Abnormalities of bone marrow B cells and plasma cells in primary immune thrombocytopenia.

Primary immune thrombocytopenia (ITP) is an autoantibody-mediated hemorrhagic disorder in which B cells play an essential role. Previous studies have focused on peripheral blood (PB), but B cells in bone marrow (BM) have not been well characterized. We aimed to explore the profile of B-cell subsets and their cytokine environments in the BM of patients with ITP to further clarify the pathogenesis of the disease. B-cell subpopulations and their cytokine/chemokine receptors were detected by using flow cytometry. Plasma concentrations of cytokines/chemokines were measured by using enzyme-linked immunosorbent assay. Messenger RNA levels of B cell-related transcription factors were determined by using quantitative polymerase chain reaction. Regulatory B cell (Breg) function was assessed by quantifying their inhibitory effects on monocytes and T cells in vitro. Decreased proportions of total B cells, naive B cells, and defective Bregs were observed in patients with ITP compared with healthy controls (HCs), whereas an elevated frequency of long-lived plasma cells was found in BM of autoantibody-positive patients. No statistical difference was observed in plasmablasts or in short-lived plasma cells between patients with ITP and HCs. The immunosuppressive capacity of BM Bregs from patients with ITP was considerably weaker than HCs. An in vivo study using an active ITP murine model revealed that Breg transfusion could significantly alleviate thrombocytopenia. Moreover, overactivation of CXCL13-CXCR5 and BAFF/APRIL systems were found in ITP patient BM. Taken together, B-cell subsets in BM were skewed toward a proinflammatory profile in patients with ITP, suggesting the involvement of dysregulated BM B cells in the development of the disease.

High-dose dexamethasone vs prednisone for treatment of adult immune thrombocytopenia: a prospective multicenter randomized trial.

This study compared the efficacy and safety of high-dose dexamethasone (HD-DXM) and conventional prednisone (PDN) on the largest cohort to date as first-line strategies for newly diagnosed adult primary immune thrombocytopenia (ITP). Patients enrolled were randomized to receive DXM 40 mg/d for 4 days (n = 95, nonresponders received an additional 4-day course of DXM) or prednisone 1.0 mg/kg daily for 4 weeks and then tapered (n = 97). One or 2 courses of HD-DXM resulted in a higher incidence of overall initial response (82.1% vs 67.4%, P = .044) and complete response (50.5% vs 26.8%, P = .001) compared with prednisone. Time to response was shorter in the HD-DXM arm (P < .001), and a baseline bleeding score ≥8 was associated with a decreased likelihood of initial response. Sustained response was achieved by 40.0% of patients in the HD-DXM arm and 41.2% in the PDN arm (P = .884). Initial complete response was a positive indicator of sustained response, whereas presence of antiplatelet autoantibodies was a negative indicator. HD-DXM was generally tolerated better. We concluded that HD-DXM could be a preferred corticosteroid strategy for first-line management of adult primary ITP. This study is registered at www.clinicaltrials.gov as #NCT01356511.

In vitro recovery of Th1/Th2 balance in PBMCs from patients with immune thrombocytopenia through the actions of IL-18BPa/Fc.

To determine the effects of IL-18BPa/Fc on the cytokine production and survival of peripheral blood mononuclear cells (PBMCs) of immune thrombocytopenia (ITP), PBMCs isolated from patients with ITP and healthy donors were treated with or without of IL-18BPa/Fc. The production of IFN-γ, IL-2, tumor necrosis factor (TNF)-α, IL-4, IL-5 and IL-10 was measured by ELISA, and mRNA expression of IFN-γ and IL-18R was evaluated by RT-PCR. Besides, flow cytometric analysis of cell apoptosis was performed by staining with annexin V-FITC/ Propidium Iodide (PI). The proliferation rate of PBMCs was examined by CCK-8 assay. IL-18BPa/Fc at 10 ng/ml significantly stimulated IL-10 secretion from PBMCs in patients with ITP and healthy donors, while it decreased IFN-γ release. Further, IL-18BPa/Fc enhanced dexamethason(DEX) reduction of PHA-induced IFN-γ production by an additional 38.9%(DEX 20 nmol/l) and 49.9%(DEX 50 nmol/l) in ITP patients. Interestingly, the treatment of PBMCs with IL-18BPa/Fc increased the percentage of early apoptotic cells in patients with ITP. In conclusion, IL-18BPa/Fc, via neutralizing the biologic activity of mature IL-18, accelerates lymphocyte apoptosis and downregulates IFN-γ, while permitting the production of Th2 cytokine IL-10. These observations suggest a role of IL-18BPa/Fc in the recovery of Th1/Th2 balance, as well as its therapeutic potential in the treatment of ITP.

