Therapeutic efficacy of intravenous immunoglobulin preparations depends on the immunoglobulin G dimers: studies in experimental immune thrombocytopenia.

Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, Academical Medical Center, University of Amsterdam, The Netherlands.
Blood (Impact Factor: 10.45). 09/2001; 98(4):1095-9.
Source: PubMed


The clinical benefit of intravenous immunoglobulin (IVIG) preparations in the treatment of immune thrombocytopenic purpura (ITP) is supposed to be mediated by blockade of Fc gamma receptor--bearing phagocytes. In 2 experimental models for ITP, it is shown that the therapeutic efficacy of IVIG preparations is related to the IgG dimer content present in these preparations. A rat monoclonal antibody (mAb; MWReg30) directed to the murine platelet-specific integrin alpha(IIb)beta(3) (gpIIb/IIIa) was administered intraperitoneally either as bolus injection or continuous infusion. With bolus injection, the circulating platelet count dropped to almost zero within 3 hours. Pretreatment with cobra venom factor did not affect platelet depletion, whereas pretreatment with anti-Fc gamma RII/III mAb 2.4G2 or IVIG greatly reduced platelet clearance. With continuous infusion, platelet numbers reached a steady state after 4 days, at approximately 25% of control. This reduction in platelets was, however, not observed in mice deficient for the FcR gamma-chain, lacking Fc gamma RI, Fc gamma RIII, and Fc gamma RIII(-/-) mice. Infusion of a single dose of IVIG with a high IgG dimer content on the 4th day--ie, mimicking therapeutic administration--resulted in a platelet increase for several days. IVIG predominantly consisting of monomeric IgG had no effect on platelet numbers. In conclusion, continuous infusion of MWReg30 induces thrombocytopenia in mice by enhancing Fc gamma receptor--mediated clearance of platelets. In this model, it is shown that IgG dimers present in IVIG preparations are responsible for the increase in platelet counts. (Blood. 2001;98:1095-1099)

