Intravenous immunoglobulins contain naturally occurring antibodies that mimic antineutrophil cytoplasmic antibodies and activate neutrophils in a TNFα-dependent and Fc-receptor–independent way

Autoantibody profiles in intravenous immunoglobulin preparations: A possible cause of mistaken autoimmunity diagnosis

BACKGROUND

Intravenous immunoglobulins (IVIgs) derived from the pooled plasma of thousands of donors contain numerous types of IgG molecules, including autoantibodies commonly used to diagnose autoimmunity. While these autoantibodies can cause misinterpretation of serological tests for IVIg recipients, their profiles in IVIg preparations are not fully understood.

STUDY DESIGN AND METHODS

Using binding-capability based immune assays, we measured 18 varieties of clinically relevant autoantibodies in domestic blood donor-derived IVIg products. In addition, we analyzed an IVIg product from a US brand to evaluate the influence of regional and racial differences. Based on the determined autoantibody titers, pharmacokinetics of passively acquired autoantibodies and their possible detection period in serum were estimated.

RESULTS

Anti-thyroglobulin (Tg), anti-thyroidperoxidase (TPO), and anti-Sjögren's-syndrome-related antigen A (SS-A) antibodies were present in considerable amounts in IVIg products. Notably, these three autoantibodies can be detected in IVIg recipients' sera for up to 3 months after infusion.

DISCUSSION

To the best of our knowledge, this is the first study that analyzed multiple autoantibody profiles in both pooled plasma and IVIg products and that further evaluated their potential influences on diagnosis of autoimmunity. Clinicians should keep in mind that IVIgs contain several autoantibodies and that their infusion can produce false-positive serology results. To establish an accurate diagnosis, serological tests must be carefully interpreted and clinical symptoms should be more purposefully considered if patients are receiving IVIg therapy.

Iatrogenic ANA: An emerging source of expensive diagnostic confusion

Intravenous immune globulin (IVIg) therapy has been shown to be useful in a multitude of disorders. IVIg is produced from pooled human plasma; therefore, autoantibodies found in the general population are also present in IVIg and transferred to those being transfused. This can prove a particular hazard for screening and diagnostic tests based on autoantibodies. We present a patient who was found to have a positive antinuclear antibody (ANA) titer after multiple IVIg transfusions, resulting in diagnostic confusion and unnecessary workup. A 45-year-old gentleman was diagnosed with atypical CIDP, initiated on a course of IVIg, and sent for inpatient rehabilitation. However, recovery was complicated by multiple readmissions for recurrent weakness, and as part of the workup for other etiologies, an ANA was found to be positive. Sub-serologies and paraneoplastic autoantibody panel were negative. In the absence of clinical symptoms, we recommended continued monitoring and repeat ANA testing 6 months after the last dose of IVIg; as any drug needs 5 half-lives to be eliminated from the body. Clinicians should consider any recent IVIg treatments when evaluating the pre-test probability of detecting an underlying connective tissue disease with ANA screening. Indiscriminate ANA levels in patients recently given IVIg lead to unnecessary and expensive further testing and consultation.

Abrogation of neutrophil inflammatory pathways and potential reduction of neutrophil-related factors in COVID-19 by intravenous immunoglobulin

Pathogenesis of lung injury in COVID-19 is not completely understood, leaving gaps in understanding how current treatments modulate the course of COVID-19. Neutrophil numbers and activation state in circulation have been found to correlate with COVID-19 severity, and neutrophil extracellular traps (NETs) have been found in the lung parenchyma of patients with acute respiratory distress syndrome (ARDS) in COVID-19. Targeting the pro-inflammatory functions of neutrophils may diminish lung injury in COVID-19 and ARDS. Neutrophils were isolated from peripheral blood of healthy donors, treated ex vivo with dexamethasone, tocilizumab and intravenous immunoglobulin (IVIG) and NET formation, oxidative burst, and phagocytosis were assessed. Plasma from critically ill COVID-19 patients before and after clinical treatment with IVIG and from healthy donors was assessed for neutrophil activation-related proteins. While dexamethasone and tocilizumab did not affect PMA- and nigericin-induced NET production ex vivo, IVIG induced a dose-dependent abrogation of NET production in both activation models. IVIG also reduced PMA-elicited reactive oxygen species production, but did not alter phagocytosis. COVID-19 patients were found to have elevated levels of cell-free DNA, neutrophil elastase and IL-8 as compared to healthy controls. Levels of both cell-free DNA and neutrophil elastase were lower 5 days after 4 days of daily treatment with IVIG. The lack of impact of dexamethasone or tocilizumab on these neutrophil functions suggests that these therapeutic agents may not act through suppression of neutrophil functions, indicating that the door might still be open for the addition of a neutrophil modulator to the COVID-19 therapeutic repertoire.