Determination of platelet-bound glycoprotein-specific autoantibodies by flow cytometric immunobead assay in primary immune thrombocytopenia.

OBJECTIVES: Primary immune thrombocytopenia (ITP) is an autoimmune disorder characterized by premature platelet destruction induced by autoantibodies directed against platelet glycoproteins (GPs). Despite being a clinically important disorder, ITP lacks a feasible diagnostic assay for routine clinical use. This study was meant to evaluate a newly developed flow cytometric immunobead assay for determination of platelet-bound GP-specific autoantibodies in comparison with indirect monoclonal antibody-specific immobilization of platelet antigen (MAIPA) in the diagnosis of ITP. METHODS: Platelet-bound and plasma GPIIb/IIIa and GPIb/IX autoantibodies were determined by flow cytometric immunobead assay and indirect modified MAIPA, respectively. The average fluorescence level for platelet-bound, GP-specific autoantibodies was given as a ratio to three normal controls tested simultaneously. RESULTS: The median value of platelet-bound GPIIb/IIIa and GPIb/IX autoantibodies in ITP group were 3.09 (range 0.78, 30.2) and 3.09 (range 0.72, 19.2), respectively, which were significantly higher than non-ITP group [1.01 (0.67, 5.59) and 1.01 (0.79, 5.56), respectively, P<0.001] and normal controls [1.02 (0.72, 1.76) and 1.03 (0.79, 1.73), respectively, P<0.001]. The receiver-operating characteristics curve analysis showed an area under the curve of 0.895 for GPIIb/IIIa autoantibody and 0.859 for GPIb/IX autoantibody, respectively. Combined detection of GPIIb/IIIa or GPIb/IX autoantibodies by flow cytometric immunobead assay showed a sensitivity of 82.11% for ITP diagnosis. CONCLUSION: This study demonstrated that determination of platelet-bound, GP-specific autoantibodies by flow cytometric immunobead assay was a convenient, sensitive, and specific test for the differential diagnosis of thrombocytopenic patients.

[Expression of interleukin-18 and interleukin-18 receptor alpha chain of the peripheral white blood cells in immune thrombocytopenia].

OBJECTIVE: To detect the expression of interleukin (IL)-18 of the peripheral blood cells and IL-18 receptor alpha chain (IL-18Ralpha) on the surface of CD(3)(+) cells in patients newly diagnosed as immune thrombocytopenia (ITP) before medication and to explore the roles of IL-18 and IL-18Ralpha in the development of ITP. METHODS: Eighteen out-patients or inpatients with acute ITP accepting treatment in Qilu Hospital were enrolled in this study and 15 matching healthy subjects were taken as control. Plasma IL-18 level was detected with enzyme linked immunosorbent assay (ELISA), the expression of IL-18Ralpha on CD(3)(+) lymphocytes and total lymphocytes were measured with flow cytometry;T-bet and GATA-3 mRNA were measured with reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: The expression of IL-18 in acute ITP plasma was (468.57 + or - 141.62) ng/L and IL-18Ralpha on the surface of CD(3)(+) cells and lymphocytes were (8.50 + or - 3.16)% and (9.16 + or - 2.98)% respectively. The levels of IL-18 and IL-18Ralpha were increased in active ITP patients as compared with those in the controls (P < 0.05). The levels of IL-18 mRNA (0.12 + or - 0.02) and T-bet mRNA (0.07 + or - 0.02) were significantly increased in patients with active ITP as compared with those in the controls (P < 0.05), while GATA-3 mRNA (0.0039 + or - 0.0014) were significantly decreased in patients with active ITP (P < 0.05). The balance between T-bet and GATA-3 was significantly disturbed in ITP. CONCLUSIONS: Through the variation of the levels of gene and protein, our study showed that IL-18 and IL-18Ralpha might upregulate the expression of Th1-cytokines in ITP patients. It is also suggested that IL-18 has potential association with the development of ITP. Especially, it may provide a new treatment method for ITP by regulating the ratio of T-bet and GATA-3 and resuming the balance of Th1/Th2.

