Neonatal autoimmune thrombocytopenia: role of high-dose intravenous immunoglobulin G therapy

Summary High-dose intravenous immunoglobulin G (IVIgG) therapy results in a rapid reversal of thrombocytopenia in over 80% of children with acute immune thrombocytopenic purpura (ITP). Comparable results were observed in eleven infants with an analogous condition, neonatal autoimmune thrombocytopenia (NATP), who received IVIgG (2 g/kg body weight) administered alone (n=6) or in combination with steroids (n=5). The median platelet count pre-IVIgG therapy was 25×10⁹/l (range 5 to 74×10⁹/l). The overall response rate to IVIgG therapy, administered alone or in combination with steroids was 75% (12 of 16 treatment episodes). A good response to therapy was defined as an increase in the platelet count to 50×10⁹/l and at least twice the pre-treatment value at 48 h after completion of the IVIgG infusion. The rapid and generally excellent response to IVIgG therapy in infants with NATP suggests that this treatment approach should be considered as first-line therapy for severely thrombocytopenic infants with this self-limiting but potentially serious disorder.Presented at the International Workshop on ITP, August 26 and 27, 1988, Lucerne, Switzerland     

Relative efficacy of intravenous immunoglobulin G in ameliorating thrombocytopenia induced by antiplatelet GPIIbIIIa versus GPIbalpha antibodies

Intravenous immunoglobulin G (IVIG) is used to treat idiopathic thrombocytopenic purpura (ITP). Although many patients benefit from IVIG, some are refractory to this therapy. ITP is characterized by platelet clearance mediated primarily by antiplatelet antibodies against GPIIbIIIa and/or the GPIbalpha complex. These 2 groups of antibodies may induce ITP through different mechanisms. We tested the hypothesis that IVIG may not be equally effective in preventing ITP caused by anti-GPIIbIIIa versus anti-GPIbalpha antibodies in mice. Thrombocytopenia was induced in BALB/c mice using monoclonal antibodies against either mouse GPIIbIIIa (JON1, JON2, and JON3) or GPIbalpha (p0p3, p0p4, p0p5, p0p9, and p0p11). Pretreatment with IVIG significantly ameliorated ITP in all anti-GPIIbIIIa-injected animals. Conversely, IVIG failed to prevent ITP in all anti-GPIbalpha-treated mice, except for p0p4. These results were repeated in C57BL/6 mice, and with different IVIG preparations. These data in mice suggest that patients with ITP mediated by anti-GPIbalpha antibodies may be less responsive to IVIG treatment.     

Platelet apoptosis in paediatric immune thrombocytopenia is ameliorated by intravenous immunoglobulin

To evaluate the role of intravenous immunoglobulin (IVIg) in platelet apoptosis in paediatric immune thrombocytopenia, we investigated the platelets of 20 paediatric patients with acute immune thrombocytopenia (ITP), before and after IVIg treatment. Healthy children with platelet counts in the normal range and children with thrombocytopenia due to chemotherapy were enrolled as controls. All ITP patients presented with platelet counts <20 × 10⁹/l and bleeding symptoms. Markers of apoptosis, including activated caspase‐3, ‐8 and ‐9, phosphatidylserine (PS) exposure, mitochondrial inner membrane potential (ΔΨm), as well as platelet‐derived microparticle formation, were analysed by flow cytometry. After IVIg treatment, platelet counts increased to >20 × 10⁹/l in all patients. ITP patients had significantly increased proportions of platelets with activated caspase‐3, ‐8 and ‐9, with PS exposure, and with decreased ΔΨm, and demonstrated increased microparticle formation. Except for ΔΨm, these markers for apoptosis were reduced by IVIg treatment. Platelets of children with thrombocytopenia after chemotherapy also demonstrated increased microparticle formation and decreased ΔΨm, but no activation of caspases 3, 8 and 9 or PS exposure. In conclusion, in acute paediatric ITP, enhanced platelet apoptosis is seen at diagnosis that normalizes after IVIg treatment.     

The association between platelet autoantibody specificity and response to intravenous immunoglobulin G in the treatment of patients with immune thrombocytopenia

We retrospectively investigated the association between platelet autoantibody specificity and response to intravenous immunoglobulin G (IVIG) in 17 patients with immune thrombocytopenia (ITP). Platelet-associated antibodies against glycoprotein (GP) IIb/IIIa, GPIb/IX, and GPIa/IIa were detected in 13, 10, and 8 patients, respectively. A response occurred in 7 of 7 patients without anti-GPIb/IX, but in only 3 of 10 patients with anti-GPIb/IX (p<0.01). There was no difference in the response rates in patients with or without anti-GPIIb/IIIa or anti-GPIa/IIa. We conclude that ITP patients with anti-GPIb/IX may be less responsive to IVIG.     

