Identification of Bakb, a new platelet-specific antigen associated with posttransfusion purpura

Baka is a platelet alloantigen whose putative allele, Bakb, has not been identified previously. By using a serum, "Har," obtained from a patient with posttransfusion purpura, we describe the platelet alloantigen Bakb. The Har serum reacted with an NP-40-extractable platelet membrane protein of 142 kd with mobility similar to platelet glycoprotein IIb alpha. We found that the antigen recognized by the Har serum is inherited in an autosomal dominant mode with an apparent gene frequency of .39. Chi-square analysis of observed and expected phenotype frequencies indicated that serum Har recognizes Bakb, the anticipated allele of Baka. Our findings provide new evidence for polymorphism of glycoprotein IIb and for the association of posttransfusion purpura with alloimmunization to determinants on this glycoprotein.

Prolonged neonatal alloimmune thrombocytopenic purpura associated with anti-Bak(a). Two cases in siblings

Two cases of prolonged neonatal alloimmune thrombocytopenic purpura in siblings due to anti-Bak(a) are reported. The first case was complicated by an intracranial hemorrhage due to severe thrombocytopenia, but the second case had no untoward complications. Delivery by cesarean section and immediate platelet support from "compatible" (nonmaternal) donors may have contributed to the more favorable outcome in the second case. An analysis of the gene frequencies of platelet-specific antigens suggests that factors other than the potential for maternal exposure to antigen determine the incidence of affected births. Knowledge of gene frequencies may, however, permit a priori prenatal calculation of the probability of an affected birth for couples with a previously affected child even if the genotype of the father is unknown.

Neonatal alloimmune thrombocytopenic purpura

We reviewed 58 literature reports of neonatal alloimmune thrombocytopenic purpura (NAITP). The mortality rate was 9%. The total incidence of suspected intracranial hemorrhage was 28%. We reviewed 17 sibship cases for the relation of birth order to treatment and outcome. Among firstborn affected infants (n = 17) the mortality rate and incidence of central nervous system sequelae were 24 and 47%, respectively, compared to rates of 5 and 15%, respectively, in their younger affected siblings (n = 20). The improved outcome in the latter group appeared to be related to more frequent cesarean section delivery and more frequent and earlier use of corticosteroids and maternal platelet transfusions in the neonate. Sensitive assays of maternal platelet alloantibody are now available, but they lack specificity for NAITP affecting the current gestation. There are two reports in which sensitive assays revealed rising titers of maternal platelet alloantibody during advancing gestation. We propose further study to determine if this is specific for the antepartum diagnosis of NAITP.

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).

HLA antigens, blood groups and immunoglobulin levels in idiopathic thrombocytopenic purpura

Thirty-three patients with idiopathic thrombocytopenic purpura (ITP) were tested for HLA-A, B and C antigens, platelet antibodies, immunoglobulin levels and ABO blood groups. With one exception, ITP proved not to be significantly associated with the HLA antigens studied; an increased frequency of HLA-A28 was found in chronic ITP patients (50 vs. 18.7% in the control population). An increased incidence of blood group A was found in ITP patients (64 vs. 37.98% in the control population), especially in those with acute ITP (84.7%). A significant reduction of IgG levels was noted in patients with chronic ITP, while below-normal levels of IgA were found in both chronic and acute ITP patients. There was no difference in levels of IgM. Circulating platelet isoantibodies were demonstrated in 67.6% of the ITP patients. No correlation was demonstrated between the presence of platelet antibodies, immunoglobulin levels of HLA antigens.

Idiopathic thrombocytopenic purpura in two elderly siblings

To our knowledge, only six families with familial idiopathic thrombocytopenic purpura (ITP) have been described in the literature. We encountered two elderly siblings with ITP, which normally occurs only in younger persons. It has been clearly demonstrated that ITP is an autoimmune disorder, and there is some evidence that it reflects an inherited immunodeficiency.