[Effect of high-dose dexamethasone on BAFF and Tregs in patients with immune thrombocytopenic purpura.].

OBJECTIVE: To investigate the change of B-cell activating factor of the TNF family (BAFF) and regulatory T-cells (Tregs) before and after high-dose dexamethasone(HD-DXM) therapy and assess the effect of BAFF on Treg cells in immune thrombocytopenic purpura (ITP). METHODS: The plasma BAFF concentration was measured by ELISA, and Treg cell numbers by flow cytometry. RESULTS: The plasma BAFF level \[(599.70 +/- 199.40) pg/ml\] was significantly increased (P < 0.05), and the percentage of Treg cells \[(1.56 +/- 0.73)%\] was significantly decreased (P < 0.01) in ITP patients before treatment as compared with that in controls \[(454.5 +/- 132.5) pg/ml and (4.08 +/- 1.08)%, respectively\]. After treatment with HD-DXM, the plasma BAFF level \[(296.9 +/- 119.7) pg/ml\] was significantly decreased (P < 0.01), and the percentage of Treg cells \[(5.94 +/- 2.22)%\] was significantly increased (P < 0.01). The BAFF level and Treg proportion had no significant correlation with platelets count (P > 0.05). In in vitro assays, no difference was found in the number of Treg cells between rhBAFF0 group and rhBAFF20 group \[(1.53 +/- 0.69)%, (1.49 +/- 0.67)%, P = 0.89)\]. CONCLUSION: BAFF level was increased and Treg cells decreased in ITP patients. HD-DXM might play a role in ITP treatment by down-regulating BAFF expression and up-regulating Treg cells number. BAFF had no influence on the number of Treg cells.

[Study of a humanized anti-platelet GP VI single chain Fv phage antibody].

OBJECTIVE: To study the anti-platelet GPVI single chain Fv phage antibody which can inhibit the aggregation function of platelet by using phage antibody library technology. METHODS: ITP patients with anti-platelet GPVI autoantibody that could inhibit the aggregation function of platelet were screened by MAIPA assay and platelet aggregation test. The gene fragments of heavy chain and light chain variable region (VH and VL) of immunoglobulin were amplified by RT-PCR from peripheral blood lymphocytes mRNA of the screened patients. The VH and and VL fragments were linked through a DNA linker encoding the peptide (Gly4Ser)3 to construct single chain Fv (ScFv) gene. The ScFv gene was digested with SfiI/NotI restriction enzymes and cloned into the pHEN2 phage display vector, then electrically transformed to E. coli TG1. The TG1 containing ScFv-pHEN2 was rescued by helper phage M13K07 to produce ScFv phage antibody. The anti-platelet GPVI phage ScFv antibody was enriched and purified. The effect of the phage antibody on platelet aggregation function was studied. RESULTS: Of 806 chronic ITP patients, 11 (1.36%) were positive for anti-platelet GPVI autoantibody and 2 (0.24%) patients'plasma significantly inhibited the collagen induced platelet aggregation. The length of VH and VL fragments was about 380 to 400 bp, and were successfully formed ScFv fragments of about 800 bp by DNA linker. After cloning ScFv to phagemid vector pHEN2 and transforming ScFv-pHEN2 to TG1, 4.1x10(7) clones were obtained. After M13K07 rescue, 2.62x10(10) cfu/ml ScFv phage antibodies were produced. The purified anti-platelet GPVI ScFv phage antibody inhibited the collagen induced platelet aggregation. CONCLUSION: Anti-platelet GPVI ScFv phage antibody produced by phage antibody library technology can inhibit the aggregation function of platelet.

