Stability of natural self-reactive antibody repertoires during aging

The effect of influenza vaccine immunization on natural antibodies

Natural, polyreactive, low-affinity antibodies are known to play an important role not only in the immediate defense against pathogens, but also in shaping the acquired immune response. On the other hand, antigen specific, high-affinity antibodies can affect the balance of natural antibodies and lead to autoimmune diseases. In this study, we have analyzed the changes that occur in the IgM and IgG pool of natural antibodies after immunization with split or whole virion influenza vaccine. For this purpose, "in-house" developed ELISAs were used. The subjects were divided, according to the vaccination status, into those who had been immunized with the influenza vaccine in previous years and those who had been immunized for the first time. The analysis indicated that the pool of natural antibodies was not impaired by the immunization, evidenced by the lack of changes in any of the groups, and that certain fluctuations were induced in order to maintain the homeostasis of the immune system.

Current Understanding of Natural Antibodies and Exploring the Possibilities of Modulation Using Veterinary Models. A Review

Natural antibodies (NAb) are defined as germline encoded immunoglobulins found in individuals without (known) prior antigenic experience. NAb bind exogenous (e.g., bacterial) and self-components and have been found in every vertebrate species tested. NAb likely act as a first-line immune defense against infections. A large part of NAb, so called natural autoantibodies (NAAb) bind to and clear (self) neo-epitopes, apoptotic, and necrotic cells. Such self-binding antibodies cannot, however, be considered as pathogenic autoantibodies in the classical sense. IgM and IgG NAb and NAAb and their implications in health and disease are relatively well-described in humans and mice. NAb are present in veterinary (and wildlife) species, but their relation with diseases and disorders in veterinary species are much less known. Also, there is little known of IgA NAb. IgA is the most abundant immunoglobulin with essential pro-inflammatory and homeostatic properties urging for more research on the importance of IgA NAb. Since NAb in humans were indicated to fulfill important functions in health and disease, their role in health of veterinary species should be investigated more often. Furthermore, it is unknown whether levels of NAb-isotypes and/or idiotypes can and should be modulated. Veterinary species as models of choice fill in a niche between mice and (non-human) primates, and the study of NAb in veterinary species may provide valuable new insights that will likely improve health management. Below, examples of the involvement of NAb in several diseases in mostly humans are shown. Possibilities of intravenous immunoglobulin administration, targeted immunotherapy, immunization, diet, and genetic modulation are discussed, all of which could be well-studied using animal models. Arguments are given why veterinary immunology should obtain inspiration from human studies and why human immunology would benefit from veterinary models. Within the One Health concept, findings from veterinary (and wildlife) studies can be related to human studies and vice versa so that both fields will mutually benefit. This will lead to a better understanding of NAb: their origin, activation mechanisms, and their implications in health and disease, and will lead to novel health management strategies for both human and veterinary species.

Immunoglobulin M: An Ancient Antiviral Weapon - Rediscovered

Recent discoveries have shed new light onto immunoglobulin M (IgM), an ancient antibody class preserved throughout evolution in all vertebrates. First, IgM – long thought to be a perfect pentamer – was shown to be asymmetric, resembling a quasi-hexamer missing one monomer and containing a gap. Second, this gap allows IgM to serve as carrier of a specific host protein, apoptosis inhibitor of macrophages (AIM), which is released to promote removal of dead-cell debris, cancer cells, or pathogens. Third, recombinant IgM delivered mucosally by passive immunization gave proof-of-concept that this antibody class can prevent mucosal simian-human immunodeficiency virus transmission in non-human primates. Finally, IgM’s role in adaptive immunity goes beyond being only a first defender to respond to pathogen invasion, as long-lived IgM plasma cells have been observed predominantly residing in the spleen. In fact, IgM produced by such cells contained somatic hypermutations and was linked to protection against lethal influenza virus challenge in murine models. Importantly, such long-lived IgM plasma cells had been induced by immunization 1 year before challenge. Together, new data on IgM function raise the possibility that vaccine strategies aimed at preventing virus acquisition could include this ancient weapon.

IgM ANCA in healthy individuals and in patients with ANCA-associated vasculitis

Low levels of IgM auto-antibodies have been reported in health and disease. IgM anti-neutrophil cytoplasmic antibodies (ANCA) have been reported in patients with ANCA-associated vasculitis (AAV). We sought to investigate if healthy individuals may have IgM ANCA in their sera. The first aim of the study was to determine whether IgM ANCA was present in healthy individuals and in patients with ANCA-associated vasculitis. The second aim was to determine what happens to IgM ANCA levels over time. The third aim was to determine whether bacterial infections affected IgM ANCA levels in non-AAV patients. Sera from healthy individuals and patients with AAV were tested for IgM ANCA by immunofluorescence on fixed neutrophils, immunoprecipitation, Western blot and ELISA. Peripheral blood mononuclear cells were isolated and tested by ELISpot for circulating IgM ANCA B cells. To determine whether infection affected IgM ANCA levels, we studied non-AAV patients with bacterial endocarditis or Staphylococcus aureus bacteraemia and measured IgM ANCA levels over time. IgM ANCA is detectable in both healthy individuals and patients with AAV and the titres decreased with increasing age. Circulating IgM ANCA B cells were identified by ELISpot. In the presence of infection, we could not find a significant change in IgM ANCA levels. We report the presence of low-level specific IgM ANCA in the sera of healthy individuals and in patients with ANCA-associated vasculitis. Bacterial infection did not affect the level of IgM ANCA in this small study.

Autoantibodies against the prion protein in individuals with PRNP mutations

OBJECTIVE

To determine whether naturally occurring autoantibodies against the prion protein are present in individuals with genetic prion disease mutations and controls, and if so, whether they are protective against prion disease.

METHODS

In this case-control study, we collected 124 blood samples from individuals with a variety of pathogenic PRNP mutations and 78 control individuals with a positive family history of genetic prion disease but lacking disease-associated PRNP mutations. Antibody reactivity was measured using an indirect ELISA for the detection of human immunoglobulin G_1-4 antibodies against wild-type human prion protein. Multivariate linear regression models were constructed to analyze differences in autoantibody reactivity between (1) PRNP mutation carriers vs controls and (2) asymptomatic vs symptomatic PRNP mutation carriers. Robustness of results was examined in matched cohorts.

RESULTS

We found that antibody reactivity was present in a subset of both PRNP mutation carriers and controls. Autoantibody levels were not influenced by PRNP mutation status or clinical manifestation of prion disease. Post hoc analyses showed anti-PrP^C autoantibody titers to be independent of personal history of autoimmune disease and other immunologic disorders, as well as PRNP codon 129 polymorphism.

