Neonatal alloimmune thrombocytopenia caused by human leucocyte antigen-B27 antibody

A combined effect of anti-HPA-1a and anti-HLA Class I in pregnancy?

BACKGROUND

Maternal anti-human leukocyte antigen (HLA) Class I is commonly detected alongside anti-human platelet antigen (HPA)-1a in fetal and neonatal alloimmune thrombocytopenia (FNAIT). Little is known regarding whether the presence of anti-HLA Class I may exert an additive effect on the risk and severity of FNAIT.

METHODS AND MATERIALS

We reanalyzed samples originally collected as part of a large Norwegian screening study on FNAIT during 1995-2004. This study identified and managed 170 pregnancies where the mother was HPA-1a negative and had detectable anti-HPA-1a during pregnancy. Maternal samples from 166 of these pregnancies were rescreened for anti-HLA Class I, revealing 111 (67%) that were antibody positive. Various regression models were used to assess if and how maternal anti-HLA Class I influenced the neonatal platelet count.

RESULTS AND CONCLUSIONS

Unadjusted neonatal platelet counts and the frequency of neonatal thrombocytopenia was not significantly affected by the presence of anti-HLA Class I alongside anti-HPA-1a, but results from regression analyses revealed a possible increased risk when the mother was nulliparous. These results warrant further investigation.

Marked thrombocytopenia in a neonate is associated with anti-HPA-5b, anti-HLA-A31, and anti-HLA-B55 antibodies

Maternal antibodies against human platelet antigen (HPA) and/or human leukocyte antigen (HLA) cause fetal and neonatal alloimmune thrombocytopenia (FNAIT) in 0.09-0.15% of live births. Severe cases account for 5-31% and the frequency of multiple kinds of alloantibodies is 6.9-9% of FNAIT. We present a case of severe FNAIT associated with anti-HPA-5b, anti-HLA-A31, and anti-HLA-B55 antibodies, successfully treated with immunoglobulin and platelet transfusion. The anti-HLA-B55 antibody was detected in the newborn's serum, but disappeared on the 20th day, which was followed by an increase of the platelet count. These findings suggested the potential involvement of an anti-HLA antibody in the pathogenesis of FNAIT.

Aplastic anemia during pregnancy: a review of obstetric and anesthetic considerations

Aplastic anemia is a hematologic condition occasionally presenting during pregnancy. This pathological process is associated with significant maternal and neonatal morbidity and mortality. Obstetric and anesthetic management is challenging, and treatment requires a coordinated effort by an interdisciplinary team, in order to provide safe care to these patients. In this review, we describe the current state of the literature as it applies to the complexity of aplastic anemia in pregnancy, focusing on pathophysiologic aspects of the disease in pregnancy, as well as relevant obstetric and anesthetic considerations necessary to treat this challenging problem. A multidisciplinary-team approach to the management of aplastic anemia in pregnancy is necessary to coordinate prenatal care, optimize maternofetal outcomes, and plan peripartum interventions. Conservative transfusion management is critical to prevent alloimmunization. Although a safe threshold-platelet count for neuraxial anesthesia has not been established, selection of anesthetic technique must be evaluated on a case-to-case basis.

Current perspectives on fetal and neonatal alloimmune thrombocytopenia - increasing clinical concerns and new treatment opportunities

Differences in platelet type between the fetus and the mother can lead to maternal immunization and destruction of the fetal platelets, a condition named fetal and neonatal alloimmune thrombocytopenia (FNAIT). FNAIT is reported to occur in ~1 per 1,000 live born neonates. The major risk is intracranial hemorrhage in the fetus or newborn, which is associated with severe neurological complications or death. Since no countries have yet implemented a screening program to detect pregnancies at risk, the diagnosis is typically established after the birth of a child with symptoms. Reports on broader clinical impact have increased clinical concern and awareness. Along with new treatment options for FNAIT, the debate around antenatal screening to detect pregnancies at risk of FNAIT has been revitalized.