Elevation of platelet associated antibody levels in patients with chronic idiopathic thrombocytopenic purpura expressing the B8 and/or DR3 allotypes

The HLA type DR3 was present in 11 of 26 patients with Chronic Idiopathic Thrombocytopenic Purpura (ITP), a significantly increased frequency (p less than 0.05). Levels of platelet associated immunoglobulin M(PAIgM) were significantly higher in the B8 and/or DR3 positive group of chronic ITP patients than in the B8 DR3 negative patients despite similar clinical outcomes. Other immunologic parameters assessed, including serum immunoglobulin levels, rate of catabolism of transfused IgG, and antibody coated autologous red cell clearances were similar for both groups. These results suggest that there is an immunobiologic abnormality associated with the B8 DR3 allotypes which may result in a predisposition not only to chronic ITP, but also to a significant increase in PAIgM. These results are in accord with studies linking autoantibody with B8 DR3.

Neonatal alloimmune thrombocytopenic purpura and congenital porencephaly in two siblings associated with a "new" maternal antiplatelet antibody

We report a brother and sister, both of whom have porencephaly, hydrocephalus, optic atrophy, severe mental retardation, and spastic quadriplegia. In the younger child, abnormal intracranial structure was demonstrated by sonography at 32 weeks' gestation and was suspected earlier. Both children had transient severe thrombocytopenia as newborns. The mother is healthy and has never had purpura or other bleeding symptoms. However, her serum was found to react strongly with platelets from the father and from both children. The antibody in the mother's serum is platelet-specific but does not appear to be directed against any of the known antigens associated with neonatal alloimmune thrombocytopenic purpura (NATP) in other families, including PlA1, PlE2, or Baka. Although the mother's serum reacts with platelets from all 47 unrelated normal donors tested and from both the mothers and the fathers of 17 other children with suspected NATP, it does not react with her own platelets or with platelets from a patient with Glanzmann's thrombasthenia. These observations suggest that the serum from this woman identifies a previously undescribed high-frequency platelet-specific alloantigen and that sensitization to this determinant caused severe immune thrombocytopenia in both her children. It is likely that this led to intracranial hemorrhage in utero in these cases.

Evidence for the clonal origin of acquired hypomegakaryocytic thrombocytopenic purpura from a sex chromosome mosaic

Cytogenetic studies performed on a 79-year-old female presenting with clinical and hematologic features of acquired hypomegakaryocytic thrombocytopenic purpura revealed sex chromosome mosaicism in blood lymphocytes (45,X/46,XX/47,XXX). The presence of only 45,X cells in the bone marrow is consistent with a unicellular origin of acquired hypomegakaryocytic thrombocytopenia in this patient. These studies also suggest that, in some instances, this disorder may originate at the level of the pluripotent hematopoietic stem cell.

Pregnancy and delivery in Bernard-Soulier syndrome

This is the first reported case of a woman suffering from the Bernard-Soulier syndrome who terminated pregnancy and gave birth normally to a healthy child. Although a great number of platelet and fresh blood units were transfused before and after delivery, a hysterectomy was performed the next day as the only solution to stop persisting gross hemorrhage.

Fibrinogen interaction with platelet receptors

In summary: Incubation of platelets with ADP or proteolytic enzymes (chymotrypsin or pronase) results in an exposure of two classes of specific binding sites on platelet surface: low and high affinity fibrinogen receptors. Fibrinogen interaction with these receptors results in platelet aggregation. High affinity fibrinogen receptors are not exposed on thrombasthenic platelets stimulated by ADP but are rendered available on chymotrypsin-treated thrombasthenic platelets; low affinity receptors cannot be exposed by ADP or chymotrypsin on these platelets. Availability of high affinity fibrinogen receptors on thrombasthenic platelets may depend on the residual glycoprotein IIIa. Fibrinogen receptors appear to be associated with glycoproteins IIb, IIIa and a 66,000 Mr platelet membrane component that is exposed during proteolysis of platelet membranes. Some of the platelet-binding sites on the fibrinogen molecule appear to be associated with the COOH-terminal portion of the gamma chain (gamma 374-411). Additional binding sites may also be located in the COOH-terminal portion of the A alpha chain. The conformation of the fibrinogen molecule may be important in its interaction with platelets. Platelet aggregation may result from bridging platelets by fibrinogen molecule in the presence of bivalent cations. In conclusion, platelet interaction with fibrinogen is a complex process involving different binding sites of the fibrinogen molecule. Our own data and review of literature suggest that platelet-interaction with fibrinogen is of major significance in hemostasis.

