Genotyping of Human Platelet Antigens by BeadChip Microarray Technology

Human platelet antigen (HPA) typing plays a critical role in the diagnosis of fetal/neonatal alloimmune thrombocytopenia, and the prevention of posttransfusion purpura and refractoriness to platelet transfusions. The recent development of high-throughput genotyping methods, allowing simultaneous genotyping of as many as 17 HPAs, is of utmost interest for saving time and money. Here, we describe a microarray technology named "BeadChip," designed for HPA-1 to -9, -11, and -15 genotyping of up to 96 individuals, in approximately 5 h. This technology was used to study allele frequencies in Brazilian blood donors, considering the heterogeneous ethnic composition.

The gray platelet syndrome: Clinical spectrum of the disease

The gray platelet syndrome (GPS) is a rare inherited disorder of the megakaryocyte (MK) lineage. Thrombocytopenia and enlarged platelets are associated with a specific absence of alpha-granules and their contents. GPS patients exhibit much heterogeneity both in bleeding severity and in their response to platelet function testing. A unique feature is that proteins endogenously synthesised by megakaryocytes (MK) or endocytosed by MK or platelets fail to enter into the secretable storage pools that characterise alpha-granules of normal platelets. Although the molecular basis of the disease is unknown, evidence suggests that alpha-granules simply fail to mature during MK differentiation. One result is a continued leakage of growth factors and cytokines into the marrow causing myelofibrosis. While for some patients platelet function may be only moderately affected, for others thrombin and/or collagen-induced platelet aggregation is markedly modified and an acquired lack of the GPVI collagen receptor has been reported. In this review, we document the clinical and molecular heterogeneity in GPS, a unique disease of the biogenesis of platelet alpha-granules and of the storage of growth factors and secretable proteins.

Is factor V Leiden a risk factor for thrombotic microangiopathies without severe ADAMTS 13 deficiency?

About 60% of patients diagnosed with acute thrombotic thrombocytopenic purpura (TTP) display a severe ADAMTS13 deficiency. Recently, Raife et al. concluded from a small case series, that factor V Leiden (FVL) might constitute a risk factor for acute thrombotic microangiopathy (TMA) without severe ADAMTS13 deficiency. Therefore, we determined ADAMTS13 activity and FVL carrier-ship in 256 consecutive patients presenting with various forms of acute TMA, including patients diagnosed with TTP or hemolytic-uremic syndrome (HUS). The overall prevalence of FVL was 8.2% (6.25% among patients diagnosed with TTP, and 9% among those with HUS) concordant with the FVL prevalence reported in Europe. FVL was present in 9.9% of patients with ADAMTS 13 activity < 10% and in 9.7% of those with normal ADAMTS13 activity (> 50%). We conclude that FVL is not more prevalent in TMA patients without as compared to those with severe ADAMTS13 deficiency. The prevalence of FVL carriers in certain HUS subgroups (HUS with ADAMTS 13 activity > 50%) reaching 12.3% suggests that a contributory role of FVL in the pathogenesis of defined forms of HUS needs further study.

Transforming growth factor-beta1 (TGF-beta1) induces thrombopoietin from bone marrow stromal cells, which stimulates the expression of TGF-beta receptor on megakaryocytes and, in turn, renders them susceptible to suppression by TGF-beta itself with high specificity

The present study was designed to test the concept that platelets release a humoral factor that plays a regulatory role in megakaryopoiesis. The results showed that, among various hematoregulatory cytokines examined, transforming growth factor-beta1 (TGF-beta1) was by far the most potent enhancer of mRNA expression of bone marrow stromal thrombopoietin (TPO), a commitment of lineage specificity. The TPO, in turn, induced TGF-beta receptors I and II on megakaryoblasts at the midmegakaryopoietic stage; at this stage, TGF-beta1 was able to arrest the maturation of megakaryocyte colony-forming units (CFU-Meg). This effect was relatively specific when compared with its effect on burst-forming unit-erythroid (BFU-E) or colony-forming unit-granulocyte-macrophage (CFU-GM). In patients with idiopathic thrombocytopenic purpura (ITP), the levels of both TGF-beta1 and stromal TPO mRNA were correlatively increased and an arrest of megakaryocyte maturation was observed. These in vivo findings are in accord with the aforementioned in vitro results. Thus, the results of the present investigation suggest that TGF-beta1 is one of the pathophysiological feedback regulators of megakaryopoiesis.

