Impact of Autoantibodies to Complement Components on the Disease Activity in SLE

INTRODUCTION

Systemic Lupus Erythematosus (SLE) is a chronic multi-system autoimmune disease with varied clinical presentations. Complement components are the major players in disease pathogenesis. This retrospective cross-sectional study was aimed at assessing the role of autoantibodies to these complement components and their association disease activity in newly diagnosed SLE patients from India.

METHOD

Clinically diagnosed SLE patients (n=57) classified as per 2015 ACR/SLICC revised criteria were enrolled between November 2016 to April 2017. Patients' sera were tested for C3 and C4 by nephelometry, while serum levels of factor H, factor P (properdin) as well as autoantibodies to C3, C4, factor H and factor P were detected by ELISA. GraphPad Prism Version 6.01 was used for statistical analysis. Mean, SD, SEM were calculated. Mann Whittney U-test, ANOVA, Chi-square test, Odd's Ratio were calculated. Pearson's correlation was used to study relativeness of the study parameters.

RESULTS

Among the 57 SLE patients, low C3 were seen in 51% patients, low C4 in 49%, low factor H in 19% and low factor P in 49% patients. Positivity for autoantibodies against complement components, anti-C3 were seen in 42% patients, anti-C4 in 7%, anti-factor H in 19% and anti-factor P in 28% patients. Serum levels of C3 (p=0.0009), C4 (p=0.0031) and anti-C3 autoantibodies (p=0.0029) were significantly associated with ACR/SLICC 2015 scores.

CONCLUSION

Hypocomplementemia was found to be associated with higher disease damage score in newly diagnosed SLE patients. This study adds novel arguments for the importance of the anti-C3 autoantibodies as a marker of SLE.

Reversing Autoimmunity Combination of Rituximab and Intravenous Immunoglobulin

In this concept paper, the authors present a unique and novel protocol to treat autoimmune diseases that may have the potential to reverse autoimmunity. It uses a combination of B cell depletion therapy (BDT), specifically rituximab (RTX) and intravenous immunoglobulin (IVIg), based on a specifically designed protocol (Ahmed Protocol). Twelve infusions of RTX are given in 6–14 months. Once the CD20⁺ B cells are depleted from the peripheral blood, IVIg is given monthly until B cells repopulation occurs. Six additional cycles are given to end the protocol. During the stages of B cell depletion, repopulation and after clinical recovery, IVIg is continued. Along with clinical recovery, significant reduction and eventual disappearance of pathogenic autoantibody occurs. Administration of IVIg in the post-clinical period is a crucial part of this protocol. This combination reduces and may eventually significantly eliminates inflammation in the microenvironment and facilitates restoring immune balance. Consequently, the process of autoimmunity and the phenomenon that lead to autoimmune disease are arrested, and a sustained and prolonged disease and drug-free remission is achieved. Data from seven published studies, in which this combination protocol was used, are presented. It is known that BDT does not affect check points. IVIg has functions that mimic checkpoints. Hence, when inflammation is reduced and the microenvironment is favorable, IVIg may restore tolerance. The authors provide relevant information, molecular mechanism of action of BDT, IVIg, autoimmunity, and autoimmune diseases. The focus of the manuscript is providing an explanation, using the current literature, to demonstrate possible pathways, used by the combination of BDT and IVIg in providing sustained, long-term, drug-free remissions of autoimmune diseases, and thus reversing autoimmunity, albeit for the duration of the observation.

Inhibitor Formation in Congenital Hemophilia A: an Immunological Perspective

The immunogenicity of therapeutic factor VIII (FVIII) in patients with hemophilia A has been puzzling scientific and clinical communities for more than 3 decades. Indeed, the development of inhibitory antibodies to FVIII remains a major clinical challenge and is associated with enormous societal costs. Thus, the reasons for which a presumably innocuous, short-lived, intravenously administered glycoprotein triggers such a deleterious, long-lasting neutralizing immune response is an enigma. This review does not pretend to bring an answer to this challenging question. It will however summarize the latest findings regarding the molecular interactions at play in the recognition of FVIII by the immune cells, the validity of the proposed risk factors for FVIII alloimmunization, and the different solutions that allow induction of FVIII-specific tolerance in preclinical models of hemophilia A.

Association of Serum Ferritin Levels with Hematological Manifestations in Systemic Lupus Erythematosus Patients from Western India

OBJECTIVE

To identify the hematological manifestations and its association with serum ferritin levels in SLE patients from Western India.