[The syndrome of post-transfusion purpura]

Thrombocytopenic purpura occurred in two women aged 67 and 77 years, who earlier on had been pregnant, six and twelve days after blood transfusions. The platelet deficient phase lasted 16 and more than 50 days. Differentiation from other causes of thrombocytopenic haemorrhage was based on immunohaematologic findings. Both patients were negative for the platelet specific antigen PlA1 (Zwa). The platelet specific antibody (anti-PlA1) responsible for the purpura could be demonstrated and characterised immunologically.

Antiplatelet antibodies and platelet counts in pregnancies complicated by autoimmune thrombocytopenic purpura

In 48 pregnant women with autoimmune thrombocytopenic purpura, no consistent correlation was found between the infant platelet count and either the maternal platelet count, a previous maternal splenectomy, or maternal treatment with corticosteroids. Although the concentration of antiplatelet antibody in maternal serum frequently reflected the severity of neonatal thrombocytopenia, a number of exceptions to this observation limited the clinical usefulness of the test for individual patients. Antiplatelet antibody levels in the amniotic fluid were always low. A twin gestation in this series of patients in which one infant was thrombocytopenic and the other was not also showed that no antepartum maternal clinical characteristic or laboratory test can accurately predict the fetal platelet count. Only fetal platelet counts from scalp samples obtained prior to or early in labor from 25 patients with autoimmune thrombocytopenic purpura proved to be reliable in assessing the degree of fetal thrombocytopenia and selecting the appropriate route of delivery.

Genetic factors predisposing to autoimmune diseases. Autoimmune hemolytic anemia, chronic thrombocytopenic purpura, and systemic lupus erythematosus

Genetic factors predisposing to autoimmune diseases were investigated in 10 families having more than one affected member. Seventy relatives and 23 spouses from two large kindreds (one in whom the proband had autoimmune hemolytic anemia and the other immune thrombocytopenic purpura) were examined for immunologically mediated disorders, autoantibodies, immunoglobulin abnormalities, and HLA genotypes. Significant differences between relatives and spouses were found for immune diseases (21 percent versus 0 percent; p = 0.02), antinuclear antibody titer of 1:80 or more (18 percent versus 0 percent; p = 0.04), single-strand DNA antibodies (18 percent versus 0 percent; p = 0.04), high-titer antinuclear antibody or antibodies to single-strand DNA or both (33 percent versus 0 percent; p = 0.001), and the combined frequencies of immune diseases and serologic abnormalities (44 percent versus 4 percent; p = 0.0004). Similar frequencies were found in 41 relatives from eight families in whom the proband had SLE. Segregation analyses using these abnormalities as genetic traits were most compatible with a Mendelian dominant model. Impressive odds (100:1) against linkage to HLA were calculated.

HLA antigens in idiopathic thrombocytopenic purpura

The lymphocytes of 52 patients with the clinical diagnosis of idiopathic thrombocytopenic purpura (ITP) were typed for the HLA-A, -B and -C antigens, and of 27 of those patients also for the DR antigens. ITP proved not to be significantly associated with any of the HLA-A, -C or -DR antigens tested for. On the platelets of 35 of these 52 patients autoantibodies were detected in the direct immunofluorescence test. In these 35 patients with autoimmune thrombocytopenia (AITP), an increased frequency of HLA-Bw38 was found (14.3% versus 2.6% in controls). The frequency of none of the HLA antigens was significantly increased in the group of 17 ITP patients without demonstrable autoantibodies. The difference in association with HLA-Bw38 between AITP and ITP without demonstrable autoantibodies was not significant.

Idiopathic thrombocytopenic purpura and Graves disease

A 31-year-old black woman was studied who, at the age of 12 years, underwent splenectomy for a bleeding disorder due to idiopathic thrombocytopenic purpura (ITP). More than 20 years after the first signs of her bleeding disorder, the patient developed signs of Graves disease. This condition was treated with 131I with resulting hypothyroidism. The rare combination of ITP and Graves disease was considered to be a manifestation of two separate autoimmune disease. For the second time in the literature, HLA typing was performed in a patient with such a disease combination, and it was found to be of the group A23, A28, and B17. This is different from B8, which is most frequently found in both isolated ITP and Graves disease. Possible racial factors may be involved. It is concluded that more cases of such combined disease need to be studied before possible genetic patterns can be established.