Antiendothelial αvβ3 Antibodies Are a Major Cause of Intracranial Bleeding in Fetal/Neonatal Alloimmune Thrombocytopenia

OBJECTIVE

Fetal/neonatal alloimmune thrombocytopenia is a severe bleeding disorder, which can result in intracranial hemorrhage (ICH), leading to death or neurological sequelae. In whites, maternal anti-human platelet antigen-1a (HPA-1a) antibodies are responsible for the majority of cases. No predictive factors for ICH are available to guide prophylactic treatment during pregnancy. In this study, we investigated antibodies from mothers with ICH-positive fetal/neonatal alloimmune thrombocytopenia and with ICH-negative fetal/neonatal alloimmune thrombocytopenia to identify serological and functional differences between the groups.

APPROACH AND RESULTS

In an antigen capture assay, we observed a stronger binding of +ICH antibodies to endothelial cell (EC)-derived αvβ3. By absorption experiments, we subsequently identified anti-HPA-1a antibodies of anti-αvβ3 specificity in the +ICH but not in the -ICH cohort. Only the anti-αvβ3 subtype, but not the anti-β3 subtype, induced EC apoptosis of HPA-1a-positive ECs by caspase-3/7 activation, and mediated by reactive oxygen species. In addition, only the anti-αvβ3 subtype, but not the anti-β3 subtype, interfered with EC adhesion to vitronectin and with EC tube formation.

CONCLUSIONS

We conclude that the composition of the anti-HPA-1a antibody subtype(s) of the mother may determine whether ICH occurs. Analysis of anti-HPA-1a antibodies of the anti-αvβ3 subtype in maternal serum has potential in the diagnostic prediction of ICH development and may allow for modification of prophylactic treatment in fetal/neonatal alloimmune thrombocytopenia.

Neonatal alloimmune thrombocytopenia: pathogenesis, diagnosis and management

Neonatal alloimmune thrombocytopenia, (NAIT) is caused by maternal antibodies raised against alloantigens carried on fetal platelets. Although many cases are mild, NAIT is a significant cause of morbidity and mortality in newborns and is the most common cause of intracranial haemorrhage in full-term infants. In this report, we review the pathogenesis, clinical presentation, laboratory diagnosis and prenatal and post-natal management of NAIT and highlight areas of controversy that deserve the attention of clinical and laboratory investigators.

Alloantibodies against MHC class I: a novel mechanism of neonatal pancytopenia linked to vaccination

Fetal/neonatal alloimmune thrombocytopenia is a frequent disease in humans where alloantibodies against platelet Ags lead to platelet destruction and hemorrhage. Although a role in the disease for Abs against MHC has been suspected, this has not been formally demonstrated. Since 2007, a hemorrhagic syndrome due to thrombocytopenia and designated as bovine neonatal pancytopenia (BNP) has been recognized in calves in several European countries. An inactivated antiviral vaccine is strongly suspected to be involved in this syndrome because of its highly frequent use in the dams of affected calves. In this study, we show that BNP is an alloimmune disease, as we reproduced the signs by transferring serum Abs from vaccinated BNP dams into healthy neonatal calves. Ab specificity was strongly associated with the presence of allogeneic MHC class I Abs in the dams. MHC class I staining was also observed on Madin-Darby bovine kidney cells, a cell line related to the one used to produce the vaccine Ag. Our report emphatically demonstrates that alloimmunization against MHC class I is associated with a substantial risk of developing cytopenia-associated syndromes in neonates when a cell line of the same species is used to produce an inactivated vaccine injected into the mother.

A signature of maternal anti-fetal rejection in spontaneous preterm birth: chronic chorioamnionitis, anti-human leukocyte antigen antibodies, and C4d

Background

Chronic chorioamnionitis is found in more than one-third of spontaneous preterm births. Chronic chorioamnionitis and villitis of unknown etiology represent maternal anti-fetal cellular rejection. Antibody-mediated rejection is another type of transplantation rejection. We investigated whether there was evidence for antibody-mediated rejection against the fetus in spontaneous preterm birth.