METHODS

Ninety clinically diagnosed SLE patients fulfilling ACR criteria were included. Disease activity was assessed at the time of evaluation using Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Sera were tested for serum ferritin levels by ELISA (Calbiotech, USA). Autoantibodies such as ANA, anti-dsDNA by indirect immunofluorescence test (IFA- Bio-Rad, USA) and anti-cardiolipin antibodies (ACA) to IgG and IgM isotypes and Anti-β2 GP antibodies to IgG and IgM isotypes were detected by ELISA using commercially available kits (Euroimmun, Lubeck, Germany).

RESULTS

Out of 90 SLE patients studied, 41 patients (45.6%) showed hematological abnormalities, where anemia (82.9%), leucopenia (26.8%), autoimmune hemolytic anemia (AIHA) (14.6%) and idiopathic thrombocytopenic purpura (ITP) were noted in (34.1%) patients. Mean±SD serum ferritin levels among SLE patients were 270.2±266.0 ng/ml as compared to 29.0±15.8 ng/ml healthy normal controls (p<0.0001). A positive correlation between serum ferritin levels and SLEDAI scores (r= 0.2640, p=0.0124) and anti-dsDNA positivity was noted (r=0.32, p<0.0001). Serum ferritin levels were negatively correlated with hemoglobin levels (r=-0.5964, p=0.0001), WBC count (r=-0.1705, p=0.2316), platelet count ((r=-0.1701, P=0.2375), C3 levels (r=-0.4417, p=0.0034) and C4 levels (r=-0.0363, p=0.8215).

CONCLUSIONS

Serum ferritin is an excellent marker of SLE which can be used for an evaluation of disease activity particularly in active stage of the disease mainly in patients having hematological and renal manifestations.

Relationship between natural and heme-mediated antibody polyreactivity

Polyreactive antibodies represent a considerable fraction of the immune repertoires. Some antibodies acquire polyreactivity post-translationally after interaction with various redox-active substances, including heme. Recently we have demonstrated that heme binding to a naturally polyreactive antibody (SPE7) results in a considerable broadening of the repertoire of recognized antigens. A question remains whether the presence of certain level of natural polyreactivity of antibodies is a prerequisite for heme-induced further extension of antigen binding potential. Here we used a second monoclonal antibody (Hg32) with unknown specificity and absence of intrinsic polyreactivity as a model to study the potential of heme to induce polyreactivity of antibodies. We demonstrated that exposure to heme greatly extends the antigen binding potential of Hg32, suggesting that the intrinsic binding promiscuity is not a prerequisite for the induction of polyreactivity by heme. In addition we compared the kinetics and thermodynamics of the interaction of heme-exposed antibodies with a panel of unrelated antigens. These analyses revealed that the two heme-sensitive antibodies adopt different mechanisms of binding to the same set of antigens. This study contributes to understanding the phenomenon of induced antibody polyreactivity. The data may also be of importance for understanding of physiological and pathological roles of polyreactive antibodies.

<i>In Vitro</i> Seed Germination and Embryo Culture in <i>Nothapodytes foetida</i> (Wight) Sleumer

In vitro seed germination and embryo culture have been achieved in Nothapodytes foetida, this plant is known for its rich source of anticancer drug i. e., Camptothecin. In present study both normal and decoated seeds were subjected to different treatments viz., H2O, GA3, H2O2, H2SO4, chlorine water and mechanical scarification, further these were germinated on water agar medium (WA), filter paper bridge (FB), half strength MS (HMS) and full strength MS (FMS) medium. The highest percentage (69%) of germination was achieved from decoated seeds treated with 10mg/L GA3 and germinated on Filter Paper Bridge. And for embryo culture mature embryos were inoculated on MS medium containing various combination and concentrations of cytokinins (BAP, Kn and TDZ) and auxin (IAA and NAA) for rapid conversion into a plantlet. Among the different combinations of growth regulators; highest frequency (100%) of plantlet conversion was obtained on MS medium containing Kn (1.0mg/L) and NAA (0.2mg/L).

