Neonatal Alloimmune Thrombocytopenia in Taiwan Due to an Antibody against a Labile Component of HPA-3a (Bak)

We report on two siblings who developed severe neonatal alloimmune thrombocytopenia (NAIT) due to an alloantibody against a labile component or components of the HPA-3a (Bak^a) antigen. The antibody reacted only with fresh, unfixed platelets by the solid-phase red cell adherence test, immunofluorescence test and mixed passive haemagglutination test. In the latter method, weakly fixed platelets also gave a weak positive reaction. Monoclonal-antibody-specific immobilization of platelet antigens and immunoblotting tests gave negative results. Our findings may possibly help to explain why in some cases of NAIT no platelet-specific antibody is demonstrable in tests with fixed or solubilized platelets.     

Severe Neonatal Alloimmune Thrombocytopenia due to Anti-HPA-3a

Background and Objectives: Neonatal alloimmune thrombocytopenia is usually attributable to HPA-la antibodies. We report a case of parental platelet antigen incompatibility associated with a severe neonatal thrombocytopenia secondary to alloimmunization to HPA-3a. Materials and Methods: Platelet antibodies were detected by the monoclonal antibody-specific immobilization of platelet antigens, genotyping of the platelets by PCR, and HLA typing by serologic procedures and PCR. Results: Genotyping of maternal and paternal platelets confirmed the incompatibility in the HPA-3a system. It is noteworthy that the mother is of the HLA type DRB3*0101, is ABO-incompatible with her husband, and also has HLA class I antibodies. Conclusion: Severe neonatal thrombocytopenia associated with HPA-3a alloimmunization is infrequent and all the factors mentioned above could have played a role in the severity of the disease.     

Neonatal Alloimmune Thrombocytopenia due to Anti-HPA-1b (PLA2) (Zwb)

Background : Neonatal alloimmune thrombocytopenia is a rare condition due to passively acquired maternal antibodies directed against paternal platelet antigens inherited by the infant. Only 5 cases have been reported due to antibodies against HPA-lb (PL^A2) (Zw^b). Case Report : We report a case of neonatal alloimmune thrombocytopenia due to anti-HPA-lb in the second pregnancy of a 26-year-old Caucasian female. The male infant was treated with a 5-day course of intravenous immunoglobulin without complications. We report the HLA phenotype of the infant's mother and summarize the previous case reports due to anti-HPA-lb. Conclusion : Based on this case and a review of the literature, intravenous immunoglobulin as well as random donor exchange transfusion and random donor platelet transfusions are effective in the treatment of neonatal alloimmune thrombocytopenia due to anti-HPA-lb. Obvious associations between HLA alleles and sensitization to HPA-lb have not been elucidated.     

Brb, a Platelet Alloantigen Involved in Neonatal Alloimmune Thrombocytopenia

Serum from a pregnant woman with the May-Hegglin anomaly contained a platelet-specific antibody. The serum reacted in the platelet indirect immunofluorescence test (PIIFT) with 97.6% of random donor platelets and those of the father but not with the mother's own platelets. This antibody induced a moderate thrombocytopenia in the infant that responded to infusion of intravenous immunoglobulin concentrates. The platelet phenotypes were PLA1+, Baka+, Bra+/Brb- for the mother, PLA1+, Baka+, Bra-/Brb+ for the father, and PLA1+, Bra+/Brb+ for the neonate. Analysis of the maternal serum with an immunoassay based on monoclonal antibody immobilization of platelet antigens (MAIPA) and immunoprecipitation techniques demonstrated the absence of antibodies directed against HLA class I antigens and that the antigen recognized was located on the platelet-GpIa/IIa complex. This antigen was present on 113/115 random donor platelets, in 7 of the 7 unrelated May-Hegglin platelets, and only absent in 3/24 Bra+ individuals, including the mother. No platelet-specific antibody was present in the serum of the 7 unrelated May-Hegglin subjects. The antigen recognized by this platelet-specific antibody thus meets the criteria defining the antithetic allele of Bra, i.e. the Brb alloantigen.     

Yuka, a New Platelet Antigen Involved in Two Cases of Neonatal Alloimmune Thrombocytopenia

We report a new platelet antigen (Yuka) defined by the sera of 2 mothers whose babies developed alloimmune thrombocytopenia. These antiplatelet antibodies were IgG detected by Mixed Passive Hemagglutination (MPHA). In the study of two families, the Yuka antigen was found to be inherited as an autosomal dominant trait. The frequency of the Yuka phenotype in the Japanese population was estimated to be 1.7% (5/300).     

Blood Components – Transfusion Support in Post-Transfusion Purpura Due to HPA-1a Immunization

Post-transfusion purpura (PTP) is usually a self-limiting disease. Nevertheless, haemorrhage in these patients may be life-threatening and hence red cell transfusions may be clinically urgent. It is widely recommended that such blood be from donors who are negative for the HPA-1a platelet antigen. However, these donors are uncommon and such blood is often in short supply. We report 2 cases of PTP in which either filtered leucodepleted red cells or washed red cells were transfused in combination with high-dose intravenous immunoglobulin (both cases) and HPA-1a negative platelets (1 case) to good effect.     

