Expression of new idiotypes following neonatal idiotypic suppression of a dominant clone

A Novel Hypothesis for Original Antigenic Sin in the Severe Disease of SARS-CoV-2 Infection

In this hypothesis, we address the biological/immunological pathway leading to severe disease or death after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The underlying immune response is described with "original antigenic sin" (OAS) whereby previous infections influence the response to future virus encounters. We cite evidence for OAS-induced immunopathology in HIV-1 disease. We hypothesize that similar immune abnormalities can occur after infection with SARS-CoV-2. This hypothesis is supported by recent analysis of the antibodies in infected patients demonstrating serological and B cell abnormalities. The concept of symmetrical clonal regulation developed earlier for the immune network illustrates the pathway suggested by our hypothesis and may be helpful to develop strategies avoiding severe coronavirus disease 2019.

Relevance of the Materno-Fetal Interface for the Induction of Antigen-Specific Immune Tolerance

In humans, maternal IgGs are transferred to the fetus from the second trimester of pregnancy onwards. The transplacental delivery of maternal IgG is mediated by its binding to the neonatal Fc receptor (FcRn) after endocytosis by the syncytiotrophoblast. IgGs present in the maternal milk are also transferred to the newborn through the digestive epithelium upon binding to the FcRn. Importantly, the binding of IgGs to the FcRn is also responsible for the recycling of circulating IgGs that confers them with a long half-life. Maternally delivered IgG provides passive immunity to the newborn, for instance by conferring protective anti-flu or anti-pertussis toxin IgGs. It may, however, lead to the development of autoimmune manifestations when pathological autoantibodies from the mother cross the placenta and reach the circulation of the fetus. In recent years, strategies that exploit the transplacental delivery of antigen/IgG complexes or of Fc-fused proteins have been validated in mouse models of human diseases to impose antigen-specific tolerance, particularly in the case of Fc-fused factor VIII (FVIII) domains in hemophilia A mice or pre-pro-insulin (PPI) in the case of preclinical models of type 1 diabetes (T1D). The present review summarizes the mechanisms underlying the FcRn-mediated transcytosis of IgGs, the physiopathological relevance of this phenomenon, and the repercussion for drug delivery and shaping of the immune system during its ontogeny.

The 1F7 idiotype is selectively expressed on CD5+ B cells and elevated in chronic hepatitis C virus infection

Antibodies against different chronic viruses, including hepatitis C virus (HCV), express a public cross-reactive idiotype (Id) designated as 1F7. The prominence of this Id may reflect selective engagement of B1 B cells by chronic pathogens. We investigated this by comparing 1F7 Id expression on CD5(+) and CD5(-) B cells, total IgG, total IgM and anti-HCV core antibodies in different HCV exposure settings. By flow cytometry, we observed a selective increase in 1F7 Id(+)CD5(+) B cells in chronic HCV infection. 1F7 Id levels in different immunoglobulin compartments were measured by enzyme-linked immunosorbent assay. 1F7 Id expression was prominent in anti-HCV core antibodies of approximately 90% of 141 HCV-exposed individuals tested. In the Canadian and Armenian study groups, participants who spontaneously cleared HCV infection had lower median 1F7 Id levels on total plasma IgG and anti-HCV core antibodies. Armenian spontaneous clearers, who were younger and more recently infected than their Canadian counterparts, also had had lower median 1F7 Id levels on total plasma IgM. Engagement by HCV of B-cell receptors within, or overlapping with the CD5(+) B1 B-cell repertoire is reflected in the production of 1F7 Id(+) anti-HCV antibodies and expansion of 1F7 Id(+)CD5(+) B cells. Higher 1F7 Id expression levels are associated with chronic infection.

Structured therapy interruption (STI) and deceptive imprinting

The immune response in individuals chronically infected with HIV-1 is unable to prevent progression of disease. Diversion of immune recognition via 'Deceptive Imprinting' allows virus variants to continue the infection. Structured Interrupting of (HAART) therapy (STI) causes rebound of virus with 'wild-type' strains that stimulate the immune system. Combining STI with suppression of the dominant response against anti-wild-type virus is proposed to enhance the beneficial effects of STI.

