Targeting Adhesion Molecules as a Potential Mechanism of Action for Intravenous Immunoglobulin

Multifaceted Tissue-Protective Functions of Polyvalent Immunoglobulin Preparations in Severe Infections-Interactions with Neutrophils, Complement, and Coagulation Pathways

Severe infections induce immune defense mechanisms and initial tissue damage, which produce an inflammatory neutrophil response. Upon dysregulation of these responses, inflammation, further tissue damage, and systemic spread of the pathogen may occur. Subsequent vascular inflammation and activation of coagulation processes may cause microvascular obstruction at sites distal to the primary site of infection. Low immunoglobulin (Ig) M and IgG levels have been detected in patients with severe infections like sCAP and sepsis, associated with increased severity and mortality. Based on Ig's modes of action, supplementation with polyvalent intravenous Ig preparations (standard IVIg or IgM/IgA-enriched Ig preparations) has long been discussed as a treatment option for severe infections. A prerequisite seems to be the timely administration of Ig preparations before excessive tissue damage has occurred and coagulopathy has developed. This review focuses on nonclinical and clinical studies that evaluated tissue-protective activities resulting from interactions of Igs with neutrophils, complement, and the coagulation system. The data indicate that coagulopathy, organ failure, and even death of patients can possibly be prevented by the timely combined interactions of (natural) IgM, IgA, and IgG with neutrophils and complement.

The velocity-diffusion equation in the exchange microvessels

In human and animal microvascular networks, the exchange microvessels are the capillaries and postcapillary venules where material transport between the circulating blood and tissue takes place. For small-size molecules, this material transport is done by the physical mechanism of diffusion through the endothelium wall and the diffusion rate J in relation to blood volume flow Q is described by the flow-diffusion (Q-J) equation. However, the volume flow is not easy to be measured in vivo. The objective of this work was to transform the classical flow-diffusion equation into a new form with axial velocity V as an independent variable instead of volume flow Q. The new form was called the velocity-diffusion (V-J) equation and has the advantage that V can be measured directly in vivo by optical imaging techniques. The V-J equation could have important applications in the calculation of the mass diffusion rate of various substances in vivo.

Mired in the glomeruli: witnessing live neutrophil recruitment in the kidney

Inflammation of the kidney is a key contributor to proliferative glomerulonephritis, and kidney damage during glomerulonephritis can lead to renal failure. The immune response associated with glomerulonephritis episodes is a major determinant of patient outcomes, and understanding this response is paramount for effective therapeutic treatment. Neutrophils are the first responders to sites of infection or tissue injury and are a significant cellular infiltrate during proliferative glomerulonephritis. This immune cell was initially recognized as a "blunt" nonspecific effector cell that was recruited to kill pathogens and then die quickly. However, recent studies have shown that the behavior and function of neutrophils are substantially more complex. Neutrophil recruitment to inflammatory sites must be carefully regulated so that these potent cells accurately arrive at tissue sites and perform their functions without nonspecific injury to other locations. As the kidney contains unique microvasculature befitting their specialized role in blood filtration, the recruitment of neutrophils in the renal environment differs from other organs. This Mini-Review will describe how advances in live-animal (intravital) imaging led to the discovery of novel recruitment pathways in the kidney, particularly in the glomeruli, and highlight these differences to canonical neutrophil recruitment. In addition, molecular engagement of surface molecules that lead to intracellular signaling, which is followed by neutrophil capture in the glomeruli, is also briefly discussed. Finally, the contribution of other immune cells in renal neutrophil recruitment, the fate of the emigrated neutrophils after inflammation, and the relevance of mouse models compared with human glomerulonephritides will also be explored.

Delayed administration of high dose human immunoglobulin G enhances recovery after traumatic cervical spinal cord injury by modulation of neuroinflammation and protection of the blood spinal cord barrier

BACKGROUND/INTRODUCTION

The neuroinflammatory response plays a major role in the secondary injury cascade after traumatic spinal cord injury (SCI). To date, systemic anti-inflammatory medications such as methylprednisolone sodium succinate (MPSS) have shown promise in SCI. However, systemic immunosuppression can have detrimental side effects. Therefore, immunomodulatory approaches including the use of human immunoglobulin G (hIgG) could represent an attractive alternative. While emerging preclinical data suggests that hIgG is neuroprotective after SCI, the optimal time window of administration and the mechanism of action remain incompletely understood. These knowledge gaps were the focus of this research study.

METHODS

Female adult Wistar rats received a clip compression-contusion SCI at the C7/T1 level of the spinal cord. Injured rats were randomized, in a blinded manner, to receive a single intravenous bolus of hIgG (2 g/kg) or control buffer at 15 minutes (min), 1 hour (h) or 4 h post-SCI. At 24 h and 8 weeks post-SCI, molecular, histological and neurobehavioral analyses were undertaken.

RESULTS

At all 3 administration time points, hIgG (2 g/kg) resulted in significantly better short-term and long-term outcomes as compared to control buffer. No significant differences were observed when comparing outcomes between the different time points of administration. At 24 h post-injury, hIgG (2 g/kg) administration enhanced the integrity of the blood spinal cord barrier (BSCB) by increasing expression of tight junction proteins and reducing inflammatory enzyme expression. Improvements in BSCB integrity were associated with reduced immune cell infiltration, lower amounts of albumin and Evans Blue in the injured spinal cord and greater expression of anti-inflammatory cytokines. Furthermore, hIgG (2 g/kg) increased expression of neutrophil chemoattractants in the spleen and sera. After hIgG (2 g/kg) treatment, there were more neutrophils in the spleen and fewer neutrophils in the blood. hIgG also co-localized with endothelial cell ligands that mediate neutrophil extravasation into the injured spinal cord. Importantly, short-term effects of delayed hIgG (2 g/kg) administration were associated with enhanced tissue and neuron preservation, as well as neurobehavioral and sensory recovery at 8 weeks post-SCI.

DISCUSSION AND CONCLUSION

hIgG (2 g/kg) shows promise as a therapeutic approach for SCI. The anti-inflammatory effects mediated by hIgG (2 g/kg) in the injured spinal cord might be explained in twofold. First, hIgG might antagonize neutrophil infiltration into the spinal cord by co-localizing with endothelial cell ligands that mediate various steps in neutrophil extravasation. Second, hIgG could traffic neutrophils towards the spleen by increasing expression of neutrophil chemoattractants in the spleen and sera. Overall, we demonstrate that delayed administration of hIgG (2 g/kg) at 1 and 4-h post-injury enhances short-term and long-term benefits after SCI by modulating local and systemic neuroinflammatory cascades.