Neonatal Immune Thrombocytopenia Due to Allo-or Autoantibodies: Clinical and Immunological Analysis of 83 Cases

Serological and clinical data were collected in 59 cases of suspected neonatal alloimmune thrombocytopenia (NAIT) and in 24 thrombocytopenic newborn of mothers with presumed autoimmune thrombocytopenic purpura (AITP). In the NAIT group, the anti-HPA-la (anti-Zw(a), anti-Pl(AI)) and the anti-HPA-5b (anti-Br(a)) account for about 68% and 11% respectively of the serologically proven cases. The findings of a high frequency (45%) of maternal anti-HLA antibodies in the HPA-la positive group, suggests an association of NAIT and maternal HLA alloimmunisation. In the AITP group, 83% of the women had increased amounts of platelet-associated IgG (PAIgG) with a predominance of IgGl and IgG3. In one third of the cases, maternal circulating autoantibodies, mainly against GPIIb/IIIa and GPIb/IX, were found. The finding of circulating platelet autoantibodies in 16% of the HPA-la positive non-thrombocytopenic mothers makes it possible that these women are suffering from compensated AITP. In the AITP group, neither maternal platelet count, maternal increased amounts of PAIgG, the pattern of PAIgG subclasses, circulating autoantibodies, the specificity of the autoantibodies nor maternal splenectomy could be used to predict the severity of the neonatal thrombocytopenia. In the NAIT group, intracerebral hemorrhage occured in 10% and in the AITP group in 4%.     

Another Example of Isoimmune Neonatal Neutropenia Due to Anti-Na1

Abstract. A review of the present knowledge of transplacental transmission of anti-neutrophil antibodies is given. A family in which one, possibly two of the three children had severe neutropenia after birth with subsequent infections, is described. An agglutinating antibody, directed against the neutrophil-specific antigen NA 1, was demonstrated in the maternal serum. The father and all three children were NA 1-positive. This case is another example of isoimmune neonatal neutropenia due to anti-NA 1 antibodies.     

Neonatal Thrombocytopenia in HLA-DR, -DQ, -DP-Typed Mother due to Rare Anti-HPA-1b (PLA2) (Zwb) Fetomaternal Immunization

A new case of rare neonatal alloimmune thrombocytopenia, due to an IgG anti-HPA-1b in a mother HPA-1 (a+, b-), was diagnosed using monoclonal antibody-specific immobilization of platelet antigens. Clinically, it was similar to the 2 previously reported observations and confirmed that, in this particular case of anti-HPA-1b, the treatment with random platelet pools may be as effective as selected single-donor platelet units when maternal platelets are unusable. The HLA-DR, -DQ, -DP genotypes of the family were obtained by PCR-SSO. The mother's typing, compared to the HLA-DR of the 6 similar cases reported in Europe, suggests that a combined effect of two rare HLA haplotypes might enhance this immunization.     

Efficacy of HPA-1a (PlA1)-negative platelets in a patient with post-transfusion purpura

Post-transfusion purpura (PTP) is a rare form of alloimmune thrombocytopenia that is self-limited but which carries a 10-15% mortality related to fatal hemorrhage. Immunomodulatory therapies such as plasmapheresis and intravenous immunoglobulin G (IVIg) can shorten the duration of thrombocytopenia. However, in a bleeding patient with PTP, more urgent therapy may be required. Textbooks of hematology [1-3] as well as reports in the literature [4,5] suggest that patients do not respond to platelet transfusions. We report a case of PTP in a patient homozygous for HPA-1b who suffered an intracranial hemorrhage. The patient was treated with IVIg and plasmapheresis. Because of her life-threatening bleeding, we also transfused the patient with HPA-1a-negative platelets. These transfusions consistently resulted in transient improvements in her platelet counts and may have limited the degree of intracranial bleeding. Our experience suggests that transfusion of platelets that lack the offending epitope in patients with PTP may be efficacious.     