The transfer of immunity from mother to child

The newborn's immune system grows fast from a small size at birth by exposure primarily to the intestinal microflora normally obtained from the mother at and after birth. While building up its immune system, the infant is supported by the transplacental IgG antibodies, which also contain anti-idiotypic antibodies, possibly also actively priming the offspring. The second mode of transfer of immunity occurs via the milk. Numerous major protective components, including secretory IgA (SIgA) antibodies and lactoferrin, are present. The breastfed infant is better protected against numerous common infections than the non-breastfed. Breastfeeding also seems to actively stimulate the infant's immune system by anti-idiotypes, uptake of milk lymphocytes, cytokines, etc. Therefore, the breastfed child continues to be better protected against various infections for some years. Vaccine responses are also often enhanced in breastfed infants. Long-lasting protection against certain immunological diseases such as allergies and celiac disease is also noted.

Generalization of single immunological experiences by idiotypically mediated clonal connections

Clonal interactions of B cells by idiotope-specific mutual recognition of their antigen receptors with the participation of T cells were assumed to form a web of unknown density, referred to as the idiotypic network. Although these clonal connections were proposed to fulfill important internal regulatory functions, their biological significance, especially in relation to antigen-induced immune responses, remained a mystery. In view of this, we postulate that the basic function of the idiotypic internal connection between B and T cell antigen receptors is to transform antigen-induced cellular activations, by idiotypic crossreactivity, into the regulation of cell clones with different antigen specificities. This process leads not only to the suppression of major clones but also to the activation of minor ones. The latter activating property may allow the generalization of single antigenic experiences, so that the immune system in its entirety benefits in its battle against environmental microbes. Such idiotypic clonal interactions are particularly effective in early ontogeny. During a short neonatal imprinting period, maternal immunological knowledge in the form of somatically mutated, high-affinity IgG antibodies, acquired through a continuous encounter with external antigens, guides the initial ontogenetic development of the immune system and so exerts long-lasting transgenerational advantageous effects in the offspring.

Modulation of the in vivo primate anti-Gal response through administration of anti-idiotypic antibodies

Polyclonal anti-idiotypic antibodies (AIA) were generated against human Gal alpha 1,3Gal antibodies (anti-Gal) isolated from a single donor. Specificity of the AIA was demonstrated by selective binding to anti-Gal antibodies (Ab) and absence of reactivity to non-Gal Ab. The idiotopes identified by AIA were present on anti-Gal Ab from all of the human samples evaluated (n=59) as well as on pooled samples, demonstrating that a restricted number of dominant idiotopes characterized the human anti-Gal Ab response. Furthermore, the AIA had cross-species reactivity with baboon serum samples (n=19), suggesting that the overall shape of the anti-Gal Ab combining site is conserved throughout the Old World primates and providing additional evidence of the limited heterogeneity of the anti-Gal Ab repertoire. In order to evaluate the potential effect of AIA in the modulation of the anti-Gal response in vivo, a baboon was injected with repeated doses of the purified AIA. Following AIA treatment, new Ab were generated that reduced Ab-mediated cytotoxicity to porcine cells. Furthermore, administration of the AIA to a baboon prolonged the survival of intravenously infused pig hematopoietic cells when compared with their survival in a control baboon that did not receive prior AIA treatment but underwent a similar conditioning regimen.

Stimulation of antiviral antibody response in SHIV-IIIB-infected macaques

Three macaques infected with SHIV-IIIB and expressing the shared 1F7-idiotypic marker on antibodies against HIV-1 gp120, were injected intravenously with 1F7 monoclonal antibodies (MoAb). As controls, a SHIV-IIIB-infected macaque was injected with a HIV-unrelated mouse monoclonal isotype antibody (TEPC-183) and two healthy, noninfected macaques were injected with MoAb 1F7. 1F7-id-expressing antibodies against gp120-IIIB decreased in two of the three MoAb 1F7-treated macaques and then rebounded. Importantly, antibodies binding to envelope proteins of heterologous HIV-1 strains MN, CM, and SF2, which were low or not detectable before the MoAb 1F7 treatment, increased rapidly following MoAb inoculations in all three 1F7 MoAb treated macaques, but not in the macaque injected with control MoAb TEPC-183. Newly arising antibodies reacting with heterologous virus, i.e. HIV-1 gp120-MN, SF2, and CM did not express 1F7-id. Surprisingly, significant increases of antibodies were also observed in the 1F7-inoculated macaques' antibodies directed to non-HIV antigens (DNP, peptides and BSA). The noninfected control animals did not produce antibodies to these antigens despite MoAb 1F7 treatment. These data show that the MoAb 1F7 injections of chronically SHIV-IIIB-infected macaques resulted in idiotype-specific clonal suppression with broadening the antibody response to HIV envelope proteins.