Low prevalence of a polymorphism of platelet membrane glycoprotein Ib beta associated with neonatal alloimmune thrombocytopenic purpura in Asian populations

Iy alloantigen system is the first polymorphism of platelet glycoprotein Ib beta reported to cause neonatal alloimmune thrombocytopenic purpura. We investigated the allelic frequency of Iy alloantigen among Japanese and Korean populations by polymerase chain reaction-restriction fragment length method to determine the possibility of alloimmunization against Iy. Two hundred and nine Japanese and 97 Korean subjects were examined. All 306 individuals were homozygous for glycine at amino acid position 15 and negative for Iy. The allelic frequency of Iy in these populations was calculated to be less than 0.0016. Alloimmunization associated with Iy antigen in Asian populations seems unlikely from these results.

Neonatal alloimmune thrombocytopenia associated with anti-human platelet antigen-3a antibody

A sister and brother with neonatal alloimmune thrombocytopenic purpura (NAITP) caused by maternal anti-human platelet antigen (HPA)-3a are reported. The children had transient severe thrombocytopenia in the newborn period, and were treated with intravenous gamma-globulin and platelet concentrates from random donors. Although the sister had intracranial hemorrhage on day 2 postnatally, the development of the child has been normal and no neurological sequelae have been observed. The brother only had bloody stool when the platelet count was low, and did not have severe hemorrhagic manifestations. The diagnosis of NAITP was made by the sera from the mother, which contained anti-HPA-3a antibody directed against platelets of the children. The rate of recurrence might be high in this family, because the father of the patients was found to be homozygous for the HPA-3a gene.

Micromegakaryocytes in a patient with partial deletion of the long arm of chromosome 11 [del(11)(q24.2qter)] and chronic thrombocytopenic purpura

Thrombocytopenia or pancytopenia is frequently reported in patients with partial 11q deletion but there are no reports on bone marrow morphology of these patients. We report on a patient with partial deletion of the long arm of chromosome 11 [del(11)(q24.2qter)] and its classical clinical manifestations including chronic thrombocytopenic purpura in whom micromegakaryocytes were found in the bone marrow aspirate. This is the first report of the presence of micromegakaryocytes in the bone marrow of a patient with 11q deletion. Accurate examination of the bone marrow of other patients with the 11q deletion may clarify whether the observation of micromegakaryocytes is common in these patients. Micromegakaryocytes may indicate a defect of development. Two genes for two DNA binding proteins that are likely to be involved in hematopoiesis map in the 11q region: Ets-1, that maps to 11q24, close to D11S912, and the nuclear-factor-related-kB gene that maps to 11q24-q25. It is possible that these genes, when present in only one copy, result in thrombocytopenia or pancytopenia as observed in this patient.

Molecular genetics of human platelet antigens

The purpose of this article is to review the molecular genetics of human platelet antigens, the application of molecular biological techniques to detect mutations underlying polymorphisms and the importance of these techniques for clinical medicine of immune-mediated platelet destruction. Review articles, original papers and preliminary (unpublished) observations from our own laboratory are the main source for this article. The nomenclature and phenotype frequency of the platelet alloantigens in different ethnic groups are described. Recent molecular biological advances are also reviewed. It appears that the human platelet antigen systems are due to single base pair substitutions. These mutations create or are responsible for the loss of a target site for a restriction enzyme in one of the alleles. Thus, DNA typing by polymerase chain reaction and subsequently allele-specific restriction enzyme analysis (PCR-ASRA) can be performed.

Molecular analysis of human platelet antigen system 1 antigen on single cells can be applied to preimplantation genetic diagnosis for prevention of alloimmune thrombocytopenia

OBJECTIVE

Our purpose was to develop a molecular assay to determine the human platelet antigen system 1 status on single nucleated cells, including human blastomeres.