Neutropenia following intravenous immunoglobulin therapy in adult patients with immune thrombocytopenic purpura: A single center experience and literature review

The purpose of this study was to evaluate neutropenia following intravenous immunoglobulin (IVIG) therapy in adults with immune thrombocytopenic purpura (ITP).Our analysis included 88 patients with ITP, who received IVIG from January 2006 to March 2016, at Pusan National University Hospital in Korea. Their white blood cell (WBC) count and absolute neutrophil count (ANC) before and after IVIG treatment were analyzed.Of 88 patients, 24 patients (27.3%) were male, and 64 patients (72.7%) were female. Neutropenia developed in 8 patients (18.7%) after IVIG treatment. In patients with a decrease in WBC count and ANC compared to baseline, median WBC count decreased from 6280/μL to 4530/μL after IVIG therapy, and median ANC decreased from 3840/μL to 2840/μL after IVIG therapy. The neutropenia induced by IVIG had resolved spontaneously after several days, and the mean recovery time was 8.72 days after the completion of the IVIG treatment. During the neutropenic episodes, only one patient developed neutropenic fever, which subsided soon without any treatment.The results of this study suggest that IVIG may cause neutropenia commonly in adults with ITP, and it seems to be transient and self-limited. This study is meaningful as the first report that not only pediatric ITP patients may develop neutropenia post IVIG administration, but also adult patients suffering ITP.

Effects of IVIg treatment on autoantibody testing in neurological patients: marked reduction in sensitivity but reliable specificity

BACKGROUND

Therapy of autoimmune diseases of the central and peripheral nervous system with intravenous IgG immunoglobulin (IVIg) is well established. Since IVIg is produced from pooled human plasma, autoantibodies can be found in IVIg products and, accordingly, in patient sera after transfusion. The de novo evidence or disappearance of anti-neural autoantibodies after IVIg treatment has so far not been systematically examined.

METHODS

We screened 50 neurological patients before and after IVIg treatment for classical onconeural and the most common neurological surface autoantibodies as well as for ganglioside autoantibodies and 23 different antinuclear autoantibodies using immunoblot or cell-based indirect immunofluorescence assays. Furthermore, we screened 31 neurological patients with previously known seropositivity for disappearance of the corresponding antibody after treatment.

RESULTS

After IVIg treatment, 90% of all sera were de novo positive for antinuclear antibodies, especially for Ro-52. In contrast, 94% of all sera did not show any de novo-positive anti-neural antibodies. In the remaining three cases, titers were very low. Importantly, 12.9% of all tested sera of patients with known antibody positivity turned false negative after IVIg treatment and titers were falsely low in 37% of the remaining sera.

CONCLUSIONS

Here, we present for the first time results of a broad screening for clinically relevant autoantibodies before and after IVIg treatment in neurological patients. We identified a high specificity but reduced sensitivity for anti-neural antibody testing after IVIg transfusion. In contrast, antinuclear antibody testing is not reliable after IVIg treatment. These results are of high practical importance for diagnostic of neuroimmunological diseases.

[MOG encephalomyelitis: international recommendations on diagnosis and antibody testing]

Over the past few years, new-generation cell-based assays have demonstrated a robust association of autoantibodies to full-length human myelin oligodendrocyte glycoprotein (MOG-IgG) with (mostly recurrent) optic neuritis, myelitis and brainstem encephalitis, as well as with acute disseminated encephalomyelitis (ADEM)-like presentations. Most experts now consider MOG-IgG-associated encephalomyelitis (MOG-EM) a disease entity in its own right, immunopathogenetically distinct from both classic multiple sclerosis (MS) and aquaporin-4 (AQP4)-IgG-positive neuromyelitis optica spectrum disorders (NMOSD). Owing to a substantial overlap in clinicoradiological presentation, MOG-EM was often unwittingly misdiagnosed as MS in the past. Accordingly, increasing numbers of patients with suspected or established MS are currently being tested for MOG-IgG. However, screening of large unselected cohorts for rare biomarkers can significantly reduce the positive predictive value of a test. To lessen the hazard of overdiagnosing MOG-EM, which may lead to inappropriate treatment, more selective criteria for MOG-IgG testing are urgently needed. In this paper, we propose indications for MOG-IgG testing based on expert consensus. In addition, we give a list of conditions atypical for MOG-EM ("red flags") that should prompt physicians to challenge a positive MOG-IgG test result. Finally, we provide recommendations regarding assay methodology, specimen sampling and data interpretation, and propose for the first time diagnostic criteria for MOG-EM.

Endometrium receptivity in premature ovarian insufficiency - how to improve fertility rate and predict diseases?