CONCLUSIONS

Pathogenic PRNP variants do not notably stimulate antibody-mediated anti-PrP^C immunity. Anti-PrP^C immunoglobulin G autoantibodies are not associated with the onset of prion disease. The presence of anti-PrP^C autoantibodies in the general population without any disease-specific association suggests that relatively high titers of naturally occurring antibodies are well-tolerated.

CLINICALTRIALSGOV IDENTIFIER

NCT02837705.

Natural antibodies - facts known and unknown

In contrast to adaptive antibodies, natural antibodies are present in a non-immunised organism from birth, and they do not include anti-Gal antibodies and/or anti-Gal natural antibodies, which are developed as a result of the effect of the α-Gal epitope and physiological flora. Natural antibodies are the first line of the organism’s defence before the formation of the immunity created via the stimulation of elements that determine specific and non-specific immunity. This is especially important in the case of infants. Despite the fact that natural antibodies differ in their function from adaptive antibodies, they are polyreactive and they detect autoantigens and new antigenic determinants. Natural antibodies are formed from the subpopulation of B lymphocytes, mainly B1 lymphocytes and B lymphocytes of the marginal zone. This phenomenon is supported by the fact that when the quantity of these cells in the organism decreases, which happens with age, the level of natural antibodies also decreases and the risk of illnesses of old age becomes higher. During ontogenesis, these antibodies participate in many physiological processes, including the “support” of the immune system and homeostasis, the prevention of inflammation, infections and other pathological states, such as autoimmune and cardiovascular diseases, or the process of carcinogenesis. The best known natural antibody is IgM, but the role of IgGs and IgAs is also considered important. Nowadays, many researchers also mention intravenous immunoglobulins, which are used in the treatment of numerous illnesses, and there are discussions on the possibility of increasing their potential if they were based on natural antibodies.

Purification of Natural Antibodies Against Tau Protein by Affinity Chromatography

Natural antibodies are now widely studied for their therapeutical potential. Therefore, their isolation and subsequent characterization is desired. Here, we describe an isolation method for natural anti-tau antibodies from human plasma by utilization of affinity chromatography with epoxy-activated copolymer resin. The evalution of isolation efficiency and avidity of isolated antibodies is decribed by modified indirect ELISA assay.

Serum titers of autoantibodies against α-synuclein and tau in child- and adulthood

Autoreactive antibodies against the proteins alpha-synuclein (α-syn) and tau are detectable in body fluids of both healthy and diseased elderly people. However, nothing is known about their presence or titers in children. To close this gap and to characterize their temporary expression levels, we used ELISA techniques to investigate the serum titers of α-syn and tau reactive autoantibodies in 37 and 32 adults and 37 and 31 children, respectively. Most serum samples from the children exhibited both antibody types and interestingly, the levels were similar to those observed in the adult serum samples. Furthermore, sex-specific analysis revealed significantly increased α-syn reactive autoantibody titers in female children. The presence of α-syn and tau reactive autoantibodies in early childhood indicates that both immunoglobulins belong to the pool of naturally occurring autoantibodies (nAbs), as their antigen-independent synthesis from birth is a crucial characteristic. Due to their general participation in the maintenance of the physiological homeostasis, we hypothesize that both investigated nAbs are involved in the metabolic regulation of their specific antigen. Therefore, they may be a part of a mechanism that already exists in the innate immunological repertoire to provide protection from pathologies caused by dysregulated α-syn and tau metabolisms.

Genetic aspects of auto-immune profiles of healthy chickens

Auto-antibody profiles binding liver antigens differed between chicken lines divergently selected for specific antibody responses to SRBC, and were affected by ageing suggesting both genetic and environmental effects. Presence and levels of IgM and IgG antibodies binding chicken liver cell lysate (CLL) fragments in plasma at 5 weeks of age from 10 individual full sibs and their parents from 5 H_srbc and 5 L_srbc line families was studied to reveal genetic relations. Non-genetic maternal effects were studied by comparing auto-antibody profiles of 36 weeks old hens from 2 other unrelated lines with the profiles from their chicks at hatch. IgM and IgG antibodies from parents and progeny from both H_srbc and L_srbc lines bound CLL fragments. Significant line and generation differences and their interactions were found for both isotypes. Higher staining of CLL fragments was usually found for H_srbc line birds. Lines were clustered by auto-antibody profiles, but staining by birds of both lines in both generations was very individual for IgG and IgM. The current data with full sibs therefore not supported a genetic basis for auto-antibody profiles. IgG but not IgM auto-antibody profiles of chicks correlated with maternal auto-antibody profiles. The results suggest that the auto-antibody repertoire of healthy chickens is largely stochastically initiated and may be affected by environmental challenges during ageing, but genetic mechanisms may underlie staining intensity of individual bound CLL fragments. The present results suggest that identification of fragments or profiles to be used at early age for genetic selection for health traits is not feasible yet. Secondly, the IgM profile of neonatal chickens seems non-organised independent of the maternal profile, but the neonatal IgG profile is much more related with the maternal profile. Consequences of these findings for disease susceptibility or breeding for optimal health are discussed.

Methods for Posttranslational Induction of Polyreactivity of Antibodies

An antibody molecule that recognizes multiple unrelated antigens is defined as polyreactive. Polyreactivity is an intrinsic characteristic of immune repertoires. Degenerated antigen binding diversifies the repertoire of specificities, thus contributing to immune defense and immune regulation. Immune repertoire contains also a fraction of immunoglobulins, which acquire polyreactivity only following contact with various protein-destabilizing or pro-oxidative substances. Posttranslational induction of the antibody polyreactivity may have important repercussion for laboratory practice, as well as in cases of pathological conditions accompanied by liberation of large quantities of pro-oxidative substances such as heme, labile iron, or reactive oxygen species. Antibodies with induced polyreactivity have been demonstrated to exert pathogen neutralization and immune regulatory potential in inflammatory conditions, suggesting that this phenomenon may be exploited for design of therapeutic strategies. In this article, we provide description of the basic procedures for uncovering of the cryptic polyreactivity of antibodies by heme, ferrous ions, and acid pH solution.