Tolerance to Maternal Immunoglobulins: Resilience of the Specific T Cell Repertoire in Spite of Long-Lasting Perturbations

T cell tolerance is established and maintained through various mechanisms, the critical component being the persistence of the specific Ag. However, at the molecular level, the nature of the recovering TCR repertoire following breakdown of tolerance is unknown. We address this important question by following κ light chain constant region (Cκ)-specific CD4+ T cells of κ light chain knock-out (κ−/−) mice born to κ+/− mothers. These cells, which were in contact with maternal κ+ Igs from early ontogeny until weaning, were strongly tolerized. Tolerance was reversible and waned with the disappearance of peptide Cκ134–148 presentation in lymphoid organs, including the thymus. Whereas three specific Vβ-Jβ rearrangements emerged in the peptide Cκ134–148-specific CD4+ T cell response of all regular κ−/− mice, soon after breakdown of tolerance only one of these rearrangements was detected. The two others displayed a significant delay in reappearance and were still rare at 26 wk of age, while the control proliferative response had already recovered 3 mo earlier. At 52 wk of age, a complete recovery of the three canonical Vβ-Jβ rearrangements was observed. Thus, although profoundly perturbed for several months, the T cell repertoire returns to equilibrium, highlighting the resilient nature of this system.

Is there a maternally induced immunological imprinting phase à la Konrad Lorenz?

In mammals, IgG antibodies are transferred from mothers to the offspring. Since these maternal antibodies result mainly from thymus-dependent immune responses which have undergone immune maturation through somatic hypermutations, they represent the highest quality of the collective maternal immunological experience. Maternal antibodies not only confer passive immunity as long as the newborn's immune system has not fully developed, but also exert an active stimulation as indicated by their regulatory influence on isotype expression, long-term idiotypic alterations, determination of the adult B and T cell repertoire, induction of antigen reactive IgM as well as an affinity enhancement of a proportion of early primary antibodies. The fact that several of these features can only be induced during limited sensitive periods shortly after birth is reminiscent of the behavioural imprinting as defined by Konrad Lorenz. We therefore propose that during early ontogeny there is an immunological imprinting phase with characteristics analogous to behavioural imprinting: (i) the internal imprinting effect is induced by external signals, (ii) in contrast to normal learning, immunological imprinting is also only possible during certain development phases and (iii) it is characterised by an (almost) irreversible result. Hence, if particular immunological experiences are only possible during such sensitive phases, maternal immunoglobulins and consequently the mother's immunological experience is of prime importance for the start of the ontogenetic development of the immune system.

Polysaccharide vaccines as probes of antibody repertoires in man

Antibodies specific for capsular polysaccharide epitopes mediate immunity to encapsulated bacterial pathogens, and accordingly, vaccine development has focused upon the induction of these specificities. Efficacious vaccines, consisting of either polysaccharide alone or polysaccharide coupled to protein carriers, have been developed for a number of pathogens. Their clinical importance notwithstanding, these vaccines serve as model antigens to study the genetic and somatic forces molding adaptive immunity in man. In this article we review progress aimed at delineating the structure and dynamics of the human antibody repertoire to the Haemophilus influenzae type b polysaccharide (Hib PS), a system which has been studied from infancy to old age. Collectively, the data reveal a repertoire which is encoded by a relatively large number of germline variable (V) region gene segments, but which is typically expressed within individuals as a markedly restricted, oligoclonal population. One particular V domain has attained canonical status because of its high penetrance at the population level and its predominance in individual repertoires. Although this combining site is assembled in early infancy and retains its prominence throughout life, its frequency of expression, affinity and protective function are dictated by the molecular form of the Hib PS immunogen (vaccine). The determinants of Hib PS binding affinity can include both germline and somatically-acquired V region polymorphisms. We discuss how these properties of the Hib PS repertoire could impact immunity to Hib, and we consider the implications of these findings towards understanding the evolution of immunoglobulin germline V genes.