More empathized approach is required and is obligatory to women with premature ovarian insufficiency (POI) interested for pregnancy. In order to improve fertility rate in POI patients our suggestions would be: (1) To decrease FSH value to 10-15 IU/L by increasing estrogen. Oocyte donation can be suggested after a minimum of six month interval from FSH between 10-15 IU/L and when no dominant follicles are found. (2) To perform oral glucose tolerance test (OGTT). Insulin sensitizing agents has to be included, when indicated, 3-6 month before pregnancy. (3) TSH has to be 1-2.5 mM/L during 3-6 months before pregnancy. (4) Tests for thrombophyllia (Leiden V, FII, MTHFR, PAI) have to be obligatory. They are less expensive than those repeated in vitro fertilizations. Therapy has to be included according to the indications. (5) In order to regulate disturbed immune response in POI patients with endometriosis oral contraceptive therapy is needed for atleast six months prior to the pregnancy. (5) Encourage the patients and advice them about healthy life style and eating habits. (6) Add other drugs, when they are indicated. Complex interplay between endocrine, immunological, haematological, and psychological factors are very often underdetected in POI patients. It is very important to find out the real time for oocyte donation after correcting all the disturbances, improving endometrium receptivity and reaching women's acceptable psychological status. Untreated disturbances induce cardiovascular diseases, diabetes mellitus, thyroid diseases, coagulopathioes etc.

MOG encephalomyelitis: international recommendations on diagnosis and antibody testing

Over the past few years, new-generation cell-based assays have demonstrated a robust association of autoantibodies to full-length human myelin oligodendrocyte glycoprotein (MOG-IgG) with (mostly recurrent) optic neuritis, myelitis and brainstem encephalitis, as well as with acute disseminated encephalomyelitis (ADEM)-like presentations. Most experts now consider MOG-IgG-associated encephalomyelitis (MOG-EM) a disease entity in its own right, immunopathogenetically distinct from both classic multiple sclerosis (MS) and aquaporin-4 (AQP4)-IgG-positive neuromyelitis optica spectrum disorders (NMOSD). Owing to a substantial overlap in clinicoradiological presentation, MOG-EM was often unwittingly misdiagnosed as MS in the past. Accordingly, increasing numbers of patients with suspected or established MS are currently being tested for MOG-IgG. However, screening of large unselected cohorts for rare biomarkers can significantly reduce the positive predictive value of a test. To lessen the hazard of overdiagnosing MOG-EM, which may lead to inappropriate treatment, more selective criteria for MOG-IgG testing are urgently needed. In this paper, we propose indications for MOG-IgG testing based on expert consensus. In addition, we give a list of conditions atypical for MOG-EM ("red flags") that should prompt physicians to challenge a positive MOG-IgG test result. Finally, we provide recommendations regarding assay methodology, specimen sampling and data interpretation.

Dimeric IgG complexes from IVIg are incapable of inducing in vitro neutrophil degranulation or complement activation

Purpose

Intravenous immunoglobulin (IVIg) products contain various amounts of dimeric IgG complexes. Current insights into the possible biological activities of these dimers remain controversial, and both immunemodulating and immune-activating effects have been reported. Here, we analyzed the putative immune-activating effects of dimers isolated from IVIg.

Methods

Dimers isolated from IVIg were purified by high-performance size-exclusion chromatography (HP-SEC) and tested for the ability to induce neutrophil degranulation in vitro.

Results

Dimers isolated from IVIg were found to be incapable of inducing in vitro neutrophil degranulation or complement activation, even at concentrations exceeding those expected to be reached upon administration in patients. These results depend on the removal of artefactual activation by using 0.1 micron filtration and the use of poloxamer to prevent adsorption of IgG onto the solid phase.

Conclusions

The data suggest dimeric IgG found in IVIg may bind to Fc-receptors without causing activation.

Effect of intravenous immunoglobulin administration on erythrocyte and leucocyte parameters

BACKGROUND

Intravenous immunoglobulins (IVIG) are an attractive therapeutic tool for therapy of toxic epidermal necrolysis and severe forms of certain autoimmune diseases, including dermatomyositis, autoimmune blistering diseases, systemic vasculitis and lupus erythematodes.

OBJECTIVES

Prompted by a case of IVIG-associated haemolytic anaemia, the effects of IVIG administrations on haematological parameters in patients with dermatological conditions were investigated.

METHODS

Erythrocyte and leucocyte parameters were retrospectively analysed in 16 patients who had received IVIG at doses from 1 to 3 g/kg bodyweight (n = 35 cycles). The influence of IVIG on leucocyte survival was determined in vitro.

RESULTS

Decreased absolute erythrocyte numbers, haemoglobin and haematocrit levels and a case of haemolytic anaemia were linked to transfusion of high-, but not low-dose IVIG. In contrast, leucopenia post-IVIG occurred in the vast majority of the recipients, unrelated to the administered IVIG amounts. In vitro investigations revealed a dose-dependent impairment of cell survival by IVIG in the neutrophil and monocyte, but not in the lymphocyte subpopulations. In several IVIG preparations, substantial amounts of blood group anti-A/anti-B antibodies were detected which could have accounted for the observed changes in the haematological parameters in our study cohort.

CONCLUSIONS

IVIG products should be administered strictly according to indications. Commercially available IVIG products can contain blood group-specific antibodies that may induce haemolysis in some recipients. Monitoring of blood counts during applied IVIG therapy, especially when high doses are administered, is recommended.

