Idiotypic regulation of the immune system by the induction of antibodies against anti-idiotypic antibodies

The immunobiology of SARS-CoV-2 infection and vaccine responses: potential influences of cross-reactive memory responses and aging on efficacy and off-target effects

Immune responses to both SARS-CoV-2 infection and its associated vaccines have been highly variable within the general population. The increasing evidence of long-lasting symptoms after resolution of infection, called post-acute sequelae of COVID-19 (PASC) or "Long COVID," suggests that immune-mediated mechanisms are at play. Closely related endemic common human coronaviruses (hCoV) can induce pre-existing and potentially cross-reactive immunity, which can then affect primary SARS-CoV-2 infection, as well as vaccination responses. The influence of pre-existing immunity from these hCoVs, as well as responses generated from original CoV2 strains or vaccines on the development of new high-affinity responses to CoV2 antigenic viral variants, needs to be better understood given the need for continuous vaccine adaptation and application in the population. Due in part to thymic involution, normal aging is associated with reduced naïve T cell compartments and impaired primary antigen responsiveness, resulting in a reliance on the pre-existing cross-reactive memory cell pool which may be of lower affinity, restricted in diversity, or of shorter duration. These effects can also be mediated by the presence of down-regulatory anti-idiotype responses which also increase in aging. Given the tremendous heterogeneity of clinical data, utilization of preclinical models offers the greatest ability to assess immune responses under a controlled setting. These models should now involve prior antigen/viral exposure combined with incorporation of modifying factors such as age on immune responses and effects. This will also allow for mechanistic dissection and understanding of the different immune pathways involved in both SARS-CoV-2 pathogen and potential vaccine responses over time and how pre-existing memory responses, including potential anti-idiotype responses, can affect efficacy as well as potential off-target effects in different tissues as well as modeling PASC.

Immune Response Regulation by Antigen Receptors' Clone-Specific Nonself Parts

Antigen determinants (epitopes) are recognized by the combining sites (paratopes) of B and T cell antigen receptors (BCR/TCR), which again express clone-specific epitopes (idiotopes) that can be recognized by BCR/TCR not only of genetically different donors but also within the autologous immune system. While xenogeneic and allogeneic anti-idiotypic BCR/TCR are broadly cross-reactive, only autologous anti-idiotypes are truly specific and of functional regulatory relevance within a particular immune system. Autologous BCR/TCR idiotopes are (a) somatically created at the third complementarity-determining regions, (b) through mutations introduced into BCRs during adaptive immune responses, and (c) through the conformational impact of both. As these idiotypic characters have no genomic counterparts they have to be regarded as antigen receptor-intrinsic nonself-portions. Although foreign, however, they are per se non-immunogenic, but in conjunction with immunogenicity- and adjuvanticity-providing antigen-induced immune responses, they induce abating regulatory idiotypic chain reactions. The dualistic nature of antigen receptors of seeing antigens (self and nonself alike) and being nonself at the same time has far reaching consequences for an understanding of the regulation of adaptive immune responses.

Anergy in self-directed B lymphocytes: A statistical mechanics perspective

Self-directed lymphocytes may evade clonal deletion at ontogenesis but still remain harmless due to a mechanism called clonal anergy. For B-lymphocytes, two major explanations for anergy developed over the last decades: according to Varela theory, anergy stems from a proper orchestration of the whole B-repertoire, such that self-reactive clones, due to intensive feed-back from other clones, display strong inertia when mounting a response. Conversely, according to the model of cognate response, self-reacting cells are not stimulated by helper lymphocytes and the absence of such signaling yields anergy. Through statistical mechanics we show that helpers do not prompt activation of a sub-group of B-cells: remarkably, the latter are just those broadly interacting in the idiotypic network. Hence Varela theory can finally be reabsorbed into the prevailing framework of the cognate response model. Further, we show how the B-repertoire architecture may emerge, where highly connected clones are self-directed as a natural consequence of ontogenetic learning.

Self-tolerance in a minimal model of the idiotypic network

We consider the problem of self-tolerance in the frame of a minimalistic model of the idiotypic network. A node of this network represents a population of B-lymphocytes of the same idiotype, which is encoded by a bit string. The links of the network connect nodes with (nearly) complementary strings. The population of a node survives if the number of occupied neighbors is not too small and not too large. There is an influx of lymphocytes with random idiotype from the bone marrow. Previous investigations have shown that this system evolves toward highly organized architectures, where the nodes can be classified into groups according to their statistical properties. The building principles of these architectures can be analytically described and the statistical results of simulations agree very well with results of a modular mean-field theory. In this paper, we present simulation results for the case that one or several nodes, playing the role of self, are permanently occupied. These self nodes influence their linked neighbors, the autoreactive clones, but are themselves not affected by idiotypic interactions. We observe that the group structure of the architecture is very similar to the case without self antigen, but organized such that the neighbors of the self are only weakly occupied, thus providing self-tolerance. We also treat this situation in mean-field theory, which give results in good agreement with data from simulation. The model supports the view that autoreactive clones, which naturally occur also in healthy organisms are controlled by anti-idiotypic interactions, and could be helpful to understand network aspects of autoimmune disorders.