Role of Natural IgM Autoantibodies (IgM-NAA) and IgM Anti-Leukocyte Antibodies (IgM-ALA) in Regulating Inflammation

Natural IgM autoantibodies (IgM-NAA) are rapidly produced to inhibit pathogens and abrogate inflammation mediated by invading microorganisms and host neoantigens. IgM-NAA achieve this difficult task by being polyreactive with low binding affinity but with high avidity, characteristics that allow these antibodies to bind antigenic determinants shared by pathogens and neoantigens. Hence the same clones of natural IgM can bind and mask host neoantigens as well as inhibit microorganisms. In addition, IgM-NAA regulate the inflammatory response via mechanisms involving binding of IgM to apoptotic cells to enhance their removal and binding of IgM to live leukocytes to regulate their function. Secondly, we review how natural IgM prevents autoimmune disorders arising from pathogenic IgG autoantibodies as well as by autoreactive B and T cells that have escaped tolerance mechanisms. Thirdly, using IgM knockout mice, we show that regulatory B and T cells require IgM to effectively regulate inflammation mediated by innate, adaptive and autoimmune mechanisms. It is therefore not surprising why the host positively selects such autoreactive B1 cells that generate protective IgM-NAA, which are also evolutionarily conserved. Fourthly, we show that IgM anti-leukocyte autoantibodies (IgM-ALA) levels and their repertoire can vary in normal humans and disease states and this variation may partly explain the observed differences in the inflammatory response after infection, ischemic injury or after a transplant. Finally we also show how protective IgM-NAA can be rendered pathogenic under non-physiological conditions. IgM-NAA have therapeutic potential. Polyclonal IgM infusions can be used to abrogate ongoing inflammation. Additionally, inflammation arising after ischemic kidney injury, e.g., during high-risk elective cardiac surgery or after allograft transplantation, can be prevented by pre-emptively infusing polyclonal IgM, or DC pretreated ex vivo with IgM, or by increasing in vivo IgM with a vaccine approach. Cell therapy with IgM pretreated cells, is appealing as less IgM will be required.

Role of Natural Autoantibodies and Natural IgM Anti-Leucocyte Autoantibodies in Health and Disease

We review how polyreactive natural IgM autoantibodies (IgM-NAA) protect the host from invading micro-organisms and host neo-antigens that are constantly being produced by oxidation mechanisms and cell apoptosis. Second, we discuss how IgM-NAA and IgM anti-leukocyte antibodies (IgM-ALA) inhibits autoimmune inflammation by anti-idiotypic mechanisms, enhancing removal of apoptotic cells, masking neo-antigens, and regulating the function of dendritic cells (DC) and effector cells. Third, we review how natural IgM prevents autoimmune disorders arising from pathogenic IgG autoantibodies, triggered by genetic mechanisms (e.g., SLE) or micro-organisms, as well as by autoreactive B and T cells that have escaped tolerance mechanisms. Studies in IgM knockout mice have clearly demonstrated that regulatory B and T cells require IgM to effectively regulate inflammation mediated by innate, adaptive, and autoimmune mechanisms. It is, therefore, not surprising why the host positively selects such autoreactive B1 cells that generate IgM-NAA, which are also evolutionarily conserved. Fourth, we show that IgM-ALA levels and their repertoire can vary in normal humans and disease states and this variation may partly explain the observed differences in the inflammatory response after infection, ischemic injury, or after a transplant. We also show how protective IgM-NAA can be rendered pathogenic under non-physiological conditions. We also review IgG-NAA that are more abundant than IgM-NAA in plasma. However, we need to understand if the (Fab)(2) region of IgG-NAA has physiological relevance in non-disease states, as in plasma, their functional activity is blocked by IgM-NAA having anti-idiotypic activity. Some IgG-NAA are produced by B2 cells that have escaped tolerance mechanisms and we show how such pathogenic IgG-NAA are regulated to prevent autoimmune disease. The Fc region of IgG-NAA can influence inflammation and B cell function in vivo by binding to activating and inhibitory FcγR. IgM-NAA has therapeutic potential. Polyclonal IgM infusions can be used to abrogate on-going inflammation. Additionally, inflammation arising after ischemic kidney injury, e.g., during high-risk elective cardiac surgery or after allograft transplantation, can be prevented by pre-emptively infusing polyclonal IgM or DC pretreated ex vivo with IgM or by increasing in vivo IgM with a vaccine approach. Cell therapy is appealing as less IgM will be required.

Natural (auto)antibodies in calves are affected by age and diet

BACKGROUND

Natural autoantibodies (N(a)ab) were found in every species tested so far, and are likely important in maintaining homeostasis.

OBJECTIVES

(1) To determine N(a)ab in Bos taurus calves, (2) evaluate effects of diet and age on N(a)ab binding repertoires in calves, and (3) delineate bovine liver cell lysate (BLL) antigens related with variation in rumen score and body weight.

ANIMALS AND METHODS

Effects of age and diet on staining of BLL fragments by IgM and IgG antibodies in serum samples collected at 20 or at 26 weeks of age from bull calves either fed a restricted or ad libitum diet were analyzed using quantitative Western blotting. Correlations between fragments stained and grouping of calves were done by Principal Component Analysis (PCA). Redundancy analysis (RDA) was done to relate rumen score and body weight variation at slaughter at 27 weeks of age with stained BLL fragments.

RESULTS

In sera from all calves IgM and IgG antibodies binding BLL antigens were found. Corresponding fragments were stained, but quantitative differences in staining intensities were related to diet and age for both IgM and IgG. PCA revealed that age had a greater influence than diet on BLL fragment staining. RDA suggested that staining by IgM or IgG of specific BLL fragments was related with variation in rumen score and body weight.

CONCLUSIONS AND CLINICAL IMPORTANCE

Analyses of N(a)ab in serum could be a potential tool to estimate the health status of cattle, and be used to evaluate effects of husbandry practices.

Age and genetic selection affect auto-immune profiles of chickens

Specificity, antibody isotype distribution and levels, of natural autoantibodies (NAAb) may be potential informative parameters for immune mediated natural disease resistance, immune modulation, and maintenance of physiological homeostasis. In a previous study we detected IgM and IgG antibodies to liver antigens in plasma from 1 year old chickens. Auto-immune profiles directed towards liver antigens differed between chicken lines divergently selected for specific antibody responses to sheep red blood cells. In the present study we measured the presence and typed levels and antibody isotypes (IgG and IgM) of NAAb binding the 'auto-antigen' complex chicken liver cell lysate (CLL) in plasma samples obtained from chickens at 5 weeks and at 1-year of age, respectively, by quantitative western blotting. Extensive staining patterns of plasma antibodies binding CLL were found for both isotypes and at both ages in all birds. At both ages, IgM and IgG bound similar numbers of CLL antigens, which remained almost constant for IgM, whereas the number of IgG stained bands in time was enhanced. Significant differences of binding patterns of NAAb (stained antigen fragments of CLL and staining intensity) were detected between the three different chicken lines at both ages and between both ages, and lines could be clustered on the basis of their auto-antibody profile. The present results indicate that analysis of the plasma NAAb repertoire of poultry like in mammals could provide a way of distinguishing differences of immune competence (as reflected by the selection criterion of antibody responses) between individuals and lines, and could provide tools to select individual birds for health and other traits. The age-dependency of the auto-immune profile suggest that such profiles may also reflect immune maturation, which should be taken into account when relating an auto-immune profile with other traits.