IVIG Associated Aseptic Meningitis in a Renal Transplant Patient

The management of antibody-mediated rejection in renal transplant recipients involves plasmapheresis with IVIG. Aseptic meningitis is a rare adverse effect of IVIG therapy and is a diagnosis of exclusion. We report a case of a renal transplant patient who developed IVIG associated aseptic meningitis in the context of management of antibody-mediated rejection, four years after transplantation.

The effect of Intravenous Immunoglobulin (IVIG) on \textit{ex vivo} activation of human leukocytes

INTRODUCTION

Intravenous immunoglobulin (IVIG) has been widely used to treat various conditions, including inflammatory and autoimmune diseases. IVIG has been shown to have a direct influence on neutrophils, eosinophils and lymphocytes. However, many aspects IVIG's effect on neutrophils activation still remain unknown.

OBJECTIVE

To evaluate the effect of IVIG on PMA-induced activation of neutrophils, with and without priming with TNF-α, in a series of in vitro experiments performed on whole blood.

RESULTS

Our data coincided with well-known literature indicating that the effect of phorbol 12-myristate 13-acetate (PMA) on human leukocytes includes activation of neutrophils, monocytes and eosinophils, increase of chemiluminescence (CL) and induction of netosis, resulting in assembly of traps. In presence of IVIG (10 mg/mL), CL was reduced by 25% in response to PMA compared to PMA-induced leukocyte activation without IVIG. Decreasing IVIG concentration to 1 mg/mL and below did not inhibit PMA-induced activation of CL.PMA-induced activation after TNF-α priming resulted in approximately 50% increase of amplitude of CL response to PMA. Moreover, maximum CL was reached by minute 5, which was more rapid than in the absence of TNF-α-priming (in this case maximum CL was reached by minute 15).The IVIG concentrations did not affect morphological changes of leukocytes after sequential addition of TNF-α and PMA. IVIG had no effect on leukocyte content and on PMA-induced CL of primed leukocytes.Addition of IVIG under TNF-α priming significantly increased the number of traps in the smears in response to PMA activation. Of note, such an increase in the number of traps was depended on the IVIG concentration in plasma.

CONCLUSION

In conclusion, we suggest that IVIG is able to reduce the degradation of traps under priming with TNF-α. Moreover, IVIG might switch the activation of primed leukocytes to netosis.

Managing patients with side effects and adverse events to immunoglobulin therapy

Immunoglobulin therapy has not only served as a lifesaving approach for the prevention and treatment of infections in primary and secondary immunodeficiency diseases, but has also been used as an immunomodulatory agent for autoimmune and inflammatory disorders and to provide passive immunity for some infectious diseases. Most of the adverse effects associated with immunoglobulin therapy are mild, transient and self-limiting. However, serious side effects also occur. Therefore, to minimize the adverse events of immunoglobulin therapy, specialist review of patient clinical status and immunoglobulin products, in addition to selection of appropriate treatment strategy for the management of patients with associated side effects and adverse events, are crucial.

Acute pulmonary embolism caused by highly aggregated intravenous immunoglobulin

BACKGROUND AND OBJECTIVES

Six patients died and one patient survived following infusion of a specific lot of intravenous immunoglobulin (IVIG) within half an hour in May 2008. This study elucidated the underlying pathogenesis.

MATERIALS AND METHODS

A variety of protein fractionation and identification approaches were employed to determine the abnormal components in IVIG products obtained from the hospital where the patients were treated. Animal studies using mice and monkeys were conducted to elucidate the pathophysiological mechanisms. In animal experiments, the effect and distribution of immunoglobulin was investigated using HE staining and immunohistochemistry (IHC) separately, while platelets and fibrinogen depletion were utilized to determine a possible link between thromboembolism formation in animals and the lethal effect of the IVIG. The size and distribution of the protein aggregates were determined with Coulter Counter Multisizer-3 after the dilution of the IVIG with plasma, and the lethal effect of the protein aggregates was simulated with artificial microparticles.

RESULTS

The IVIG retrieved from the hospital was found to have striking similarities to the heat-treated IVIG in terms of protein aggregation profiles and lethal effects. Post-mortem examination indicated that immunoglobulin aggregates were mainly found in the lung of the animals, while depletion of platelets and fibrinogen from the IVIG preparations failed to prevent the death of the animals. Similar amount of artificial microparticles caused animal death in similar fashion.

CONCLUSIONS

Our findings indicate that the retrieved IVIG exerted its lethal effects by blocking the pulmonary circulation without markedly altering the coagulation cascade or immunological events.

Acute aseptic meningitis due to intravenous immunoglobulin therapy in Guillain-Barré syndrome

The majority of adverse reactions of intravenous immunoglobulin (IVIG) therapy are mild, transient and self-limiting with potentially serious complications occurring in <5% of patients. IVIG-associated transient aseptic meningitis is one such rare adverse effect, which has been seldomly described in the literature. We report a case of aseptic meningitis due to IVIG therapy in a Guillain–Barré syndrome (GBS) patient. The cerebrospinal fluid analysis revealed high cell counts with predominance of lymphocytic cells, raised protein, normal glucose level and no growth of the organisms on culture. The patient improved with supportive care such as intravenous fluids and analgesics without neurological complications. This case emphasizes the importance of recognizing IVIG-associated complications like aseptic meningitis in GBS patients.