In Vitro Seed Germination and Embryo Culture in Nothapodytes foetida (Wight) Sleumer

In vitro seed germination and embryo culture have been achieved in Nothapodytes foetida, this plant is known for its rich source of anticancer drug i. e., Camptothecin. In present study both normal and decoated seeds were subjected to different treatments viz., H2O, GA3, H2O2, H2SO4, chlorine water and mechanical scarification, further these were germinated on water agar medium (WA), filter paper bridge (FB), half strength MS (HMS) and full strength MS (FMS) medium. The highest percentage (69%) of germination was achieved from decoated seeds treated with 10mg/L GA3 and germinated on Filter Paper Bridge. And for embryo culture mature embryos were inoculated on MS medium containing various combination and concentrations of cytokinins (BAP, Kn and TDZ) and auxin (IAA and NAA) for rapid conversion into a plantlet. Among the different combinations of growth regulators; highest frequency (100%) of plantlet conversion was obtained on MS medium containing Kn (1.0mg/L) and NAA (0.2mg/L).

Recommended indications for the administration of polyclonal immunoglobulin preparations

The following recommendations, which aim at standardising and rationalising the clinical indications for administering polyclonal immunoglobulins in Belgium, were drawn up by a working group of the Superior Health Council. To this end, the Superior Health Council organised an expert meeting devoted to"Guidelines for the use of immunoglobulins". The experts discussed the indications for immunoglobulin use, the'ideal'immunoglobulin preparation, its mechanisms of action, the practical issues involved in administering immunoglobulins and their potential side effects. The recommendations formulated by the experts were validated by the Superior Health Council working group with the purpose of harmonising immunoglobulin use in Belgium

Physiological induction of regulatory Qa-1-restricted CD8+ T cells triggered by endogenous CD4+ T cell responses

T cell-dependent autoimmune diseases are characterized by the expansion of T cell clones that recognize immunodominant epitopes on the target antigen. As a consequence, for a given autoimmune disorder, pathogenic T cell clones express T cell receptors with a limited number of variable regions that define antigenic specificity. Qa-1, a MHC class I-like molecule, presents peptides from the variable region of TCRs to Qa-1-restricted CD8+ T cells. The induction of Vß-specific CD8+ T cells has been harnessed in an immunotherapeutic strategy known as the “T cell vaccination” (TCV) that comprises the injection of activated and attenuated CD4+ T cell clones so as to induce protective CD8+ T cells. We hypothesized that Qa-1-restricted CD8+ regulatory T cells could also constitute a physiologic regulatory arm of lymphocyte responses upon expansion of endogenous CD4+ T cells, in the absence of deliberate exogenous T cell vaccination. We immunized mice with two types of antigenic challenges in order to sequentially expand antigen-specific endogenous CD4+ T cells with distinct antigenic specificities but characterized by a common Vß chain in their TCR. The first immunization was performed with a non-self antigen while the second challenge was performed with a myelin-derived peptide known to drive experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. We show that regulatory Vß-specific Qa-1-restricted CD8+ T cells induced during the first endogenous CD4+ T cell responses are able to control the expansion of subsequently mobilized pathogenic autoreactive CD4+ T cells. In conclusion, apart from the immunotherapeutic TCV, Qa-1-restricted specialized CD8+ regulatory T cells can also be induced during endogenous CD4+ T cell responses. At variance with other regulatory T cell subsets, the action of these Qa-1-restricted T cells seems to be restricted to the immediate re-activation of CD4+ T cells.

Control of T cell reactivation by regulatory Qa-1-restricted CD8+ T cells

Administration of attenuated pathogenic T cell clones, a procedure known as T cell vaccination, induces CD8+ T cells specific for peptides derived from the Vbeta-chain of the TCR presented by the MHC class Ib molecule, Qa-1 expressed on the vaccine cells. These regulatory CD8+ T cells have the capacity to control the activation of endogenous T cells expressing the same TCR Vbeta-chain as the vaccinating cells. We hypothesized that vaccination with NKT cells could also induce Qa-1-restricted CD8+ T cells that would control NKT cell activation. We tested this hypothesis in a murine model of Con A-induced hepatitis that is induced by NKT cells. Vaccination with NKT cells effectively induced protective Qa-1-restricted CD8+ T cells that prevented hepatitis. Surprisingly, upon vaccination with T cells expressing Vbeta-chains irrelevant to NKT cells, we discovered that the specificity of vaccine-induced Qa-1-restricted CD8+ T cells was not limited to the Vbeta-chain of the vaccinating cells. We further show that these regulatory Qa-1-restricted CD8+ T cells arise spontaneously upon polyclonal activation of T cells in the absence of deliberate T cell vaccination. These experiments provide new insight into a CD8+ T cell compartment that regulates the immediate reactivation of conventional T cells and NKT cells.

