慢性ITP患者血小板膜表面GPⅣ、GPⅤ特异性自身抗体的测定

目的：检测慢性ITP患者血小板膜表面GPⅣ、GPⅤ特异性自身抗体。方法：应用改良直接MAIPA(单克隆抗体俘获血小板抗原技术)检测血小板膜糖蛋白(GPⅣ、GPⅤ)特异性自身抗体。结果：慢性ITP患者血小板洗脱液中GPⅣ特异性和GPⅤ特异性自身抗体的阳性率分别为6．3％和4．8％。结论：血小板膜GPⅣ、GPⅤ分子是慢性ITP自身抗体的靶抗原，但多与GPⅡb／Ⅲa或GPⅠb自身抗原共存。     

人源性抗血小板膜糖蛋白Ⅱb/Ⅲa Fab抗体的研制及其对血小板聚集功能的影响

目的:构建人源性抗血小板膜糖蛋白Ⅱb/Ⅲa(GPIⅡb/Ⅲa)Fab噬菌体抗体库,筛选抗GPⅡb/Ⅲa特异性的噬菌体抗体,并对其功能进行研究.方法:取血小板膜糖蛋白抗体(抗GPⅡIb/Ⅲa)阳性的特发性血小板减少性紫癜(ITP)患者脾细胞,采用噬菌体抗体库技术构建人源性抗GPⅡb/Ⅲa Fab噬菌体抗体库,以表达GPⅡb/Ⅲa的CHO123细胞筛选抗体库,并以ELISA法检测噬菌体抗体;用Western blot对抗体进行鉴定,并测定其与血小板抗原的结合;观察筛选到Fab抗体对血小板聚集的影响.结果:筛选出2株能够与血小板膜GPⅡb/Ⅲa特异性结合的Fab抗体,其序列与人免疫球蛋白轻、重链可变区序列具有高度同源性,表达纯化的Fab抗体能抑制血小板聚集.结论:成功地从人源性抗血小板膜糖蛋白Ⅱb/Ⅲa Fab抗体库筛选出特异性识别GPⅡb/Ⅲa,具有抑制血小板聚集作用的人源性抗体.     

免疫性血小板减少症相关免疫负调控因子研究进展

正ITP患者血小板减少的机制包括血小板消耗过多及产生不足,两者皆主要由IgG抗血小板抗体介导~([1]),自身免疫的主要靶点是血小板糖蛋白,如GPⅡb/Ⅲa和GPⅠb/Ⅸ。已经证实,ITP与血小板自身抗原的失耐受有关,而失耐受的原因仍不清楚。大量的研究表明ITP患者体内也存在着细胞免疫紊     

用单克隆抗体对ITP自身抗血小板抗体及其相关抗原的初步研究

本文应用三种抗血小板膜糖蛋白单克隆抗体,按ELISA 间接法、ELISA双抗体夹心法、ELISA竞争法,对ITP患者自身抗血小板抗体及其相关抗原进行了初步研究。实验结果表明,抗血小板抗体的相关抗原呈多态性,包括:GPⅠb、GPⅡb及/或 GPⅢa,以 GPⅡb及/或 GPⅢa占多数,还可能包括血小板膜蛋白以外的其它抗原成分。这提示,ITP可能是一组复杂的、不均一的自身免疫性疾病。     

噬菌体抗体库中筛选血小板膜糖蛋白Ⅱ b/Ⅲa特异的人源性Fab抗体

本研究利用特发性血小板减少性紫癜(idiopathic thrombocytopenic purpura,ITP)患者产生抗血小板自身抗体的特点,从ITP患者脾脏细胞中提取RNA,扩增抗体轻链和重链Fd基因,插入噬粒载体pComb3H,构建人源性抗GP Ⅱ b/ⅢaFab噬菌体抗体库.以表达GP Ⅱ b/Ⅲa的CHO123细胞筛选抗体库,制备人源性GPⅡb/Ⅲa Fab噬菌体抗体.     