Polyclonal and monoclonal antibodies in clinic

Immunoglobulins (Ig) or antibodies are heavy plasma proteins, with sugar chains added to amino-acid residues by N-linked glycosylation and occasionally by O-linked glycosylation. The versatility of antibodies is demonstrated by the various functions that they mediate such as neutralization, agglutination, fixation with activation of complement and activation of effector cells. Naturally occurring antibodies protect the organism against harmful pathogens, viruses and infections. In addition, almost any organic chemical induces antibody production of antibodies that would bind specifically to the chemical. These antibodies are often produced from multiple B cell clones and referred to as polyclonal antibodies. In recent years, scientists have exploited the highly evolved machinery of the immune system to produce structurally and functionally complex molecules such as antibodies from a single B clone, heralding the era of monoclonal antibodies. Most of the antibodies currently in the clinic, target components of the immune system, are not curative and seek to alleviate symptoms rather than cure disease. Our group used a novel strategy to identify reparative human monoclonal antibodies distinct from conventional antibodies. In this chapter, we discuss the therapeutic relevance of both polyclonal and monoclonal antibodies in clinic.

Adverse effects of IgG therapy

IgG is widely used for patients with immune deficiencies and in a broad range of autoimmune and inflammatory disorders. Up to 40% of intravenous infusions of IgG may be associated with adverse effects (AEs), which are mostly uncomfortable or unpleasant but often are not serious. The most common infusion-related AE is headache. More serious reactions, including true anaphylaxis and anaphylactoid reactions, occur less frequently. Most reactions are related to the rate of infusion and can be prevented or treated just by slowing the infusion rate. Medications such as nonsteroidal anti-inflammatory drugs, antihistamines, or corticosteroids also may be helpful in preventing or treating these common AEs. IgA deficiency with the potential of IgG or IgE antibodies against IgA increases the risk of some AEs but should not be viewed as a contraindication if IgG therapy is needed. Potentially serious AEs include renal dysfunction and/or failure, thromboembolic events, and acute hemolysis. These events usually are multifactorial, related to combinations of constituents in the IgG product as well as risk factors for the recipient. Awareness of these factors should allow minimization of the risks and consequences of these AEs. Subcutaneous IgG is absorbed more slowly into the circulation and has a lower incidence of AEs, but awareness and diligence are necessary whenever IgG is administered.

Adverse effects of human immunoglobulin therapy

Human immunoglobulin (IG) is used for IgG replacement therapy in primary and secondary immunodeficiency, for prevention and treatment of certain infections, and as an immunomodulatory agent for autoimmune and inflammatory disorders. IG has a wide spectrum of antibodies to microbial and human antigens. Several high-titered IGs are also available enriched in antibodies to specific viruses or bacterial toxins. IG can be given intravenously (IGIV), intramuscularly (IGIM) or by subcutaneous infusions (SCIG). Local adverse reactions such as persistent pain, bruising, swelling and erythema are rare with IGIV infusions but common (75%) with SCIG infusions. By contrast, adverse systemic reactions are rare with SCIG infusions but common with IGIV infusions, occurring as often as 20% to 50% of patients and 5% to 15% of all IGIV infusions. Systemic adverse reactions can be immediate (60% of reactions) occurring within 6 hours of an infusion, delayed (40% of reactions) occurring 6 hours-1 week after an infusion, and late (less than 1% of reactions), occurring weeks and months after an infusion. Immediate systemic reactions such as head and body aches, chills and fever are usually mild and readily treatable. Immediate anaphylactic and anaphylactoid reactions are uncommon. The most common delayed systemic reaction is persistent headache. Less common but more serious delayed reactions include aseptic meningitis, renal failure, thromboembolism, and hemolytic reactions. Late reactions are uncommon but often severe, and include lung disease, enteritis, dermatologic disorders and infectious diseases. The types, incidence, causes, prevention, and management of these reactions are discussed.

Neutrophil extracellular traps mediate transfer of cytoplasmic neutrophil antigens to myeloid dendritic cells toward ANCA induction and associated autoimmunity

Antineutrophil cytoplasmic antibodies (ANCAs) target proteins normally retained within neutrophils, indicating that cell death is involved in the autoimmunity process. Still, ANCA pathogenesis remains obscure. ANCAs activate neutrophils inducing their respiratory burst and a peculiar form of cell death, named NETosis, characterized by formation of neutrophil extracellular traps (NETs), decondensed chromatin threads decorated with cytoplasmic proteins endorsed with antimicrobial activity. NETs have been consistently detected in ANCA-associated small-vessel vasculitis, and this association prompted us to test whether the peculiar structure of NET favors neutrophil proteins uploading into myeloid dendritic cells and the induction of ANCAs and associated autoimmunity. Here we show that myeloid DCs uploaded with and activated by NET components induce ANCA and autoimmunity when injected into naive mice. DC uploading and autoimmunity induction are prevented by NET treatment with DNAse, indicating that NET structural integrity is needed to maintain the antigenicity of cytoplasmic proteins. We found NET intermingling with myeloid dendritic cells also positive for neutrophil myeloperoxidase in myeloperoxidase-ANCA-associated microscopic poliangiitis providing a potential correlative picture in human pathology. These data provide the first demonstration that NET structures are highly immunogenic such to trigger adaptive immune response relevant for autoimmunity.