STUDY DESIGN

Eighty single cultured lymphoblasts of known human platelet antigen system 1 genotype and 24 media blanks were mixed in blinded fashion. Amplification of a 246 bp deoxyribonucleic acid fragment and subsequent Nci I restriction digestion were performed to distinguish human platelet antigen system 1a from 1b alleles. Specificity and sensitivity of the technique were determined. Eight blastomeres were also tested.

RESULTS

Deoxyribonucleic acid amplification at the human platelet antigen system 1 locus was successful in 95% of the reactions. No media blanks showed amplified deoxyribonucleic acid. The diagnosis was correct in all homozygous human platelet antigen system 1a or 1b cells; three of 23 heterozygous cells amplified but failed to digest with Nci I. Overall specificity was 95%. All blastomeres successfully amplified.

CONCLUSIONS

The human platelet antigen system 1 status determination is reliable from a single cell and can be used for preimplantation genetic diagnosis for the prevention of alloimmune thrombocytopenia.

Acquired amegakaryocytic thrombocytopenic purpura with a Philadelphia chromosome

A 30-year-old Chinese man with acquired amegakaryocytic thrombocytopenic purpura (AATP) and a Ph chromosome is reported. At presentation, he had severe thrombocytopenia resulting in epistaxis, gingival bleeding, and ecchymoses, while other hematologic values were within the normal range. Bone marrow aspiration showed no megakaryocytes, with a normal appearance of erythroblastic and granulopoietic series. He failed to respond to prednisone treatment, and underwent a progress from isolated thrombocytopenia to full pancytopenia. At last he died of spontaneous intracranial hemorrhage. An in vitro culture for granulocyte-macrophage precursors showed very few colonies. Karyotypic analysis revealed a standard Ph chromosome translocation, t(9;22)(q34;q11), in the majority of bone marrow cells. Southern blot analysis using a 3' bcr-HE probe didn't detect a rearrangement within the bcr DNA sequence. This patient, in fact, was a myelodysplastic disorder, initially presenting as AATP. The diagnosis of chronic myelogenous leukemia was excluded on the basis of clinical and hematologic findings. The heterogeneity of Ph chromosome in myelodysplastic syndrome is discussed.

Neonatal alloimmune thrombocytopenic purpura associated with sensitization against the platelet-specific antigen Yuk(a)

We report a Japanese newborn who developed alloimmune thrombocytopenia by the antibodies to the newly discovered platelet antigen Yuk(a). The infant recovered uneventfully in 10 days without specific treatment. Antiplatelet alloantibodies in the patient were IgG class detected by mixed passive hemagglutination (MPHA). Family study showed that Yuk(a) antigen was inherited as an autosomal dominant trait. Cases with Yuk(a)-associated alloimmune thrombocytopenia are reviewed.

Analyses of thrombocytopenia in idiopathic thrombocytopenic purpura-prone mice by platelet transfer experiments between (NZW x BXSB)F1 and normal mice

Male (NZW x BXSB) F1 (W/B F1) mice, which develop lupus nephritis, myocardial infarction, and thrombocytopenia, showed reduced platelet lifespan (PLS) and increased platelet-associated antibody (PAA) values. There were statistically significant correlations between the increase in PAA values and either the reduction in PLS or the decrease in platelet counts. This and the results of platelet transfer experiments between old male W/B F1 mice and either female W/B F1 or normal BALB/c mice indicate that PAAs on the platelet surface play a crucial role in the destruction of platelets in W/B F1 mice. The mechanism of thrombocytopenia observed here appears similar to that of human idiopathic thrombocytopenic purpura (ITP). Therefore, we think that W/B F1 mice are a potentially useful animal model for investigating the effectiveness and mode of action of therapeutic agents in human ITP, and that they may provide additional information on the basic mechanisms of this autoimmune phenomenon.