Neuroinflammation after SCI: Current Insights and Therapeutic Potential of Intravenous Immunoglobulin

Traumatic spinal cord injury (SCI) elicits a complex cascade of cellular and molecular inflammatory events. Although certain aspects of the inflammatory response are essential to wound healing and repair, post-SCI inflammation is, on balance, thought to be detrimental to recovery by causing "bystander damage" and the spread of pathology into spared but vulnerable regions of the spinal cord. Much of the research to date has therefore focused on understanding the inflammatory drivers of secondary tissue loss after SCI, to define therapeutic targets and positively modulate this response. Numerous experimental studies have demonstrated that modulation of the inflammatory response to SCI can indeed lead to significant neuroprotection and improved recovery. However, it is now also recognized that broadscale immunosuppression is not necessarily beneficial and may even carry the risk of contributing to the development of serious adverse events. Immune modulation rather than suppression is therefore now considered a more promising approach to target harmful post-traumatic inflammation following a major neurotraumatic event such as SCI. One promising immunomodulatory agent is intravenous immunoglobulin (IVIG), a plasma product that contains mostly immunoglobulin G (IgG) from thousands of healthy donors. IVIG is currently already widely used to treat a range of autoimmune diseases, but recent studies have found that it also holds great promise for treating acute neurological conditions, including SCI. This review provides an overview of the inflammatory response to SCI, immunomodulatory approaches that are currently in clinical trials, proposed mechanisms of action for IVIG therapy, and the putative relevance of these in the context of neurotraumatic events.

The effects of human immunoglobulin G on enhancing tissue protection and neurobehavioral recovery after traumatic cervical spinal cord injury are mediated through the neurovascular unit

Background

Spinal cord injury (SCI) is a condition with few effective treatment options. The blood-spinal cord barrier consists of pericytes, astrocytes, and endothelial cells, which are collectively termed the neurovascular unit. These cells support spinal cord homeostasis by expressing tight junction proteins. Physical trauma to the spinal cord disrupts the barrier, which leads to neuroinflammation by facilitating immune cell migration to the damaged site in a process involving immune cell adhesion. Immunosuppressive strategies, including methylprednisolone (MPSS), have been investigated to treat SCI. However, despite some success, MPSS has the potential to increase a patient’s susceptibility to wound infection and impaired wound healing. Hence, immunomodulation may be a more attractive approach than immunosuppression. Approved for modulating neuroinflammation in certain disorders, including Guillain-Barre syndrome, intravenous administration of human immunoglobulin G (hIgG) has shown promise in the setting of experimental SCI, though the optimal dose and mechanism of action remain undetermined.

Methods

Female adult Wistar rats were subjected to moderate-severe clip compression injury (35 g) at the C7-T1 level and randomized to receive a single intravenous (IV) bolus of hIgG (0.02, 0.2, 0.4, 1, 2 g/kg), MPSS (0.03 g/kg), or control buffer at 15 min post-SCI. At 24 h and 6 weeks post-SCI, molecular, histological, and neurobehavioral effects of hIgG were analyzed.

Results

At 24 h post-injury, human immunoglobulin G co-localized with spinal cord pericytes, astrocytes, and vessels. hIgG (2 g/kg) protected the spinal cord neurovasculature after SCI by increasing tight junction protein expression and reducing inflammatory enzyme expression. Improvements in vascular integrity were associated with changes in spinal cord inflammation. Interestingly, hIgG (2 g/kg) increased serum expression of inflammatory cytokines and co-localized (without decreasing protein expression) with spinal cord vascular cell adhesion molecule-1, a protein used by immune cells to enter into inflamed tissue. Acute molecular benefits of hIgG (2 g/kg) led to greater tissue preservation, functional blood flow, and neurobehavioral recovery at 6 weeks post-SCI. Importantly, the effects of hIgG (2 g/kg) were superior to control buffer and hIgG (0.4 g/kg), and comparable with MPSS (0.03 g/kg).

Conclusions

hIgG (2 g/kg) is a promising therapeutic approach to mitigate secondary pathology in SCI through antagonizing immune cell infiltration at the level of the neurovascular unit.

Clinical outcome of patients with refractory Kawasaki disease based on treatment modalities

Purpose

Although a significant number of reports on new therapeutic options for refractory Kawasaki disease (KD) such as steroid, infliximab, or repeated intravenous immunoglobulin (IVIG) are available, their effectiveness in reducing the prevalence of coronary artery lesions (CAL) remains controversial. This study aimed to define the clinical characteristics of patients with refractory KD and to assess the effects of adjuvant therapy on patient outcomes.

Methods

We performed a retrospective study of 38 refractory KD patients from January 2012 to March 2015. We divided these patients into 2 groups: group 1 received more than 3 IVIG administration+ steroid therapy, (n=7, 18.4%), and group 2 patients were unresponsive to initial IVIG and required steroid therapy or second IVIG (n=31, 81.6%). We compared the clinical manifestations, laboratory results, and echocardiographic findings between the groups and examined the clinical utility of additional therapies in both groups.

Results

A significant difference was found in the total duration of fever between the groups (13.0±4.04 days in group 1 vs. 8.87±2.30 days in group 2; P=0.035). At the end of the follow-up, all cases in group 1 showed suppressed CAL. In group 2, coronary artery aneurysm occurred in 2 patients (6.4 %). All the patients treated with intravenous corticosteroids without additional IVIG developed CALs including coronary artery aneurysms.

Conclusion

No statistical difference was found in the development of CAL between the groups. Prospective, randomized, clinical studies are needed to elucidate the effects of adjunctive therapy in refractory KD patients.