Anti-ganglioside anti-idiotypic vaccination: more than molecular mimicry

Surgery, chemotherapy, and radiation therapy are standard modalities for cancer treatment, but the effectiveness of these treatments has reached a plateau. Thus, other strategies are being explored to combine with the current treatment paradigms in order to reach better clinical results. One of these approaches is the active immunotherapy based on the induction of anti-tumor responses by anti-idiotypic vaccination. This approach arose from Jerne’s idiotypic network theory, which postulates that B lymphocytes forms a functional network, with a role in the establishment of the immune repertoires, in the regulation of natural antibody production and even in the establishment of natural tolerance. Due to the large potential diversity of the immunoglobulin variable regions, the idiotypes repertoire can mimic the universe of self and foreign epitopes, even those of non-protein nature, like gangliosides. Gangliosides are sialic acid-containing glycolipids that have been considered attractive targets for cancer immunotherapy, based on the qualitative and quantitative changes they suffer during malignant transformation and due to their importance for tumor biology. Although any idiotype could be able to mimic any antigen, only those related to antigens involved in functions relevant for organism homeostasis, and that in consequence has been fixed by evolution, would be able not only to mimic, but also to activate the idiotypic cascades related with the nominal antigen. The present review updates the results, failures and hopes, obtained with ganglioside mimicking anti-idiotypic antibodies and presents evidences of the existence of a natural response against gangliosides, suggesting that these glycolipids could be idiotypically relevant antigens.

Idiotypic networks: toward a renaissance?

Idiotypic networks, after being a dominating paradigm for more than a decade, have fallen out of fashion in parallel with the rapid success of molecular immunobiology. Today signs of a possible renaissance in idiotypic network studies are visible. For system biologists and also for physicists, the network idea remains attractive. Herein, a short account of the historical development of the paradigm is given. The necessary technical and conceptual ingredients for a theoretical description of idiotypic networks are briefly reviewed, and previous approaches are discussed. We also describe a minimalistic model developed in our group that allows for understanding the random evolution toward a highly non-trivial complex architecture. In the network, a connected large cluster of idiotype clones and many disconnected ones coexist, thus resembling the notion of central and peripheral parts proposed in the 'second-generation' version of the paradigm. The connected cluster consists of groups of idiotypic clones with clearly distinct statistical properties. The simplicity of the model allows for calculating the size of the groups and the number of inter- and intragroup links, which define the architecture. Aspects of idiotypic interactions in experimental medicine are discussed, along with the challenges to theory and experimentation.

Maintenance of antigen-specific immunological memory through variable regions of heavy and light chains of anti-idiotypic antibody

Immunological memory is characterized by a quick and enhanced immune response after re-exposure to the same antigen. To explain the mechanism involved in generation and maintenance of immunological memory, we had earlier proposed a hypothesis involving the relay of memory by idiotypic and anti-idiotypic B cells. The peptidomimic present in the hypervariable region of anti-idiotypic antibody was hypothesized to carry forward immunological memory. In the present work, we provide evidence supporting a role for the anti-idiotypic antibody in eliciting antigen-specific B-cell and T-cell responses. Employing the idiotypic monoclonal antibody (Ab(1)) specific for haemagglutinin (H) protein of rinderpest virus, Ab(2beta) was generated, which possesses an internal image of the H protein in the region between amino acids 527 and 556. We demonstrate that antigen-specific memory is perpetuated by immunization with Ab(2), as shown by maintenance of antigen-specific T-cell responses upon restimulation in vitro of Ab(2) immune splenocytes by antigen-presenting cells expressing H protein or pulsed with H-protein-derived peptides. We have also shown that boosting with antigen-specific anti-idiotypic B cells generates a memory response in antigen-primed mice. Evidence has been provided for the existence of an antigen-specific B-cell idiotypic network in the body that supports the perpetuation of immunological memory as proposed in the relay hypothesis.

Second symmetry in the BALB/c-C57BL/6 (B6) system, and anti-antiself antibodies in ageing B6 mice

Using an ELISA assay and inhibition of antibody mediated cytotoxicity we found that there was a higher level of anti-antiself activity in B6 anti-BALB/c alloimmune mice than in BALB/c anti-B6 mice. In contrast, when an inhibition of cellular cytotoxicity assay was used to assay for the activity, similar levels of anti-antiself antibodies were seen in B6 anti-BALB/c and BALB/c anti-B6 sera. Anti-antiself antibodies in alloimmune sera are not absorbed by the cellular immunogen as readily as are anti-foreign antibodies. These results are interpreted in terms of anti-antiself antibodies being directed mainly against T cell receptors specific for self. Anti-antiself antibodies are found also in old B6 mice, that are also known to make autoantibodies.

Circulating clonotypic B cells in the biology of multiple myeloma: speculations on the origin of myeloma

The population of circulating B cells in myeloma patients includes an apparently large but variable subset with the IgH VDJ rearrangement diagnostic for the malignant clone of plasma cells in individual myeloma patients. Although the biological significance is at present unknown, it is likely that they include both malignant and non-malignant clonal relatives of the myeloma plasma cells. This article presents speculations on the significance of these cells in the origin of myeloma and the relationship between monoclonal gammopathy of undetermined significance (MGUS) and frank myeloma. MGUS appears to represent the establishment of clonal dominance probably by a chronically antigen-stimulated B cell clone. It seems likely that malignant transformation event(s) occurring in a clonal daughter cell give rise to myeloma. If correct, this implies that in a myeloma patient, non-malignant antigen-responsive B cells expressing the patient-specific IgH rearrangement coexist in the circulation and probably all lymphoid tissues, with their malignant antigen-independent relatives. However, the significance one attributes to the clonotypic B cells detected in the blood of myeloma patients depends in part on the view one takes of the progression from MGUS to myeloma. An alternative perspective is that MGUS represents a dormant state of malignancy held in check by controlled apoptosis, arrested cell cycling, and/or by immunoregulatory networks. Although lacking in experimental support, if this interpretation were correct, myeloma would occur when the regulatory mechanisms fail, allowing uncontrolled malignant cell renewal. This alternative view would imply that the majority of circulating clonotypic B cells might be malignant. Thus, an analysis of the biology of these clonotypic circulating B cells, with an emphasis on measures of malignancy, is likely to shed considerable light on the events underlying myeloma genesis, progression and spread.