Genetic and phenotypic selection affect natural (auto-) antibody reactivity of chickens

Specificity, antibody isotype distribution and levels of natural antibodies (NAb) may be potential informative parameters for immune mediated natural disease resistance, immune modulation, and maintenance of physiological homeostasis. A large proportion of mammalian NAb have affinity for or are directed against self-antigens; so called natural auto antibodies (N(A)Ab). In the present study we showed the presence and typed levels and isotypes (total immunoglobulins, IgG and IgM) of N(A)Ab in plasma binding the 'auto-antigen' complex chicken liver cell lysate (CLL) of one-year old chickens from different genotype and phenotype backgrounds by ELISA and quantitative Western blotting. Higher levels of N(A)Ab binding CLL were found in plasma from chickens genetically selected for high specific antibody responses. In all birds, extensive staining patterns of plasma antibodies binding CLL were found for all isotypes, with IgG binding the highest number of CLL antigens and also showing the highest variation in staining patterns between individuals. Patterns of IgM antibodies binding CLL appeared to be more similar in all lines. Significant differences of binding patterns of N(A)Ab (antigen fragments of CLL and staining intensity) were detected between the different chicken lines, and lines could be clustered on the basis of their auto-antibody profile. In addition, also individual differences within lines were found. The present results indicate that analysis of the levels and the N(A)Ab repertoire of poultry like in mammals could provide a new way of distinguishing differences of immune competence and immune maturation between individuals, and could provide tools to select birds for health traits, or optimize hygiene and husbandry procedures.

Altered serum IgG levels to α-synuclein in dementia with Lewy bodies and Alzheimer's disease

Natural self-reactive antibodies in the peripheral blood may play a considerable role in the control of potentially toxic proteins that may otherwise accumulate in the aging brain. The significance of serum antibodies reactive against α-synuclein is not well known. We explored serum IgG levels to monomeric α-synuclein in dementia with Lewy bodies (DLB) and Alzheimer’s disease (AD) with a novel and validated highly sensitive ELISA assay. Antibody levels revealed stark differences in patients compared to healthy subjects and were dependent on diagnosis, disease duration and age. Anti-α-synuclein IgG levels were increased in both patient groups, but in early DLB to a much greater extent than in AD. Increased antibody levels were most evident in younger patients, while with advanced age relatively low levels were observed, similar to healthy individuals, exhibiting stable antibody levels independent of age. Our data show the presence of differentially altered IgG levels against α-synuclein in DLB and AD, which may relate to a disturbed α-synuclein homeostasis triggered by the disease process. These observations may foster the development of novel, possibly preclinical biomarkers and immunotherapeutic strategies that target α-synuclein in neurodegenerative disease.

Natural IgG autoantibodies are abundant and ubiquitous in human sera, and their number is influenced by age, gender, and disease

The presence of self-reactive IgG autoantibodies in human sera is largely thought to represent a breakdown in central tolerance and is typically regarded as a harbinger of autoimmune pathology. In the present study, immune-response profiling of human serum from 166 individuals via human protein microarrays demonstrates that IgG autoantibodies are abundant in all human serum, usually numbering in the thousands. These IgG autoantibodies bind to human antigens from organs and tissues all over the body and their serum diversity is strongly influenced by age, gender, and the presence of specific diseases. We also found that serum IgG autoantibody profiles are unique to an individual and remarkably stable over time. Similar profiles exist in rat and swine, suggesting conservation of this immunological feature among mammals. The number, diversity, and apparent evolutionary conservation of autoantibody profiles suggest that IgG autoantibodies have some important, as yet unrecognized, physiological function. We propose that IgG autoantibodies have evolved as an adaptive mechanism for debris-clearance, a function consistent with their apparent utility as diagnostic indicators of disease as already established for Alzheimer’s and Parkinson’s diseases.

The natural autoantibody repertoire in newborns and adults: a current overview

Antibody networks have been studied in the past based on the connectivity between idiotypes and anti-idiotypes-antibodies that bind one another. Here we call attention to a different network of antibodies, antibodies connected by their reactivities to sets of antigens-the antigen-reactivity network. The recent development of antigen microarray chip technology for detecting global patterns of antibody reactivities makes it possible to study the immune system quantitatively using network analysis tools. Here, we review the analyses of IgM and IgG autoantibody reactivities of sera of mothers and their offspring (umbilical cords) to 300 defined self-antigens; the autoantibody reactivities present in cord blood represent the natural autoimmune repertories with which healthy humans begin life and the mothers' reactivities reflect the development of the repertoires in healthy young adults. Comparing the cord and maternal reactivities using several analytic tools led to the following conclusions: (1) The IgG repertoires showed a high correlation between each mother and her newborn; the IgM repertoires of all the cords were very similar and each cord differed from its mother's IgM repertoire. Thus, different humans are born with very similar IgM autoantibodies produced in utero and with unique IgG autoantibodies found in their individual mothers. (2) Autoantibody repertoires appear to be structured into sets of reactivities that are organized into cliques-reactivities to particular antigens are correlated. (3) Autoantibody repertoires are organized as networks of reactivities in which certain key antigen reactivities dominate the network-the dominant antigen reactivities manifest a "causal" relationship to sets of other correlated reactivities. Thus, repertoires of autoantibodies in healthy subjects, the immunological homunculus, are structured in hierarchies of antigen reactivities.

Statistical identifiability and the surrogate endpoint problem, with application to vaccine trials

Given a randomized treatment Z, a clinical outcome Y, and a biomarker S measured some fixed time after Z is administered, we may be interested in addressing the surrogate endpoint problem by evaluating whether S can be used to reliably predict the effect of Z on Y. Several recent proposals for the statistical evaluation of surrogate value have been based on the framework of principal stratification. In this article, we consider two principal stratification estimands: joint risks and marginal risks. Joint risks measure causal associations (CAs) of treatment effects on S and Y, providing insight into the surrogate value of the biomarker, but are not statistically identifiable from vaccine trial data. Although marginal risks do not measure CAs of treatment effects, they nevertheless provide guidance for future research, and we describe a data collection scheme and assumptions under which the marginal risks are statistically identifiable. We show how different sets of assumptions affect the identifiability of these estimands; in particular, we depart from previous work by considering the consequences of relaxing the assumption of no individual treatment effects on Y before S is measured. Based on algebraic relationships between joint and marginal risks, we propose a sensitivity analysis approach for assessment of surrogate value, and show that in many cases the surrogate value of a biomarker may be hard to establish, even when the sample size is large.

Network theory analysis of antibody-antigen reactivity data: the immune trees at birth and adulthood

MOTIVATION

New antigen microarray technology enables parallel recording of antibody reactivities with hundreds of antigens. Such data affords system level analysis of the immune system's organization using methods and approaches from network theory. Here we measured the reactivity of 290 antigens (for both the IgG and IgM isotypes) of 10 healthy mothers and their term newborns. We constructed antigen correlation networks (or immune networks) whose nodes are the antigens and the edges are the antigen-antigen reactivity correlations, and we also computed their corresponding minimum spanning trees (MST)--maximal information reduced sub-graphs. We quantify the network organization (topology) in terms of the network theory divergence rate measure and rank the antigen importance in the full antigen correlation networks by the eigen-value centrality measure. This analysis makes possible the characterization and comparison of the IgG and IgM immune networks at birth (newborns) and adulthood (mothers) in terms of topology and node importance.