Potentiation of cytokine-induced proliferation of human Natural Killer cells by intravenous immunoglobulin G

Intravenous IgG (IVIG) therapy can be used for immunomodulation. IL-2 is an immunoregulatory cytokine. We evaluated IVIG modulation of human blood lymphocyte response to IL-2 and other cytokines. Neither IVIG nor low concentrations of IL-2 (3-30U/ml) induced lymphocyte proliferation, but in combination they synergistically enhanced proliferation of NK cells. The CD56(bright) cells expanded more than CD56(dim) NK cells, with 90% of NK cells dividing up to 8 generations by day 6, while <8% of T cells divided. IVIG also potentiated NK cell proliferation with IL-12, IL-15 and IL-18. The IVIG+cytokine-expanded NK cells were less cytotoxic for K562 cells, than NK cells with cytokine alone. IVIG also enhanced interferon-γ production with IL-2, IL-12 and IL-18. In conclusion, IVIG selectively potentiates NK cell proliferation and interferon-γ secretion with IL-2, IL-12, IL-15 and IL-18 in vitro. These findings warrant evaluation in vivo in relation to NK cells and the immunoregulatory actions of IVIG.

Single-dose intravenous gammaglobulin can stabilize neutrophil Mac-1 activation in sickle cell pain crisis

Intravenous immunoglobulin (IVIG) decreases neutrophil adhesion to endothelium and red blood cell-neutrophil interactions in sickle cell mice undergoing vaso-occlusion. In this Phase I clinical trial of sickle cell anemia (SCA) patients admitted with pain crisis, we evaluated the status of adhesion molecules on neutrophils in control and IVIG-treated subjects pre- and post-infusion up to 800 mg/kg, the same dose used in murine studies. Mac-1 function significantly decreased from baseline in the low-dose IVIG (200-400 mg/kg) cohorts. IVIG-related adverse events may have occurred in the high-dose (600-800 mg/kg) cohorts. There were no significant increases in neutrophil and leukocyte counts, suggesting that IVIG may more selectively inhibit Mac-1 function as opposed to neutrophil adhesion. This study provides the first in-human validation of pre-clinical murine studies that IVIG can decrease Mac-1 function.

Use of IVIg to identify potential miRNA targets for allograft rejection and GvHD therapy

Allograft rejection (AR) and graft-versus-host disease (GvHD) are serious complications following transplantation. Micro-RNAs (miRNAs) have recently been identified as key players in the regulation of these disorders. Because intravenous immunoglobulin (IVIg) has shown therapeutic potential for the prophylaxis and post-transplant reduction of AR and GvHD, we hypothesized that the effect of IVIg could result from the modulation of specific miRNA expression. To identify such miRNA, we performed mixed lymphocyte reactions (MLRs) as an in vitro model of AR and GvHD, with or without IVIg. We herein show that IVIg strongly inhibits the MLRs. This inhibition is associated with a modulation in the expression of miRNAs implicated in the regulation of pro-inflammatory cytokine (IL-2, IL-6, IFN-γ) and costimulatory molecule (CD80) expression. We propose that these identified miRNAs could represent potential therapeutic targets for the prevention and therapy of AR and GvHD.

A Case of Kawasaki Disease with Coronary Aneurysm Responding to the 4th IVIG Treatment

Kawasaki disease is an acute febrile illness that usually occurs in children younger than 5 years of age. The use of intravenous immunoglobulin (IVIG) within the first 10 days of illness has been shown to reduce the incidence of coronary artery aneurysms significantly. The relative roles of repeated doses of intravenous immunoglobulin (IVIG) are controversial in refractory Kawasaki disease (KD). Most experts recommend the second retreatment with IVIG, 2 g/kg in refractory KD. However, the dose-response effect of the third or fourth IVIG was uncertain. Although there have been a significant number of reports on new therapeutic options for refractory KD, such as steroid, infliximab, methotrexate, and other immunosuppressants, their effectiveness in reducing the prevalence of coronary artery aneurysms was unproven. We present here KD patient with small coronary artery aneurysm who is resistant to the third IVIG and steroid pulse therapy but showed improvement immediately after the infusion of the 4th IVIG on fever day 18.

Treatment of spinal cord injury with intravenous immunoglobulin G: preliminary evidence and future perspectives

Neuroinflammation plays an important role in the secondary pathophysiological mechanisms of spinal cord injury (SCI) and can exacerbate the primary trauma and thus worsen recovery. Although some aspects of the immune response are beneficial, it is thought that leukocyte recruitment and activation in the acute phase of injury results in the production of cytotoxic substances that are harmful to the nervous tissue. Therefore, suppression of excessive inflammation in the spinal cord could serve as a therapeutic strategy to attenuate tissue damage. The immunosuppressant methylprednisolone has been used in the setting of SCI, but there are complications which have attenuated the initial enthusiasm. Hence, there is interest in other immunomodulatory approaches, such as intravenous Immunoglobulin G (IVIg). Importantly, IVIg is used clinically for the treatment of several auto-immune neuropathies, such as Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy (CIPD) and Kawasaki disease, with a good safety profile. Thus, it is a promising treatment candidate for SCI. Indeed, IVIg has been shown by our team to attenuate the immune response and result in improved neurobehavioral recovery following cervical SCI in rats through a mechanism that involves the attenuation of neutrophil recruitment and reduction in the levels of cytokines and cytotoxic enzymes Nguyen et al. (J Neuroinflammation 9:224, 2012). Here we review published data in the context of relevant mechanisms of action that have been proposed for IVIg in other conditions. We hope that this discussion will trigger future research to provide supporting evidence for the efficiency and detailed mechanisms of action of this promising drug in the treatment of SCI, and to facilitate its clinical translation.

Intravenous immunoglobulin-mediated immunosuppression and the development of an IVIG substitute

Immunoglobulins are glycoproteins produced by the cells of the immune system. Their primary function is to protect the body from pathogenic infection. Moreover, a concentrated polyclonal mixture of immunoglobulin G (IgG), the so-called intravenous IgG (IVIG), has been used to treat various chronic and systemic disorders of the immune system. Studies on the effects of IVIG in autoimmune disease models have revealed that IgG Fc fragments confer protection against various autoimmune diseases. The identification of this IgG Fc immunomodulatory component is important for the development of IVIG substitutes. The focus of this review is to introduce one of the Fc regulatory entities and to provide a summary of the current knowledge of the putative general mechanisms underlying IVIG activity in vivo on the basis of these Fc fragments. We also address the recent insights into several approaches for the development of IVIG substitutes.