[A scientific object interlinking the biological and social sciences: the immune system]

Immunology gained legitimacy when it became the science of the immune system, a definition that announced the existence of a previously unknown body function. The very concept of immune system goes beyond the biological, offering opportunities for a renewed dialogue between biological science and the human sciences. This paper discusses the manifold viewpoints regarding the immune system.

Antibody synthesis induced by endogenous internal images

In this study, immunization with a vaccine consisting of multiple F(ab')2 fragments of affinity-purified antitetanus toxoid antibodies covalently bound to a carrier protein successfully induced antitetanus toxoid antibodies. Further studies showed that this vaccine preparation contained no biologically detectable tetanus antigen. The induced antitetanus antibody (Ab1') titer was higher than the titer of antibodies binding control antigens. The immunizing F(ab')2 preparation did not elicit a secondary antitetanus response from mice primed with tetanus toxoid and, hence, appeared free of tetanus epitopes. The specificity of Ab1' was established by absorption and inhibition with antigen. Immunization with antitetanus F(ab')2 (Ab1') fragments appears to have elicited naturally occurring autologous antitetanus toxoid antibody (Ab1') through an idiotypic pathway. As predicted by network theory, anti-idiotype (Ab2) and antitetanus (Ab1') cycled reciprocally. Clonotypic characterization of Ab1' using isoelectric focusing and affinity immunoblotting showed increases in Ab1' titer to be the result of increased synthesis by limited subsets of antitetanus toxoid B-cell clones and not increased synthesis by multiple clones, as is characteristic of antigen-driven Ab1 responses. Many Ab1 and Ab1' clonotypes had identical pIs, suggesting that they either share V region genes or are the product of the same B-cell clones. These findings indicate that immunization with polyclonal multivalent Ab1 preparations can trigger active synthesis of antibodies with the same specificity. The results provide further evidence for naturally occurring idiotypic cascades that could be exploited for studies of catalytic antibodies.

Molecular characterization of monoclonal CRIA-positive anti-arsonate antibodies derived from idiotype-negative mice bearing a light chain polymorphism

We have elicited anti-arsonate antibodies bearing the major cross-reactive idiotype (CRIA) in a double congenic idiotype-negative strain (C.C58.AL-20) bearing a light chain polymorphism that has previously been shown serologically not to complement idiotype-positive heavy chains. Using the idiotype cascade (Ab1-->Ab2-->Ab3-->-->Ab1'), CRIA-positive antibodies were raised and monoclonal antibodies were isolated and characterized serologically and by nucleotide sequence analysis. Two types of idiotype-positive anti-arsonate antibodies were generated in the C.C58.AL-20 strain. One group of hybridomas used the canonical VH1.8 heavy chain gene segment with V kappa 10 variant light chains. A second group used a VHGAM3.8 heavy chain with V kappa 10 variant light chains. This latter heavy-light pairing has been observed in CRIA-like responses previously in BALB/c mice after idiotypic manipulation (or rarely after antigen alone). These studies demonstrate the plasticity of the immune response when manipulated with idiotype reagents as well as its structural variability. Additionally, they provide important insights into the potentials of idiotype vaccines.

Active specific immunotherapy of malignant melanoma with anti-idiotypic monoclonal antibodies

In this study, we have utilized the human high molecular weight-melanoma associated antigen (HMW-MAA) as a target for active specific immunotherapy with mouse anti-idiotypic (anti-id) monoclonal antibodies (mAb) in patients with malignant melanoma. After having summarized the characteristics of HMW-MAA which account for its selection as a target for immunotherapy, we describe the development and characterization of mouse anti-id mAb MK2-23 which bears the internal image of HMW-MAA. Furthermore, we describe the results of the first clinical trial performed with mouse anti-id mAb MK2-23 in patients with malignant melanoma.

Idiotypic vaccination: immunoprotection mediated by anti-idiotypic antibodies with antibiotic activity

Anti-Id antibodies were raised in mice against a monoclonal antibody (MoAb KT4) that neutralized the in vitro activity of a Pichia anomala yeast killer toxin. Monoclonal antibody was administered to BALB/C syngeneic mice with different schedules of immunization before intravenous challenge with increasing amounts of yeast killer toxin-sensitive Candida albicans cells. The course of candidosis was studied in comparison with mice non-immunized and immunized with an isotype-matched unrelated MoAb subdivided into control groups. Protection was reflected by statistically significant increases in survival rate of mice immunized with MoAb KT4 which showed variable serum levels of yeast killer toxin-like anti-Id antibodies. MoAb KT4 affinity chromatography purified mouse anti-Id antibodies were capable of killing in vitro the yeast cells of the Candida albicans strain used for the experimental infection. This is the first report of antimicrobial protection that exploits the role of anti-idiotypic antibodies presumably acting in vivo as antibiotics (idiotypic vaccination).