IgM-enriched human intravenous immunoglobulin suppresses T lymphocyte functions in vitro and delays the activation of T lymphocytes in hu-SCID mice

Previous studies of an experimental human immunoglobulin preparation for intravenous use, containing normal pooled IgM (IVIgM), have shown its beneficial therapeutic effect in experimental autoimmune diseases. The mechanisms of its immunomodulatory activity remain however, poorly understood. In the experiments reported here, IVIgM inhibited the proliferation of various autonomously growing human lymphoid cell lines in vitro, as well as of MLR- and of PHA-stimulated human T-lymphocytes. These effects of IVIgM were observed at non-apoptotic concentrations and were stronger on a molar basis than those of normal pooled IgG for intravenous use (IVIg). Both preparations, when administered to SCID mice, repopulated with human peripheral blood mononuclear cells, delayed the expression of the early activation marker CD69 on both human CD4+ and CD8+ T-lymphocytes, activated by the mouse antigenic environment. The data obtained show that normal pooled human IgM exerts a powerful antiproliferative effect on T-cells that is qualitatively similar but quantitatively superior to that of therapeutic IVIg. Our results suggest that infusions with IVIgM might have a significant beneficial immunomodulating activity in patients with selected autoimmune diseases.

Skin immunoglobulin deposition following intravenous immunoglobulin therapy in toxic epidermal necrolysis

Human intravenous immunoglobulins (IVIg) which contain anti-CD95 antibodies have been proposed to treat toxic epidermal necrolysis (TEN). Presently, there is no evidence that IVIg reach the keratinocytes in TEN patients. The aim of this study was to assess the Ig distribution in the serum, blister fluid and skin of six consecutive TEN patients treated with IVIg (1 g/kg/day) for 3 days. They were compared with five TEN patients who only received supportive therapy. In all patients, IgA, IgM and IgG concentrations were measured in the serum and blister fluid using an immuno-nephelometric method. Immunohistochemistry was performed on skin biopsies taken from both TEN clinically involved and uninvolved skin to search for IgG deposits. On admission, the IgG concentrations were significantly higher in both TEN serum and TEN blister fluid compared with their respective IgA and IgM contents. The IgG, IgA and IgM concentrations in blister fluid were significantly lower than their respective serum concentrations. The serum and blister fluid IgG concentrations, but not that of IgA and IgM, were markedly increased at the completion of the IVIg treatment. By contrast, they remained unchanged in the TEN patients that were untreated with IVIg. In the IVIg-treated patients, the IgG intraepidermal deposits raised markedly in both TEN-involved and uninvolved skin. This was not the case in patients who did not receive IVIg. These results suggest that IVIg perfusions brought a prominent increase in IgG concentration in the serum, blister fluid and epidermis of both TEN-involved and clinically uninvolved skin. The presence of potentially protective IgG in TEN epidermis following IVIg treatment could help limiting the disease progression.

Mechanisms of action of intravenous immunoglobulin in autoimmune and inflammatory diseases

Intravenous immunoglobulins (IVIg) exert a broad range of immunoregulatory functions that provide a basis for the beneficial effects of IVIg in autoimmune and systemic inflammatory disorders. This review focuses on the effects f IVIg on humoral and cellular immunity that may be of relevance for the treatment of inflammatory neurological diseases.

Lupus-specific kidney deposits of HSP90 are associated with altered IgG idiotypic interactions of anti-HSP90 autoantibodies

Previous studies have shown that autoantibodies to heat shock protein 90 (HSP90) are elevated in a significant proportion of patients with systemic lupus erythematosus (SLE) who are more likely to have renal disease and a low C3 level. Using samples from 24 patients, we searched for glomerular deposits of HSP90 in renal biopsy specimens from seven patients with lupus nephritis and 17 cases of glomerulonephritis from patients without SLE. Positive glomerular immunofluorescent staining for HSP90 was observed in six of seven cases of SLE and positive tubular staining in two of seven SLE patients. The staining for HSP90 was granular in nature and was located in subepithelial, subendothelial and mesangial areas. None of the non-SLE renal biopsies revealed positive staining for HSP90 deposition. Further we showed the presence of anti-HSP90 IgG autoantibodies in IgG from sera of patients with SLE as well as in normal human IgG (IVIg). In normal IgG this autoreactivity could be adsorbed almost completely on F(ab')2 fragments from the same IgG preparation, coupled to Sepharose and could be inhibited by the effluent obtained after subjecting normal IgG to HSP90 affinity column. These findings indicate that anti-HSP90 natural autoantibodies are blocked by idiotypic interactions within the IgG repertoire. Unlike natural autoantibodies, anti-HSP90 IgG from SLE patients' sera were only moderately adsorbed on F(ab')2 fragments of normal IgG. These results demonstrate that immunopathogenesis of lupus nephritis is associated with HSP90 (as an autoantigen) and that the pathology is associated with altered idiotypic regulation of the anti-HSP90 IgG autoantibodies.