Neonatal Exposure to Idiotype Induces Schistosoma mansoni Egg Antigen-Specific Cellular and Humoral Immune Responses

Exposure of neonatal mice to appropriate, cross-reactive Id (CRI) preparations alters immune responsiveness, ameliorates pathology, and prolongs survival of animals upon subsequent Schistosoma mansoni infection. However, because schistosome infections profoundly affect host immunobiology, which responses are effected by neonatal Id exposure alone and which responses are influenced by infection is unclear. To directly examine the schistosome soluble egg Ag (SEA)-specific immune responses altered by CRI exposure, neonatal mice were injected with CRI-expressing (CRI+) SEA-specific Ab preparations, SEA-specific Abs that did not express CRI (CRI−), or normal mouse Ig. At 9 wk of age, only mice that were neonatally exposed to CRI+ anti-SEA Abs displayed significant SEA-specific IgG serum levels and spleen cell proliferative responses. SEA-stimulated spleen cells from these CRI+-exposed mice also produced IFN-γ, although not at significantly higher levels than mice receiving CRI− Id or normal mouse Ig. If CRI+-exposed mice were also injected with SEA at 8 wk of age, the 9-wk IFN-γ responses were significantly higher than those of the other neonatal injection groups. The presence of both CRI and anti-CRI in the sera of animals neonatally injected with CRI, but receiving no exposure to S. mansoni Ags or infection, suggested a functional idiotypic network led to these responses. These data demonstrate that appropriate idiotypic exposure induces B and T cell responsiveness to the Ag recognized by the Id and support the hypothesis that neonatal idiotypic exposure can be an important immunoregulatory factor in schistosomiasis.

Neonatal idiotypic exposure alters subsequent cytokine, pathology, and survival patterns in experimental Schistosoma mansoni infections

Exposure to maternal idiotypes (Ids) or antigens might predispose a child to develop an immunoregulated, asymptomatic clinical presentation of schistosomiasis. We have used an experimental murine system to address the role of Ids in this immunoregulation. Sera from mice with 8-wk Schistosoma mansoni infection, chronic (20-wk infection) moderate splenomegaly syndrome (MSS), or chronic hypersplenomegaly syndrome (HSS) were passed over an S. mansoni soluble egg antigen (SEA) immunoaffinity column to prepare Ids (8WkId, MSS Id, HSS Id). Newborn mice were injected with 8WkId, MSS Id, HSS Id, or normal mouse immunoglobulin (NoMoIgG) and infected with S. mansoni 8 wk later. Mice exposed to 8WkId or MSS Id as newborns had prolonged survival and decreased morbidity compared with mice that received HSS Id or NoMoIgG. When stimulated with SEA, 8WkId, or MSS Id, spleen cells from mice neonatally injected with 8WkId or MSS Id produced more interferon gamma than spleen cells from mice neonatally injected with HSS Id or NoMoIgG. Furthermore, neonatal exposure to 8WkId or MSS Id, but not NoMoIgG or HSS Id, led to significantly smaller granuloma size and lower hepatic fibrosis levels in infected mice. Together, these results indicate that perinatal exposure to appropriate anti-SEA Ids induces long-term effects on survival, pathology, and immune response patterns in mice subsequently infected with S. mansoni.

Genetic analysis of the maternally induced affinity enhancement in the non-Ox1 idiotypic antibody repertoire of the primary immune response to 2-phenyloxazolone

The early phases of ontogeny are decisive for the development of the B-cell repertoire. Here, we demonstrate that maternal tertiary immunization of BALB/c mice with 2-phenyloxazolone (phOx) caused a drastic alteration of the primary antigen-specific repertoire of the offspring. Maternal tertiary immunization or quaternary antibodies, which exhibited an extremely weak cross-reactivity with the major Ox1 idiotype (IdOx1), induced a change in the proportion of IdOx1/non-IdOx1 antiphOx antibodies in the F1 and F2 primary repertoire. The observed variability in the level of IdOx1 expression (10-90%) exceeded even the seemingly genetically based differences between various mouse strains. In comparison with the non-IdOx1 of control mice, half of the non-IdOx1 antibodies showed a 5-100-fold enhanced affinity. Sixty per cent of these antibodies exhibited an affinity identical to that of IdOx1 antibodies, which are normally of the highest affinity, while the remaining 40% exceeded even that of IdOx1 by a factor of 10. The non-IdOx1 were encoded by VH/VL genes and/or combinations thereof which are either new, hitherto unobserved in the antiphOx response, or typical of memory responses in normal mice. The significance of these data is discussed with respect to the possibility that maternal antibodies, which are acquired through multiple immune maturation processes, may have an epigenetic (non-Mendelian) inheritable potential for the offspring.