Methods and Findings

This cross-sectional study included women with (1) normal pregnancy and term delivery (n = 140) and (2) spontaneous preterm delivery (n = 140). We analyzed maternal and fetal sera for panel-reactive anti-HLA class I and class II antibodies, and determined C4d deposition on umbilical vein endothelium by immunohistochemistry. Maternal anti-HLA class I seropositivity in spontaneous preterm births was higher than in normal term births (48.6% vs. 32.1%, p = 0.005). Chronic chorioamnionitis was associated with a higher maternal anti-HLA class I seropositivity (p<0.01), significant in preterm and term birth. Villitis of unknown etiology was associated with increased maternal and fetal anti-HLA class I and II seropositivity (p<0.05, for each). Fetal anti-HLA seropositivity was closely related to maternal anti-HLA seropositivity in both groups (p<0.01, for each). C4d deposition on umbilical vein endothelium was more frequent in preterm labor than term labor (77.1% vs. 11.4%, p<0.001). Logistic regression analysis revealed that chronic chorioamnionitis (OR = 6.10, 95% CI 1.29–28.83), maternal anti-HLA class I seropositivity (OR = 5.90, 95% CI 1.60–21.83), and C4d deposition on umbilical vein endothelium (OR = 36.19, 95% CI 11.42–114.66) were associated with preterm labor and delivery.

Conclusions

A major subset of spontaneous preterm births has a signature of maternal anti-fetal cellular and antibody-mediated rejections with links to fetal graft-versus-host disease and alloimmune reactions.

Neonatal alloimmune thrombocytopenia caused by anti-HLA-A24 alloantibodies

Neonatal alloimmune thrombocytopenia (NAIT) occurs as a result of maternal alloimmunization against paternally inherited antigens on foetal platelets. Platelets express platelet specific antigens (HPA) along with human leucocyte antigens (HLA) class I. Although anti-HLA class I antibodies are often detectable in pregnant women, their role in NAIT is considered controversial. We report a case of NAIT where the most sensitive serological analysis and molecular methods could not detect platelet specific antibodies. Only HLA incompatibility and presence of anti-HLA-A24 antibodies in both the mother's and the newborn's serum were proven.

CONCLUSION

This case supports the idea that some anti-HLA class I antibodies could cause NAIT.

Neonatal alloimmune thrombocytopenia associated with maternal-fetal incompatibility for blood group B

BACKGROUND

Blood group A and B antigens are expressed only weakly on platelets (PLTs) of most individuals but are very strongly expressed on PLTs from approximately 1 percent of normal subjects (Type II high expressers). The implications of this trait for transfusion medicine are undefined.

STUDY DESIGN AND METHODS

A family was studied in which two Group B infants were born with neonatal thrombocytopenia, whereas a third infant whose blood group was A(2) had a normal PLT count at birth.

RESULTS

Serologic studies demonstrated a maternal antibody that reacted strongly with PLTs from the father and the two group B children in flow cytometry and with GPIIb/IIIa from their PLTs in solid-phase assays. No PLT-specific antibodies were detected in maternal serum sample, but it contained a high-titer immunoglobulin G antibody specific for blood group B. All PLT-reactive antibody in the mother's serum was removed by absorption with pooled, washed group A and B red cells (RBCs). Studies with monoclonal anti-B and measurement of serum B-glycosyltransferase activity showed that the father and both group B children were Type II high expressers of blood group B.

CONCLUSIONS

The findings indicate that high-titer blood group antibodies acquired from the mother can cause thrombocytopenia in infants possessing the Type II high-expresser phenotype despite competition for antibody binding by blood group antigens expressed on RBCs and other tissues.

Blood product replacement in the perinatal period

OBJECTIVE

In this article, we will describe some of the special compatibility testing procedures and blood component preparation and modification techniques used in intrauterine and neonatal transfusion medicine. We also will review the transfusion therapy used in hemolytic disease of the fetus and newborn (HDFN) and fetal and neonatal alloimmune thrombocytopenia (FNAIT).

FINDING

Transfusion therapy in the fetus and neonate requires blood typing and compatibility testing techniques not routinely used for adults. These include: cord blood testing, special attention to the volume and speed of infusion, cytomegalovirus risk reduction, and routine irradiation of cellular blood components. The treatment of HDFN and FNAIT involves phenotyping and/or genotyping of fetal and paternal red blood cells and platelets. In FNAIT, platelet products are chosen based on the absence of platelet-specific antigens.

CONCLUSION

Fetal and neonatal transfusion medicine require special attention to the unique anatomic and physiologic features of early human development.