Effect of human immunoglobulins on the immunogenicity of porcine bioprostheses

BACKGROUND

Glutaraldehyde fixation (GT) is known to reduce immunologic reactions and tissue degeneration after implantation in humans. Sterilization after glutaraldehyde fixation (G-ST) improves the safety and reduces the tendency of GT valves to calcify. Intravenous immunoglobulins (IVIg) have been shown to reduce xenogeneic response against porcine tissue. We have investigated the effect of these fixation procedures combined with and without IVIg on the antigenicity of bioprostheses.

METHODS

Lewis adult rats were implanted subcutaneously with a fresh, GT, or G-ST porcine heart valve pre- or posttreated with different amounts of IVIg. We followed by enzyme-linked immunosorbent assay and IgM and IgG titers against protein extracts from the porcine heart valves after implantation. Cellular reactivity was assessed in xenogeneic lymphoendothelial coculture experiments. Calcification content was also examined.

RESULTS

Glutaraldehyde fixation partially decreased the humoral response against proteins of the implant but elicited a cellular xenogeneic response. Sterilization reduced these reactivities, but retained antigenicity. Intravenous immunoglobulin postincubated with GT valves before implantation reduced the antigenicity of the tissue to the same extent as G-ST valves, but had no effect on valvular tissue calcification.

CONCLUSIONS

Our studies demonstrate that IVIg or the sterilization procedure (ST) reduced the cellular response against glutaraldehyde-fixed valves (GT), whereas reduced calcification was observed only with ST.

Modulation of endothelial cell function by normal polyspecific human intravenous immunoglobulins: a possible mechanism of action in vascular diseases

Intravenous immunoglobulin (IVIg) is increasingly used in the treatment of autoimmune and inflammatory diseases, including vasculitides and Kawasaki disease. However, the outcome of IVIg interaction with endothelial cells of the vascular bed is not clear as yet. We have investigated the effect of IVIg on the in vitro activation of human endothelial cells, as assessed by cell proliferation and reverse transcription-polymerase chain reaction-detected expression of mRNA coding for adhesion molecules (intercellular adhesion molecule-1 and vascular cellular adhesion molecule-1), chemokines (monocyte chemoattractant protein-1, macrophage colony-stimulating factor, and granulocyte-macrophage colony-stimulating factor), and proinflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6). IVIg inhibited proliferation of endothelial cells in a time-dependent manner. This effect was dependent on both Fc and F(ab')2 fragments of the immunoglobulin molecule and was fully reversible. Tumor necrosis factor-alpha and interleukin-1beta also inhibited thymidine incorporation, but to a lesser degree. IVIg had no effect on basal levels of mRNA coding for the adhesion molecules, chemokines, and proinflammatory cytokines. IVIg fully down-regulated the expression induced by tumor necrosis factor-alpha or interleukin-1beta of mRNA coding for these molecules. Thus, blockade of cellular proliferation and of cytokine-induced expression of adhesion molecules, chemokines, and cytokines may explain the therapeutic effect of IVIg in vascular and inflammatory disorders.

Immunoglobulin treatment reduces atherosclerosis in apo E knockout mice

Atherosclerosis is associated with immune activation. T cells and macrophages infiltrate atherosclerotic plaques and disease progression is associated with formation of autoantibodies to oxidized lipoproteins. In the apo E knockout mouse, a genetic model of cholesterol-induced atherosclerosis, congenital deficiency of macrophages, lymphocytes, or interferon-gamma receptors result in reduced lesion formation. We have now evaluated whether immune modulation in the adult animal affects disease development. Injections of 7-wk-old male apo E knockout mice with polyclonal immunoglobulin preparations (ivIg) during a 5-d period reduced fatty streak formation over a 2-mo period on cholesterol diet by 35%. Fibrofatty lesions induced by diet treatment for 4 mo were reduced by 50% in mice receiving ivIg after 2 mo on the diet. ivIg treatment also reduced IgM antibodies to oxidized LDL and led to inactivation of spleen and lymph node T cells. These data indicate that ivIg inhibits atherosclerosis, that it is effective both during the fatty streak and plaque phases, and that it may act by modulating T cell activity and/or antibody production. Therefore, immunomodulation may be an effective way to prevent and/or treat atherosclerosis.