RESULTS

Comparison of the immune network topology at birth and adulthood revealed partial conservation of the IgG immune network topology, and significant reorganization of the IgM immune networks. Inspection of the antigen importance revealed some dominant (in terms of high centrality) antigens in the IgG and IgM networks at birth, which retain their importance at adulthood.

Human anti-60 kD heat shock protein autoantibodies are characterized by basic features of natural autoantibodies

Anti-human Hsp60 autoantibodies--known risk factor of atherosclerosis--were investigated in a mouse model and in samples of healthy subjects: polyreactivity, presence in cord blood samples of healthy newborns and life-long stability were tested. In IgM hybridoma panel from mouse spleens, polyreactivity of anti-Hsp60 autoantibodies was studied. In healthy pregnant women, umbilical vein and maternal blood samples were collected after childbirth, anti-Hsp-60 and -65 IgM and IgG levels were measured. Life-long stability of anti-Hsp-60 levels was studied on healthy patients during 5 years. ELISA was used in all studies. Polyreactivity of IgM clones of newborn mice and lifelong stability of these autoantibodies in healthy adults were established. IgM anti-Hsp60 autoantibodies in cord blood of healthy human infants were present, however, there was no correlation between maternal and cord blood IgM anti-Hsp60 concentrations. It is proposed that presence of anti-Hsp60 autoantibodies--as part of the natural autoantibody repertoire--may be an inherited trait. Level of anti-Hsp60 autoantibodies may be an independent, innate risk factor of atherosclerosis for the adulthood.

Immunotherapy for Alzheimer's disease

Patients with Alzheimer's disease (AD) express severe cognitive deficiencies with a concurrent increase in brain deposits of aggregated amyloid-beta (Abeta), a catabolic derivative of the ubiquitous amyloid precursor protein (APP). Interference in the homeostasis of Abeta has been suggested as a treatment for AD patients. In AD murine models it has been shown that active and passive immunization against Abeta alters the equilibrium of the different forms of Abeta in brain and serum, leading to a concomitant cognitive improvement. Generally, the clinical trials that followed the study of the murine AD model confirmed the results of the AD models, although safety issues advocate the passive vaccination approach rather than the active one. However, passive vaccination of patients with monoclonal antibodies derived from nonhuman sources is limited. Anti-Abeta IgM and IgG antibodies, which are present in the serum of every healthy individual and probably play a role in the homeostasis of Abeta in healthy subjects, might be beneficial to AD patients, as shown for the effect exerted by the commercial preparation of intravenous immunoglobulin. Human monoclonal anti-Abeta antibodies, which correspond to the ubiquitous anti-Abeta antibodies, are plausible candidates for future immunotherapy of AD patients.

HLA-association of serum levels of natural antibodies

Natural antibodies of IgM or IgG types are present in sera of most healthy individuals and are important participants of the immune response. Little is known, however, about the genetic regulation of their plasma levels in humans. We determined the concentrations of three IgM type natural autoantibodies (NAAbs) reactive to certain conserved self-antigens (citrate synthase (A-CIT), chondroitin sulphate C (A-COS) and 60 kDa heat shock proteins (A-HSP) in the sera of 78 healthy individuals and in their 86 children. In case of all the 164 individuals alleles of several polymorphisms were determined in class II (HLA-DQ, -DR), class III (AGER-429T>C, HSP70-2 1267A>G, TNF-308G>A, CFB S/F, copy number of the C4A and C4B genes), and class I (HLA-A, -B) regions of the major histocompatibility complex (MHC). Since the samples originated from a family study, extended MHC haplotypes were also determined for each study participant. Our results show that children of parents with low NAAb concentration have significantly lower serum concentrations of all the three NAAbs, as compared to offsprings of parents without reduced serum concentration. This indicates that the serum levels of these NAAbs were partly regulated by factors which are inherited from the parents to offsprings. In further studies performed only in genetically independent parents, we found significant differences in the serum levels of the IgM type A-CIT and A-COS antibodies (Abs) between carriers and non-carriers of the HLA-DR2 (15 and 16) antigens. In both cases the Ab concentrations were higher in the HLA-DR15 carriers (p=0.002 and p=0.008, respectively) and lower in DR16 carriers (p=0.029 and p=0.049, respectively) than in the non-carriers. Even more significant differences were found when the levels of two Abs were evaluated together. Frequency of the DR15 carriers was significantly lower among subjects with one or two low (in the lowest quartile) titers of A-CIT/A-COS Abs (p=0.014), A-CIT/A-HSP Abs (p=0.016) and A-COS/A-HSP Abs (p=0.013) as compared to those with normal Ab titers for both antigens. By contrast, frequency of the DR16 carriers was significantly higher among subjects with one or two low A-CIT/A-COS Abs (p=0.001), A-CIT/A-HSP Abs (p=0.002) and A-COS/A-HSP Abs (p=0.021) as compared to those with normal Ab titers for both antigens. Similar differences were found for both IgM type antibodies when carriers and non-carriers of the HLA-DR15-DQ6 and HLA-DR16-DQ5 haplotypes were considered. These novel observations indicate that not only adaptive immune response but also natural autoantibody pattern, as a part of innate immune response, is influenced by the MHC allele composition.

Acquired immunity: immunosenescence and physical activity

Several lines of evidence indicate that infectious diseases, cancer, and autoimmune disorders occur more frequently in elderly people, thus suggesting that altered function of immune organs and cells, such as thymus and T and B lymphocytes are of primary importance in the pathogenesis of these diseases. Furthermore, old subjects are less responsive to vaccine than younger because of immune changes. The most common changes accompanying the adaptive immune system include decrement of T and B cells proliferation, repertoire degeneracy, increase of the memory cell type, decreased numbers of naive cells, and shift from T helper1 (Th1) to T helper2 (Th2) response. Regular exercise in the elderly may improve the alterations in acquired immunity which follow the physiological process of aging, allowing a major resistance against external pathogens and a better quality of life.

Naturally occurring B-cell autoreactivity: A critical overview

In over one century of research in immunology marked progress in the scientific knowledge and the implications derived from it has been made. At the same time several contradictory and seemingly opposing results have been obtained. The term autoimmunity is still conceived by many as a term directly related to an immunopathological state. However, strong evidence exist that not only the immune system is able to recognize self-constituents, but it appears also that this property is essential for homeostasis. Direct or indirect alterations of such self-recognition properties of the immune system may contribute to pathology. In this review, the most recent advances in the field of naturally occurring B-cell autoreactivity in health as well as in disease are presented and discussed.