Naturally occurring autoantibodies in mediating clearance of senescent red blood cells

Germline-encoded naturally occurring autoantibodies (NAbs) developed about 400 to 450 million years ago to provide specificity for clearance ofbody waste in animals with 3 germ layers. Such NAbs became a necessity to selectively clear aged red blood cells (RBC) surviving 60 to 120 d in higher vertebrates. IgG NAbs to senescent RBC are directed to the most abundant integral membrane protein, the anion-transport protein or band 3 protein, but only bind firmly upon its oligomerization, which facilitates bivalent binding. The main constituent of RBC, the oxygen-carrying hemoglobin, is susceptible to oxidative damage. Oxidized hemoglobin forms hemichromes (a form of aggregates) that bind to the cytoplasmic portion of band 3 protein, induces their clustering on the cytoplasmic, as well as the exoplasmic side and thereby provides the prerequisites for the low affinity IgG anti-band 3 NAbs to bind bivalently. Bound anti-band 3 NAbs overcome their low numbers per RBC by stimulating complement amplification. An affinity for C3 outside the antigen binding region is responsible for a preferential formation of C3b(2)-IgG complexes from anti-band 3 NAbs. These complexes first bind oligomeric properdin, which enhances their affinity for factor B in assembling an alternative C3 convertase.

A differential concentration-dependent effect of IVIg on neutrophil functions: relevance for anti-microbial and anti-inflammatory mechanisms

BACKGROUND

Polymorphonuclear neutrophils (PMN) play a key role in host defences against invading microorganisms but can also potentiate detrimental inflammatory reactions in case of excessive or misdirected responses. Intravenous immunoglobulins (IVIg) are used to treat patients with immune deficiencies and, at higher doses, in autoimmune, allergic and systemic inflammatory disorders.

METHODOLOGY/PRINCIPAL FINDINGS

We used flow cytometry to examine the effects of IVIg on PMN functions and survival, using whole-blood conditions in order to avoid artifacts due to isolation procedures. IVIg at low concentrations induced PMN activation, as reflected by decreased L-selectin and increased CD11b expression at the PMN surface, oxidative burst enhancement, and prolonged cell survival. In contrast, IVIg at higher concentrations inhibited LPS-induced CD11b degranulation and oxidative burst priming, and counteracted LPS-induced PMN lifespan prolongation.

CONCLUSIONS/SIGNIFICANCE

IVIg appears to have differential, concentration-dependent effects on PMN, possibly supporting the use of IVIg as either an anti-microbial or an anti-inflammatory agent.

Clinical characteristics of aseptic meningitis induced by intravenous immunoglobulin in patients with Kawasaki disease

BACKGROUND

Aseptic meningitis is a serious adverse reaction to intravenous immunoglobulin (IVIG) therapy. We studied the clinical characteristics of patients with acute Kawasaki disease (KD) who developed IVIG-induced aseptic meningitis.

METHODS

A retrospective analysis of the medical records of patients with KD who developed aseptic meningitis after IVIG treatment was performed.

RESULTS

During the 10-year period from 2000 through 2009, among a total of 384 patients with Kawasaki disease, 4 (3 females and 1 male; age range, 19-120 months) developed aseptic meningitis after IVIG. All 4 developed aseptic meningitis within 48 hours (range, 25-40 hours) of initiation of IVIG. The analyses of cerebrospinal fluid (CSF) revealed elevated white blood cell counts (22-1,248/μL) in all 4 patients; a predominance of polynuclear cells (65%-89%) was noted in 3. The CSF protein level was elevated in only 1 patient (59 mg/dL), and the glucose levels were normal in all 4 patients. Two patients were treated with intravenous methylprednisolone; the other 2 children were observed carefully without any special therapy. All patients recovered without neurological complications.

CONCLUSIONS

In our patients with Kawasaki disease, aseptic meningitis induced by IVIG occurred within 48 hours after initiation of IVIG, resolved within a few days, and resulted in no neurological complications, even in patients who did not receive medical treatment.

A report of the natural history of leptomeningeal gliomatosis

Primary leptomeningeal gliomatosis (PLG) is a rare condition, with fewer than 50 patients reported. Our report illustrates the natural history of PLG in full, from the prodromal phase of subacute meningitis to the final stages characterised by extensive nerve root infiltration, cranial nerve palsies and widespread peripheral neurogenic muscle wasting. We provide correlative neuroimaging with serial MRI, and present the first published positron emission tomography imaging of this condition. We emphasise the importance of considering PLG in the differential diagnosis of chronic aseptic meningitis, the difficulties of making the diagnosis ante mortem, and the utility and potential limitations of early meningeal biopsy in this condition.

