Immune thrombocytopenia (ITP) is an autoimmune hemorrhagic disease. It is considered that production of platelet auto-antibodies was one of the pathogenesis of ITP, first-line therapy including corticosteroid and immunoglobulin could reduce destruction of platelets by inhibiting production of auto-antibodies and blocking Fc-receptor of reticuloendothelial system, but some of the patients were refractory to first-line therapy and have persistent duration of the disease, having worse prognosis and developing into chronic/refractory ITP(C/RITP) . Platelet membrane glycoprotein like GPIIb/IIIa and GPIbα are the most common antigen targets, but first-line therapy was less effective to patients whose anti-GPIbα antibodies are positive. Further studies revealed that the way causing platelet destruction by anti-GPIIb/IIIa antibodies and anti-GPIbα antibodies are different: the former is mainly dependent to Fc-pathway, and the latter mainly cleared platelet by Fc-independent way. Results above indicated that detection of type of platelet auto-antibodies maybe potential to treatment and prognosis of ITP. This article summarizes relationship between platelet specific antibodies and the onset, clinical manifestation, treatment and prognosis of ITP.
Antibodies ; immunology ; Autoimmune Diseases ; Blood Platelets ; immunology ; Humans ; Platelet Membrane Glycoproteins ; Prognosis ; Thrombocytopenia ; immunology ; therapy

OBJECTIVETo evaluate the clinical significance of MAIPA test in diagnosis of idiopathic thrombocytopenic purpura (ITP) and in the differential diagnosis of antoimmune thrombocytopenias from nonimmune thrombocytopenias.

METHODSA total of 321 thrombocytopenic patients (118 males, 203 females) from 14 centers were studied. A modified monoclonal antibody immobilization of platelet antigen (MAIPA) method was used to detect the platelet glycoprotein-specific autoantibodies (anti-GP IIb/IIIa, anti-GPIb/IX) to double-blindly evaluate its sensitivity and specificity for the diagnosis of ITP and to investigate the impact of the antibodies on platelet count.

RESULTSThe results showed that for the diagnosis of ITP, anti-GPIIb/IIIa, anti-GPIb/IX and both of them had the sensitivity of 39.75%, 32.64% and 55.23%; the specificity of 97.56%, 93.94% and 92.68%; the positive predictive value of 97.94%, 93.98% and 95.65%; the negative predictive value of 35.71%, 32.35% and 41.53%; and the total efficiency of 54.51%, 48.29% and 64.80%, respectively. The positivity of the autoantibodies in immune thrombocytopenias was incredibly higher than that in nonimmune thrombocytopenias. The platelet counts in the immune thrombocytopenias with autoantibody positivities were significantly lower than those without the autoantibodies. The platelet counts were negatively correlated with the concentration of the autoantibodies. The levels of anti-GPIIb/IIIa or anti-GPIb/IX or both of them dropped or disappeared in patients being responsive to steroid therapy.

CONCLUSIONMAIPA assay is proved to be of great value for the diagnosis of ITP and for differential diagnosis of immune thrombocytopenias from nonimmune thrombocytopenias.

Antibodies, Monoclonal ; immunology ; Antigens, Human Platelet ; immunology ; Autoantibodies ; immunology ; Blood Platelets ; Humans ; Prospective Studies ; Purpura, Thrombocytopenic, Idiopathic ; immunology

The purpose of this study was to explore the clinical value of the platelet antibody screening and typing in platelets transfusion by using microcolumn gel immunoassay (MGIA). The platelets antigen-antibody reactions including the antibody screen and blood crossmatch were detected by MGIA. The results indicated that the detection of platelet antibody showed positive in 30 cases of aplastic anemia (AA), 11 cases of myelodysplastic syndrome (MDS), 24 out of 25 cases of leukemia and 1 out of cases of other diseases, while detection of platelet antibody showed negative in 20 normal volunteer donors. The number of platelet antibody crossmatch coincidence in 112 specimens of AA, 42 specimens of MDS and 95 specimens of leukemia were 45, 20 and 40, the coincidence rates were 40.18%, 47.62% and 42.11%. The mean corrected count increment (CCI) in 20 patients received platelet transfusion many times was 18.2 after crossmatch and 4.7 before crossmatch. It is concluded that the positive rate of platelet antibody screening is very high in patients with hematologic malignancies, the coincidence rate of platelet antibody crossmatch in 249 blood samples is between 40% and 48%, and the efficiency of using crossmatched platelets in clinic is enhanced significantly.
Anemia, Aplastic ; immunology ; Antigens, Human Platelet ; immunology ; Blood Grouping and Crossmatching ; Blood Platelets ; immunology ; Hematologic Neoplasms ; immunology ; Humans ; Immunoassay ; methods ; Isoantibodies ; blood ; immunology ; Platelet Transfusion ; methods

OBJECTIVETo investigate the correlation between the platelet GP specific antibodies/HLA antibodies and platelet transfusion refractoriness (PTR).

