Study of platelet-associated immunoglobulins of IgG,IgM, IgA,and IgE classes and platelet kinetics in 33 patients with idiopathic thrombocytopenic purpura

Summary The role of platelet-associated immunoglobulins (PAIg) of four different immunoglobulin classes -IgM, IgG, IgA, and IgE- and their relation to platelet count and platelet kinetics was studied in 33 patients with idiopathic thrombocytopenic purpura (ITP). During the course of 1 year, repeated determinations of PAIg were made. The results indicate that PAIgG, PAIgM, and PAIgA are present in all ITP patients, and that autoantibodies of all three Ig classes show highly significant correlations to the platelet counts (p< 0.0001). Double logarithmic negative correlations have been found between PAIgG and platelet count (r=–0.71), PAIgM and platelet count (r=–0.84), and PAIgA and platelet count (r=–0.79). Statistical analyses using partial correlation and multiple regression methods showed that PAIgM is predominantly related to the platelet count, whereas PAIgG and PAIgA are only of secondary importance. Accordingly, a relation of PAIgM (and PAIgA) to increased liver destruction of platelets was found in kinetic studies using¹¹¹indium-labeled platelets. Taken together, these results suggest a predominant role of PAIgM in the pathogenesis of ITP.     

Pattern of Immunoglobulin Classes and IgG Subclasses of Platelet-Associated Immunoglobulin in HIV-Seropositive Haemophiliacs

Abnormal amounts of platelet-associated immunoglobulins (PAIg) and seropositivity for HIV were demonstrated in 18 haemophiliacs suffering from thrombocytopenia of varying severity. Among 34 non-thrombocytopenic haemophiliacs seropositivity for HIV was found in association with increased levels of PAIg in 18 patients, whereas increased amounts of PAIg were seen only in 4 of the 16 patients seronegative for HIV. In most of the haemophiliacs with thrombocytopenia, the PAIg represented all classes of immunoglobulins and in half of the cases all subclasses of IgG, while in 33 patients with autoimmune thrombocytopenic purpura (AITP), PAIg was IgG1 and IgM in most cases. Our data show a difference in the pattern of PAIg in AITP patients and in thrombocytopenic haemophiliacs seropositive for HIV. We suggest that the thrombocytopenia in haemophiliacs is related to the polyclonal B cell activation also found in other patients seropositive for HIV and perhaps indicative of AIDS-related complex.     

Platelet-associated immunoglobulins in patients with primary Sj?gren's syndrome

Ten patients with primary Sj?gren's syndrome (7 females) were examined in order to evaluate whether in vivo-bound platelet-associated immunoglobulins (PAIg) and/or in vitro binding of circulating Ig to normal platelets influences platelet function. With an ELISA technique it was found that 9/10 patients had increased amounts of in vivo PAIgG, 4/10 patients of in vivo PAIgA and 5/10 patients of in vivo PAIgM. There was no correlation between patients platelet aggregability and the presence of in vivo PAIg. Incubation of platelets from a healthy person with plasma from the 10 patients caused in vitro binding of IgG in 7/10 cases, of IgA in 0/10 cases and of IgM in 1/10 cases. Adenosine diphosphate (ADP)-induced aggregability of the normal platelets was impaired in 7/10 incubation experiments (no correlation to in vitro PAIg) and unchanged in 3/10 cases. Epinephrine- and collagen-induced platelet aggregability was unchanged in all cases. It is concluded that increased amounts of in vivo and in vitro PAIg seem to occur frequently in patients with primary Sj?gren's syndrome, but do not influence platelet aggregability.     

免疫抑制治疗无效的特发性血小板减少性紫癜患者血小板相关免疫球蛋白的亚型分析

目的分析糖皮质激素、环孢菌素A治疗无效的特发性血小板减少性紫癜(ITP)患者血小板相关免疫球蛋白(PAIg)的亚型。方法采用酶联免疫法(ELISA)对19992004年绵阳市中心医院收治的17例激素治疗无效、4例激素 环孢菌素A治疗无效以及30例激素治疗有效ITP患者的PAIg亚型进行检测。结果17例激素治疗无效的患者PAIg各亚型抗体较之激素治疗有效ITP患者差异有显著性(P<0·01),激素治疗无效组PAIg各亚型水平均明显增高;激素 环孢菌素A治疗无效组PAIgM较之激素治疗有效ITP患者有所增高(P<0·05)。结论激素治疗无效的ITP患者PAIg各亚型均显著增高,提示PAIg在介导ITP患者异常免疫反应过程中起重要作用,PAIg各亚型水平的增高可能有助于预测ITP患者对激素治疗的敏感性。     