Selective impairment of serum antibody repertoires toward muscle and thymus antigens in patients with seronegative and seropositive myasthenia gravis

We analyzed the antibody (Ab) repertoires of IgM and IgG of patients with seropositive and patients with seronegative myasthenia gravis (MG) toward self antigens by means of a quantitative immunoblotting technique using normal human tissue extracts as sources of self antigens. Repertoires of reactivities of IgG and IgM with liver, kidney and stomach antigens were conserved between myasthenic patients and controls. IgG and IgM Ab repertoires toward muscle antigens differed significantly between patients with seropositive MG and healthy donors, as assessed by multiparametric statistical analysis. Patterns of Ab reactivities to muscle antigens were similar in patients with seronegative MG and healthy controls. Antibody repertoires of IgG and IgM toward thymus antigens of both seropositive and seronegative MG patients, differed significantly from those of healthy individuals. Our results indicate that MG is characterized by a selective impairment of self-reactive Ab repertoires toward muscle and thymus antigens. The observation that self-reactive Ab repertoires toward thymus antigens are similar in patients with seropositive and seronegative MG suggests that both forms of MG share common immunopathological features.

Intravenous immunoglobulins for therapeutic use contain anti-idiotypes against xenophile antibodies and prolong discordant graft survival

Xenotransplantation between discordant species leads to a graft survival of a few minutes, due to binding of natural antibodies to the xenogeneic endothelial cells, complement activation, and endothelial cell activation. Polyclonal human immunoglobulins for intravenous use (IVIg) from normal donors have been proven effective in a variety of antibody-mediated disorders and contain anti-idiotypic antibodies directed against a number of disease-associated and natural antibodies. We have shown that administration of IVIg delays rejection of a guinea pig heart to a rat. We demonstrate herein that IVIg can inhibit the binding of xenoreactive rat IgG antibodies to guinea pig endothelial cells. This inhibition is likely due to the presence, among IVIg, of anti-idiotypic antibodies as F(ab')2 fragments of IVIg were as effective as whole IVIg. In addition, natural anti-endothelium rat antibodies were retained on a column of F(ab')2 fragments of IVIg coupled to Sepharose. The degree of inhibition of binding of IgG natural antibodies correlated with the survival of the xenograft when IVIg was administered prior to transplantation. Thus IVIg prolong xenograft survival through idiotypic-anti-idiotypic interactions with natural xenoreactive antibodies of the IgG isotype.

Modulation of autoimmune responses by intravenous immunoglobulin (IVIg)

Significant progress has been made in understanding the mechanisms by which intravenous immunoglobulins (IVIg) exert immunomodulatory effects in the treatment of autoimmune diseases. A unique property of immunoglobulins is the diversity of variable (V) regions. The evidence discussed in this communication supports our notion that the diversity of V regions in IVIg preparations is a determining factor for the anti-inflammatory substitutive and immunomodulatory functions of IVIg therapy. We have demonstrated the presence in IVIg, of anti-idiotypic antibodies directed against various autoantibodies. The ability of IVIg to interact through V regions with complementary V regions of antibodies and antigen receptors as well as with relevant soluble and surface molecules provides the basis for inducing the selection of immune repertoires. The study of the mechanisms by which IVIg mediates selection of autoreactive repertoires is essential for our understanding of the mechanisms underlying the emergence of pathological autoimmunity and of the physiological role of natural antibodies in the establishment and maintenance of tolerance to self and homeostasis of autoreactivity in healthy individuals.

[Regulation of autoreactivity by the idiotypic network and therapeutic modulation of autoimmunity by polyvalent intravenous immunoglobulins (IgIV)]

A beneficial effect after intravenous administration of immunoglobulins (IgIV) has been reported in a large number of autoimmune diseases, whether mediated by autoantibodies or T cells. The short-term immunoregulator effect of IgIV, mediated by interaction of the Fc fragment of the immunoglobulins with the Fc receptors on the surface of leukocytes has been thoroughly described. The arguments presented in this review indicate that one of the consequences of IgIV administration is to restore regulation of autoreactivity via a network of interactions between "natural" autoreactive IgG in the infusion and elements of the immune system. Via this network, IgIB can i) produce transient or long-term suppression of specific autoreactive clones and stimulation of reactive B cells with IgIV fragments F(ab); ii) restore normal fluctuations in natural autoantibody titre in the serum; and iii) modulate synthesis of cytokine secretion.