Platelets in inflammation and immune modulations: functions beyond hemostasis

Platelets play central roles for maintaining the homeostasis of the blood coagulation. As they are also involved in immune responses and host defenses, increasing evidences have suggested that platelets exert other roles beyond their well-recognized function in preventing bleeding. This review is focused on inflammation, allergy and immune modulations of platelets. Platelets conduct immunoregulation through secretion of functional mediators, interaction with various immune cells, endothelial cells and beneficial for the leukocyte infiltration to inflamed/allergic tissues. In these regulations, the leukocytes are influenced by and receiving the signals from platelets. In contrast, rare attentions were focused on platelet regulations by immune system. An intriguingly example in the intravenous immunoglobulin (IVIg) treatment is discussed, in which dendritic cells exert anti-inflammatory effect through platelets. This further suggests that coagulant and immune systems are tightly associated rather than separate entities. The cross-talks between these two systems implicate that platelet therapy may have application beyond thrombosis, and immune interventions may have potentials to treat thrombosis diseases.

Intravenous immunoglobulins modulate neutrophil activation and vascular injury through FcγRIII and SHP-1

RATIONALE

Intravascular neutrophil recruitment and activation are key pathogenic factors that contribute to vascular injury. Intravenous immunoglobulin (IVIG) has been shown to have a beneficial effect in systemic inflammatory disorders; however, the mechanisms underlying IVIG's inhibitory effect on neutrophil recruitment and activation are not understood.

OBJECTIVE

We studied the mechanisms by which IVIG exerts protection from neutrophil-mediated acute vascular injury.

METHODS AND RESULTS

We examined neutrophil behavior in response to IVIG in vivo, using real-time intravital microscopy. We found that an antibody that blocks both FcγRIII and its inhibitory receptor counterpart, FcγRIIB, abrogated the inhibitory effect of IVIG on leukocyte recruitment and heterotypic red blood cell (RBC) interactions with adherent leukocytes in wild-type mice. In the context of sickle cell disease, the blockade of both FcγRIIB and III abrogated the protective effect of IVIG on acute vaso-occlusive crisis caused by neutrophil recruitment and activation. Analysis of FcγRIIB- and FcγRIII-deficient mice revealed the predominant expression of FcγRIII on circulating neutrophils. FcγRIII mediated IVIG-triggered inhibition of leukocyte recruitment, circulating RBC capture, and enhanced Mac-1 activity, whereas FcγRIIB was dispensable. In addition, FcγRIII-induced IVIG anti-inflammatory activity in neutrophils was mediated by recruitment of Src homology 2 (SH2)-containing tyrosine phosphatase-1 (SHP-1). Indeed, the protective effect of IVIG on leukocyte recruitment and activation was abrogated in SHP-1-mutant mice.

CONCLUSIONS

FcγRIII, a classic activating receptor, has an unexpected inhibitory role on neutrophil adhesion and activation via recruitment of SHP-1 in response to IVIG. Our results identify SHP-1 as a therapeutic target in neutrophil-mediated vascular injury.

Corticosteroid pulse combination therapy for refractory Kawasaki disease: a randomized trial

OBJECTIVE

This study examined the clinical efficacy and safety of intravenous methylprednisolone-pulse plus intravenous immunoglobulin (IVIG) combination therapy (IVMP+IVIG) for the initial treatment of patients predicted to have refractory Kawasaki disease (KD).

METHODS

One hundred twenty-two patients with KD were studied at Kitasato University. Refractory KD was predicted at diagnosis using the Egami score, and the patients were randomly divided to receive either IVMP+IVIG or IVIG alone. The Egami score is used to predict refractory KD patients before treatment using the patient's age, days of illness, platelet count, C-reactive protein, and alanine aminotransferase level (cutoff: ≥3 points; 78% sensitivity and 76% specificity).

RESULTS

Forty-eight patients (39.3%) were predicted to have refractory KD on the basis of the Egami score. The predicted IVIG responders (n = 74) received the standard therapy. The 48 predicted refractory KD patients were randomly assigned to a single-IVIG group (n = 26) or an IVMP+IVIG group (n = 22). Nineteen of the 22 patients (86.4%) in the IVMP+IVIG group had a prompt defervescence compared with 6 of the 26 patients (23.1%) in the single-IVIG group. The number of patients who had a z score ≥2.5 at 1 month was significantly higher in the single-IVIG group than in the IVMP+IVIG group. No serious adverse events were observed in either treatment group.

CONCLUSION

This study demonstrated that IVMP+IVIG therapy is safe and effective for KD patients predicted as refractory.

Regulation of immunity and inflammation by intravenous immunoglobulin: relevance to solid organ transplantation

Intravenous immunoglobulin (IVIg) products are derived from pooled human plasma from thousands of donors and have been used for the treatment of primary immunodeficiency disorders for more than 30 years. IVIg products are also effective in the treatment of autoimmune and inflammatory disorders, however, the precise mechanism(s) of action are not known. Recent data suggest that IVIg has a much broader ability to regulate cellular immunity, including innate and adaptive components. IVIg-induced upregulation of Fcγ receptor IIB on B cells appears to be an important mode of action in suppression of antigen-presenting cell activity and antibody production. IVIg is also a recently recognized modifier of complement activation and injury. Analysis of clinical studies examining the use of IVIg in desensitization protocols and for treatment of antibody-mediated rejection in transplant recipients are supportive. Here, we discuss these important advancements and their relevance to transplant medicine.

Intravenous immunoglobulin G (IVIG) inhibits IL-1- and TNF-α-dependent, but not chemotactic-factor-stimulated, neutrophil transendothelial migration

High-dose intravenous immunoglobulin (IVIG) has anti-inflammatory effects via incompletely understood mechanisms. By investigating whether IVIG might modulate neutrophil (PMN) recruitment, we observed that IVIG dose-dependently inhibited (by 30-50%) PMN transendothelial migration (TEM) across human umbilical vein endothelial cells (EC) stimulated with IL-1α, IL-1β, TNF-α or IL-1β+TNF-α. Inhibition required the presence of IVIG with the responding PMNs, was attributable to the F(ab)(2) portion and was unrelated to putative contaminants in IVIG. IVIG did not inhibit IL-1β- or TNF-α-induced increase of PMN adhesion to EC, nor did it affect C5a- or IL-8-induced PMN TEM across unstimulated EC. Effects of IVIG and F(ab)(2) fragments were not associated with PMN activation, assessed by CD62L shedding, CD11b upregulation or PMN shape. Thus, IVIG selectively inhibits PMN TEM across inflammatory-cytokine-stimulated - but not unstimulated - EC, perhaps contributing to therapeutic benefit in chronic inflammation with minimal impact on chemotactic-factor-induced PMN recruitment during acute infection.