ITP血小板特异性自身抗体（GPⅡb/Ⅲa和GPIbα）与糖皮质激素和静脉丙种球蛋白临床疗效的关系

目的检测特发性血小板减少性紫癜（ITP）患者体内的抗血小板膜糖蛋白（GPⅡb/Ⅲa和GPIbα）特异性自身抗体,并探讨特异性自身抗体与糖皮质激素和静脉丙种球蛋白（静丙）治疗的临床疗效是否存在针对性,以便得到更经济和个体化的治疗方案,为ITP提出新的分型依据。方法应用改良的单克隆抗体特异性俘获血小板抗原（MAIPA）法检测抗GPⅡb/ⅡIa,GPIbα特异性自身抗体。结果双抗体阳性组与单一抗GPIbα抗体阳性组总疗效比较,差异无显著性（χ^2=0.995,P〉0.05）双抗体阳性组与单一抗GPⅡb/ⅡIa抗体阳性组总疗效比较,差异有显著性（χ^2=17.439,P〈0.01）,后者优于前者;单一抗GPⅡb/ⅡIa抗体阳性组,双抗体阳性组,双抗体阴性组,糖皮质激素治疗与糖皮质激素联合静丙治疗比较,差异无显著性（P〉0.05）。结论血小板特异性自身抗体种类（GPⅡb/Ⅲa和GPIbα）及种类数目与ITP的临床疗效（糖皮质激素、静丙）有一定关系,对临床治疗方案的选择有一定意义。以抗血小板膜糖蛋白（GPⅡb/Ⅲa和GPIbα）特异性自身抗体为ITP进行新的分型依据尚不足,需扩大样本量进一步研究。     

特发性血小板减少性紫癜患者GPⅡb/Ⅲa、CD62P表达探讨

目的检测原发性血小板减少性紫癜(ITP)患者血小板表面GPⅡb/Ⅲa、CD62P的表达情况,以探讨其在ITP患者中的临床应用价值.方法采用美国BD公司的FACSCalibur流式细胞仪,对32例ITP患者、17例非免疫性血小板减少、21例其它自身免疫性疾病及20例健康正常人的血小板表面GPⅡb/Ⅲa、CD62P的表达情况进行了分析测定.结果ITP患者GPⅡb/Ⅲa血小板阳性表达率明显高于其它三组(P＜0.01),但CD62P血小板阳性表达率四组无明显差别(P＞0.05),15例无临床症状ITP患者GPⅡb/Ⅲa表达明显高于17例有临床症状ITP患者的表达(P＜0.01).结论GPⅡb/Ⅲa作为监测血小板活化指标,对ITP的鉴别诊断及监测病情发展、判断预后具有重要意义;ITP患者的GPⅡb/Ⅲa表达明显增高,但CD62P表达并不增高,CD62P并非监测ITP患者循环中活化血小板的理想标志物.     

慢性ITP病人抗血小板糖蛋白Ⅱ_b/Ⅲ_a复合物自身抗体

慢性特发性血小板减少性紫癜(ITP)是由抗血小板膜的自身抗体而引起,这些抗体的抗原特异性尚不清楚。最近Van Leeuwen等报道:ITP病人的血清抗体或血小板上的抗体能与正常血小板结合,但不能与Glanymann血小板减少症病人的血小板结合。后者血小板上缺少糖蛋白Ⅱb/Ⅲa,因此推测某些ITP病人抗血小板的自身抗体可能是针对糖蛋白Ⅱb/Ⅲa复合物的。但Kunicki等发现ITB病人抗血小板抗体对正常和Glanzmann病人血小板都     

血小板无力症的流式细胞术分析方法

板膜糖蛋白(glycoprotein, GP)Ⅱb/Ⅲa属整合素家族, 是纤维蛋白原受体, 介导血小板的聚集.GPⅡb/Ⅲa复合物质的数量不够和质量缺陷都可导致血小板聚集功能障碍, 并导致产生患血小板无力症(Glanzmann′s thrombasthenia, GT)[1].检测血小板膜上GPⅡb/Ⅲa复合物的缺陷, 可从分子水平诊断GT.本文介绍一种用荧光单抗标记血小板, 通过流式细胞术分析诊断GT的方法.     