METHODSSixty-five patients with PTR were selected in this study and were genotyped for HLA-A and HLA-B as well as HPA systems by standard PCR-SSP assays. The platelet GP specific antibodies and HLA antibodies in serum and platelet elution were tested with a solid phase ELISA.

RESULTSThe HLA-A/B antigens and the frequencies of HPA-1, 2, 4, 5, 6, 9, 15 antigens in PTR patients had no difference from those in healthy donors. The freguencies of HPA-3a and 3b were 0.65 and 0.35, respectively. There was statistical difference between the 65 PTR patients and the healthy donors in HPA-3 freguencies (P < 0.05). Twenty-four patients (36.9 %) only expressed HLA antibodies, and 14 (21.5%) expressed HLA and platelet GP specific antibodies. The highest expression of anti-HLA-A/B specific antibodies was -A*9(46.2 %)/-B*40(33.6%), respectively. In serum, GPIIb/IIIa was expressed (26.2%), followed by GPIa/IIa (21.5 %). In platelet elution, GPIIb/IIIa was expressed of 41.5% and GPIb/IX 41.5%. Pedigree study was carried out for 2 patients. The results showed that the platelet GP specific antibody/HLA antibody developed in PTR patients was highly related to the mismatch with the platelet antigen/HLA antigen in their parents.

CONCLUSIONThe expressions of the HLA and platelet GP specific antibodies are the most important reason in PTR, it's meaningful to explore the correlation between PTR and HLA and HLA-A/B antigen in guiding platelet transfusion.

Antigens, Human Platelet ; immunology ; Blood Platelets ; Humans ; Isoantibodies ; immunology ; Platelet Transfusion ; Thrombocytopenia

Blood Platelets ; physiology ; Cytokines ; blood ; Drug Therapy, Combination ; Humans ; Immune Tolerance ; Thrombocytopenia ; drug therapy ; etiology ; immunology

OBJECTIVETo detect the frequencies of anti-GPIIb/IIIa antibody secreting B cells and platelet-specific antibody in patients with idiopathic thrombocytopenic purpura (ITP) and non-immune thrombocytopenia, and to evaluate their roles in the diagnosis of ITP and their clinical significance.

METHODSThe frequencies of circulating B cells secreting anti-GPIIb/IIIa antibody and platelet-specific antibody in 58 ITP patients, 33 non-ITP patients and 31 healthy controls were tested by Enzyme-linked Immunospot Assay (ELISPOT) and modified monoclonal antibody immobilization of platelet antigens assay (MAIPA) respectively.

RESULTSThe frequencies of circulating B cells secreting anti-GPIIb/IIIa antibody in ITP patients \[(6.6 ± 4.2)/10(5) PBMNC\] were significantly increased (P < 0.05) than that of the controls \[(1.3 ± 0.5)/10(5) PBMNC\] and non-immune thrombocytopenic purpura patients \[(2.2 ± 2.0)/10(5) PBMNC\]. However there was no apparent difference between the latter two groups (P > 0.05). ELISPOT had a sensitivity of 70.69%, a specificity of 90.91% for the diagnosis of ITP, the sensitivity being higher than that of modified MAIPA's (43.10%) (χ(2) = 7.03, P < 0.05). The ROC curve showed the discriminative validity of cytometric bead array was 0.886.

CONCLUSIONThe frequencies of circulating B cells secreting anti-GPIIb/IIIa antibody may reflect the pathogenesis of ITP. ELISPOT assay have high sensitivity and specificity than modified MAIPA for the diagnosis of ITP and the guidance for clinical therapy.

Autoantibodies ; immunology ; B-Lymphocytes ; Blood Platelets ; Humans ; Platelet Glycoprotein GPIIb-IIIa Complex ; immunology ; Purpura, Thrombocytopenic, Idiopathic ; immunology

OBJECTIVETo investigate a specific and sensitive assay for the diagnosis of autoimmune thrombocytopenic purpura (AITP).

METHODSGlycoprotein specific autoantibodies in platelet eluate and plasma were detected by a modified monoclonal antibody immobilization of platelet antigens assay (MAIPA).