Adoptively transferred anti-idiotype pulsed B cells mediate autoimmune myocarditis

Syngeneic mice receiving adoptively transferred enriched B cells or splenocytes pulsed in vitro with polyclonal anti-idiotypic antibodies (anti-Ids) against anti-CVB3 virus antibodies developed coxsackievirus B3 antigen-binding and virus-neutralizing antibodies during a 30-day period, in addition to overt expression of autoimmune myocarditis. Adoptive transfer of anti-Id pulsed T cells resulted in delayed appearance and transient expression of antiviral antibodies, and antiviral antibodies were marginal to absent in syngeneic animals receiving anti-Id pulsed macrophage populations. Proliferation analysis of recipient splenocytes indicated lack of proliferative capacity in response to monoclonal or polyclonal anti-Ids and only marginal proliferative capacity in response to coxsackievirus B3 virus antigen(s). In vitro assessment of delayed hypersensitivity in recipient animals demonstrated some specific immunity to anti-Ids in recipients receiving splenocytes or T cells. Anti-Ids expressing mimicry for heart-associated and/or viral antigen(s) interacting with B cells or other accessory cells suggest an autoantibody or anti-Id triggering of B-cell-mediated mechanisms involved in the development of myocarditis.

Immunogenicity of an engineered internal image antibody

We engineered an antibody expressing in the third complementarity-determining region of its heavy chain variable region a "foreign" epitope, the repetitive tetrapeptide Asn-Ala-Asn-Pro (NANP) of the circumsporozoite protein of Plasmodium falciparum parasite, one of the etiologic agents of malaria in humans. A monoclonal antibody to P. falciparum specific for the (NANP)n amino acid sequence bound to the engineered antibody, and a synthetic (NANP)3 peptide blocked this interaction. Immunization of rabbits and mice with the engineered antibody resulted in the elicitation of a humoral response to (NANP)3 synthetic peptide and P. falciparum parasite. In mice, in which immunity to the (NANP)n epitope is highly restricted by immune response genes, antibodies were induced in responder and nonresponder haplotypes of the major histocompatibility complex. Rabbit antibodies efficiently inhibited the in vitro invasion of cultured liver cells by P. falciparum parasite. Collectively, this study indicates that immunity to malaria in the absence of the parasite can be induced using antibody variable regions engineered to mimic the parasite's molecular structure. In general terms, the results suggest that antibody (idiotype) mimicry of an exogenous antigen is possible and may only require a discrete stretch of identity between the two molecules. The implication for the preparation of antibody-based vaccines and idiotype regulation of immunity are discussed.

Autoanti-idiotypes exhibit mimicry of myocyte antigens in virus-induced myocarditis

Mice infected with coxsackievirus B develop immunologically mediated inflammatory myocarditis in heart tissue that results in the development of autoantibodies with multiple idiotypes. The specificity and temporal development of autoantibodies produced during coxsackievirus B3 infection were assessed. Antiviral idiotypes and anti-idiotypic antibodies against coxsackievirus B3 idiotypes were detected and quantitated over 21- and 42-day periods, respectively. Both polyclonal and monoclonal anti-idiotypes exhibited greater but nonspecific binding to heart, liver, kidney, and spleen cells from virus-exposed animals and normal tissue. Binding of anti-idiotypes was also demonstrated to myosin and to solubilized heart-associated antigens but not to virus. Western immunoblot analysis revealed that monoclonal and polyclonal anti-idiotypes selectively bound to hypertonic, salt-extracted, solubilized proteins of myocyte extracts of virus-exposed animals.

Interfaces of the yeast killer phenomenon

A new prophylactic and therapeutic antimicrobial strategy based on a specific physiological target that is effectively used by killer yeasts in their natural ecological competition is theorized. The natural system exploited is the yeast killer phenomenon previously adopted as an epidemiological marker for intraspecific differentiation of opportunistic yeasts, hyphomycetes, and bacteria. Pathogenic microorganisms (Candida albicans) may be susceptible to the activity of yeast killer toxins due to the presence of specific cell wall receptors. On the basis of the idiotypic network, we report that antiidiotypic antibodies, produced against a monoclonal antibody bearing the receptor-like idiotype, are in vivo protecting animals immunized through idiotypic vaccination and in vitro mimicking the antimicrobial activity of yeast killer toxins, thus acting as antibiotics.

A private idiotype can become recurrent through genetic recombination and gene(s) unlinked to the Igh locus governs its expression

Any immune response is characterized by its idiotypic profile. Two different kinds of idiotype (Id) have been described. Private Id are restricted to a few individuals from a species while recurrent Id appear in a large majority of individuals from the same species immunized with the same antigen. We describe, in this report, an experimental model whereby a private Id can become recurrent through genetic recombination. The immune response of A mice against the hapten arsonate is characterized by a recurrent Id called cross-reactive idiotype A (CRIA). A strongly CRI, called CRIA-like, can be occasionally detected in some BALB/c mice (5% to 10%) immunized with arsonate. Molecular studies show that CRIA and CRIA-like antibodies have highly homologous D segments and identical light chains. By contrast, their VH segments are vastly dissimilar. We have examined the anti-arsonate response of inbred strains of mice whose Igh loci are recombinant between those of A/He and BALB/c. Interestingly, we have observed that the CRIA-like Id which is private in BALB/c becomes recurrent in the AXC-1 strain which harbors the VH genes from BALB/c, the DH and CH genes from A/He. Structural studies demonstrate that highly homologous, VH, VL and D segments are used in BALB/c and AXC-1 mice. The basis for this differential expression of highly similar genes could be linked to the DH locus. However, F1 mice stemming from the cross between AXC-1 and BALB/c do not express the Id. The backcross analysis shows that the non-expression of the Id in F1 mice depends on genes unlinked to the Igh locus.