Suppressive effects of intravenous immunoglobulin (IVIG) on human umbilical cord blood immune cells

We investigated in vitro immunomodulatory effects of intravenous immunoglobulin (IVIG) on cord blood mononuclear cells (CBMNC), macrophages, dendritic cells and CD3(+) T cells were isolated from umbilical venous blood. Cell proliferation used (3)H-TdR incorporation, culture supernatants were assayed for cytokines using ELISA, and surface marker expressions were determined by flow cytometry. IVIG suppressed CBMNCs and CD3(+) T-cells proliferation, secretions of IL-10, INF-γ and TGF-β(1), but not IL-4, and PHA-induced expressions of surface molecules (CD25, CD45RA and CD45RO), with more pronounced effects for CBMNCs. IVIG decreased cord blood (CB) macrophage phagocytosis and CD14, HLA-DR and CD86 expressions. IVIG increased CD14 expression and decreased MCH II expression for differentiation-stage CB dendritic cells (DCs) and increased CD14 expression and decreased CD80 and CD83 expressions of mature DCs, suggesting that IVIG intervention inhibited DC differentiation and maturation. In addition to T cells, IVIG immunomodulatory effects on CBMNCs involve a variety of cells and molecules. CB macrophages and CBMNC-DCs are targets of IVIG.

Dendritic cells modulate platelet activity in IVIg-mediated amelioration of ITP in mice

Intravenous immunoglobulin (IVIg) is an effective treatment against immune thrombocytopenia (ITP). Previous studies suggested that IVIg exerts this ameliorative role through 2 different leukocyte subsets. Dendritic cells (DCs) modulate the immunosuppression in an adoptive cell transfer model, and phagocytes up-regulate their inhibitory IgG Fc receptors (FcγR)IIB expression and thereby ameliorate the inflammatory response and platelet clearance. However, whether or not regulatory mechanisms exist among DCs, phagocytes, and platelets is still largely unknown. In this study we present findings that IVIg-primed splenic CD11c+ DCs (IVIg-DCs) primarily mediate their anti-inflammatory effects at the level of the platelet rather than the phagocyte. IVIg-DCs did not ameliorate ITP in Fcgr2b−/−, Fcgr3−/−, nor P-Selp−/− mice, implicating the potential involvement of these pathways in IVIg action. As platelets are a component of DC regulatory circuits, these findings may suggest an alternative perspective for the use of IVIg treatment.

High-dose intravenous immunoglobulin (IVIG) therapy in autoimmune skin blistering diseases

Treatment of autoimmune bullous skin diseases can often be challenging and primarily consists of systemic corticosteroids and a variety of immunosuppressants. Current treatment strategies are effective in most cases but hampered by the side effects of long-term immunosuppressive treatment. Intravenous immunoglobulin (IVIG) is one potential promising therapy for patients with autoimmune bullous skin diseases, and evidence of its effectiveness and safety is increasing. A number of autoimmune bullous skin diseases have been identified in which IVIG treatment may be beneficial. However, experience with IVIG in patients with autoimmune skin blistering disease is limited, where it is recommended for patients not responding to conventional therapy. The mode of action of IVIG in autoimmune diseases, including bullous diseases is far from being completely understood. We here summarize the clinical evidence supporting the notion, that IVIG is a promising therapeutic agent for the treatment of patients with autoimmune bullous skin disease. In addition, we review the proposed modes of action. In the future, randomized controlled trials are necessary to better determine the efficacy and adverse effects of IVIG in the treatment of autoimmune bullous skin diseases. In addition, insights into IVIG's mode of action might enable us to develop novel therapeutics to overcome the current shortage of IVIG.

Effects of anti-cardiolipin antibodies and IVIg on annexin A5 binding to endothelial cells: implications for cardiovascular disease

OBJECTIVES

Anti-phospholipid antibodies (aPL), including anti-cardiolipin antibodies (aCL), are risk factors for cardiovascular disease (CVD) in the general population and in patients with the anti-phospholipid syndrome (APS; Hughes syndrome). APS may be primary but is also common in patients with systemic lupus erythematosus (SLE). The anti-coagulant protein annexin A5 (ANXA5) is implicated in CVD by interfering with phospholipids and aPL.

METHODS

ANXA5 binding to human umbilical venous endothelial cells (HUVECs) was determined by flow cytometry.

RESULTS

When cells were cultured in serum from APS patients with a high aPL titre (aPL-S), binding of ANXA5 to HUVECs was reduced. Monoclonal immunoglobulin (Ig)G aPL against cardiolipin (mAb-CL) dose-dependently reduced ANXA5 binding to endothelium. Preincubation of intravenous (IV)Ig at therapeutically relevant doses with aPL-S and mAb-aCL restored ANXA5 binding to comparable levels when normal healthy serum (NHS) was used. By contrast, IVIg per se had the capacity to reduce ANXA5 binding to endothelium when added to NHS (but not to aPL-S).

CONCLUSIONS

Decreased ANXA5 binding to endothelium, mediated by aPL, is a novel mechanism of atherothrombosis that can be countered by IVIg in vitro. IVIg per se could, to a lesser degree, cause decreased ANXA5 binding in NHS, which raises the possibility that some antibodies in IVIg can be involved in a side-effect reported in IVIg treatment, namely atherothrombosis and CVD. Increasing ANXA5 binding, either by addition of ANXA5 or by use of neutralizing antibodies in IVIg, represents a possible therapeutic strategy that deserves further study.