Flow cytometry detection of platelets autoantibodies in children with idiopathic thrombocytopenic purpura

Abstract  

Immune thrombocytopenic purpura is an acquired disorder, in which accelerated platelet consumption is due to platelet autoantibodies. The aim of this study was to investigate the clinical value of platelet autoantibodies assay in children with ITP and to evaluate flow cytometry in the detection of platelet autoantibodies in comparison with monoclonal antibody specific immobilization of platelet antigen (MAIPA) assay. We measured platelet autoantibodies by flow cytometry and MAIPA in 18 children with ITP (6 acute, 7 chronic and 5 in remission), in addition to 5 healthy children with matched age and sex as a control group. Significant elevation of platelet-associated immunoglobulin G (PAIgG), PAIgM and PAIgA was demonstrated in children with acute ITP compared to controls and children with chronic ITP (P < 0.05). There was significant elevation of PAIgG and PAIgM in children with acute ITP compared to children with ITP in remission (P < 0.05). There was significant negative correlation between platelet count and PAIgG levels in ITP children (r = −0.717; P = 0.001). Flow cytometry found PAIgG in 94.4% of ITP children. MAIPA has detected platelet specific IgG autoantibodies in 83.3% of ITP children. ROC analysis revealed sensitivity of 94%, specificity of 57% with overall accuracy of 83% for detection of PAIgG by flow cytometry compared to MAIPA.     

小儿特发性血小板减少性紫裥抗血小板抗体亚类的研究

采用鼠抗人IgG亚类单克隆抗体酶联免疫吸附法对急、慢性ITP患儿进行血小板表面相关IgG(PAIgG)亚类及血清IgG亚类测定。结果表明:ITP患儿抗血小板抗体有IgG亚类限制性,主要以PAIgG_1和PAIgG_3增高为主。其原因可能与某些感染及免疫调节异常有关。血清IgG亚类缺陷可能是ITP病因之一。PAIgG亚类在诊断和判断疗效中起重要作用。     

Platelet-associated IgG and IgM in myelofibrosis

Elevated levels of platelet-associated IgG and/or IgM were found in 15 of 18 patients with myelofibrosis (83 %). All but 5 patients with elevated PAIg had active disease. The amounts of PAIg were not correlated to either S-Ig, platelet count or spleen size. Levels of PAIgG well above the normal range were especially found in patients with short duration of disease and/or a transitional myeloproliferative state. It is debated whether immune-mediated platelet dysfunction may be of importance for the development of bone marrow fibrosis, mediated by the release of platelet-derived growth factors in the bone marrow. Elevated PAIg may also contribute to abnormal haemostasis and thrombocytopenia in myelofibrosis.     

Antiplatelet antibodies and their correlation with clinical findings in childhood immune thrombocytopenic purpura

The demonstration of antiplatelet antibodies (PAIgG, PAIgM) and decreased detection of platelet surface antigens (CD41, CD61, CD42b) in children with immune thrombocytopenic purpura (ITP) have a diagnostic role. This study was conducted to determine whether these parameters differed in acute and chronic ITP. Chronic ITP was defined as thrombocytopenia persisting for more than 6 months from the onset of illness. A total of 80 subjects were divided into three groups: group 1 included 39 patients with acute ITP; group 2 included 31 patients with chronic ITP, and group 3 included 10 healthy children. At diagnosis, blood samples were obtained for platelet count, mean platelet volume, plateletcrit and platelet distribution width along with platelet surface antigens and antiplatelet immunoglobulins. We found that platelet surface antigens were significantly decreased in both acute and chronic ITP when compared to the control group (p = 0.001). In contrast, PAIgG was increased in acute and chronic ITP patients compared to the control group. PAIgM was significantly higher in acute ITP. We conclude that decreased platelet surface antigens and increased antiplatelet antibodies are observed in both acute and chronic ITP. In patients with chronic progress, a relatively lower level of PAIgM can be identified.     