Platelet HPA-1 a/HPA-1 b polymorphism and the risk of periprocedural myocardial infarction in patients undergoing elective PCI

Abstract

Periprocedural myocardial infarction (PMI) represents a relatively common complication of percutaneous coronary intervention (PCI) and large interests have been focused on platelets in order to prevent such a complication. The single nucleotide polymorphism Leu33Pro of platelet glycoprotein IIIa has been related to an increased platelet reactivity, a lower response to antiplatelet agents and higher risk of stent restenosis. Therefore, aim of our study was to evaluate the impact of this polymorphism on PMI in elective patients undergoing PCI. Our population is represented by 422 consecutive patients with cardiac biomarkers within normality undergoing elective PCI. We measured cardiac biomarkers (CK–MB and Troponin I) at baseline, and 8, 24 and 48 hours after the procedure. For all subjects, we performed genetic analysis to assess the presence of Leu33Pro polymorphism. A total of 136 patients (32.2%) were polymorphic. Those patients were younger (p?=?0.03) and more often dislypidemic (p?=?0.01). Angiographic features did not differ according to genetic status. Pharmacological treatment pre and during angioplasty was similar. PCI-related complications did not differ according to genotype, with the only exception of higher rate of distal embolization in polymorphic patients. However, Leu33Pro polymorphism was not associated with increased risk of periprocedural myonecrosis and PMI even after correction for baseline differences, (respectively OR?=?1.22 [0.81–1.84], p?=?0.34 for myonecrosis and OR?=?1.66 [0.85–3.23]; p?=?0.14 for PMI). At subgroup analysis, the Leu33Pro substitution was associated with higher risk of PMI only among diabetics (adjusted OR?=?4.46 [1.12–17.76], p?=?0.03). Among patients undergoing elective PCI, the polymorphism Leu33Pro of platelet glycoprotein IIIa is associated with increased risk of PMI only in diabetic patients.     

Genetic typing of human platelet antigen 1 (HPA-1) by oligonucleotide ligation assay in a specific and reliable semi-automated system

Genotyping of platelet alloantigens with the possibility of using any type of cellular material as a source of DNA has become a preferred procedure, particularly in thrombocytopenic patients when platelet counts are too low for phenotyping. Recently human platelet antigen 1 (HPA-1) has been identified as an inherited risk factor for coronary thrombosis. The different detection methods currently used have disadvantages for large-scale DNA diagnosis, including the need for electrophoresis (allele-specific restriction enzyme analysis, amplification with sequence-specific primers) or the potential risk of reduced specificity (allele-specific oligonucleotide hybridization). In this report we describe the adaptation of an automated oligonucleotide ligation assay to genotype HPA-1 in polymerase chain reaction (PCR)-amplified DNA samples. HPA-1a and HPA-1b phenotypes corresponded to the results of the different genotyping assays. The genotypes determined with the ELISA-based PCR-oligonucleotide ligation assay were in 100% concordance with the results obtained by conventional allele-specific restriction enzyme site analysis and PCR amplification with sequence-specific primers. The automated oligonucleotide ligation assay provides a rapid, reliable, nonisotopic method to genotype human platelet antigens that can rapidly be applied to large population screening.     

Characteristics of Different Rhesus Alloantibodies in Lymphocyte Dependent (K Cell) Cytotoxicity to Human Erythrocytes

The property of rhesus alloantibodies to elicit antibody-dependent, cell-mediated cytotoxicity (ADCC) against target erythrocytes carrying various Rh genotypes was studied. The killer activity of normal peripheral lymphocytes on human erythrocyte target cells carrying the appropriate antigens elicited by alloantisera was measured by 51Cr release at 18 h. There was no correlation between ADCC and antibodies directed to the antigens present on the surface of different genotypes of Rh-positive red blood cells. The agglutinin titre of different Rh antibodies showed no correlation with the level of ADCC although the degree of cellular cytotoxicity was different with different anti-D sera. Anti-C + D+ E antibody caused higher ADCC than anti-C + D and the lowest cytotoxicity was observed with anti-D and anti-D+ E. This raised the possibility that ADCC was elicited by antibodies directed to other specificities. K cell lysis of human red cells by human peripheral blood lymphocytes in vitro suggests that a similar mechanism may operate in vitro in the destruction of erythrocytes coated by allo or autoantibodies.     

Elevated lipoprotein(a) levels and homozygous human platelet antigen 1b (HPA-1b) genotype are risk factors for intrauterine growth restriction (IUGR)

The risk of premature manifestation of cardiovascular disease is higher in women after a maternal placental syndrome, especially with a history of fetal IUGR. Aim of the study was to assess hereditary risk factors for arterial thrombosis as risk factors for IUGR. 183 women with fetal IUGR birth weight below the 10th percentile for gestational age and 300 control women were evaluated using a case–control design. In 121 of the 183 women, the newborns’ birth weight was below the 5th percentile for gestational age. A risk association could be shown for homozygous human platelet antigen 1b genotype (OR 3.2, P = 0.038) in women with a history for a newborn’s birth weight below the 5th percentile. Elevated levels of lipoprotein(a) (>0.7 g/l [95 % percentile], OR 2.9, P = 0.048) also represent a risk association in the same group of subjects. So did elevated levels of lipoprotein(a) (>0.7 g/l [95 % percentile], OR 3.4, P = 0.015) in women with a history for a newborn’s birth weight below the 10th percentile. Risk factors of arterial thrombosis such as platelet receptor genotypes associated with platelet thrombogenicity and elevated levels of lipoprotein(a) might be of importance in the pathogenesis of IUGR.