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    • "Obviously, the rate and extent of oligomerization in soluble IgG samples are to be controlled. While the content of oligomers is to be kept at a minimum level to avoid serious side effects [4] [5], the presence of dimers appears to be necessary for effective immunomodulatory action [6] [7]. In a guidance document of the EU Committee for Proprietary Medicinal Products (Core SPC for human normal immunoglobulin for intravenous administration [IVIg], CPMP/BWG/859/95 rev. 1) the warning ''Rarely, human normal immunoglobulin can induce a fall in blood pressure with anaphylactic reaction, even in patients who had tolerated previous treatment with human normal immunoglobulin'' is read. "
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    ABSTRACT: Stability of therapeutic IgG preparations is an important issue as adequate efficacy and safety has to be ensured throughout a long shelf life. To this end, denaturation and aggregation have to be avoided. In many cases sugars are applied for stabilizing IgG in relatively high concentration (5-10%). However, certain sugars (sucrose, maltose) are responsible for adverse effects including renal failure. In this work we reassessed the effect of pH and stabilizers to optimize the solvent environment and minimize the amount of additives without endangering quality and stability. Since both biological function and aggregation depend on the conformational properties of individual IgG molecules, two sensitive and rapid physical methods were introduced to assess conformational changes and structural stability as a function of pH and addition of standard stabilizers. It was observed that the conformational stability decreases with decreasing pH, while the resistance against aggregation improves. The optimum pH range for storage is 5.0-6.0, as a compromise between conformational stability and the tendency for oligomerization. Intriguingly, additives in physiologically acceptable concentration have no effect on the thermal stability of IgG. On the other hand, glucose or sorbitol, even at a concentration as low as 1%, have significant effect on the tertiary structure as revealed by near-UV-CD spectroscopy, reflecting changes in the environment of aromatic side-chains. Although, 0.3% leucine does not increase conformational stability, it decreases the aggregation tendency even more efficiently than 1% glucose or sorbitol. Both pH and storage temperature are decisive factors for the long-term stability of IgG solutions. An increase in the dimer content was observed upon storage at 5 degrees C which was partly reverted upon incubation at 37 degrees C. Storage at temperatures higher than 5 degrees C may help to maintain an optimal proportion of dimers. Regarding the known side effects, and their limited stabilizing capacity at low concentration, it is advisable to omit sugars at intravenous immunoglobulin (IVIG) formulation. Hydrophobic amino acids give promising alternatives.
    Preview · Article · Apr 2006 · Biologicals
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    • "Although these authors proposed that this could be due to IVIg's impact to reduce endotoxin levels and Kupffer cell function, we propose that an alternative explanation could be that IVIg directly inhibits leucocyte adhesion. One final study worth mentioning is that IVIg could reduce aIIb/a3 integrin mediated platelet aggregation (Teeling et al., 2001). This is worth noting, as platelets can contribute quite Fig. 4 IVIg reduces interactions of human leucocytes with HUVECs. "
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    ABSTRACT: Several studies have reported beneficial effects of intravenous immunoglobulin (IVIg) in diseases of the neuroaxis. However, IVIg effects on leucocyte recruitment, a hallmark feature of autoimmunity and acute inflammation, remain largely unexplored. Using intravital microscopy, we studied the effects of IVIg on leucocyte recruitment in experimental autoimmune encephalomyelitis, a model of multiple sclerosis. In IVIg-treated mice, a significant decrease in recruitment (rolling and adhesion) was observed prior to and following disease onset, and this was concomitant with improved clinical score. Since much of the recruitment is dependent upon alpha4-integrin (ligand for VCAM-1) we used an in vitro flow chamber system and demonstrated a 60% decrease in alpha4-integrin-dependent leucocyte adhesion to immobilized VCAM-1. Finally, we used leucocytes from multiple sclerosis patients and demonstrated that IVIg treatment decreased recruitment by 60% on human endothelium. However, when we visualized the role of IVIg in a second model of brain inflammation, cerebral ischaemia-reperfusion, IVIg actually promoted the formation of platelet-leucocyte aggregates in post-ischaemic cerebral vessels. In conclusion, we report a new mechanism of action of IVIg through interference of alpha4-integrin-dependent leucocyte recruitment in both an animal model and human multiple sclerosis. We also report that IVIg will not be beneficial in all types of pro-adhesive states and may in fact be detrimental in a situation such as stroke.
    Preview · Article · Jan 2005 · Brain
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    • "However, it is likely that the effects observed using these experimental protocols could also be observed in assays using thrombocytopenic animals made by the continuous infusion of antiplatelet antibodies, which would more closely mimic a clinical situation. Indeed Teeling et al (2001) and Crow et al (2001) showed that thrombocytopenia could be reversed by IVIg after continuous infusion of antiplatelet antibodies as efficiently as when IVIg was injected prior to induction of thrombocytopenia. It thus appears that the mouse model of thrombocytopenia is versatile and can be used with different experimental protocols to study the action of IVIg or their substitutes in ITP. "
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    ABSTRACT: Intravenous immunoglobulins (IVIg) have immunomodulatory effects in vivo and are widely used in the treatment of autoimmune diseases, such as idiopathic thrombocytopenic purpura (ITP). The mechanisms by which IVIg can prevent platelet clearance in ITP patients are not fully understood but are known to require the participation of low affinity Fcgamma receptors (FcgammaRs), which interact poorly with monomeric immunoglobulin G (IgG). Given the importance of low affinity FcgammaRs in the treatment of ITP, we hypothesized that immune complexes (IC) produced in vitro could reproduce the effects of IVIg. Small-size tetramolecular IC were prepared using mouse monoclonal anti-human IgG and human Fc fragments. The effects of tetramolecular IC and IVIg on the in vitro and in vivo inhibition of phagocytosis of opsonized blood cells were compared. The results obtained showed that tetramolecular IC were at least six times more efficient than IVIg to prevent phagocytosis of opsonized red blood cells in vitro, and clearance of platelets in the thrombocytopenic mouse model.
    Full-text · Article · Nov 2004 · British Journal of Haematology
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