血小板自身抗体的流式细胞仪检测与意义

目的：应用流式细胞术（ＦＣＭ）测定血小板自身抗体ＰＡＩｇＧ,研究其对待发性血小板减少性紫癜（ＩＴＰ）诊断的意义。方法：应用ＦＣＭ检测２０例ＩＴＰ患者血小板膜表面及血浆中的抗血小板抗体,并与ＥＬＩＳＡ所测结果进行比较。结果：ＦＣＭ测得１４例（７０％ＩＴＰ患者血小板膜自身抗体ＰＡＩｇＧ阳性,９例（４５％）血浆抗血小板抗体阳性。ＥＬＩＳＡ显示１２例（６０％）患者ＰＡＩｇＧ阳性,７例（３５％）血浆抗血小板     

Detection of platelet-associated immunoglobulins by flow cytometry for the diagnosis of immune thrombocytopenia: a prospective study and critical review

BACKGROUND AND OBJECTIVE: Flow cytometry (FC) to identify platelet-associated (PA) immunoglobulin (Ig) is a potentially useful diagnostic test for idiopathic thrombocytopenic purpura (ITP). However, the restricted application of PAIg measurement to thrombocytopenic populations primarily comprised of ITP patients will artificially enhance the test's diagnostic specificity. For this reason, we performed a prospective study in which the results of a sensitive technique for detecting PAIg, as is FC, were correlated to the cause of the thrombocytopenia. DESIGN AND METHODS: A total of 118 patients with platelet counts <100 x 10(9)/L and 30 normal donors with a platelet count >200 x 10(9)/L were studied for PAIg employing a flow cytometer. Forty-two children and 20 adults were diagnosed as having immune thrombocytopenia and 27 children and 29 adults had nonimmune thrombocytopenia of different etiology. RESULTS: Raised levels of PAIg were found in 56/62 patients with immune thrombocytopenia and in 34/56 patients with non-immune thrombocytopenia. Diagnostic values of PAIg for the detection of immune thrombocytopenia were: sensitivity 90.3% and specificity 39. 3%. An enzyme-linked immunoabsorbant assay (ELISA) for the detection of autoantibodies to platelet glycoprotein (GP) complexes was used in adults, 9 with immune-related thrombocytopenia and 16 with non-immune thrombocytopenia, in order to determine the true non-specific nature of the positive PAIg test. By ELISA, 8/9 patients with immune thrombocytopenia and 7/16 with non-immune thrombocytopenic disorders showed autoantibodies to platelet GP complexes. INTERPRETATION AND CONCLUSIONS: PAIg detection by FC constitutes a sensitive but non-specific assay thus making it unnecessary and inappropriate for establishing the diagnosis of ITP.     

Platelet-associated immunoglobulins IgG, IgM, IgA and complement C3c in chronic idiopathic autoimmune thrombocytopenia: relation to the sequestration pattern of 111indium labelled platelets

Levels of platelet-associated immunoglobulins (PAIg) IgG, IgM, IgA and complement C3c were related to parameters of 111Indium-labelled platelet kinetics in 17 patients with chronic idiopathic autoimmune thrombocytopenia (cAITP). Elevated levels of PAIg/C3c were found in 14 patients (82%) (PAIgG n = 13, PAIgM n = 11, PAIgA n = 1, PAC3c n = 5). Only PAIgG correlated with platelet counts (RS = -0.71, p less than 0.01). Mean platelet life span (MLS) was shortened in all patients (median 12.0 h, range 0.3-45.6 h) and correlated with the platelet counts (RS = 0.49, p less than 0.05). MLS was correlated with PAIgG (RS = -0.52, p less than 0.05), but not with PAIgM, PAIgA, or PAC3c. The site of sequestration was splenic in 10 patients and splenic-hepatic in 7 patients. Although no significant correlation between either site of platelet sequestration and any of the investigated PAIg/C3c was demonstrable, platelets coated with higher PAIgG levels were more readily sequestrated in the spleen, while elevations of PAC3c were found in 4 out of 7 patients with hepatic involvement.     