Alteration of the humoral immune response against muscle acetylcholine receptor by timed administration of alpha(1----3)dextran

Previously, we discovered a profound idiotypic connectivity among antibodies involved in the immune responses to alpha(1----3)dextran (Dex) and the acetylcholine receptor (AChR). The present studies were undertaken to assess whether these connections represent functional pathways for regulation. It was found that immunization of mice with Dex prior to challenge with AChR reduced the subsequent response to receptor. The timing of the Dex administration was crucial for this effect with a 6-day delay between Dex and AChR being optimal whereas 0- or 12-day delays proved ineffective. The suppressive effect was specific for Dex, as treatment with the closely related, but idiotypically distinct, alpha(1----6)dextran did not diminish the anti-AChR response. Consistent with functional connections in the AChR-Dex network, an inverse relationship between anti-AChR and anti-Dex antibodies was observed in these studies. Thus, high levels of anti-AChR antibodies were associated with low levels of anti-Dex antibodies and vice versa. A similar relationship was observed for serum antibodies from patients with myasthenia gravis. To investigate the mechanism for the antigen-induced cross-regulation, hybridomas were constructed from spleen cells of mice treated 6 days earlier with Dex. A variety of idiotypes (Id), anti-Id and anti-anti-Id were obtained from this fusion. In addition, sera from day-6 mice were examined for the expression of key anti-Id which might provide regulation in the anti-AChR response. The main feature of these sera was the presence of EB3-7-reactive antibodies which did not bind Dex, and hence were not identical to J558. A monoclonal antibody with similar properties was obtained from the day-6 fusion (DX6) which had additional binding specificity for anti-AChR antibodies. Antibodies induced by Dex immunization appear to participate in the cross-regulation observed here. Understanding the mechanisms involved in this phenomenon will have important implications for network theory and for prediction of immune responsiveness.

Idiotypic cascades associated with the CD4-HIV gp120 interaction: principles for idiotype-based vaccines

Idiotypes (Id) are antigenic determinants expressed on the variable (V) region of the immunoglobulin molecule. Id-bearing antibodies, or Ab-1, are produced upon stimulation with a given antigen. Ab-1 may elicit the production of anti-idiotypic antibodies (anti-Id) or Ab-2. The anti-Id also expresses Id determinants and may in turn elicit the production of anti-anti-Id or Ab-3. The production of Ab-1, Ab-2, and Ab-3 responses resulting from stimulation with the antigen is representative of components within an Id cascade. The existence of this Id cascade is the basis for the development of Id based strategies for controlling the immune response to infectious agents and tumors. In this review we will focus on several aspects regarding the Id cascades that may be operational during the immune response to the human immunodeficiency virus (HIV). In light of several studies which suggest the existence of Id-anti-Id interactions operating during the course of HIV infection, we will discuss the potential applications of Id based strategies in manipulating the immune response to HIV.

A simple model for the immune network

In this note I present a simple model for the idiotypic network among antibodies and study its relevance for the maintenance of immunological memory; in particular, the memory capacity of such a model is studied. Some of the similarities with the spin glass model and with neural networks are discussed.

Monoclonal anti-idiotypic antibodies regulate the expression of virus-induced murine myocarditis

A monoclonal anti-idiotypic antibody (anti-Id), produced by electrofusion and designated anti-Id88, was able to modulate expression of murine autoimmune myocarditis mediated by coxsackievirus B3 (CVB3). The anti-Id was characterized as an immunoglobulin G2b species possessing kappa light chains and was able to reduce expression of inflammatory myocarditis in anti-Id-pretreated mice challenged with CVB3. Anti-Id88 was able to stimulate specific cell-mediated immunity against anti-Id88, as well as CVB3, and exerted a suppressive effect on the proliferation of mixed spleen cell populations from virus-exposed mice. Anti-Id stimulated an anti-anti-Id antibody 3 population able to bind antibody 2 F(ab')2 fragments or virus antigen in an indirect enzyme-linked immunosorbent assay. Western blot (immunoblot) analysis of anti-Id88 exhibited binding of syngeneic anti-Id antibody to idiotypes present on immunoglobulin G molecules from virus-immunized mice.

Parasite exposure elicits a preferential T-cell response involved in protective immunity against Eimeria species in chickens primed by an internal-image anti-idiotypic antibody

Polyclonal anti-idiotype 1073 (anti-Id 1073), raised against a monoclonal antibody specific for the protective epitope(s) of Eimeria tenella sporozoites, induced cell-mediated immune (CMI) responses in bursectomized chickens. Whereas alhydrogel-adsorbed anti-Id 1073 was sufficient to engender the CMI response at 4 h after injection, induction of the CMI response at 24 h required both alhydrogel and muramyl dipeptide sterol. Exposure of immunized chickens to live parasites prompted a dichotomous effect on the CMI response engendered by anti-Id in that the 4-h CMI response was preferentially stimulated and the 24-h CMI response was down regulated. Both types of CMI response were transferable to naive chickens by T cells from anti-Id 1073 immune donors or by parasite-specific T cells from clones 21 and 27. These T-cell clones were generated from chickens immunized by repeated infections with E. tenella and showed in vitro proliferative responses to anti-Id 1073. The abilities of T cells from clone 21 to selectively transfer the 4-h CMI response and to generate gamma interferon to activate macrophages for their cytotoxic effects on Eimeria sporozoites correlate with the preferential stimulation by parasites of the 4-h CMI response in chickens immunized with anti-Id 1073. These data show that anti-Id 1073 mimics the protective epitope(s) of the parasite and primes chickens for protective CMI responses. Cytotoxic T cells, equivalent to the mammalian T-cell subset of the Lyt2+ phenotype, appear to be the primary effector T cells in the CMI response engendered by anti-Id 1073 against Eimeria parasites.