[The impact of platelet membrane autoantibodies on high-dose dexamethasone therapy in patients with idiopathic thrombocytopenic purpura].

OBJECTIVE: To evaluate the impact of platelet membrane glycoprotein (GP)-specific autoantibodies on high-dose dexamethasone therapy in patients with idiopathic thrombocytopenic purpura (ITP). METHODS: Modified direct monoclonal antibody immobilization of platelet antigen assay (MAIPA) was used to detect platelet GPIIb/IIIa and/or GPI b specific autoantibodies. All patients received oral dexamethasone 40 mg/d for 4 days. RESULTS: The response rate of high-dose dexamethasone in GPIIb/IIIa and/or GPIb specific autoantibody-negative patients was significantly different from that of antibody-positive patients (P<0.05). The response rate of GPIIb/IIIa specific autoantibody-positive patients was lower than that of antibody-negative patients (P<0.05). GPIb specific autoantibody had no significant impact on the efficacy of high-dose dexamethasone (P>0.05). CONCLUSION: Platelet membrane GPIIb/IIIa-specific autoantibody can be a potential negative indicator for ITP patients'response to high-dose oral dexamethasone.

[The role of interleukin-18 and interleukin-18 receptor in predominant Th1 immune response of patients with immune thrombocytopenia].

OBJECTIVE: To evaluate the role of interleukin (IL)-18 and IL-18 receptor (IL-18R) in the predominant Th1 type cytokine response in patients with immune thrombocytopenia (ITP). METHODS: Fifteen patients with active phase ITP, eighteen in remission and thirteen healthy controls were enrolled in this study. T-bet and GATA-3 mRNA levels in peripheral blood mononucleated cells (PBMNC) were measured by reverse transcriptase polymerase chain reaction (RT-PCR); the plasma IL-18 level by enzyme linked immunosorbent assay (ELISA), the expression of IL-18R on CD3(+) lymphocytes and total lymphocytes by flow cytometry(FCM). RESULTS: The T-bet mRNA levels in patients with active phase ITP was 3.572 fold as much as that in the controls (P < 0.05), while the GATA-3 mRNA levels were 0.378 fold of that in controls (P < 0.05). The levels of plasma IL-18 and IL-18R on CD3(+) lymphocytes were significantly increased in active phase ITP than in remission phase and controls. There was no difference in ratio of T-bet/GATA-3 between remitted ITP and controls and so was for T-bet mRNA, GATA-3 mRNA, plasma IL-18 and IL-18R on CD3(+) lymphocytes. CONCLUSION: ITP as a disease of Th1-dominant response there is an unbalance between T-bet and GATA-3 in its active phase; IL-18 and IL-18R being upregulated.

The effects of BAFF and BAFF-R-Fc fusion protein in immune thrombocytopenia.

Elevated level of B-cell activating factor (BAFF) has been implicated in the pathogenesis of some autoimmune diseases. Blockade of receptor and ligand binding by decoy receptor has demonstrated a clinical benefit in both oncologic and immunologic diseases. In this report, we have detected plasma BAFF and BAFF mRNA expression in immune thrombocytopenia (ITP) patients by enzyme-linked immunosorbent assay (ELISA) and real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR). The effects of recombinant human BAFF (rhBAFF) and BAFF-R-Fc fusion protein (BR3-Fc) on B cells, T cells, platelets, secretion of interferon gamma (IFNgamma), and interleukin-4 (IL-4) were measured by flow cytometry and ELISA. Patients with active disease had higher levels of plasma BAFF and BAFF mRNA than patients in remission and controls. In in vitro assays, rhBAFF promoted the survival of CD19(+) and CD8(+) cells, and increased the apoptosis of platelets and the secretion of IFN-gamma. BR3-Fc successfully corrected the effects of rhBAFF on lymphocytes, platelets, and cytokines. These findings suggest that BAFF may play a pathogenic role in ITP by promoting the survival of CD19(+) and CD8(+) cells, and increasing the apoptosis of platelets and the secretion of IFN-gamma. Blockade of BAFF by BR3-Fc might be a promising therapeutic approach for ITP.