Platelet-associated immunoglobulins IgG, IgM, IgA and complement C3 in immune and nonimmune thrombocytopenic disorders

A two-stage radioactive antiglobulin test--using unlabelled antisera specific for IgG, IgA, IgM and C3 followed by binding of 125I-staphylococcal protein A--was applied to determine platelet-associated immunoglobulins (PAIg) and complement (PAC3) in thrombocytopenias of various etiologies. One hundred and one patients with immune thrombocytopenia (chronic autoimmune, 48; acute autoimmune, 37; Evans syndrome, nine; connective tissue diseases, seven) and 20 patients with presumed nonimmune thrombocytopenia (bone marrow aplasia or malignancy, six; septicemia, five; hypersplenism, five; cirrhosis of liver, three; others, one) were studied. Increased levels of PAIg/C3 were found in 76% of patients with immune thrombocytopenia. PAIgG was raised in 66%, PAIgM in 57%, PAIgA in 44%, and PAC3 in 29%. Isolated elevation of PAIgG and of PAIgM was found in four and three cases, respectively; PAIgA and PAC3 were elevated in one case each. PAIgG was associated with PAIgM in 56%, with PAIgA in 34%, and with PAC3 in 27%. Both patients with Evans' syndrome and patients with connective tissue diseases had significantly higher PAIgM levels than the other patients with immune thrombocytopenia. In patients with nonimmune thrombocytopenia, increased rates of PAIg/C3 were also encountered. Positive test results were found in 88% (PAIgG 88%, PAIgM 47%, PAIgA 35%, and PAC3 24%). In immune-mediated thrombocytopenia, we observed a significant inverse correlation between platelet counts and PAIgG, PAIgA, and PAC3, but not with PAIgM. In contrast, no such correlation was found in patients with nonimmune thrombocytopenia. Our data indicate that the evaluation of neither parameter alone nor the combination of PAIg/C3 will discriminate between immune and nonimmune thrombocytopenia. Preferential coating with certain immunoglobulins, however, may be present in some subgroups of immune thrombocytopenias.     

The Clinical Significance of Platelet-Associated IgG: a Study on 298 Patients with Various Disorders

S ummary . Platelet-associated IgG (PAIgG) was studied by a quantitative platelet radioactive anti-IgG test (PRAT) in 298 patients. At the time of investigation, 171 patients were thrombocytopenic (platelet count <100 × 10⁹/1), 127 had normal platelet counts. Patients fell into the following disease categories: Idiopathic thrombocytopenic purpura (ITP) ( N =81), possible ITP (19), acute ITP (9), systemic lupus erythematosus (22), autoimmune haemolytic anaemia of warm-type (18), systemic blood disease (65), liver diseases (35), others (49). A significant elevation of PAIgG was found in all disease categories. There was a significant correlation between PAIgG and the reciprocal values of platelet counts for most disease groups. No relationship was discernible between PAIgG and hypergammaglobulinaemic states (serum IgG >1.8 g/l), Platelet survival studies ( N=30 ) revealed that normal and increased values of PAIgG were associated with normal or shortened platelet mean life span. It is concluded that an elevated PAIgG is only one of several factors involved in the development of immunologically mediated thrombocytopenia.     

血浆置换与血小板洗涤对ITP患者血小板及相关抗体影响的研究

目的：探讨血浆置换（PE）和血小板洗涤（PW）对特发性血小板减少性紫癜（ITP）患者体内血小板相关抗体（PAIg）水平及血小板计数（BPC）变化的影响。方法：对各组测定PAIg和BPC的变化并作统计学处理比较。结果：PE加PW治疗组PAIg含量的递减速度均明显快于普通治疗组（P〈0．01）,普通治疗组BPC的回升速度明显慢于PE加PW组（P〈0．01）。结论：血浆置换及血小板洗涤治疗ITP可迅速降低患者体内PAIg水平、促进体内BPC的回升;BPC的回升与PAIg水平的递减呈负相关,动态监测PAIg和BPC的变化有助于及时评估患者病情转归情况和指导临床治疗方案。     

