytopenia in FNAIT in the future.