The use of intravenous immunoglobulin (endobulin) in patients with immune thrombocytopenia

Six adults were treated for chronic immune thrombocytopenia (ITP) with high dose intravenous immunoglobulin (ENDOBULIN). Five patients were evaluable. In four patients the platelet associated IgG (PAIgG) levels were increased. All four responded to i.v. Ig and two subsequently underwent splenectomy. One patient had normal PAIgG and had no response to i.v. Ig. Endobulin is useful in the treatment of chronic ITP and is followed in some patients by a prolonged response. High levels of PAIgG may predict a favourable outcome.     

Co-incidental Von Willebrands disease and immune thrombocytopenia in pregnancy: treatment with high dose intravenous immunoglobulin

We report a rare association of Von Willebrands disease and idiopathic immune thrombocytopenia in pregnancy. The major threat to the successful outcome of the pregnancy was posed by the acquired disorder. The use of high dose immunoglobulin allowed a normal delivery, without any adverse effects on mother or child.     

Identification of predictive factors for response to intravenous immunoglobulin treatment in children with immune thrombocytopenia

Acute immune thrombocytopenia (ITP) is a common benign bleeding disorder of variable etiology characterized by isolated thrombocytopenia. Intravenous immunoglobulin (IVIG) treatment is generally given as an initial treatment to pediatric patients with ITP, but markers predictive of the response to IVIG remain poorly defined. We retrospectively evaluated whether clinical and laboratory findings before treatment could predict response to IVIG and progression to chronic ITP in Japanese children with ITP. Between April 1997 and December 2011, a total of 49 children with newly diagnosed ITP were initially treated with IVIG. Their medical records were retrospectively reviewed. In multivariate analyses, lower white blood cell (WBC) count was the only unfavorable factor for response to IVIG and progression to chronic ITP. Patients with WBC count <7.0 × 10⁹/L had a lower probability of thrombocytopenia-free survival (41 vs. 77 %, P = 0.003) and a higher rate of progression to chronic ITP (29 vs. 6 %, P = 0.040) than those with WBC count ≥7.0 × 10⁹/L. These results suggest that ITP with lower WBC count may represent a distinct subgroup requiring initial treatment other than IVIG.     

Picogram doses of lipopolysaccharide exacerbate antibody-mediated thrombocytopenia and reduce the therapeutic efficacy of intravenous immunoglobulin in mice

Exacerbation of antibody-mediated thrombocytopenia following infection with viruses has recently been demonstrated in a mouse model of the disease. The phenomenon was caused by an increased activation of phagocytes through gamma-interferon secretion in response to infection. Endotoxins from Gram-negative bacteria are also known to be potent activators of phagocytic cells. The objective of the present work was to determine whether lipopolysaccharide (LPS) could exacerbate antibody-mediated thrombocytopenia in vivo and so alter the therapeutic efficacy of intravenous immunoglobulin (IVIg), using a mouse model of thrombocytopenia. Very low doses of LPS (picogram range) and of anti-platelet antibodies (nanogram range), which did not induce thrombocytopenia individually, could synergize in vivo, resulting in significant decreases in platelet counts. The therapeutic efficacy of IVIg in antibody-mediated thrombocytopenia was significantly reduced in presence of LPS. These in vivo observations further support a role for bacterial infections in the aetiology of immune thrombocytopenic purpura (ITP) and may contribute to better understand the recognized lack of efficacy of IVIg in a significant proportion of patients with ITP.     

High-dose intravenous immunoglobulin and splenectomy for the treatment of HIV-related immune thrombocytopenia in patients with severe haemophilia

Four patients with severe haemophilia A and one patient with severe Christmas disease developed severe immune thrombocytopenia (platelet count less than 20 x 10(9)/l). All five patients were HIV-antibody positive and one was HIV-antigen positive. Four patients were treated initially with prednisolone, but with only a transient platelet response in three and no response in the fourth. All patients were treated with high dose intravenous immunoglobulin (0.4 g/kg daily for 5 d) resulting in a rise in platelet count in all cases (range 138-300 x 10(9)/l) and then proceeded to splenectomy. Three remain in complete remission after 6-14 months, and one showed a good response with platelet counts ranging from 103 to 187 x 10(9)/l. The fifth patients achieved a normal platelet count for 3 months post-splenectomy, but suffered a relapse with platelet counts ranging from 25 to 108 x 10(9)/l over the next 3 years. However, following a severe Varicella infection 10 months ago, during which he developed a marked transient thrombocytosis, he has also maintained a normal platelet count.     