Junctional adhesion molecule (JAM)-B supports lymphocyte rolling and adhesion through interaction with alpha4beta1 integrin

Junctional adhesion molecule-A (JAM-A), JAM-B and JAM-C have been implicated in leucocyte transmigration. As JAM-B binds to very late activation antigen (VLA)-4, a leucocyte integrin that contributes to rolling and firm adhesion of lymphocytes to endothelial cells through binding to vascular cell adhesion molecule (VCAM)-1, we hypothesized that JAM-B is also involved in leucocyte rolling and firm adhesion. To test this hypothesis, intravital microscopy of murine skin microvasculature was performed. Rolling interactions of murine leucocytes were significantly affected by blockade of JAM-B [which reduced rolling interactions from 9.1 +/- 2.6% to 3.2 +/- 1.2% (mean +/- standard deviation)]. To identify putative ligands, T lymphocytes were perfused over JAM-B-coated slides in a dynamic flow chamber system. JAM-B-dependent rolling and sticking interactions were observed at low shear stress [0.3 dyn/cm(2): 220 +/- 71 (mean +/- standard deviation) versus 165 +/- 88 rolling (P < 0.001; Mann-Whitney rank sum test) and 2.6 +/- 1.3 versus 1.0 +/- 0.7 sticking cells/mm(2)/min (P = 0.026; Mann-Whitney rank sum test) on JAM-B- compared with baseline], but not at higher shear forces (1.0 dyn/cm(2)). As demonstrated by antibody blocking experiments, JAM-B-mediated rolling and sticking of T lymphocytes was dependent on alpha4 and beta1 integrin, but not JAM-C expression. To investigate whether JAM-B-mediated leucocyte-endothelium interactions are involved in a disease-relevant in vivo model, adoptive transfer experiments in 2,4,-dinitrofluorobenzene (DNFB)-induced contact hypersensitivity reactions were performed in mice in the absence or in the presence of a function-blocking JAM-B antibody. In this model, JAM-B blockade during the sensitization phase impaired the generation of the immune response to DNFB, which was assessed as the increase in ear swelling in untreated, DNFB-challenged mice, by close to 40% [P = 0.037; analysis of variance (anova)]. Overall, JAM-B appears to contribute to leucocyte extravasation by facilitating not only transmigration but also rolling and adhesion.

Intravenous immunoglobulin a natural regulator of immunity and inflammation

Intravenous immunoglobulin (IVIG) products are derived from pooled human plasma and have been used for the treatment of primary immunodeficiency disorders for more than 25 years. IVIG products are also effective in the treatment of autoimmune and inflammatory disorders; however, the precise mechanism(s) of action is not known. Recent investigations suggest that IVIG has a much broader ability to regulate cellular immunity including innate and adaptive components. IVIG is also a recently recognized modifier of complement activation and injury. Here, we discuss these important advancements and how this knowledge applies to desensitization protocols and to the treatment of antibody-mediated rejection.

Blockade of K(ATP) channels reduces endothelial hyperpolarization and leukocyte recruitment upon reperfusion after hypoxia

Ischemia/reperfusion injury in renal transplantation leads to slow or initial nonfunction, and predisposes to acute and chronic rejection. In fact, severe ischemia reperfusion injury can significantly reduce graft survival, even with modern immunosuppressive agents. One of the mechanisms by which ischemia/reperfusion causes injury is activation of endothelial cells resulting in inflammation. Although several therapies can be used to prevent leukocyte recruitment to ischemic vessels (e.g. antiadhesion molecule antibodies), there have been no clinical treatments reported that can prevent initial immediate neutrophil recruitment upon reperfusion. Using intravital microscopy, we describe abrogation of immediate neutrophil recruitment to ischemic microvessels by the K(ATP) antagonist glibenclamide (Glyburide). Further, we show that glibenclamide can reduce leukocyte recruitment in vitro under physiologic flow conditions. ATP-regulated potassium channels (K(ATP)) are important in the control of cell membrane polarization. Here we describe profound hyperpolarization of endothelial cells during hypoxia, and the reduction of this hyperpolarization using glibenclamide. These findings suggest that control of endothelial membrane potential during ischemia may be an important therapeutic tool in avoiding ischemia/reperfusion injury, and therefore, enhancing transplant long-term function.

Neuroprotection in stroke by complement inhibition and immunoglobulin therapy

Activation of the complement system occurs in a variety of neuroinflammatory diseases and neurodegenerative processes of the CNS. Studies in the last decade have demonstrated that essentially all of the activation components and receptors of the complement system are produced by astrocytes, microglia, and neurons. There is also rapidly growing evidence to indicate an active role of the complement system in cerebral ischemic injury. In addition to direct cell damage, regional cerebral ischemia and reperfusion (I/R) induces an inflammatory response involving complement activation and generation of active fragments, such as C3a and C5a anaphylatoxins, C3b, C4b, and iC3b. The use of specific inhibitors to block complement activation or their mediators such as C5a, can reduce local tissue injury after I/R. Consistent with therapeutic approaches that have been successful in models of autoimmune disorders, many of the same complement inhibition strategies are proving effective in animal models of cerebral I/R injury. One new form of therapy, which is less specific in its targeting of complement than monodrug administration, is the use of immunoglobulins. Intravenous immunoglobulin (IVIG) has the potential to inhibit multiple components of inflammation, including complement fragments, pro-inflammatory cytokine production and leukocyte cell adhesion. Thus, IVIG may directly protect neurons, reduce activation of intrinsic inflammatory cells (microglia) and inhibit transendothelial infiltration of leukocytes into the brain parenchyma following an ischemic stroke. The striking neuroprotective actions of IVIG in animal models of ischemic stroke suggest a potential therapeutic potential that merits consideration for clinical trials in stroke patients.

Effect of Conventional and More Aggressive Rosuvastatin Treatment on Markers of Endothelial Activation

Treatment of hypercholesterolemia with HMG-CoA reductase inhibitors results in an earlier reduction of morbidity and mortality than expected from trials using conventional cholesterol-lowering therapies. Possible explanations for this effect include improvement of endothelial function, plaque stabilization, and inhibition of the inflammatory response associated with atherosclerosis. In this study we assessed the effects of low and moderate dose rosuvastatin treatment, on circulating markers of endothelial activation in patients admitted for acute coronary syndromes without ST segment elevation. Thirty patients with unstable angina and non ST segment elevation myocardial infarction were rando - mized into two groups, and received rosuvastatin 10 mg/day (n =16) or rosuvastatin 20 mg/day (n =14) for 12 weeks. Circulating levels of soluble vascular cell adhesion molecule (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1) were measured at admission, and at the end of the study. Lipid values were significantly reduced in both treatment groups, but with significantly greater reduction in the aggressively treated group. Serum levels of sICAM-1 and sVCAM-1 were significantly decreased in both rosuvastatin-treated groups during 12 weeks of follow-up with a more pronounced decrease in the more aggressively treated group. Therefore, rosuvastatin modulates endothelial activation in patients after acute coronary syndromes.