Humoral immune response to MUC1 and to the Thomsen-Friedenreich (TF) glycotope in patients with gastric cancer: relation to survival

Humoral immune responses to the MUC1 peptide and to MUC1-related Thomsen-Friedenreich (TF) glycotope was investigated in patients with gastric cancer (n = 247), chronic gastroduodenal diseases (n = 199) and in healthy blood donors (n = 100). Data were correlated with disease type, stage of cancer, tumor morphology and survival. MUC1 IgG antibody levels were higher in patients with gastric cancer (p < 0.0001) than in healthy controls. Higher levels of anti-MUC1 IgG were also detected in patients with ulcer of the stomach (p = 0.015) and in atrophic gastritis (p = 0.027). Compared to blood donors, significantly lower levels of anti-TF IgG were found both in the cancer (p = 0.002) and in the benign group (p < 0.0001). At early stages of cancer a positive correlation (p < 0.0001) was found between MUC1 IgG and TF IgG antibody levels. High levels of TF IgG antibodies were significantly associated with a benefit in survival of gastric cancer patients (p = 0.003). A similar though weaker association was observed for patients with high levels of MUC1 IgG antibodies and locoregional disease (stage I-III) (p = 0.037). Thus IgG immune responses to MUC1 are increased in patients with gastric cancer. High levels of either TF IgG or MUC1 IgG antibodies may predict better outcome in surgically treated patients with gastric cancer.

Self-Reactivity in the Dimeric Intravenous Immunoglobulin Fraction

Therapeutic intravenous immunoglobulin (IVIg) preparations contain antibodies reflecting the cumulative antigen experience of the donor population. IVIg contains variable amounts of monomeric and dimeric IgG, but there is little information available on their comparative antibody specificities. We have isolated highly purified fractions of monomeric and dimeric IgG by size-exclusion chromatography. Following treatment of all fractions at pH4, analyses by immunodot and immunocytology on human cell lines showed a preferential recognition of autoantigens in the dimeric IgG fraction. Investigation of the HEp-2 cytoplasmic proteome by 2D-PAGE, Western blot, and subsequent identification of IVIg reactive spots by mass spectrometry (LC-MS/MS) showed that IVIg recognized only a restricted set of the total proteins. Similar experiments showed that more antigens were recognized by the dimeric IgG fraction, especially when the dissociated dimer fraction was used, as compared to its monomeric counterpart. These observations are consistent with idiotype-anti-idiotype masking of auto-specific Abs in the dimeric fraction of IVIg.

Dynamic stability in random and scale-free B-lymphocyte networks

One of the most intriguing features of the immune system is regulation: a limited response when perturbed repeatedly. We propose a minimal network model for immune regulation in a lymphocyte network containing two types of elements: B lymphocytes and ligands that bind to their receptors. Effective interactions between B cells, mediated by other components of the immune system can be excitatory or inhibitory. In our model, B cell clones and ligand species are represented by nodes, and interactions by links. We expect that, as in many complex systems, the connectivity distribution is broad, motivating study of the model on a scale-free network; for comparison we study the same dynamics on a random graph. We characterize the dynamics of the model and its response to perturbations. Our model reproduces several key features of immune system dynamics: regulation (saturation of response), and more rapid response upon repeated perturbation with the same agents. Our results suggest that a scale-free network of interactions contributes to the regulation and dynamics of the immune system.

Antinuclear antibodies in the oldest-old women and men

The aim of this study was to compare the prevalence of antinuclear antibodies (ANA) in very old individuals (>or=86 years of age) with healthy younger (18-68 years) blood donors (n=200) regarding gender, health status, ratio of circulating CD4/CD8 cells and cytomegalovirus (CMV) serology. Frozen plasma was used for ANA detection in two study groups, i.e. 'OCTO' (97 persons aged 86-92 years, 65% women) and 'NONA' (136 persons aged 86-95 years, 70% women). OCTO participants were recruited on the basis that they were healthy or moderately healthy according to a selection protocol. No exclusion criteria regarding health status were applied in the NONA sample. The prevalence of ANA was significantly higher in the oldest-old samples compared to blood donors. There was no association between health status and the presence of ANA in the oldest-old. The difference across age was most pronounced in men, with low levels at younger age, whereas the prevalence among the oldest-old men reached similar levels as in women. There were no associations between the presence of ANA and CD4/CD8 ratio or with CMV status in the oldest-old. Our findings confirm an increased prevalence of ANA in the oldest-old, and emphasize the importance of taking gender and age into consideration when evaluating ANA.

Abdominal Aortic Aneurysm as a Complex Multifactorial Disease: Interactions of Polymorphisms of Inflammatory Genes, Features of Autoimmunity, and Current Status of MMPs

The role of matrix metalloproteinases (MMPs) in the pathogenesis of abdominal aortic aneurysm (AAA) has focused on the degradation of the extracellular matrix (ECM). The new frontier of MMP biology involves the role of MMPs in releasing cryptic fragments and neoepitopes from the ECM and the impact of MMPs on the regulation of the inflammatory response. The ECM is a complex structure, much more important than an inert scaffold. Both MMP-2 and MMP-9 expose a cryptic epitope that controls angiogenesis. MMPs inhibit angiogenesis through the release of endostatin, endorepellin, arresten, canstatin, and tumstatin. Other breakdown products of the ECM include fragments of fragmin and elastin degradation products (EDPs). In addition, the ECM contains embedded vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGF-beta). Inflammation is a complex, highly regulated system that involves the identification of injury or infection, response to the injury or infection, repair and healing, and return to normal homeostasis. In some instances, the inflammatory process leads to a pathologic process that is damaging to the host. MMPs play an important role in the control of the inflammatory response through the modification of proinflammatory cytokines, chemokines, and shedding of membrane receptors. Genetic association studies have been performed to help determine the genetic risk associated with certain single nucleotide polymorphisms (SNPs) However, because of the variability in the patient populations and the size of the population, it is difficult to draw any conclusions from these studies. While the etiology of AAA remains unknown, understanding of the inflammatory process and its regulatory points will develop new strategies for the treatment of AAA. Perhaps one difficulty with understanding the pathogenesis of AAA is the lack of precise definition of the phenotype.