[The immunoreactivity of IgG and its fragments from ITP patients and their effects on platelet aggregation function].

OBJECTIVE: To prepare ITP plasma IgG and its F(ab')2 fragments and investigate their immunoreactivity to platelet GPIIb/IIIa and/or GPIb/IX and their effects on platelet aggregation function. METHODS: The ITP patients having inhibitory autoantibody to the platelet aggregation were selected by modified MAIPA and platelet aggregation test with turbidimetry. Plasma IgG and its F(ab')2 fragments were prepared by streptococcal protein A affinity column and pepsin digestion. The immunoreactivity and the effects on platelet aggregation function of the whole antibody and its fragments were detected by modified MAIPA and platelet aggregation test, respectively. RESULTS: (1) Anti-platelet GPIIb/IIIa and/or GPIb/IX autoantibodies were detected in 34 of 68 (53.6%) ITP patients' plasmas and that from 5 patients significantly inhibited the platelet aggregation induced by ADP or ristocetin. (2) By using protein A column combined with protease digestion, pure IgG and its F(ab')2 fragments were successfully obtained. (3) The purified IgG and its F(ab')2 fragments retained the ability to bind to their respective glycoproteins and inhibited the platelet aggregation function, whereas the IgG depleted plasma lost the ability of binding to the platelet GPs. CONCLUSIONS: F(ab')2 fragment of the IgG antibody is a functional fragment, which not only has the binding ability to the platelet GPs but also inhibits the platelet aggregation function in a dose-dependent manner.

Effects of IgG and its F(ab')2 fragments of some patients with idiopathic thrombocytopenic purpura on platelet aggregation.

OBJECTIVES: To make humanized monoclonal antibodies by phage surface display technology, we screened out the specific anti-platelet glycoproteins (GPs) IgG antibody from patients with chronic idiopathic thrombocytopenic purpura (ITP), which can inhibit platelet aggregation. METHODS: We studied plasmas from 68 patients with ITP for the presence of IgG antibodies specific for GPIIb/IIIa and/or GPIb/IX using modified monoclonal antibody immobilization of platelet antigen assays. The IgG antibody and its F(ab')(2) fragments of the positive plasmas which could inhibit platelet aggregation function were prepared and purified. Their immunoreactivity to platelet GPs and effects on platelet function were further analyzed. RESULTS: GPIIb/IIIa- and GPIb/IX-specific antibodies were found in 21 and 19 patients, respectively. Six of them had antibodies against both GP complexes. Among the 34 positive plasmas, four with positive anti-GPIIb/IIIa autoantibody showed significant inhibition of platelet aggregation induced by adenosine diphosphate (ADP), whereas one with GPIb/IX-specific antibody inhibited ristocetin-induced platelet aggregation. The purified IgG and its F(ab')(2) fragments from two patients not only retained the ability to bind to platelet GPs but also impaired the in vitro ADP-induced platelet aggregation. CONCLUSIONS: F(ab')(2) portion of the IgG is a functional fragment, which is responsible for the autoantibody interaction with platelet GPs in ITP, and some of them also affect platelet function, which can be used to develop completely humanized anti-GPIIb/IIIa small molecular phage antibody.

[Construction and clinical applications of a humanized phage library of platelet GPIIb/IIIa single chain Fv antibody].