Treatment of immune-mediated thrombocytopenia purpura with concurrent intravenous immunoglobulin and platelet transfusion: a retrospective review of 40 patients

We performed a retrospective review of patients with immune-mediated thrombocytopenia (ITP) treated with prolonged infusions of intravenous immunoglobulin (IVIg) (1 g/kg by continuous infusion over 24 hr) and concurrent platelets (1 pheresis unit every 8 hr), to determine the response rate of this therapy. Patient inclusion criteria included clinically significant thrombocytopenia, with either active bleeding, need for anticoagulation, or a needed surgical procedure. The average pretreatment platelet count was 10,000/microl, which increased to 55,000/microl after 24 hr and 69,000/microl after 48 hr. After 24 hr, 62.7% of patients had a platelet count >50,000/microl. Bleeding was controlled initially in all patients, and those requiring a procedure experienced no bleeding complications. Over half of the patients (52.5%) required additional treatments for recurrent or refractory ITP. Six of the 21 patients requiring retreatment (29%) received IVIg and platelets again in a similar fashion, with similar results. No side effects of the combined treatment were noted. There is limited literature on the optimal dose and schedule for administration of IVIg and platelets. Our approach for administration of IVIg and platelets concurrently was associated with minimal side effects, resolution of bleeding, ability to safely undergo procedures, and rapid restoration of adequate platelet counts.

A novel mechanism of erythrocyte capture from circulation in humans

OBJECTIVE

The capture of blood cells from the circulation is mediated by highly specialized adhesion molecules. These molecules contribute to the specificity of recruitment for various subsets. Here, we used a simple substrate of hyaluronic acid to investigate the specificity of CD44-mediated recruitment from human whole blood under shear conditions.

MATERIALS AND METHODS

Human whole blood was perfused through a parallel-plate flow chamber, which mimics intravascular conditions. Microscopy was used to directly observe blood-cell interactions with adhesion molecule substrates.

RESULTS

Erythrocytes, but not leukocytes, efficiently tethered to and rolled on the hyaluronic acid substrate. These interactions were demonstrated to be mediated by CD44 and regulated by the sialic acid content of the cells. Inflammatory stimuli did not result in enhanced erythrocyte rolling. Rather, interactions were restricted to aged erythrocytes approaching senescence. This mechanism of erythrocyte capture from the blood flow was found to be restricted to primates and not conserved across mammalian species.

CONCLUSION

This is the first report of erythrocyte tethering and rolling under shear conditions, a behavior, until now, thought to be exclusive to leukocytes. It may represent an important mechanism to identify, capture, and clear old erythrocytes during normal homeostasis or clot formation.

Intravenous immunoglobulins reverse acute vaso-occlusive crises in sickle cell mice through rapid inhibition of neutrophil adhesion

Previous studies using intravital microscopy in a sickle cell disease (SCD) mouse model suggest that adherent white blood cells (WBCs) play a key role in vaso-occlusion by capturing circulating red blood cells (RBCs) in venules. Commercial intravenous immunoglobulin (IVIG) given before the inflammatory stimuli increased microcirculatory blood flow and survival. To mimic the clinical situation in which SCD patients seek medical attention after the onset of symptoms, we developed an in vivo model in which the therapeutic intervention (eg, IVIG) was administered after in the inflammatory challenge. In this setting, IVIG rapidly (<10 minutes) reduced adherent leukocyte numbers and dramatically inhibited interactions between RBCs and WBCs, resulting in improved microcirculatory blood flow and survival of sickle cell "Berkeley" mice. Longer survival correlated positively with blood flow (P=.001) and negatively with the number of adherent leukocytes (P=.001) and RBC-WBC interactions (P=.002). Using multichannel digital fluorescence videomicroscopy, we found that IVIG affected specifically the recruitment of neutrophils. Moreover, further analyses of leukocyte behavior revealed that IVIG significantly increased rolling velocities, indicating that it alters adhesion pathways involved in slow rolling. These data suggest that the potential therapeutic benefits of IVIG in SCD crises should be evaluated in a clinical trial.

14th International HLA and Immunogenetics Workshop: Report on understanding antibodies in transplantation

A session of the 14 International Histocompatibility Workshop brought together experts representing the major clinical protocols, clinical research, and basic research dealing with overcoming the barrier of alloantibody in transplantation and in understanding the mechanisms by which those antibodies exert their effect on a transplanted organ. This report is an integration of the presentations of those scientists.

Platelet TLR4 activates neutrophil extracellular traps to ensnare bacteria in septic blood

It has been known for many years that neutrophils and platelets participate in the pathogenesis of severe sepsis, but the inter-relationship between these players is completely unknown. We report several cellular events that led to enhanced trapping of bacteria in blood vessels: platelet TLR4 detected TLR4 ligands in blood and induced platelet binding to adherent neutrophils. This led to robust neutrophil activation and formation of neutrophil extracellular traps (NETs). Plasma from severely septic humans also induced TLR4-dependent platelet-neutrophil interactions, leading to the production of NETs. The NETs retained their integrity under flow conditions and ensnared bacteria within the vasculature. The entire event occurred primarily in the liver sinusoids and pulmonary capillaries, where NETs have the greatest capacity for bacterial trapping. We propose that platelet TLR4 is a threshold switch for this new bacterial trapping mechanism in severe sepsis.