Evidence for a functional idiotypic network among natural antibodies in normal mice

We monitored in normal adult BALB/c mice the serum concentrations of four natural IgM antibodies, two of which show idiotypic complementarity in in vitro assays. In each individual, serum concentration of all four idiotypes were found to fluctuate in complex dynamical patterns with low correlation. The spectral power of some such patterns was found to be compatible with the existence of a chaotic regime. Groups of normal adult mice were injected intravenously with low (10 ng) or moderate (10 micrograms) doses of either of the two complementary idiotypes in saline. This treatment resulted in a pronounced inhibition of the fluctuation in the serum concentration of both complementary idiotypes for periods up to 3 months. Such compensations were not detected for the two unrelated natural idiotypes and were specifically induced, for they did not occur following the injection of unrelated antibodies. These results indicate the functional operation of an idiotypic network among natural antibodies.

Vaccines against tumor antigens

Effective vaccines against tumor antigens have not yet been produced. However, immunomodulators hold much promise in cancer therapy. Such treatments will probably involve using combinations of various immunomodulators together with activated killer cells. Development of vaccines against tumor-causing viruses seems to be a rational approach to preventing the onset of virus-induced cancers. It seems that efficient vaccines have already been developed for hepatitis B virus; such vaccines have the potential to decrease the incidence of its associated hepatoma. However, successful vaccines against RNA-containing tumor viruses have yet to be developed, although they hold much promise.

Idiotype regulation of thymus autoantibodies

Rabbit antisera specific for idiotypic determinants (Id) of monoclonal Thy-1 autoantibodies were tested for their capacity to elicit Id-bearing thymus autoantibodies in mice. Rabbits were immunized with the 20-10-5 monoclonal IgM Thy-1 autoantibody, and idiotype-specific antibodies (anti-Id) were obtained by affinity chromatography. BALB/c and C3H mice were immunized by repeated i.p. injections of the anti-Id reagent. Control mice received repeated injections of purified normal rabbit immunoglobulin (NRIg) sheep red blood cells (SRBC) or human serum albumin (HSA). The sera of the treated mice were examined for their reactivity with anti-Id xenoantisera and for their capacity to react with thymus cells. The injection of anti-Id sera into either BALB/c or C3H mice resulted in a significant increase in the serum concentration of Id-bearing immunoglobulins, while no such change was observed in the sera of mice injected with NRIg. The administration of anti-Id, NRIg, SRBC or HSA resulted in a gradual increase in the concentration of autoantibodies reactive with thymus cells. Incubation with anti-Id sera prevented the binding to thymus cells of autoantibodies induced by anti-Id treatment. In contrast, the binding capacity of autoantibodies induced by NRIg, SRBC or HSA was unaffected by anti-Id sera. Thus, only the thymus autoantibodies induced by anti-Id treatment expressed Id-determinants. These results demonstrate the existence of a regulatory network in the formation of thymus autoantibodies.

Protein A immunoadsorption therapy in HIV-related immune thrombocytopenia: a preliminary report

Nine homosexual patients with immune thrombocytopenia were treated with autologous plasma that had been perfused over silica-immobilized Staphylococcus aureus protein A (SpA). Pretreatment platelet counts ranged from 10,000 to 98,000 cells/mm3 (mean: 54,000 cells/mm3). Six patients responded to therapy. Platelets increased by a mean of 95,000 cells/mm3 (p less than 0.007) and reached normal levels (greater than 150,000 cells/mm3) in four patients. Increased platelet counts are presently sustained in these four individuals after 5 months of follow-up. Increases in platelet counts significantly correlated with decreases in platelet-associated IgG (PAIgG), platelet-directed IgG (PDIgG), and immune complexes (CIC). PAIgG and PDIgG declined by a mean of 67% (p less than 0.003) and 58% (p less than 0.007), respectively. CIC decreased by a mean of 37% (p = 0.02). Complement was concomitantly activated in all four examined patients. C3a and C5a increased 23-fold and 2.6-fold, respectively, while total hemolytic complement decreased by 50%. Activated complement components and removal of CIC and IgG thus may contribute to the platelet-enhancing activity of SpA immunoadsorption therapy.

Changes in idiotypic predominance in the anti-arsonate response by priming with anti-idiotypic antibodies

The predominant selection of CRI-A-bearing antibodies during the anti-arsonate (ARS) response of A/J mice has been used as a model to analyse the mechanism involved in the process of clonal selection and establishment of predominance. In order to assess the importance of the affinity and adaptability of CRI-A clones in this process, we tested the capability of a minor recurrent idiotype (id-1A3), present in a CRI-Aanti-ARS monoclonal antibody (65-1A3), to develop a normal anti-ARS response. Our results show that the id-1A3 predominance, established by anti-id-1A3 administration was stable during the primary and secondary anti-ARS response and that this predominance occurred concomitantly with low levels of CRI-A. Thus, a change in the idiotype predominance was achieved. In spite of the high levels of id-1A3, the anti-ARS antibody concentration, the affinity values, and the kinetics of the immune response were similar to those of the control group. All these results show that CRI-A clones are not essential in the normal development of the anti-ARS antibody response of A/J mice, and suggest that factors other than affinity could be involved in the establishment of the CRI-A predominance.