病毒性肝炎血小板减少症影响因素的研究

目的探讨病毒性肝炎血小板减少症的发病机制.方法 84例病毒性肝炎患者和20名健康志愿者分为3组,A组(48例病毒性肝炎并血小板减少症患者)、B组(36例病毒性肝炎血小板正常患者)和C组(20名健康志愿者),分别采用酶联免疫吸附法、流式细胞术、腹部彩色B超检测3组血清血小板生成素(TPO)水平、血小板相关免疫球蛋白(PAIg)及其类别PAIgG、PAIgA、PAIgM水平、脾脏大小,采用骨髓穿刺术对其中74例行骨髓细胞学检查.结果血清TPO水平A组低于C组(P<0.01)和B组(P<0.05),严重肝病血清TPO水平与血小板数相关(r=0.374,P<00.01).PAIg、PAIgG水平A组明显高于B组(P<0.001)和C组(P<0.01),血小板数与PAIg水平呈负相关(r=0.446,P<0.01),血小板数与PAIgG水平亦呈负相关(r=-0.462,P<0.01).脾脏肿大发生率A组(77.1%)明显高于B组(47.2%,P<0.01),C组无脾脏肿大发生,血小板数与脾脏大小呈负相关(r=-0.5 81,P<0.01).74例骨髓象显示A组有4例呈骨髓抑制象改变,B组和C组无一例有上述改变.结论严重肝功能受损时血清TPO水平下降,与血小板数减少直接相关.PAIg介导的自身免疫机制在病毒性肝炎血小板减少症中可能起重要作用.脾脏肿大是引起病毒性肝炎血小板减少的因素.初步发现慢性肝病有骨髓抑制现象,可能成为引起病毒性肝炎血小板减少的因素之一.     

Platelet associated IgG, platelet survival, and platelet sequestration in thrombocytopenic states

S ummary . Platelet-associated IgG (PAIgG), platelet mean life span (MLS), and platelet sequestration sites were studied in 69 patients with immune (ITP) and presumed nonimmune thrombocytopenias (NTP). A shortened MLS was associated with elevated PAIgG (N=46), and with normal PAIgG (N=15), Four patients had a normal MLS, but elevated PAIgG, four patients were normal for both parameters. The highest PAIgG values occurred in ITP patients with a very short MLS. Nine NTP patients had also elevated PAIgG, but a normal or slightly shortened MLS. There was a significant double log correlation between PAIgG and MLS for ITP, but not for NTP patients. Judged from the coefficient of determination, only 10% of PAIgG were directly related to a shortened MLS.
70% of patients (N= 63) had exclusively splenic and 30% hepatosplenic sequestration. PAIgG was elevated in 29/44 patients with splenic (66%) and in 16/19 patients with hepatosplenic sequestration (84%). In ITP, PAIgG-positive cases were observed in 69% of splenic v 82% of hepatosplenic sequestration, while in NTP the corresponding figures were 6/11 and 2/2. No significant correlation between PAIgG and either sequestration type was demonstrable.
We conclude that in immunologically mediated thrombocytopenia only a small portion of PAIgG accounts for a decreased MLS, and that the concentration of PAIgG per se does not determine the platelet sequestration type.     

Platelet-associated IgG in childhood idiopathic thrombocytopenic purpura: measurements on intact and solubilized platelets and after gammaglobulin treatment

An immunoradiometric assay was developed for determining platelet-associated IgG (PAIgG) both on intact and solubilized platelets. In 20 healthy subjects PAIgG was 0.28 +/- 0.20 ng/10(6) platelets and 2.2 +/- 1.1 ng/10(6) platelets on intact and on solubilized platelets, respectively. 13 children with acute ITP all had increased concentrations of PAIgG, but no correlation was found between the severity of thrombocytopenia and PAIgG concentrations, either on intact or on solubilized platelets. Neither was there any correlation of the increase in PAIgG between intact and solubilized preparations. 3 out of 4 children who received high-dose i.v. gammaglobulin showed a concomitant normalization of the platelet count and of the PAIgG concentration both on intact and lyzed platelets. The remaining child did not respond to gammaglobulin and continued to have abnormal PAIgG.     