Intravenous immunoglobulin therapy in rheumatic diseases

Prepared from the collective plasma of several thousand people, therapeutic intravenous immunoglobulin (IVIg) consists mostly of human polyspecific IgG. In addition to its use in primary and secondary immune deficiencies, IVIg is used in the treatment of several rheumatic conditions, including Kawasaki disease, dermatomyositis and antineutrophil cytoplasmic antibody (ANCA)-positive vasculitis. In these diseases, IVIg therapy generally involves the use of 2 g/kg administered over either 2 or 5 consecutive days. However, dosage regimens have not been thoroughly explored, and indications for IVIg in most rheumatic diseases, such as systemic lupus erythematosus, polymyositis and catastrophic antiphospholipid syndrome, derive from its off-label usage. Randomized clinical trials are warranted to support the evidence-based use of IVIg, and to identify the ideal administration protocols to maximize the benefits of what is a limited resource. Further research to improve the therapeutic application of IVIg relies essentially on the conception of next-generation immunoglobulin preparations and optimization of combined therapies with immunomodulatory drugs and biologic agents.

Comparison of characteristics of natural autoantibodies against myeloperoxidase and anti-myeloperoxidase autoantibodies from patients with microscopic polyangiitis

OBJECTIVE

Natural autoantibodies (NAAs) against MPO exist in normal human plasma. In the current study, the immune characteristics of MPO-NAA and MPO-ANCA were examined and compared with the aim to investigate the pathogenesis of MPO-ANCA.

METHODS

MPO-NAAs were affinity purified from normal plasma of five healthy blood donors and one batch of IVIG. MPO-ANCAs were purified from plasma of 10 patients with MPA. Antigen specificity of the antibodies was tested by western blot analysis. The titre, the avidity, the Immunoglobulin G (IgG) subclasses and the effect of the antibodies towards the binding between ceruloplasmin and MPO were tested using ELISAs. The MPO-NAA-induced production of reactive oxygen species was assessed using oxidation of dihydrorhodamine (DHR) to rhodamine.

RESULTS

MPO-NAA recognized epitope(s) in the heavy chains of MPO with conformation-dependent structure, the same as MPO-ANCA. The median titre of MPO-NAA was lower than that of MPO-ANCA (1 : 40 vs 1 : 4800, P < 0.001). The median avidity of MPO-NAA was lower than that of MPO-ANCA (2.2 × 10(7) vs 8.7 × 10(7)/M, P = 0.014). The IgG subclasses of MPO-NAA were mainly restricted to IgG1 (100%) and lack of IgG3. The inhibition effect on the binding between ceruloplasmin and MPO was lower for MPO-NAA than MPO-ANCA (P = 0.046). The MPO-NAA-induced respiratory burst of neutrophils was significantly weaker than that of MPO-ANCA (P = 0.036).

CONCLUSION

The lower titre, lower avidity and lack of IgG3 subclass compared with MPO-ANCA may contribute to the non-pathogenic co-existence of MPO-NAA with MPO in serum.

Does a gating policy for ANCA overlook patients with ANCA associated vasculitis? An audit of 263 patients

BACKGROUND

Antineutrophil cytoplasm antibodies (ANCA) are used as diagnostic markers for small-vessel vasculitis of the Wegener Granulomatosis-microscopic polyangiitis (WG-MPA) spectrum, but if testing is applied indiscriminately, its value is diminished. The authors measured the effect of a targeted ANCA testing policy introduced in our institution in an attempt to improve the diagnostic value of testing in patients with suspected vasculitis.

METHODS

The authors measured the rate of ANCA requests at a single regional centre in the year prior to and following the introduction of clinical guidelines to ensure appropriate test usage. The authors also audited clinical outcomes in patients in whom ANCA testing was declined.

RESULT

Following implementation of the antineutrophil cytoplasm antibodies (ANCA) gating policy, the number of monthly ANCA tests carried out fell from 287+/-30 to 143+/-18 (p<0.0001) and was associated with an increased rate of positivity, from 18.5% (95% CI 17.0 to 20.1%) to 30.3% (27.5 to 33.1%; p<0.0001). The authors undertook a careful review of the case records from 263 patients in whom testing was declined according to the gating policy over an 8-month period. After 6 months' follow-up, no diagnoses of small-vessel vasculitis of the WG-MPA spectrum were reached.

CONCLUSIONS

The rational use of ANCA testing to aid in the diagnosis of vasculitis should include a clinical gating policy to improve diagnostic performance. Adherence to a gating policy for ANCA testing coupled with close liaison between clinician and laboratory does not result in either a missed or delayed diagnosis of small-vessel vasculitis belonging to the WG-MPA spectrum.

The effect of IgG levels on the number of natural killer cells and their Fc receptors in chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND AND PURPOSE

High-dose intravenous immunoglobulin (IVIg) is an established treatment for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Although Fc receptors on natural killer cells have been suggested as a target for IVIg, the pharmacological effects are not yet clarified. We hypothesize that IVIg therapy, dependent on the plasma IgG level, suppresses the cytotoxic capacity by a reduction in numbers of NK cells and their Fc receptor CD16.