人类白细胞抗原DRB1 等位基因与儿童特发性血小板减少性紫癜的相关性研究

目的研究人类白细胞抗原(human leukocyte antigen, HLA)DRB1等位基因与儿童特发性血小板减少性紫癜(idiopathic thrombocytopenic purpura, ITP)的关系.方法用聚合酶链反应-序列特异的寡核苷酸探针杂交技术对42例ITP患儿进行了HLA-DRB1等位基因分型,同时用改良的血小板抗原单抗特异性固相化法检测了其中36例ITP患儿血清中的抗GPⅡb/Ⅲa和抗GPIb/Ⅰx自身抗体.结果与健康对照相比,ITP患儿HLA-DRB1*17基因频率显著升高(P<0.05,RR＝2.76,EF=0.1064),而HLA-DRB1*1202基因频率显著降低(P<0.025,RR＝0.20,PF=0.7616);慢性难治性ITP患儿与非难治性患儿相比,HLA-DRB1*11基因频率显著升高(χ2＝6.091,P<0.025),且具有DRB1*11的患儿主要(5/6)为女性年长患儿;抗GPⅡb/Ⅲa及抗GPIb/Ⅰx自身抗体的阳性率都与HLA-DRB1*02(15/16)基因显著相关(P分别为0.02和0.01),但难治性和非难治性ITP患儿间抗体阳性率差异无显著性(P>0.1).结论 DRB1*17可能与儿童ITP的易感性有关,而DRB1*1202则可能对儿童ITP的发病具有保护作用;具有DRB1*11基因的患儿易发展为慢性难治性ITP;血小板自身抗体与抗原表位的反应可能受DRB1*02限制,但自身抗体阳性与否并不能提示ITP患儿的预后.     

几种临床疾病的血小板相关抗体检测结果分析

目的 :探讨血小板相关抗体在血小板减少症中的临床应用。方法 :选择健康者、血小板低于正常的体检者、血小板减少性紫癜(ITP)、再障 (AA)、肝脏疾患、系统性红斑狼疮 (SLE)患者等采用ELISA法定量测定血小板抗体PAIgG、PAIgM、PAIgA ,并分析ITP患者治疗前后血小板相关抗体的变化。结果 :血小板低于正常的体检者血小板抗体的阳性率 14 .9% ,ITP、AA、SLE等患者血小板相关抗体阳性率与正常组比较有显著差异 ,分别为 78.9%、3 1.2 %、62 .5 % ,肝病者血小板相关抗体与正常组无差异。ITP患者治疗前后三种血小板抗体均有非常显著性变化 (P <0 .0 1)。结论 :血小板相关抗体测定在自身免疫性疾病引起的血小板减少的诊疗中有重要意义     

Target platelet antigen in homosexual men with immune thrombocytopenia

A syndrome of isolated immune thrombocytopenic purpura (ITP) has recently been described in homosexual men. We have identified an antiplatelet antibody in the serum of 29 of 30 homosexual men with isolated ITP. The antibody binds to a platelet membrane antigen of 25,000 daltons, and binding is effected by the F(ab)2 portion of the immunoglobulin. Similar antibody activity was not detected in serum from 30 nonhomosexual patients with either ITP or nonimmune thrombocytopenia. The 25,000-dalton antigen was not found on other hematopoietic cells, and it was distinct from the core protein of the AIDS-associated retrovirus. In contrast, serum antibody reacted with a 25,000-dalton antigen associated with cultured herpes simplex virus Types I and II. In these experiments the antigen appeared to be derived from green-monkey kidney cells in which the herpes simplex viruses were grown. Identical antigenic activity was also demonstrated in uninfected human skin fibroblasts. We conclude that ITP in homosexual men is accompanied by a serum antibody directed against a platelet antigen of 25,000 daltons. The nature of the antigen and the relation of the serum antibody to ITP require further study.     

Antibody binding to platelet antigens in acute and chronic idiopathic thrombocytopenic purpura: a platelet membrane ELISA for the detection of antiplatelet antibodies in serum.