Immunoglobulins and the regulation of autoimmunity through the immune network

Beneficial effects of the administration of intravenous immunoglobulins (IVIg) have now been reported in a large number of autoimmune diseases, whether mediated by autoantibodies or by autoaggressive T cells. We have proposed that the immunoregulatory effect of IVIg in autoimmune disease is dependent on the selection of the recipient's immune repertoires by the variable (V) region reactivities of infused immunoglobulins. Thus IVIg contains antibodies reactive with idiotypes of natural and disease-related autoantibodies and surface immunoglobulins of B cells; IVIg also contains antibodies reactive with the idiotype, framework and constant regions of the beta chain of the alpha beta T cell receptor. Infusion of IVIg results in transient or long lasting suppression of specific autoantibody clones in vivo and in stimulation of a distinct subset of B cells reactive with the F(ab')2 fragments of IVIg Infusion of IVIg alters the general "architecture" of the network as assessed by studying the kinetic patterns of spontaneous fluctuations of natural autoantibodies in serum. Infusion of normal mouse Ig in healthy adult mice selects expressed immune repertoire by removing late pre-B and B cells in the bone marrow, mostly those expressing D proximal Vh genes, and by activating distinct subsets of B cells and CD4+ T cells in the spleen. Although dependent on the V region reactivities (composition) or injected preparations, these effects probably also require that the infused immunoglobulin contains an intact Fc moiety. If one considers the effect of IVIg on the structure, function and dynamics of the immune network IVIg may be viewed as a substitutive therapy for the quantitative/qualitative defects in network regulation that are associated with autoimmune diseases.

Antibodies to a conserved region of HLA class I molecules, capable of modulating CD8 T cell-mediated function, are present in pooled normal immunoglobulin for therapeutic use

Intravenous immunoglobulin (IVIg) is increasingly used for the treatment of autoimmune diseases and the prevention of infections and of graft versus host reactions in recipients of allogeneic bone marrow transplants. The immunomodulatory effects of IVIg are largely dependent on their ability to interact with membrane molecules of lymphocytes. We report here that IVIg recognizes the B07.75-84 peptide, corresponding to a conserved region of the alpha I helix of the first domain of HLA-B7 01, which represents a nonpolymorphic determinant of HLA class I molecules. Intact IVIg and its F(ab')2 fragments bound to the peptide as well as to purified soluble HLA and to HLA on a human T cell line. Binding of IVIg to HLA was assessed by ELISA, immunofluorescence, and real-time analysis of the interaction using the BIAlite system. The binding of antipeptide antibodies to HLA was inhibited by free peptide. Antipeptide antibodies isolated from IVIg by affinity chromatography inhibited CD8 cell-mediated cytotoxicity of an influenza virus-specific human T cell line. The presence in IVIg of antibodies to critical regions of HLA class 1 molecules suggests a possible role for IVIg in modulation of class-I-restricted cellular interactions in the immune response.

Catalytic activity of anti-thyroglobulin antibodies

Thyroglobulin (Tg)-specific autoantibodies from a patient with Hashimoto's thyroiditis hydrolyzed radiolabeled Tg, shown by production of several smaller sized products on SDS electrophoresis gels. The apparent Km value for Tg was in the nanomolar range, a property typical of an Ab combining site. The Tg antibodies also hydrolyzed tripeptide-methylcoumarinamide (MCA) substrates with lower affinity, displaying a preference for Arg-MCA and Lys-MCA containing conjugates. The hydrolysis of one of these conjugates, Pro-Phe-Arg-MCA, was inhibited competitively by Tg, suggesting a catalytic site located in the Ab combining site. In control experiments, 1) the hydrolytic activities were removed by immunoadsorption with immobilized anti-human IgG; 2) IgG depleted of the Tg-specific Abs by affinity chromatography did not display Tg and Pro-Phe-Arg-MCA hydrolyzing activities; and 3) the peptide-MCA hydrolyzing activity tracked exactly with the 150-kDa IgG peak on a gel filtration column run in denaturing solvent (6 M guanidine chloride).