RESULTSThe overall positive rate of specific autoantibodies against platelet GPIIb/IIIa and GPIb/IX in plasma was 38.89% and in eluated platelet membrane was 68.52%. The difference between them was significant (corrected chi(2) = 19.39, P < 0.005). The proportion of positive MAIPA results between primary AITP and secondary AITP was not significantly different. There was a significant inverse correlation between antibody level and platelet count.

CONCLUSIONDetection of eluated GP-specific autoantibodies by MAIPA is highly specific and much more sensitive as compared with the measurement of their plasma counterparts in the diagnosing and therapeutic monitoring of AITP.

Adolescent ; Adult ; Autoantibodies ; blood ; Blood Platelets ; immunology ; Female ; Humans ; Male ; Middle Aged ; Platelet Glycoprotein GPIIb-IIIa Complex ; immunology ; Platelet Glycoprotein GPIb-IX Complex ; immunology ; Purpura, Thrombocytopenic, Idiopathic ; immunology

In autoimmune thrombocytopenic purpura (AITP) specific autoantibodies bind platelet GP via their Fab fragments. Both splenic CD5+ B and CD5- B cells produce platelet glycoprotein-specific antibodies. There is limited number of antigenic determinants, and the GP-specific autoantibodies are derived from a restricted number of B-cell clones in chronic AITP. Blocking co-stimulatory signals could induce platelet-specific T cell anergy. MMF could be used as a second line agent for the treatment of steroid-resistant AITP. Detection of plasma thrombopoietin levels play an important role in the differentiation of thrombocytopenic states caused by platelet destruction or due to bone marrow hypoplasia. Endogenous TPO level is also important on the differential diagnosis of ET and RT. Quinine- or heparin-dependent antibodies could induce thrombocytopenia. PCR-SSP is useful for the genotyping of the platelet-specific alloantigen HPA. Biotinylated platelets have an impaired response to agonists as evidenced by in vitro platelet aggregation tests.
Antigens, Human Platelet ; immunology ; Blood Platelets ; immunology ; Heparin ; adverse effects ; Humans ; Platelet Membrane Glycoproteins ; immunology ; Purpura, Thrombocytopenic, Idiopathic ; etiology ; immunology ; Thrombopoietin ; blood

Platelet plays an important role in bleeding and thrombotic diseases. Humanized anti-platelet antibodies have great clinical effects in treatment of ITP and preventing thrombosis. The important role of platelet in bleeding and thrombotic diseases, the present status of development on study of humanized anti-platelet antibody and its application in treatment of bleeding and thrombotic diseases were summarized in this review.
Animals ; Antibodies, Monoclonal ; biosynthesis ; immunology ; therapeutic use ; Autoantibodies ; immunology ; Blood Platelets ; immunology ; Humans ; Platelet Glycoprotein GPIIb-IIIa Complex ; biosynthesis ; immunology ; Platelet Glycoprotein GPIb-IX Complex ; immunology

This study was aimed to investigate the effects of intact platelets on antigen presentation by either tumor cells or bone-marrow derived dendritic cells (BMDCs). The antigen presentation assay models included BMDC stimulated mixed allogenic lymphocyte reaction and antigen presentation by OVA-harboring EG7 cells to OVA-specific TCR transgenic OT-I T lymphocytes. Fresh platelets prepared from hemogenic murine bloods were added to the culture systems to different levels. Lymphocyte proliferation, level of secreted cytokines in the culture and phenotype of BMDCs were measured by isotope incorporation, ELISA and flow cytometry respectively. The results indicated that when platelets at certain concentrations were added in co-culture system containing both OVA-harboring EG7 cells and OVA-specific TCR transgenic OT-I T lymphocytes, both lymphocyte proliferation and IFNγ production were inhibited. The addition of platelets to the BMDC culture followed by LPS or CpG ODN treatment blocked B7-2 upregulation, cytokine production of the BMDCs, and stimulation potency of such BMDCs for allogenic lymphocytes. Furthermore, platelets inhibited the ability of BMDCs to present both soluble and cellular antigens to clonal specific T lymphocytes, which reflected by decreased lymphocyte proliferation and cytokine production. All these platelet-dependent effects were related to the concentrations of platelets in culture. FACS analysis also revealed that platelets bound to BMDCs induced slightly higher cell death rate of BMDCs. It is concluded that under certain conditions, platelets may affect antigen presentation and the overall outcome of immune responses in a negative way, providing new evidence for the hypothesis that platelets play much more complicated roles in the regulation of immune compartments than originally believed.
Animals ; Antigen Presentation ; immunology ; Blood Platelets ; immunology ; Cell Line, Tumor ; Coculture Techniques ; Dendritic Cells ; immunology ; Mice ; Mice, Inbred BALB C ; Platelet Count ; T-Lymphocytes ; cytology