Detection by in situ hybridization of HIV I RNA in spleens of HIV I sero-positive patients with thrombocytopenic purpura

In situ hybridization with a 3H labelled probe on cryosections from 6 spleens of HIV I sero-positive patients with thrombocytopenic purpura showed the presence of HIV RNA in 4 of the 6 spleens at the follicular hyperplasia stage. Two patterns of hybridization were observed: first, a diffuse autoradiographic signal, displaying an irregular network, detected in 1 or 2 germinal centres (GC) per section (17%); secondly, the presence of very few distinct radioactive cells in the labelled GC. A similar pattern was observed in an ARC (Acquired immunodeficiency syndrome-Related Complex) lymph node, but with a more intense and frequent hybridization signal. These results indicate that the spleens, like the lymph nodes, are involved in the course of HIV infection but with a less intense tissue-virus interaction, which may explain the minor morphological changes observed in the spleens. In addition, a careful examination of the lymph node tissue indicated that lymphocytes are the predominant cell type infected with the virus. As for the follicular dendritic cells (FDC), a similarity of the hybridization signal observed in the GC and in vitro HIV infected cells suggests that the FDC could also be sensitive to the virus.

Biologic false-positive serologic tests for syphilis and other serologic abnormalities in autoimmune hemolytic anemia and thrombocytopenic purpura

Autoimmune hemolytic anemia (AIHA), the first autoimmune disease to be recognized, is a manifestation of defective immune regulation. Although often associated with a lymphoid neoplasm or an overt immunologic disorder, AIHA frequently appears without apparent cause. Many patients with the "idiopathic" disease have been found to have various immunologic abnormalities in addition to the antibodies reacting with red cells. Although familial AIHA is uncommon, other autoimmune diseases and serologic abnormalities have been encountered in relatives of numerous patients. Few detailed family studies have been performed, but the available data suggest that predisposition to AIHA and to the associated immunologic disorders often is genetically transmitted. Less information is available about autoimmune thrombocytopenic purpura, in part because of the historic difficulty in recognizing autoantibodies that react with platelets. However, there is good evidence for genetically determined predisposing factors in some cases. Using the BFP reaction as an indicator, we add to the evidence that AIHA and autoimmune thrombocytopenia, like SLE, tend to occur in persons with a long-standing occult immunologic defect that often has a genetic basis. In our studies, 11 patients with AIHA or ITP had BFP reactions. The serologic abnormality in 4 had been known to precede the blood disorder by 6 to 44 years. Five of the patients had an additional disease believed to have an immunologic pathogenesis. Serologic abnormalities apart from the BFP reaction and the red cell or platelet antibodies were demonstrated in 9. Autoimmune diseases or serologic changes are known to have affected relatives of 5 patients, including 4 who had 1 or more relatives with BFP reactions. Serologic tests for syphilis were negative in 2 sibs with autoimmune thrombocytopenic purpura whose father had a chronic BFP reaction and thyroiditis, but all 3 had low levels of IgA and IgM. Lymphoproliferative disorders appeared in 3 of the patients with BFP reactions, and 2 had relatives with lymphoid neoplasms. A lymphoma occurred in a woman with cold agglutinin disease 21 years after the discovery of the erythrocyte antibody. Our observations support the view that an abnormality of cells of the immune system, often genetically determined, may predispose to serologic changes, immune deficiency, autoimmune diseases and neoplasia.

Clonal B-cell proliferation in an infant with congenital HIV infection and immune thrombocytopenia

An infant with congenital human immunodeficiency virus (HIV) infection had immune thrombocytopenic purpura (ITP) develop at four months of age. A bone marrow aspirate had normal results in morphologic characteristics and cellularity. Flow cytometry analysis of the marrow cells showed that the predominant cell in the "lymphocyte" cluster was of B-lineage and common acute lymphocytic leukemia antigen (CALLA) positive. Southern blot analysis of marrow DNA demonstrated gene rearrangements in both the immunoglobulin (Ig) heavy chain and kappa light chain loci, confirming the presence of a clonal B-cell lymphoid proliferation. At one year of age the patient is clinically well without evidence of malignant lympho-proliferative disease. This case exemplifies a limited clonal B-cell expansion in the bone marrow of a patient with HIV infection and a benign hematologic condition.