Oligoclonality of serum immunoglobulin G antibody responses to Streptococcus pneumoniae capsular polysaccharide serotypes 6B, 14, and 23F

Serum antibodies (Abs) specific for the capsular polysaccharides of Streptococcus pneumoniae provide protection against invasive pneumococcal disease. Previous studies indicate that Abs to pneumococcal polysaccharide (PPS) serotypes 1 and 6B have limited clonal diversity. To determine if restricted diversity was a feature common to other PPS specificities, we examined the light (L)-chain expression and isoelectric heterogeneity of type 6B, 14, and 23F Abs elicited in 15 adults following PPS vaccination. At the population level, both PPS-6B and PPS-14 Abs expressed kappa and lambda chains, although 6B Abs more frequently expressed lambda chains lambda and 14 Abs more frequently expressed kappa chains. In individual sera, Abs were generally skewed towards either kappa or lambda expression. 23F-specific Abs had predominantly kappa chains. Isoelectric focusing analyses showed that sera contained one or at most a few immunoglobulin G Ab spectrotypes to all three respective capsular serotypes, a result indicative of oligoclonality. A sequence analysis of a purified PPS-14-specific Ab having a single spectrotype gave uniform amino-terminal sequences for both the heavy chain (V(H)III subgroup) and the L chain (kappaIII-A27 V region). From these results we conclude that within individual adults, serum Ab responses to PPS serotypes 6B, 14, and 23F derive from a small number of dominant B-cell clones, and consequently variable-region expression is probably individually limited as well. Oligoclonality appears to be a general characteristic of human PPS-specific Ab repertoires, and we suggest that this property could lead to individual differences in Ab fine specificity and/or functional activity against encapsulated pneumococci.

Autologous anti-idiotypic antibody response is regulated by the level of circulating complementary idiotype

BALB/c mice injected with lyophilized vaccine from Streptococcus pneumoniae R36a (Pn) predominantly responded with antibody molecules the vast majority of which expressed the public idiotype T15 and were directed to the immunodominant epitope phosphorylcholine (PC). However, after a single immunization with Pn vaccine young (3-month-old) BALB/c mice did not produce any specific anti-T15 antibody response. In contrast, young D1.LP mice were able to mount a specific anti-T15 response upon primary immunization with pneumococcal vaccine. The anti-PC response in the two mouse strains differed in that the proportion of antibody molecules that expressed the T15 idiotype for Pn-primed D1.LP mice showed a smaller proportion of PC-specific antibody expressing the T15 idiotype. Neonatal injection of anti-T15 monoclonal antibodies led to a long-term suppression of the PC-specific T15+ B-cell clones but at young/adult age these mice maintained the ability to produce a normal amount of PC-specific antibody. Interestingly, the idiotypically-suppressed BALB/c mice mounted a significant anti-T15 response during the primary response to Pn. We interpreted these data as showing that the level of circulating idiotype may regulate the production of the complementary anti-idiotypic antibody. In addition, in vitro experiments demonstrated that the lack of the anti-T15 response during primary antibody response in BALB/c mice is probably because of a state of tolerance that is regulated by T cells.

A syngeneic idiotype is immunogenic when borne by IgM but tolerogenic when joined to IgG