OBJECTIVE: To screen out the anti-platelet GPIIb/IIIa autoantibody which can inhibit with aggregation function of platelet and construct a humanized anti-platelet GPIIb/IIIa single chain Fv library by phage surface display technology. METHODS: Idiopathic thrombocytopenic purpura (ITP) patients whose plasma contains anti-platelet GPIIb/IIIa autoantibodies were screened out. The antibodies can inhibit the aggregation function of platelet by using MAIPA assay and platelet aggregation test. The heavy chain and light chain variable region genes of human immunoglobulin were amplified by RT-PCR from peripheral blood lymphocytes mRNA of the patients screened out and randomly combined through a DNA linker encoding the peptide (Gly(4)Ser)(3) to construct single chain Fv gene. ScFv gene was digested with SfiI/NotI restricted digest enzyme to ligate the pHEN2 cloning vector, then were electrically transformed to E.coli TG1. The TG1 containing ScFv-pHEN2 was rescued by helper phage M13K07 to produce ScFv phage antibody. RESULTS: Of 95 chronic ITP patients, 41 (43.2%) were found positive for anti-platelet GPIIb/IIIa autoantibody, 5 (5.3%) were markedly positive. 2 (2.1%) patients plasma significantly inhibited the aggregation function of platelet. The lengths of VH and VL were about 380 to 400 bp. They were successfully linked by DNA linker to form ScFv fragment of about 780 bp. After cloning ScFv to phagemid pHEN2 and transforming ScFv-pHEN2 to TG1, 2.1 x 10(7) clones formed. After M13K07 rescue, 1.62 x 10(10) cfu/ml ScFv phage antibodies were produced. CONCLUSION: Few anti-platelet GPIIb/IIIa antibodies can inhibit the aggregation function of platelet. A phage antibody library has been constructed by phage surface display technology. Humanized anti-platelet GPIIb/IIIa ScFv phage antibody can be screened from this library.

[Identification of human platelet specific functional antibody and its fragments].

OBJECTIVE: To study the immunoreactivity of the specific anti-platelet glycoprotein (GP) IgG antibody and its F(ab')2 fragments from patients with chronic idiopathic thrombocytopenic purpura (ITP) and to investigate their effects on platelet aggregation function. METHODS: Peripheral blood samples were collected from 84 patients with ITP. Modified monoclonal antibody immobilization of platelet antigen assays was used to detect the IgG antibodies specific for GP I b/II a, GP I b/IX and GP VI. The IgG antibody and its F(ab')2 fragments in the positive plasma inhibiting platelet aggregation function were prepared and purified. Plate-rich Peripheral blood sample was collected from a normal person with O type blood and platelet-rich plasma (PRP) and platelet-poor plasma (PPP) were prepared. Plasma pf ITP patient or purified IgG or F(ab')2 fragments of different concentrations were added into PRP, and then inducers of platelet aggregation ADP, ristocetin, or collagen were added. The platelet aggregation was measured. Platelet GP II b/III a specific human-rat chimeric antibody 7E3 and GP I b specific antibody SZ2 were used as positive controls and PBS was used as negative control. RESULTS: GP II b/III a and/or GP I b/IX and/or GP VI specific antibodies were found in 48 (57.1%) patients. The plasma, purified IgG and F(ab')2 fragments of 7 of these 48 patients (14.6%) with positive autoantibody showed significant activity against GP II b/III a (4 patients), GP I b/IX (2 patients), or GP VI (one patient). The purified IgG and F(ab')2 fragments of 2 patients positive in GP II b/ III a autoantibody out of the 7 patients significantly inhibited the platelet aggregation induced by ADP, the purified IgG and F(ab')2 fragments of 1 patients positive in GP I b/IX out of the 7 patients significantly inhibited the platelet aggregation induced by ristocetin, and the purified IgG and F(ab')2 fragments of 1 patients positive in GP VI out of the 7 patients significantly inhibited the platelet aggregation induced by collagen. CONCLUSION: A functional fragment, F(ab')2 portion of IgG is responsible for the autoantibody interaction with platelet GPs in ITP, and some of them also affect the platelet function. It can be used to develop completely humanized anti-GP small molecular phage antibody.