Fcgamma receptor deficiency confers protection against atherosclerosis in apolipoprotein E knockout mice

IgG Fc receptors (FcgammaRs) play a role in activating the immune system and in maintaining peripheral tolerance, but their role in atherosclerosis is unknown. We generated double-knockout (DKO) mice by crossing apolipoprotein E-deficient mice (apoE(-/-)) with FcgammaR gamma chain-deficient mice (gamma(-/-)). The size of atherosclerotic lesions along the aorta was approximately 50% lower in DKO compared with apoE(-/-) control mice, without differences in serum lipid levels. The macrophage and T-cell content of lesions in the DKO were reduced by 49+/-6% and 56+/-8%, respectively, compared with the content in apoE(-/-) lesions. Furthermore, the expression of monocyte chemoattractant protein-1 (MCP-1), RANTES (Regulated on Activated Normal T-cell Expressed and Secreted), and intercellular adhesion molecule-1 (ICAM-1) and the activation of nuclear factor-kappaB (NF-kappaB) were significantly reduced in aortic lesions from DKO mice. In vitro, vascular smooth muscle cells (VSMCs) from both gamma(-/-) and DKO mice failed to respond to immune complexes, as shown by impaired chemokine expression and NF-kappaB activation. ApoE(-/-) mice have higher levels of activating FcgammaRI and FcgammaRIIIA, and inhibitory FcgammaRIIB, compared with wild-type mice. The DKO mice express only the inhibitory FcgammaRIIB receptor. We conclude that FcgammaR deficiency limits development and progression of atherosclerosis. In addition to leukocytes, FcgammaR activation in VSMCs contributes to the inflammatory process, in part, by regulating chemokine expression and leukocyte invasion of the vessel wall. These results underscore the critical role of FcgammaRs in atherogenesis and support the use of immunotherapy in the treatment of this disease.

Relation between soluble intercellular adhesion molecule-1, statin therapy, and long-term risk of clinical cardiovascular events in patients with previous acute coronary syndrome (from PROVE IT-TIMI 22)

High levels of adhesion molecules, such as soluble intercellular adhesion molecule-1 (sICAM-1), are associated with long-term risk of cardiac events in patients with and without stable coronary artery disease. The relation between sICAM-1 and long-term risk after acute coronary syndromes (ACSs) and the influence of statin treatment has not been explored. Using a nested case-control design, patients with ACS who were enrolled in the PROVE IT-TIMI 22 trial were matched for age, gender, smoking, diabetes, type of ACS presentation, and revascularization for index event (583 patients with recurrent events vs 581 controls). Patients with recurrent events were identified as such by death, myocardial infarction, or hospitalization for recurrent ACS. Soluble ICAM-1 was measured at study entry (approximately 7 days after ACS). After adjusting for statin regimen and other risk factors, patients in quartiles 2 to 4 were at a higher risk of clinical events compared with those in quartile 1 (odds ratio 1.6 for quartile 4 vs 1, 95% confidence interval 1.1 to 2.3, p = 0.02). The risk of adverse events in patients with sICAM-1 levels in quartiles 2 to 4 was most marked in subjects who were allocated to standard dose statin therapy, even after adjusting for low-density lipoprotein cholesterol and C-reactive protein at day 30. The risk in quartiles 2 to 4 was somewhat attenuated in the intensive therapy group. In conclusion, in this large study of patients with ACS, we provide evidence that increased endothelial activation after ACS is independently associated with increased long-term risk of death, myocardial infarction, or recurrent ACS.

The role of intravenous immunoglobulin in the treatment of chronic heart failure

Chronic heart failure (HF), including both ischemic and idiopathic dilated cardiomyopathies, is accompanied by a dysregulated cytokine network characterized not only by a rise in inflammatory cytokines, but also by an inadequate elevation of anti-inflammatory mediators. This dysregulation has been implicated in the development and progression of chronic HF, and in the last decade, attempts have been made to modulate this persistent inflammation. Failure of anti-tumor necrosis factor therapy in HF has led to further interest in a more general immunomodulatory approach, directed against the inflammatory imbalance rather than one particular cytokine. Treatment with intravenous immunoglobulin (IVIg) may represent such a broad-based approach trying to restore the dysregulated cytokine network through various mechanisms such as Fc receptor blockade, neutralization of microbial antigens and superantigens and more direct anti-inflammatory effects on the cytokine network. However, although one randomized placebo-controlled study in patients with chronic HF showed that IVIg improved left ventricular ejection fraction, accompanied by anti-inflammatory net effects, IVIg had no effect in another placebo-controlled study examining the effect of this medication in recent-onset cardiomyopathy. So far, few patients have been included in clinical trials, and there is clearly a need for larger placebo-controlled mortality studies involving a diverse group of patients with regard to cause and severity of HF.

Presensitization: the problem and its management

Much attention has been placed recently on transplantation in highly HLA-sensitized patients. In attempts to remove these antibodies and enable successful transplantation, several novel approaches have been developed. These include intravenous Ig (IVIg), mycophenolate mofetil, sirolimus, alemtuzumab, protein A immunoabsorption, and rituximab. IVIg has emerged as a very effective agent when used alone in high dose or when used in low dose and combined with plasmapheresis. Although alemtuzumab has been used to eliminated B cells, it fails to prevent antibody-mediated rejection and therefore probably is not suitable for desensitization. Rituximab, a B cell-specific antibody, seems to be safe and to have some efficacy as a sole agent in elimination of alloantibodies but most likely will require combination therapy with IVIg or other agents. Newer agents, such as humanized anti-CD20, are being developed. Despite the great interest in the problem of allosensitization, with one notable exception, there is a major deficiency in controlled clinical trials, the conduct of which should be a focus for the near future.

Intravenous gammaglobulin (IVIG): a novel approach to improve transplant rates and outcomes in highly HLA-sensitized patients

Intravenous immunoglobulin (IVIG) products are derived from pooled human plasma and have been used for the treatment of primary immunodeficiency disorders for more than 24 years. Shortly after their introduction, IVIG products were also found to be effective in the treatment of autoimmune and inflammatory disorders. Over the past 2 decades, the list of diseases where IVIG has a demonstrable beneficial effect has grown rapidly. These include Kawasaki disease, Guillain-Barre syndrome, myasthenia gravis, dermatomyositis and demyelinating polyneuropathy. Recently, we have described a beneficial effect on the reduction of anti-HLA antibodies with subsequent improvement in transplantation of highly HLA-sensitized patients as well as a potent anti-inflammatory effect that is beneficial in the treatment of antibody-mediated rejection (AMR). These advancements have enabled transplantation of patients previously considered untransplantable. These studies and relevant mechanism(s) of action will be discussed here.

Intravenous immunoglobulin and multiple sclerosis

Intravenous immunoglobulin (IVIg) has been used as an immunomodulatory therapy for the treatment of multiple sclerosis (MS). In the current review, we summarize the up-to-date data related to IVIg clinical trials in MS, and the suggested mechanisms of action by which IVIg modulates the relevant immunological pathways impaired in MS.