Some syngeneic monoclonal antibodies (mAb) elicit immune responses like conventional T-dependent antigens. To find out whether the heavy chain class (isotype) plays a role for the immunogenicity of an idiotype (Id), we isolated rare subclones of an IgM mAb (termed Id3) in which the variable region of the heavy chain (VH) is associated with a new constant region (CH). The VH-Id3 gene is a member of the murine 36-60 family and probably has three replacement mutations. The light chain V gene is germ-line V lambda 2. IgM, IgG1, IgG2a and IgG2b variants of Id3 were purified from protein-free medium and injected without adjuvant into BALB/c mice. The parental 19S IgM mAb given subcutaneously (s.c.) elicited a vigorous humoral response against Id3; in comparison, monomeric 8S IgM was a much weaker immunogen. Unlike IgM, multiple challenges with the IgG switch variants failed to induce anti-Id3 Ab. IgG variants gained immunogenicity if they were purified from medium containing fetal calf serum, mixed with complete Freund's adjuvant or injected into mice primed with IgM-Id3. Pretreatment with 100 micrograms s.c. + 50 micrograms of the IgG2a variant extinguished the Ab response to parental IgM, but the response to adjuvant-free bovine serum albumin was intact. Therefore, the tolerance induced by the IgG2a switch variant is antigen-specific and not due to toxicity. Significant inhibition of the Ab response to parental IgM was observed after treatment with 4 micrograms of the IgG2a switch variant. Administration of the IgG1 and IgG2b switch variants also inhibited this response significantly. Thus, the outcome of an encounter with Id3 is strongly influenced by the CH isotype to which the Id is joined. This suggests novel ways to minimize unwanted Ab responses against Id of human therapeutic mAb. In the context of the theory of Id networks, we suggest that dominant B cell clones can preempt anti-Id Ab responses against themselves by early switching from IgM to IgG secretion, before immunogenic IgM Ab have had time to activate anti-Id B cells.

Maternal immunization modulates the primary immune response to 2-phenyl-oxazolone in BALB/c mice

The development of the antibody repertoire in newborn mice is greatly influenced by idiotype network interactions. It has been demonstrated that anti-idiotypic antibodies either directly injected or transferred from the mother may alter the repertoire for life. For an elucidation of the underlying mechanisms we have analyzed the primary immune response to 2-phenyl-5-oxazolone (phOx) coupled to chicken serum albumin (CSA) in BALB/c mice after complete disappearance of maternal antibodies which originated from different stages of affinity maturation. Depending on the serum titers of the mothers after primary (1 degree mo), secondary (2 degrees mo) or tertiary (3 degrees mo) immunization, maternal anti-phOx IgG persisted in F1 mice for up to 9 months. In addition, F1 mice born to 2 degrees mo developed--even without immunization--an anti-phOx IgM titer which reached levels similar to an antigen-induced primary response. An enhancement of the early primary anti-phOx as well as anti-CSA response was seen in F1 mice born from 1 degree mo, whereas the response was delayed when born to 2 degrees mo and 3 degrees mo. The antibody titers in the latter group of mice remained at a lower level for 3 months. In contrast, mice of the F2 generation which received a smaller amount of the same collection of maternal antibodies as F1 mice from 3 degrees mo exhibited a quite different primary response: (i) They showed an earlier onset in their anti-CSA response. (ii) Whereas normally a plateau in antibody titer was reached by the 4th weak after immunization, in 55% of the F2 mice a prolonged increase of the anti-phOx and anti-CSA antibody titers was observed. At 12 weeks after antigenic challenge, titers reached plateau levels of 6 x 10(5) which were never before seen in a primary phOx or CSA response. Thus, depending on its own immunological experience, the maternal immune system induces a state of memory in the offspring which results in a faster and/or enhanced immune response in the F1 and F2 [corrected] generations.

Comparison of junctional diversity in the neonatal and adult immunoglobulin repertoires

Junctional diversity in immunoglobulin (Ig) from an adult mouse contributes significantly to the size of the final Ig repertoire. In adult pre-B cells, N region addition and deletion of nucleotides form coding regions produces very heterogenous CDR3 sequences. In contrast, Ig from fetal and newborn mice show very restricted junctional diversity. The reasons for this are: (a) the lack of N regions; and (b) the predominance of certain junctional sequences. These common junctional sequences all appear to occur by targeted rearrangement to short stretches of sequence homology near the ends of the segments to be joined. Targeted rearrangement may play a role in the overexpression of certain Vh genes early in ontogeny. These non-random junctional sequences in the neonate will reproducibly create certain Ig, for example, the dominant T15 anti-PC antibodies. Thus the immune system first creates a small repertoire of predictable Ig sequences. To the extent that these Ig are expressed in long-lived B cells, these early Ig sequences may persist in the adult. Superimposed upon this early repertoire is an enormously diverse adult Ig repertoire.