PATIENTS AND METHODS

Ten consecutive patients with CIDP in maintenance therapy with IVIg were studied before and immediately after the infusion of 0.7-2.0 g/kg IVIg. Peripheral blood mononuclear cell samples from these patients were analyzed immediately after isolation using flow cytometry and cytotoxicity assays.

RESULTS

We found that following IVIg treatment, the cytotoxic activity of NK cells in CIDP patients was suppressed, partly caused by a dose-dependent decline in the number of circulating NK cells. In addition, a dose-dependent blockage of CD16 occurred.

CONCLUSIONS

The study implies that IVIg infusion induces a substantial decline in the number of peripheral NK cells and a suppression of NK-cell-mediated cytotoxicity. We propose that these impairments of the NK cells contribute to the therapeutic effect of IVIg in CIDP.

Modulation of the cellular immune system by intravenous immunoglobulin

Intravenous immunoglobulin (IVIg) is therapeutically used in a variety of immune-mediated diseases. The beneficial effects of IVIg in auto-antibody-mediated diseases can be explained by neutralization, accelerated clearance and prevention of Fcgamma-receptor binding of auto-antibodies. However, the means by which IVIg exerts therapeutic effects in disorders mediated by cellular immunity have remained enigmatic. Clinical improvements, followed by IVIg treatment, often extend beyond the half-life of infused IgG, thereby indicating that IVIg modifies the cellular immune compartment for a prolonged period. Here, we discuss recent advances in the understanding of different, mutually non-exclusive mechanisms of action of IVIg on cells of the innate and adaptive immune system. These mechanisms might explain the beneficial effects of IVIg in certain autoimmune and inflammatory diseases.

Natural and disease associated anti-myeloperoxidase (MPO) autoantibodies

Myeloperoxidase (MPO) is a cationic protein present in primary azurophilic granules of neutrophils and monocytes. MPO produces a highly deleterious reactive oxygen species, the hypochlorous acid (HOCl), using hydrogen peroxide (H(2)O(2)) and chloride ions as substrate. Anti-MPO antibodies (Abs) are present in 70% of the cases in patients with microscopic polyangiitis (MPA), a small-sized vessel vasculitis. Anti-MPO Abs from patients with MPA can trigger the release of MPO by neutrophils and monocytes. Anti-MPO Abs can activate MPO to generate an oxidative stress deleterious for the endothelium. Thus, we recently demonstrated that MPA sera with anti-MPO Abs activated MPO in vitro, and generated hypochlorous acid, whereas sera from MPA patients with no anti-MPO Abs or healthy individuals did not. Both hypochlorous acid production and endothelial lysis were abrogated by N-acetylcysteine (NAC), an antioxidant molecule. Thus, anti-MPO Abs could play a pathogenic role in vivo by triggering an oxidative burst leading to severe endothelial damages.

Monoclonal antibody and intravenous immunoglobulin therapy for rheumatic diseases: rationale and mechanisms of action

Advances in our understanding of the pathogenesis of rheumatic diseases such as rheumatoid arthritis and systemic lupus erythematosus have led to the emergence of immunoglobulin-based therapy as a major therapeutic force. Numerous monoclonal antibodies that target proinflammatory cytokines or their receptors (e.g. infliximab, adalimumab, tocilizumab, belimumab, HuMax-IL-15), and cell-surface or co-stimulatory molecules (e.g. rituximab) are either in clinical development or have been approved for clinical use. These antibodies are safe and effective in the long-term therapy of many rheumatic diseases. In addition, polyclonal immunoglobulins (intravenous immunoglobulin) obtained from pooled plasma from healthy blood donors are an effective therapeutic approach in certain rheumatic diseases. The mechanisms of action of monoclonal antibodies and intravenous immunoglobulin include cytolysis of target cells through complement or antibody-dependent cell-mediated cytotoxicity, induction of apoptosis of target cells, blockade of co-stimulatory molecules, and neutralization of pathogenic antibodies and soluble factors such as cytokines and their receptors, which ultimately lead to amelioration of the inflammatory process. The success of currently available therapeutic immunoglobulins has led to considerable interest in the identification of novel molecular therapeutic targets in rheumatic diseases.

Intravenous immunoglobulin: an update on the clinical use and mechanisms of action

Initially used as a replacement therapy for immunodeficiency diseases, intravenous immunoglobulin (IVIg) is now widely used for a number of autoimmune and inflammatory diseases. Considerable progress has been made in understanding the mechanisms by which IVIg exerts immunomodulatory effects in autoimmune and inflammatory disorders. The mechanisms of action of IVIg are complex, involving modulation of expression and function of Fc receptors, interference with activation of complement and the cytokine network and of idiotype network, regulation of cell growth, and effects on the activation, differentiation, and effector functions of dendritic cells, and T and B cells.