The amount of platelet-bound albumin parallels the amount of IgG on washed platelets from patients with immune thrombocytopenia

The biologic relevance of the increased platelet-associated IgG (PAIgG) on platelets from patients with idiopathic thrombocytopenic purpura (ITP) is unclear. Platelets from ITP patients are often larger than normal, and it is possible that the increased IgG is not specific but passively related to platelet size. The measurement of platelet-bound albumin could provide information concerning the specificity of the platelet-bound IgG, since albumin, like IgG, is a plasma protein, but unlike IgG, is not an active participant in immunologic reactions. Albumin is also a normal constituent of platelet membrane, and increased platelet albumin could indicate an increased platelet mass. Platelet-bound albumin, IgG, and total platelet protein were measured on both intact and disrupted platelets from healthy individuals (n = 25) and patients with ITP (n = 21). Platelet IgG and albumin were measured in an immunoradiometric assay using intact antisera and F(ab')2 fragments prepared from the same antisera. There was no relationship between platelet-bound IgG or albumin, and platelet size measured by either platelet protein or platelet volume, (r less than 0.3 for all interactions). In contrast, there was a significant correlation between platelet-bound albumin and platelet-bound IgG (r = 0.7, n = 21, p less than 0.001). Those patients with elevated platelet PAIgG also had elevated platelet albumin, and this relationship was irrespective of the total platelet protein content or mean platelet volume. It is possible that the increased platelet-bound IgG in ITP reflects an increase in platelet surface area or contaminating platelet fragments that are not manifested as an increase in platelet volume or total platelet protein. Alternatively, a platelet membrane abnormality may occur in ITP that results in the uptake of significant amounts of plasma proteins. Either possibility implies that not all of the IgG on platelets from patients with ITP is pathologic IgG.     

Human herpesvirus 6 in hematologic diseases in China

BACKGROUND AND OBJECTIVE: The prevalence and pathogenic role of human herpesvirus 6 (HHV-6) in various benign and malignant hematologic diseases remain largely unknown. The aim of this study was to search for a possible involvement of HHV-6 in the pathogenesis of hematologic diseases. DESIGN AND METHODS: The presence of HHV-6 DNA sequences was examined by polymerase chain reaction (PCR) in bone marrow mononuclear cells from 241 patients with benign and malignant hematologic diseases in China. Platelet-associated immunoglobulin (PAIg) of 66 idiopathic thrombocytopenic purpura (ITP) patients was measured by competitive enzyme-linked immunosorbent assay. The presence of HHV-6 DNA in sera from 31 ITP patients was examined by PCR. Paired serum samples from 19 ITP patients were analyzed for anti-HHV-6 IgG titers using an indirect immunofluorescence assay. RESULTS: HHV-6 DNA was detected in 41% and 37.5% of ITP and acute leukemia patients respectively, but in only 6.7% of patients with iron deficiency anemia. HHV-6 positivity for ITP patients with excessive PAIgG was significantly higher than in patients with a normal level of PAIgG. HHV-6 DNA was not detected in any of the serum samples from ITP patients. None of the 19 cases of ITP showed a significant increase in anti-HHV-6 antibody titers during the convalescent phase compared with the onset phase. INTERPRETATION AND CONCLUSIONS: Our results indicate that HHV-6 infection might be associated with excessive PAIgG in some cases of ITP, and that the virus persists in a latent state. The pathogenic role of HHV-6 in ITP needs to be confirmed by further investigations.     

Quantification of platelet-associated IgG with competitive solid-phase enzyme immunoassay

In order to measure platelet-associated IgG (PAIgG), we devised a solid-phase enzyme immunoassay employing a competitive binding of peroxidase-conjugated anti-IgG antiserum between platelets and polystyrene tubes coated with IgG. The amounts of peroxidase bound to the tubes were measured in a spectrophotometer by an enzymatic reaction. This method is highly sensitive, reproducible and can be carried out more simply. the PAIgG values of normal controls averaged 21.6 +/- 6.6 (SD) ng/10(7) platelets. 27 (93%) of 29 patients with idiopathic thrombocytopenic purpura (ITP), who had a platelet count of less than 15 X 10(4)/microliter, had PAIgG values greater than those of controls by 2 SD and averaged 205.5 +/- 323 ng. There was a significant inverse correlation between platelet count and PAIgG value of ITP patients. the PAIgG values of patients with aplastic anemia were within normal range.