In vivo effects of neonatal administration of antiidiotype antibodies on experimental autoimmune myasthenia gravis

The in vivo effects of neonatal administration of varying doses of anti-idiotype antibodies on serum anti-acetylcholine receptor (AChR) antibody titers, idiotype expression, and disease severity was studied in experimental autoimmune myasthenia gravis. Polyclonal affinity purified anti-idiotype antibodies and monoclonal anti-idiotype antibodies directed at anti-AChR monoclonal antibody 65 were administered in dosages varying from the nanogram to the microgram range. Mab 65 is directed against the main immunogenic region of mammalian AChR. In 1 out of 4 experiments administration of a nanogram dosage of anti-idiotype antibodies led to an enhanced anti-AChR antibody response after immunization with AChR. But no enhancing effect on idiotype expression could be demonstrated during this experiment. Adoptive transfer of spleen cells from rats pretreated with a nanogram dosage of anti-idiotype antibodies resulted in an significantly increased antibody response against rat AChR after immunization. From these experiments we conclude that in vivo administration of polyclonal or monoclonal anti-idiotypes does not reproduceably modify the serum antibody level against the acetylcholine receptor, nor influences the idiotype profile of the immune response. Secondly, the idiotype mediated manipulation of the immune response against large antigens, like the acetylcholine receptor, is clearly more complicated than that against small haptens. Adoptive transfer models, might be helpful in analysing the possibilities of anti-idiotype treatment in myasthenia gravis in more detail.

Idiotype-directed interactions during ontogeny play a major role in the establishment of the adult B cell repertoire

IgM hybridomas derived from perinatal B cells show a high degree of auto-reactivity and many had demonstrable anti-idiotypic reactivities by binding studies. Selected multispecific antibodies were also shown to have potent idiotype-specific biological activities and if administered at appropriate stages of development could dramatically alter the responses of these mice when challenged with appropriate antigens in adult life. The results obtained suggest that idiotype-directed interactions between neonatal B cells play an important role in the early establishment of the B cell repertoire which is subsequently expressed in adult mice.

In vivo suppression of perinatal multispecific B cells results in a distortion of the adult B cell repertoire

The isolation of multispecific B cell hybridomas with a variety of anti-idiotype (anti-Id) activities from the lymphoid organs of fetal and neonatal BALB/c mice suggested that the development of the immune system may depend on Id interactions among autologous B cells. In vitro analysis of antibodies secreted by these hybridomas showed extensive sharing of an idiotope defined by the monoclonal antibody FD5-1. Early and timed administration of this antibody during the perinatal period results in a distortion of the phosphorylcholine (PC) and alpha (1----3)dextran (Dex)-specific B cell precursor compartment of the developing repertoire and is reflected by a drastic reduction of antibody responses to these antigens when challenged as adults. These observations provide strong evidence for the involvement of the early appearing multispecific B cells in Id interactions that bring about the uniform development of the normal adult B cell repertoire. Interference with these interactions at critical stages of developmental results in permanent deficiencies in the adult B cell repertoire.

A role for antiidiotypic antibodies in immunologically mediated nephritis

In summary, evidence exists that immunologically mediated renal diseases can be modulated by interfering with the mechanism of production of autoantibodies by specific antiidiotypic immunity. However, more studies are necessary to establish efficient and safe parameters from which to suggest such treatment in human immune nephritides. Although the evidence is still circumstantial, it is necessary to keep in mind that antiidiotypic antibodies may also add to glomerular immune deposits and potentially could contribute to the chronicity of some forms of immunologic nephritis. The fate of the majority of immunologic nephritides is a slow progression toward end-stage renal insufficiency. Although in most cases the etiology remains to be determined, it is generally felt that a better understanding of the initial immune dysregulation may lead to a greater possibility of control and cure. In this perspective, new directions of research, such as the one reviewed here, should be considered. Modulation of the damaging autoimmune responses in SLE or Goodpasture's Syndrome might be possible. For instance, the identification of a cross-reacting idiotype among anti-GBM antibodies would be the first step for a possible future use of natural or synthetic idiotypes for autovaccination purposes. Antiidiotype antibodies, particularly in the form of monoclonal chimaeric (mouse/human) hybridomas, could be utilized for passive immunosuppression, particularly in combination with plasmapheresis, with or without conventional immunosuppressive drugs. Clearly, this is part of a long-term process that may or may not be realized. The success of new forms of specific immunologic treatment for kidney diseases may ultimately depend upon ongoing efforts in the study of the new molecular aspects of regulation of potential nephritogenic immune responses.