IgG and IgM autoantiidiotype antibodies against antibody to HBsAg in chronic hepatitis B

Antibody directed against HBsAg carries idiotypic determinants that may induce an autoantiidiotype antibody response. We describe a solid-phase radioimmunoassay which allows specific detection of either IgG or IgM antibody to antibody directed against HBsAg. Among 138 chronic hepatitis B virus carriers, IgG autoantiidiotype was detected in 98 (71%) and IgM autoantiidiotype in 10 (80%). The autoantiidiotype reaction was blocked with antibody directed against HBsAg after removal of immune complexes by polyethylene glycol precipitation. The prevalence and levels of both classes of autoantiidiotype antibodies were highest in patients with hepatitis B virus DNA or HBeAg in serum. During follow-up, patients who lost hepatitis B virus DNA and HBeAg from serum had lower titers of autoantiidiotype and were less likely to have autoantiidiotype than patients who persisted in having hepatitis B virus DNA and HBeAg in serum. Thus, the presence and titer of autoantiidiotype correlated with serologic evidence of active viral replication in chronic hepatitis B. These findings suggest that the antibody directed against HBsAg response may play a role in modulating viral replication in chronic hepatitis B.

Perturbation of the autoimmune network. I. Immunization with anti-idiotypic antibodies prior to challenge with antigen induces quantitative variations in the autoantibody response

The effect of immunization with anti-idiotypes on the production of autoantibodies subsequently induced with nominal antigen, thyroglobulin, was investigated in BALB/c mice with three distinct rabbit antibodies and one syngeneic monoclonal antibody (mAb) specific for an idiotype (Id62) borne on a mouse monoclonal autoantibody to thyroglobulin. In these in vivo experiments, dose, route and form of the anti-idiotypic immunization were kept constant, but the time interval between exposure to anti-idiotype and antigen challenge was varied. When the interval was short (two weeks), heterologous anti-Id62 antibodies predisposed to suppression of the autoantibody response in 2/3 instances. Suppression was also obtained in mice immunized with a syngeneic mAb directed against Id62. In each case, a prominent idiotype-positive (Id') response was measured in the serum. Adsorption/elution studies indicated that Id' molecules in suppressed mice were principally non antigen-binding. On the other hand, when the time interval between injections was long (14 weeks), mice preimmunized with one rabbit anti-Id62 antibody showed a markedly increased autoantibody response. The Id' component in enhanced mice was largely enriched for antibodies reacting with the antigen. These findings suggest that the state of activation of autoreactive clones and the type of anti-idiotypes used may be determinant factors in the overall effect of manipulation of autoimmune responses with anti-idiotypic antibodies.

Cross-reactive variable-region associated epitopes of human IgG1 lambda paraprotein detected by a monoclonal antibody panel

This paper describes the production and characterization of a panel of 15 mouse monoclonal antibodies selected for putative activity against V-region related or allotypic determinants of a single IgG1 lambda paraprotein obtained from a patient with malignant lymphoplasmacytoid lymphoma. The specificity of each reagent for epitopes on the heavy (H) or light (L) chain or for conformational determinants (CD) of the immunogen was determined and the ability of one reagent to compete with another for these sites investigated. The fine specificity of the antibodies was assessed by screening on a large series of normal and paraprotein-containing sera. One monoclonal showed specificity for the Glm(f) allotype. The 14 other reagents identified a minimum of nine different epitopes in the V region of the immunogen, with four antibodies detecting private conformationally determined idiotypic specificities. Eight determinants were V-region markers also expressed on other paraproteins. A total of 30 out of 159 different paraproteins cross-reacted with one or more of the antibodies. Four of the shared epitopes were lambda-chain associated, three were H-chain associated and one was a conformational determinant. Homologies of lambda chain were identified more frequently among other paraproteins than those of H chain. The relationship between epitope expression and H-chain class of paraprotein was not random. The frequency of expression of cross-reactivities in association with IgG1 proteins was always exceeded by higher frequency of epitope expression in association with other classes of H-chain isotype. The potential therapeutic value of such panels of characterized monoclonal reagents is discussed.

Turning (Ir gene) low responders into high responders by antibody manipulation of the developing immune system

The ability of helper T cells directed against trinitrophenyl-modified syngeneic spleen cells to recognize low-hapten densities on target cells is under major histocompatibility complex-linked Ir gene control. Thus, BALB/c (H-2d) mice are low responders while H-2 congenic BALB.C3H (H-2k) mice are high responders. Immunization of adult BALB/c mice with the monoclonal antibody F6(51), directed to shared idiotopes by anti-trinitrophenyl antibodies and clonal receptors on anti-trinitrophenyl-self helper T cells, leads to the production of high titers of circulating idiotype, has no influence on helper T cell idiotypic profiles, but shifts to a high-responder phenotype the ability of helper T cells to recognize low-hapten densities. These effects on Ir gene phenotype are even more striking in untreated progenies from F6(51)-immunized BALB/c females, which are better responders than genetically high-responder BALB.C3H mice, although completely different in the expression of the F6(51)-defined clonotype. The general significance of these findings on Ir gene-directed T-cell repertoire selection is discussed, for they constitute formal evidence against antigen-presentation as a mechanism of Ir gene effects and strong support for the importance of maternal influences on the development of T-cell repertoires.