Effects of intravenous immunoglobulin on platelet count and antiplatelet antibody disposition in a rat model of immune thrombocytopenia

Experiments were conducted to investigate the effects of intravenous immunoglobulin (IVIG) in a rat model of immune thrombocytopenia (ITP). Rats were pretreated with 0 to 2 g/kg IVIG and then challenged with an antiplatelet antibody (7E3, 8 mg/kg). IVIG effects on 7E3-induced thrombocytopenia and on 7E3 pharmacokinetics were determined. IVIG pretreatment led to significant changes in the degree and time-course of 7E3-induced thrombocytopenia (P =.031). Nadir percent platelet counts were 121% to 279% greater in animals treated with IVIG (0.4-2 g/kg) than in animals receiving 7E3 alone. IVIG treatment also led to dose-dependent increases in 7E3 clearance (P <.001), with more than 2-fold increases in 7E3 clearance seen following the highest dose of IVIG. In vitro experiments showed that IVIG effects on platelet count are not likely due to anti-idiotypic inhibition of 7E3-platelet binding and that IVIG did not directly bind to 7E3. Consequently, IVIG-7E3 binding cannot explain the increase of 7E3 clearance following IVIG treatment. We propose that the observed increase in 7E3 clearance with IVIG therapy is due to saturation of the FcRn salvage receptor for IgG. The importance of the effect of IVIG on 7E3 clearance to the prevention of thrombocytopenia in these animals is unclear at present; nonetheless, these data provide experimental support for a new mechanism of IVIG action in ITP (ie, IVIG-mediated increases in antiplatelet antibody elimination). This model of ITP will be useful for further investigations of IVIG mechanism of action and for development of new therapies for ITP.     

Reticuloendothelial system Fc-receptor function in patients with immune thrombocytopenia after treatment with high dose intravenous immunoglobulin

Reticuloendothelial system Fc-receptor (FcR) function was measured in 4 healthy controls and 9 patients with immune thrombocytopenia before and after therapy with high dose i.v. gammaglobulin (HDIg). Idiopathic thrombocytopenic purpura (ITP) was diagnosed in 5 patients. 2 patients with hemophilia A, 1 with acute tuberculosis and 1 with psoriasis vulgaris had thrombocytopenia that clinically resembled ITP. 4 out of 9 patients received prednisone prior to or during the study. FcR blockade was observed only in patients with ITP not receiving prednisone. In all other patients, HDIg did not induce a measurable FcR blockade. However, all except 1 patient (with acute tuberculosis) showed a marked rise in platelet counts for 2 to 12 wk. This is consistent with therapeutic efficacy of HDIg in various clinical settings of immune thrombocytopenia. All platelets were fully hemostatic and clinically no difference could be observed. This indicates that the effect of HDIg cannot be due to FcR blockade alone.     

Reversal of immune thrombocytopenia in mice by cross-linking human immunoglobulin G with a high-affinity monoclonal antibody

Intravenous immunoglobulins (IVIgs) are used to treat an increasing number of autoimmune diseases, but their exact mechanism of action remains unknown. This study showed that cross-linking of human IgG present in IVIg preparations using a mouse monoclonal anti-human IgG generated complexes that prevented or reversed thrombocytopenia in mice more efficiently than IVIg. Furthermore, biologically active complexes were obtained simply by adding the monoclonal antibody to human serum. These results suggest the possible development of an IVIg-free substitute through the ex vivo, and possibly in vivo, formation of immune complexes containing autologous IgG of immune thrombocytopenic purpura patients.     

Effect of intravenous immunoglobulin on inhibition of fibrinogen binding to platelets by sera from patients with immune thrombocytopenia

We previously described an ELISA to measure the inhibition of platelet glycoprotein llb/IIIa (GPIIb/IIIa) binding to fibrinogen due to immune complexes and/or anti-platelet antibodies from patients with immune thrombocytopenia (ITP) or HIV-related ITP. Circulating immune complexes (CIC) were the main factor in the inhibition of GPIIb/IIIa binding to fibrinogen in HIV-related ITP, whereas in non-HIV ITP, inhibition was only partially due to CIC; anti-platelet antibodies specific to GPIIIa were also shown to play a role. In this study, we correlated the rise in the platelet count after intravenous immunoglobulin (IVIG) infusion with the decrease in inhibition of fibrinogen binding to GPIIb/IIIa by the sera of patients with ITP and HIV-related ITP. In the majority of the patients' sera tested, as the platelet count increased following the administration of IVIG, the degree of inhibition of GPIIb/IIIa binding to fibrinogen decreased. We also observed a decrease and/or disappearance of the antibodies specific to GPIIb and/or GPIIIa after IVIG administration. In HIV-seronegative ITP patients, the decrease or disappearance of anti-platelet antibodies directly correlated with the decreased inhibition of GPIIb/IIIa binding to fibrinogen by the 2% PEG supernatants of sera which contained anti-platelet antibodies. These findings suggest that IVIG directly affects the binding of CIC and anti-platelet antibodies to platelets and thereby improves platelet survival. Our results also suggest that the anti-idiotypic effect may contribute to IVIG's therapeutic action. In contrast, in the HIV-seropositive group, the decreased inhibition by PEG precipitates after IVIG administration was more strongly associated with an increase in the platelet count. © 1993 Wiley-Liss, Inc.     