Analysis of autoantibody repertoires in small- and medium-sized vessels vasculitides. Evidence for specific perturbations in polyarteritis nodosa, microscopic polyangiitis, Churg-Strauss syndrome and Wegener's granulomatosis

In order to identify new antibody reactivities, we have used a quantitative immunoblotting technique on extracts of normal human tissues to analyze the repertoires of serum IgM, serum IgG and purified IgG autoantibodies of patients with systemic vasculitides. Patients fulfilled the American College of Rheumatology and Chapel Hill criteria for the diagnosis of polyarteritis nodosa (PAN) (n=8), PAN related to hepatitis B virus (HBV) infection (n=5), Wegener's granulomatosis (WG) (n=6), microscopic polyangiitis (MPA) (n=18) or Churg-Strauss syndrome (CSS) (n=8). Sera from patients with chronic HBV infection without PAN (n=5) and age- and gender-matched healthy individuals (n=45) were used as controls. In the lung extract, IgM from 12/18 MPA patients reacted with high intensity with a 50 kDa band and serum IgG from 3/8 CSS patients bound to a 70 kDa protein band. In the artery extract, serum IgG from 6/18 MPA patients bound to an 85 kDa antigen, whereas purified IgG from all WG patients tested bound to a 28 kDa protein band and IgM from CSS patients bound to 2 main antigens of 38 and 60 kDa. These results provide evidence for the specificity of autoantibody repertoires from patients with PAN, WG, CSS and MPA.

Thyroid peroxidase autoantibodies in euthyroid subjects

Thyroid peroxidase (TPO) is a key enzyme in the formation of thyroid hormones and a major autoantigen in autoimmune thyroid diseases. Titers of TPO antibodies also correlate with the degree of lymphocytic infiltration in euthyroid subjects, and they are frequently present in euthyroid subjects (prevalence 12-26%). Even within the normal range for thyrotropin (TSH), TPO antibody titers correlate with TSH levels, suggesting that their presence heralds impending thyroid failure. Assays for serum TPO antibodies have become much more sensitive, and very low titers can be found in virtually all subjects. However, titers above an assay-dependent cut-off are a clear risk factor for hypothyroidism; in the Whickham survey the annual risk of developing hypothyroidism in TPO-positive women with normal thyrotropin levels was 2.1%. Measuring TPO antibodies in euthyroid subjects can be used to identify subjects with increased risk for hypothyroidism: e.g. as triage to measure thyrotropin. This could be done in women who wish to become pregnant and those with an increased risk per se who are pregnant (to predict first trimester hypothyroidism, and postpartum thyroid dysfunction), patients with other autoimmune diseases, subjects on amiodarone, lithium, or interferon-alpha, and in relatives of patients with autoimmune thyroid diseases.

IgM and IgG autoantibodies from microscopic polyangiitis patients but not those with other small- and medium-sized vessel vasculitides recognize multiple endothelial cell antigens

Using a quantitative immunoblotting technique on extracts of macrovascular and microvascular endothelial cells (EC), we analyzed serum IgM and IgG reactivities of patients with active disease fulfilling the ACR and Chapel Hill criteria for the diagnosis of polyarteritis nodosa (PAN) (n = 8), PAN related to hepatitis B virus (HBV) infection (HBV-PAN) (n = 5), Wegener's granulomatosis (n = 6), microscopic polyangiitis (MPA) (n = 18), Churg-Strauss syndrome (n = 8), and patients with chronic HBV infection without PAN (n = 5) and age- and gender-matched healthy individuals (n = 45). MPA patients' IgM bound to 200-, 105-, 80-, 65-, 45-, 35-, and 33-kDa major bands, whereas IgM from controls and other patients bound predominantly to the 65-kDa band in EC extracts. MPA patients' IgG reacted mainly with 105-, 70-, 55-, and 38-kDa protein bands, whereas IgG from controls and other patients did not. Our results provide evidence that IgM and to a lesser degree IgG from MPA patients specifically recognize multiple EC antigens.

The conservative physiology of the immune system

Current immunological opinion disdains the necessity to define global interconnections between lymphocytes and regards natural autoantibodies and autoreactive T cells as intrinsically pathogenic. Immunological theories address the recognition of foreignness by independent clones of lymphocytes, not the relations among lymphocytes or between lymphocytes and the organism. However, although extremely variable in cellular/molecular composition, the immune system preserves as invariant a set of essential relations among its components and constantly enacts contacts with the organism of which it is a component. These invariant relations are reflected, for example, in the life-long stability of profiles of reactivity of immunoglobulins formed by normal organisms (natural antibodies). Oral contacts with dietary proteins and the intestinal microbiota also result in steady states that lack the progressive quality of secondary-type reactivity. Autoreactivity (natural autoantibody and autoreactive T cell formation) is also stable and lacks the progressive quality of clonal expansion. Specific immune responses, currently regarded as the fundament of the operation of the immune system, may actually result from transient interruptions in this stable connectivity among lymphocytes. More permanent deficits in interconnectivity result in oligoclonal expansions of T lymphocytes, as seen in Omenn's syndrome and in the experimental transplantation of a suboptimal diversity of syngeneic T cells to immunodeficient hosts, which also have pathogenic consequences. Contrary to theories that forbid autoreactivity as potentially pathogenic, the physiology of the immune system is conservative and autoreactive. Pathology derives from failures of these conservative mechanisms.

Red blood cell transfusions are associated with alterations in self-reactive antibody repertoires of plasma IgM and IgG, independent of the presence of a specific immune response toward RBC antigens

Immunization to allogeneic RBC antigens occurs in transfused patients, and may be associated with the development of RBC-destructive antibodies directed against autologous RBC. The present study investigates the effect of transfusion of allogeneic RBC on self-reactive antibody repertoires, independent of the presence of a specific immune response directed toward RBC antigens. Antibody repertoires of IgM and IgG in plasma of hematological patients prior to starting a transfusion regime and of hematological patients receiving regular transfusions of leukocyte-depleted RBC were analyzed using quantitative immunoblotting on a panel of antigens derived from tissue and cell extracts, followed by multiparametric statistical treatment of the data. Multiparametric statistical analysis discriminated between self-reactive antibody repertoires of patients prior to starting a transfusion regime and those receiving regular RBC transfusions (IgM, 0.0001 < P < 0.0244/IgG, 0.0002 < P < 0.0088, depending on the tissue extract), whereas antibody repertoires of plasma IgM and IgG toward bacterial antigens were similar between groups of patients (P > 0.05). We conclude that the challenge of the immune system with allogeneic RBC antigens influences self-reactive antibody repertoires of plasma IgM and IgG, independent of the presence of a specific immune response toward RBC antigens.

Long-term kinetics of adult human antibody repertoires

In healthy humans, antibody repertoires change during ontogeny and senescence. The dynamics of antibody repertoires among adults over a longer period of time in one and the same individual has, however, not been extensively studied. In this study we analysed peripheral blood samples from five healthy adults, taken over a period of 10 weeks and once 9 years later. A competitive, quantitative polymerase chain reaction (PCR) was developed to investigate short and long-term variations in VH gene family repertoires. Serum antibody levels to common self and non-self antigens were determined in samples taken at the same time-points as the cell samples to analyse possible correlations between molecular and serological expression profiles. We found a high degree of stability in the VH gene family repertoire over time as well as between individuals with a Caucasian background. A specific change in the usage of primarily the VH3 and VH5 gene families was observed in one individual at one time-point. The deviating pattern resembled the VH gene family utilization pattern observed in naturally activated B lymphocytes. The fluctuations in VH3 and VH5 gene family expression correlated with the presence of rheumatoid factor in serum. We discuss the possible influence of polyclonal, transient stimulation of B cells on VH gene repertoires, as measured in circulating B cells.