A solid-phase platelet membrane enzyme linked immunosorbent assay (ELISA) was developed for the detection of circulating platelet binding IgG in serum. 18 out of 28 (64%) sera from patients with chronic idiopathic thrombocytopenic purpura (ITP) and 10 out of 21 (48%) sera from patients with acute ITP contained more platelet binding IgG than the mean +2 s.d. of 25 normal control sera. IgG-F(ab')2 fragments from two anti-PlA1 sera, from six out of seven positive chronic ITP sera and from four out of eight positive acute ITP sera bound to normal platelet membrane. When IgG-F(ab')2 preparations, which reacted with normal membrane, were tested against glycoprotein IIb-IIIa-deficient platelet membrane obtained from a patient with Glanzmann's thrombasthaenia, the reactions of F(ab')2 fragments from two anti-PlA1 sera, from three out of four acute ITP sera and from four out of six chronic ITP sera were reduced to control levels. It is concluded that IgG-F(ab')2 antibody binding to platelet specific antigens, some of which are associated with the glycoprotein IIb-IIIa complex, can be demonstrated not only in anti-PlA1 sera or sera from chronic ITP patients but also in sera from some patients with acute ITP. Moreover, when the IgG binding to platelet membrane of whole sera is tested, positive results may sometimes be ascribed to the presence of immune complexes.     

Antiplatelet antibody‐induced thrombocytopenia does not correlate with megakaryocyte abnormalities in murine immune thrombocytopenia

Immune thrombocytopenia (ITP ) is an autoimmune bleeding disorder characterized by increased peripheral immune platelet destruction and megakaryocyte defects in the bone marrow. Although ITP was originally thought to be primarily due to antibody‐mediated autoimmunity, it is now clear that T cells also play a significant role in the disease. However, the exact interplay between platelet destruction, megakaryocyte dysfunction and the elements of both humoral and cell‐mediated immunity in ITP remains incompletely defined. While most studies have focused on immune platelet destruction in the spleen, an additional possibility is that the antiplatelet antibodies can also destroy bone marrow megakaryocytes. To address this, we negated the effects of T cells by utilizing an in vivo passive ITP model where BALB /c mice were administered various anti‐αII b, anti‐β3 or anti‐GPI b antibodies or antisera and platelet counts and bone marrow megakaryocytes were enumerated. Our results show that after 24 hours, all the different antiplatelet antibodies/sera induced variable degrees of thrombocytopenia in recipient mice. Compared with naïve control mice, however, histological examination of the bone marrow revealed that only 2 antibody preparations (mouse‐anti‐mouse β3 sera and an anti‐ αII b monoclonal antibody (MWR eg30) could affect bone marrow megakaryocyte counts. Our study shows that while most antiplatelet antibodies induce acute thrombocytopenia, the majority of them do not affect the number of megakaryocytes in the bone marrow. This suggests that other mechanisms may be responsible for megakaryocyte abnormalities seen during immune thrombocytopenia.     

Pathogenesis of immune thrombocytopenia in common variable immunodeficiency

Immune Thrombocitopenic Purpura (ITP) is an autoimmune disease characterized by antibody-mediated platelet destruction and variable reduced platelet production. Besides antibody-mediated platelet destruction, new pathogenic mechanisms have been reported to be involved in reducing platelet count. Among these, desialylation is one of the most recent and innovative mechanisms that has been found to be implied, at least in part, in non-antibody mediated platelet clearance.Common Variable Immunodeficiency (CVID) is the most common Primary Immunodeficiency seen in clinical practice. About 25–30% of CVID patients are affected by autoimmune manifestation, among which ITP is the most common. Little is know about pathophysiological mechanisms that lead to ITP in CVID.Given the poor antibody production typical of CVID patients, we aimed at verifying whether platelet desialylation could be responsible for CVID associated thrombocytopenia.According to our results, we may suggest that in CVID patients, ITP is due to a decreased bone marrow platelets production, rather than an increased peripheral platelet destruction, which is more common in patients with primary ITP. An increased platelet desialylation does not appear to be implicated in the thrombocytopenia secondary to CVID, while it is implicated in the pathogenesis of primary ITP. Nevertheless an intriguing aspect has emerged from this study: regardless the presence of thrombocytopenia, the majority of CVID patients present a double platelet population as far as desialylation concerns, whilst no one of the healthy donors and of the patients with primary ITP shows a similar characteristic.     

Anti-glycoprotein IIb/IIIa autoantibodies are reversibly internalized into platelets in idiopathic (autoimmune) thrombocytopenic purpura.