Lack of efficacy of high-dose intravenous immunoglobulin treatment of severe thrombocytopenia in patients with secondary dengue virus infection

Because most cases of secondary dengue virus infection are associated with an increased level of platelet-associated IgG, a high dose of intravenous immunoglobulin (IVIG) may have an effect on the development of severe thrombocytopenia in this disease. A randomized, controlled study was conducted with two treatment groups consisting of a treatment (IVIG) group (n = 15) and a non-treatment (non-IVIG) group (n = 16) to determine whether a high dose of IVIG is effective in hastening the recovery from thrombocytopenia in patients with secondary dengue virus infection. No significant difference was found in the baseline demographic data between the two groups. No adverse effect of IVIG was observed, but no effect in hastening the recovery of platelet counts was found in patients with secondary dengue infections. The lack of efficacy of IVIG suggests that platelet clearance by macrophages through Fc gamma receptors is not a primary mechanism in this disease.     

Thymic-derived tolerizing dendritic cells are upregulated in the spleen upon treatment with intravenous immunoglobulin in a murine model of immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by low platelet counts. First-line treatment includes intravenous immunoglobulin (IVIg), however, its working mechanism remains incompletely understood. We investigated splenic and thymic dendritic cell (DC) subsets upon IVIg treatment in a well-characterized active murine model of ITP. During active disease, there was a significant peripheral deficiency of splenic tolerizing SIRPα+ DCs which could be rescued by IVIg therapy, increasing platelet counts. These splenic tolerizing DC changes were associated with an abrogation of the thymic-retention of tolerizing DCs, suggesting that IVIg may raise platelet counts in ITP by modulating peripheral numbers of tolerizing DCs.     

Effect of intravenous gammaglobulin on circulating and platelet-bound antibody in immune thrombocytopenia

Ten patients with idiopathic thrombocytopenic purpura (ITP) were studied before and following a rise in circulating platelets subsequent to infusions of intravenous gammaglobulin (400 mg/kg/day x 5 days). We quantitated the amount of circulating IgG capable of binding to normal donor platelets in vitro using an 125I-monoclonal anti-human IgG assay, as well as the amount of IgG associated with the patients' platelets before and following therapy. We found no evidence for a decrease in platelet-specific IgG antibodies in these patients undergoing an acute response to therapy. These data suggest that the short-term efficacy of intravenous gammaglobulin is due to effects other than a substantive reduction in platelet reactive antibodies, such as the alteration of IgG-coated platelet destruction.     

In vitro comparison of the complement-scavenging capacity of different intravenous immunoglobulin preparations

Background and Objectives  Complement inhibition is considered important in the mechanism of action of intravenous immunoglobulin (IVIG) in a number of inflammatory and autoimmune disorders. The capacity of different IVIG preparations to 'scavenge' activated C3 and thereby inhibit complement activation was assessed by a new in vitro assay.
Materials and Methods  Diluted human serum as a complement source, with or without addition of different concentrations of IVIG, was incubated in microtitre plates coated with heat-aggregated human IgG. Complement scavenging was measured by detecting reduced C3 binding and determining fluid phase C3b–IgG complex formation. Complement activation induced by the IVIG preparations was measured as C5a formation.
Results  All IVIG preparations exhibited a dose-dependent inhibition of C3b deposition, correlating strongly with binding of C3b to fluid-phase IgG, but the extent of complement scavenging varied considerably between different IVIG preparations. At an IVIG concentration of 0·9 mg/ml, the inhibition of C3b deposition ranged from 72 ± 16% to 22 ± 4·1%. The reduction of C3b deposition on the complement-activating surface was not due to IVIG-induced complement activation in the fluid phase, as shown by the low C5a formation in the presence of serum.
Conclusion  In vitro analysis allows comparison of the complement-inhibitory properties of IVIG preparations. The extent of complement scavenging varies between the products.