Helicobacter pylori infection in connective tissue disorders is associated with high levels of antibodies to mycobacterial hsp65 but not to human hsp60

BACKGROUND

To investigate whether the Helicobacter pylori status influences levels of antibodies against mycobacterial heat shock protein (hsp) 65 and human hsp60 in systemic autoimmune diseases and to study the concentration of anti-H. pylori antibodies in autoimmune patients and healthy controls.

MATERIALS AND METHODS

Antibodies against human heat-shock protein hsp60, mycobacterial heat-shock protein hsp65 were analyzed by ELISA. Anti-Helicobacter antibodies were determined by enzyme immunoassay.

RESULTS

There was a markedly higher prevalence of H. pylori infection in undifferentiated connective tissue disease (82%) (n = 33) and systemic sclerosis (78%) (n = 55) but not in systemic lupus erythematosus (n = 49), polymyositis/dermatomyositis (n = 14), rheumatoid arthritis (n = 21) or primary Raynaud's syndrome (n = 26) compared with controls (59%) (n = 349). In autoimmune diseases H. pylori infection was associated with elevated levels of antihsp65 (p =.008) but not of antihsp60. Anti-hsp65 levels were significantly higher in H. pylori-infected (n = 129) than in uninfected patients (n = 69) (p =.0007).

CONCLUSIONS

These findings indicate that in autoimmune diseases the infection with the H. pylori bacterium is associated with increased concentration of antimycobacterial hsp65.

Conditional autoimmunity mediated by human natural anti-Fc(epsilon)RIalpha autoantibodies?

Natural antibodies provide an early defense mechanism against pathogens, show a frequent self-reactivity, and are present throughout life. Two questions concern the physiological control of self-reactivity and the pathogenetic link to autoimmune disease. Here we propose a concept of conditional autoimmunity involving natural antibodies against the alpha chain of the high-affinity receptor for IgE (Fc(epsilon)RIalpha ). Like other natural antibodies, anti-Fc(epsilon)RIalpha antibodies are found in sera of healthy donors. We now report the first human recombinant anti-Fc(epsilon)RIalpha autoantibodies isolated by repertoire cloning from a human tonsillar IgM library. These high-affinity antibodies recognize Fc(epsilon)RIalpha on cells and trigger histamine release from freshly isolated blood basophils. However, the latter effect requires IgE removal from the Fc(epsilon)RI. The same conditional histamine release is seen when using sera from individual normal donors and affinity-purified anti-Fc(epsilon)RIalpha antibodies isolated from multidonor therapeutic IgG preparations. We propose that such anti-Fc(epsilon)RIalpha antibodies can become pathogenic and that this is dependent on the state of occupancy of the Fc(epsilon)RIalpha by its natural ligand IgE. We suggest that an imbalance between Fc(epsilon)RIalpha occupancy and natural anti-Fc(epsilon)RIalpha antibodies may be implicated in the pathogenesis of autoimmune urticaria.

Broad alterations of self-reactive antibody-repertoires of plasma IgM and IgG in B-cell chronic lymphocytic leukemia (B-CLL) and B-CLL related target-restricted autoimmunity

B-cell chronic lymphocytic leukemia (B-CLL) is characterized by a malignant CD5+ B-cell clone. The leukemic clone commonly expresses IgM antibodies exhibiting reactivity toward a wide range of self-antigens. However, B-CLL associated autoimmunity is typically restricted to self-antigens expressed by blood cells, and mediated by IgG autoantibodies of polyclonal origin. In the present study, we addressed the question whether self-reactive antibody repertoires of plasma IgM and IgG are disturbed by monoclonal immunoglobulins of B-CLL patients, and whether antibody repertoires of patients exhibiting B-CLL associated target-restricted autoimmune disease (AID) differ from those of B-CLL patients without AID. We investigated antibody repertoires at a global level, using a technique of quantitative immunoblotting that allows for the quantitative screening of antibody reactivities in complex antibody mixtures toward a large panel of antigens derived from homologous tissue extracts, followed by multiparametric statistical analysis of the data. We demonstrate that self-reactive antibody repertoires of plasma IgM and IgG are broadly altered in patients with B-CLL, that alterations in self-reactive antibody repertoires are not restricted to B-CLL patients exhibiting AID, and that target-restricted autoimmunity in B-CLL patients is associated with altered antibody repertoires not restricted to the target organ. We conclude that monoclonal alterations of immunoglobulin production in B-CLL are associated with broad defects of self-reactive antibody repertoires. Our observations suggest that the application of therapeutic IVIg preparations might influence B-CLL by restoring normal self-reactive antibody repertoires in plasma.

Comparative study on antibodies to human and bacterial 60 kDa heat shock proteins in a large cohort of patients with coronary heart disease and healthy subjects

BACKGROUND

Recent observations indicate an association between antibodies against mycobacterial heat shock protein (hsp65) and coronary heart disease (CHD). Previously, we reported on marked differences in antigen specificity and complement activating ability of anti-hsp65 antibodies and auto-antibodies against human heat shock protein, hsp60. Here, we investigated whether there are differences between antih-sp65 and anti-hsp60 antibodies in their association with CHD.

DESIGN

We measured by ELISA the levels of antibodies to hsp65, hsp60 and E. coli-derived GroEL in three groups: Group I, 357 patients with severe CHD who underwent by-pass surgery; Group II, 67 patients with negative coronary angiography; Group III, 321 healthy blood donors. Antibodies against Helicobacter pylori were also measured by commercial ELISA.

RESULTS

As calculated by multiple regression analysis, the levels of anti-hsp60 auto-antibodies were significantly higher in Group I compared to Group II (P = 0.007) or Group III (P < 0.0001). By contrast, although concentrations of anti-hsp65 and anti-GroEL antibodies in Group I were higher than in Group III, no significant differences between Group I and Group II were found. Antibodies to the two bacterial hsp strongly correlated to each other, but either did not correlate or weakly correlated to hsp60. In Group I, serum concentrations of anti-H.pylori antibodies significantly correlated with those of anti-hsp65 and anti-GroEL antibodies but they did not correlate with the anti-hsp60 antibodies.

CONCLUSIONS

As to their clinical relevance, a remarkable difference become evident between antibodies to human hsp60 and antibodies against bacterial hsp in the extent of association with CHD. On the basis of these findings and some pertinent literature data, an alternative explanation for the association between high level of anti-hsp antibodies and atherosclerotic vascular diseases is raised.