Catalytic activity of anti-thyroglobulin antibodies

Thyroglobulin (Tg)-specific autoantibodies from a patient with Hashimoto's thyroiditis hydrolyzed radiolabeled Tg, shown by production of several smaller sized products on SDS electrophoresis gels. The apparent Km value for Tg was in the nanomolar range, a property typical of an Ab combining site. The Tg antibodies also hydrolyzed tripeptide-methylcoumarinamide (MCA) substrates with lower affinity, displaying a preference for Arg-MCA and Lys-MCA containing conjugates. The hydrolysis of one of these conjugates, Pro-Phe-Arg-MCA, was inhibited competitively by Tg, suggesting a catalytic site located in the Ab combining site. In control experiments, 1) the hydrolytic activities were removed by immunoadsorption with immobilized anti-human IgG; 2) IgG depleted of the Tg-specific Abs by affinity chromatography did not display Tg and Pro-Phe-Arg-MCA hydrolyzing activities; and 3) the peptide-MCA hydrolyzing activity tracked exactly with the 150-kDa IgG peak on a gel filtration column run in denaturing solvent (6 M guanidine chloride).

Immune modulating effects of intravenous immunoglobulin (IVIg) in autoimmune diseases

Administration of intravenous immunoglobulins (IVIg) have now been reported to be beneficial in a large number of autoimmune diseases, whether mediated by autoantibodies or by T cells. We have proposed that the immunoregulatory effect of IVIg in autoimmune diseases is dependent on the selection of recipient's immune repertoires by variable (V) regions of infused immunoglobulins. Thus: (a) IVIg contains antibodies reactive with idiotypes of natural and disease-related autoantibodies and surface immunoglobulins of B cells; IVIg also contains antibodies reactive with idiotype, framework and constant regions of the beta chain of the alpha beta T cell receptor; (b) infusion of IVIg results in transient or long-lasting suppression of specific autoantibody clones in vivo and in stimulation of a distinct subset of B cells reactive with F(ab')2 fragments of IVIg; (c) infusion of IVIg alters the general "architecture" of the network as assessed by studying the kinetic patterns of spontaneous fluctuations of natural autoantibodies in serum; (d) infusion of normal mouse Ig in healthy adult mice selects expressed immune repertoire by removing late pre-B and B cells in the bone marrow, mostly those expressing D proximal VH genes, and by activating distinct subsets of B cells and CD4+ T cells in the spleen; and (e) infusion of IVIg results in a modulation of synthesis and release of cytokines. Although dependent on the V-region reactivities (composition) or injected preparations, these effects probably also require that the infused immunoglobulin contains an intact Fc moiety. This review focuses on autoimmune and inflammatory diseases in which IVIg therapy has been beneficial. Recent recommendations from a committee of experts for IVIg therapy have been pointed out.

Internalization of beta-adrenergic receptor in A431 cells involves non-coated vesicles

To characterize the mechanism of internalization of beta-adrenergic catecholamine receptors on human epidermoid A431 carcinoma cells, their distribution was analyzed by immunocytochemistry using the monoclonal anti-receptor antibody BRK2. In preconfluent cultures, the receptors appeared to be randomly distributed on the cell surface. Exposure to the agonist isoproterenol induced an overall decrease in the number of cell surface receptors as determined by binding experiments and visualized by immunofluorescence. When cells were incubated at 4 degrees C with BRK2 and anti-mouse IgG-gold and then transferred at 37 degrees C, non-coated invaginations and vesicles were labeled. The addition of isoproterenol resulted in an increased rate of internalization of the receptor-BRK2-anti-IgG-gold complex. When incubation with the two antibody reagents was prolonged (with or without isoproterenol), non-coated vesicles fused in the endosomal compartment, and receptors were transferred to multivesicular bodies and lysosomes. At no stage in this process was there any indication that clathrin-coated pits or vesicles participated. Furthermore, we found that an intracellular potassium depletion treatment known to inhibit endocytosis, did not affect the normal pattern of desensitization of beta-adrenergic receptors.

Revised immune network concepts

The idiotype network concept needs to be revised in order to be in agreement with current data on protein/protein interactions, with the phenomenon of T and B cell recognition of idiotopes, and with the failure of certain anti-idiotypes to stimulate a given immune response. It is proposed that the distinction among Ab2 alpha, beta, and gamma is abandoned, as well as the concept of an internal image idiotope which mimics the three-dimensional shape of nominal antigen. In place of these definitions, the concept of "network antigen" is introduced. Network antigens are potentially the entire repertoire of anti-idiotypes. However, their biological effectiveness is controlled and established by two factors: (i) the affinity to the idiotype Ig receptor; and (ii) the preexisting regulatory network segment that controls the outcome of immune stimulation or suppression. Screening for effective idiotype therapeutic agents has to be done with panels of anti-idiotype and idiotype antibodies in order to establish correlations between idiotope expression and disease progression. Recognizing the importance of network segments will be the first step in the direction toward a rational design of idiotype-based therapies.