We used flow cytometry to investigate the binding of platelet-binding IgG (PBIgG) to unfixed platelets in idiopathic thrombocytopenic purpura (ITP), including that of anti-glycoprotein (GP) IIb/IIIa antibodies. Anti-GPIIb/IIIa antibodies were detected in 13/64 ITP patients using antigen-capture ELISA and immunoblotting. When unfixed platelets were incubated with ITP plasma, the PBIgG level was significantly higher than after incubation with normal plasma. When 1 microM ADP was added to unfixed platelets, which were incubated with ITP plasma and washed, the PBIgG level increased additively. GMP-140 is a constituent of platelet alpha-granules, and a monoclonal antibody directed against this protein showed weak binding to platelets after 1 microM ADP stimulation. The increase of PBIgG produced by ADP was significantly greater when ITP plasma positive for anti-GPIIb/IIIa antibody was used compared with that obtained using antibody-negative ITP plasma. This increase of PBIgG was markedly inhibited by the removal of extracellular calcium with EDTA or the dissociation of the GPIIb/IIIa complex by EDTA treatment at 37 degrees C. These results suggest that anti-GPIIb/IIIa autoantibodies are internalized by unfixed ITP platelets and stored somewhere other than the alpha-granules. This stored antibody pool can be reversibly redistributed on the platelet surface by weak stimulants such as ADP and a functional GPIIb/IIIa complex appears to be necessary for this to occur.     

Case report: passively acquired anti-D in a D+ pregnant patient

A sample was submitted for serologic evaluation from a pregnant patient with immune thrombocytopenic purpura (ITP) for possible transfusion in the future because of a decreased platelet count. Anti-D and -E were identified in the patient's serum using several antibody identification techniques, and anti-D was recovered in an acid eluate prepared from the patient's red cells. It was discovered that WinRho had been administered to treat the ITP. This product has been licensed for treatment of nonsplenectomized D+ children and adults with ITP to increase the platelet count. Administration of anti-D to D+ individuals for treatment of ITP can cause a red cell anemia.     

Passive neonatal thrombocytopenia. A case study of factors predicting the response to i.v. IgG therapy

A term male infant was noted at birth to have petechiae over the face and trunk and a platelet count of 3 x 10(9) per L. Maternal immune thrombocytopenia (ITP) was suspected from the clinical data and confirmed by the presence of antiplatelet antibody (both in the mother and infant) detected by recently described flow cytometry method. Initial treatment with exchange transfusions, platelet transfusions, steroids, failed to correct thrombocytopenia and, hence, seven doses of high-dose gamma globulin (IV-IgG) were given intravascularly. Initiation of IV-IgG was followed by stabilization of platelet counts with marked reduction in the need for platelet transfusions. In this case of passive ITP, the therapeutic efficiency of high dose IV-IgG seems to depend upon maintaining a certain critical level of serum IgG (which in turn may depend upon the serum antiplatelet antibody titers).     

Sequence analysis of monoclonal antibodies derived from a patient with idiopathic thrombocytopenic purpura

Autoantibodies directed at the platelet membrane glycoprotein Ib (GPIb) can mediate a severe form of idiopathic thrombocytopenic purpura (ITP). The platelet-specific antibody from plasma of one patient (DM) with this form of ITP displays a public idiotype termed DMId. The DMId idiotype has been found in the plasma of several patients with ITP, usually in association with GPIb-specific autoantibodies. As a step in the understanding of the molecular genetics of this form of ITP we have determined the nucleotide sequences of expressed V region genes selected from a panel of five human lymphoblastoid cell lines derived from patient DM. Two of the lines secreted antibodies that bound GPIb, and three of the lines secreted antibodies that expressed DMId. The H chain sequences of the DMId-positive antibodies and of one of the GPIb-binding antibodies belong to the VH4 family. The second GPIb-binding antibody belongs to the VH1 family. All have multiple substitutions from previously published sequences giving these antibodies the appearance of having been antigen driven. These results are consistent with the hypothesis that autoantibodies in ITP arise from a "normal" immune response inappropriately directed at platelet antigens. Further, our results suggest that VH4 gene segments may be recruited preferentially into the DMId-positive, GPIb-specific autoantibody response.