Crossreactivity and inheritance of idiotypes restricted to human anti-tetanus toxoid antibodies

The presence of cross-reactive idiotypes on human IgG antibodies of tetanus toxoid (TT) antigen was assessed by examining the capacity of two anti-idiotypic (ID) antisera raised against IgG (Fab')2 anti-TT (idiotype) from two subjects to bind radiolabeled "idiotype" and to inhibit the binding of radiolabeled TT to IgG from unrelated subjects and from family members of the idiotype donors. Idiotypic crossreactivity with unrelated individuals was infrequent and weak but was frequent and stronger among siblings. The strongest idiotypic crossreactivity was seen between identical twins in studies using four anti-ID raised against the anti-TT idiotypes of two sets of twins. The results of the present study suggest that idiotypic determinants restricted to human anti-TT antibodies are, at least in part, encoded by inherited genes, which are infrequently shared among unrelated individuals.

Molecular interactions in the "GAT" idiotypic network: an approach using synthetic peptides

In order to approach some of the dominant epitopes which are recognized in the GAT (Glu60 Ala30Tyr10)n random terpolymer, a variety of peptides containing 7 to 14 residues were synthesized using glutamic acid and tyrosine as building blocks, and thus were able to mimic determinants common to GAT and GT (Glu50Tyr50)n. One decapeptide and on dodecapeptide were found to inhibit GT-mAb1 (or mAb1') binding to the same extent as GAT. Antibodies were also raised against synthetic peptides which reproduced the sequence of the 6 CDR of the germline anti-GAT Ab1 antibody. Antibodies were obtained against all peptides except L1, and were shown to recognize the native Ab1-Fab. Surprisingly, some of these antibodies also recognized GAT, i.e. anti-L2, anti-H2 and anti-H3, an observation which speaks in favour of a triggering of the idiotypic network at the Ab3 level. Finally, a monoclonal antibody derived from an immunization with an Ab2-D region synthetic peptide was found to be of the Ag+Id- type. Sequence data indicate that the light chain at least is completely different from that the of Ab1/Ab1', which uses only a very precise pair of V germline genes.

Influence of a minor recurrent idiotype on the regulation of immune response: route dependence

Sp6, a BALB/c hybridoma, produces anti-TNP IgM antibodies (AB), which carry a minor recurrent idiotype (ID). Despite the fact that only about 20% of BALB/c anti-TNP AB carry the Sp6 ID, injection of Sp6-coated spleen cells (Sp6-SC) significantly influenced the anti-TNP B cell response. Repeated intratrail (i.t.) or intravenous (i.v.) injections of Sp6-SC resulted only in a minor increase of the anti-TNP background response. When mice consecutively were challenged with TNP-horse red blood cells (HRBC), i.t. injections of Sp6-SC resulted in a 2-3-fold increase in the number of anti-TNP plaque-forming cells (PFC), while i.v. injection of Sp6-SC displayed no effect on a primary anti-TNP response. But, after i.v. as well as i.t. application of Sp6-SC, it was not possible to obtain hapten-specific suppression by i.v. injection of TNP-haptenized lymphocytes. In vitro characterization of the underlying mechanism revealed that the helper effect, which only was observed after i.t. injection, was due to a Lyt-1+ population, not adhering to Sp6-coated plates, while counterregulation of hapten-specific suppression was found in a Lyt-2+ population, adhering to Sp6-coated plates. Hence, depending on the route of priming, injection of AB with a recurrent ID can augment the response towards the nominal antigen either directly via activation of helper cells or indirectly via activation of counterregulatory cells.

Idiotypic games within the immune network

In this paper, we have considered the problem of selection of available repertoires. With Ab2 as immunogens, we have used the idiotypic cascade to explore potential repertoires. Our results suggest that potential idiotypic repertoires are more or less the same within a species or between different species. A given idiotype "à la Oudin" can become a recurrent one within the same outbred species or within different species. Similarly, an intrastrain crossreactive idiotype can be induced in other strains, even though there is a genetic disparity between these strains. The structural basis of this phenomenon has been explored. We next examined results showing the loss and gain of recurrent idiotypes without any intentional idiotypic manipulation. A recurrent idiotype can be lost in a syngeneic transfer and a private one can become recurrent by changing the genetic background. The change of available idiotypic repertoires at the B cell level has profound influences on the idiotypic repertoires of suppressor T cells. All these results imply that idiotypic games are played by the immune system itself, a strong suggestion that the immune system is a functional idiotypic network.

Studies of monoclonal antibodies specific for major histocompatibility complex products of the rat. IV. Production and characterization of polyclonal and monoclonal anti-anti-idiotypic antibodies

Polyclonal syngeneic, allogeneic, and xenogeneic and monoclonal syngeneic anti-anti-idiotypic antibodies have been produced against previously described monoclonal anti-idiotypic antibodies with specificity for monoclonal RT1 alloantigen-specific antibodies. The anti-anti-idiotypes could again be shown to be highly specific for the monoclonal anti-idiotype used for the induction of the anti-anti-idiotypic antibodies and to carry the same, or a very similar, idiotype as the original monoclonal idiotypic antibody used to induce the monoclonal anti-idiotypic. Among the 30 syngeneic and allogeneic and the five xenogeneic polyclonal anti-anti-idiotypic antisera and the three monoclonal anti-anti-idiotypes, only one polyclonal antiserum showed binding capacity to the corresponding RT1-encoded antigenic determinants on spleen cells. All the other antibodies were idiotypic but not antigen binding.