Suppression of established IgE antibody responses with isologous anti-idiotypic antibodies in guinea pigs

Guinea pigs of strains 2 and 13 can produce isologous anti-idiotypic (aIds) antibodies against anti-benzylpenicilloyl (anti-BPO) IgG, following immunization with affinity-purified anti-BPO antibodies of the same strain. The specificity of aId was determined by inhibition of binding of aId to Fab(t) in ELISA. The results showed that the reaction of strain 2 (anti-BPO)aId can be inhibited with syngeneic anti-BPO Fab(t) and to a smaller degree with anti-BPO Fab(t) of strain 13. On the other hand, strain 13 (anti-BPO)aId reacted exclusively with syngeneic anti-BPO Fab(t). In both cases, binding of aId to anti-BPO Fab(t) could not be inhibited with BPO-epsilon-aminocaproic acid, indicating that these aId are not directed against the antigen-combining site. The effect of isologous aId on both short- and long-time established IgE responses was studied in guinea pigs of strain 13. In both situations, administration of isologous aId resulted in suppression of the anti-BPO IgE antibody response. The suppressive effect was antigen-specific and lasted for several weeks: in the case of an early-response IgE remained suppressed despite additional booster injections of antigen. In contrast to the IgE response, the production of anti-BPO IgG antibodies was only slightly affected.

Effect of passive administration of alloantiserum containing antibody against putative acceptor(s) for T cell-replacing factor (TRF) in the neonatal stage on development of B cell activity responsive to TRF

Previously, we showed that the antiserum raised in male (DBA/2Ha X BALB/c)F1(DCF1) mice (T cell-replacing factor [TRF]-low response animals) by immunizing them with activated B cells from BALB/c mice (TRF-high-responders) contained antibodies against putative TRF-acceptor site(s). We have now evaluated the hypothesis that neonatal treatment of mice with the above antiserum suppresses the development of B cells responsive to TRF. Male DCF1 mouse anti-BALB/c B-cell antiserum or normal DCF1 mouse serum as a control was injected into BALB/c mice within 24 hr after birth. In the antiserum-treated mice, no augmented primary immunoglobulin M (IgM) antibody responses to sheep red blood cells (SRBC) were observed under the conditions in which markedly augmented IgM anti-SRBC responses were induced in control BALB/c mice, suggesting that development of B cells reacting with male DCF1 mouse anti-BALB/c B-cell antiserum is suppressed by the neonatal treatment with the antiserum. Furthermore, the development of B cell activity responsible for helper factors derived from T cells, such as TRF, was markedly suppressed in the neonatally antiserum-treated mice, whereas activity of B cells capable of interacting directly with helper T cells through antigen-bridges was not significantly affected by the same treatment. Such suppression of the B cell activity could be induced only when the antiserum was administered within 48 hr after birth. Moreover, neonatal treatment of mice with the antiserum induced suppressed responsiveness of B cells to a T-independent type 2 antigen, TNP-Ficoll. Neither serum-borne suppressive serum components nor suppressor cells were detected by the system employed. These results support the hypothesis that TRF responsive B cells constitute a subpopulation distinct from the other B cells capable of cooperating with helper T cells via cognate interaction.

Cellular basis for neonatally induced T-suppressor activity. Primary B cell maturation is blocked by suppressor-helper interactions restricted by loci on chromosome 12

The cellular mechanism and genetic restriction of neonatally induced HA-specific suppressor T (Ts) cells have been examined. The in vivo effect of these Ts cells on antibody production, primary B cell proliferation, B cell surface marker changes, and helper T (Th) cell priming during primary responses to HA have been determined. The results indicate that, although antigen-induced B cell proliferative responses and surface marker changes occur in the presence of Ts cells, differentiation to Ig secretion, and long-lived memory B cell production are prevented. Further, antigen-specific Th cell priming is completely ablated by Ts cells, suggesting that Ts act by preventing the delivery of Th signals required for both the later stages of primary B cell maturation, and the formation of memory B cell populations. Finally, in vivo cell mixing experiments using congenic mice indicate that this Ts-Th interaction is restricted by loci on mouse chromosome 12.

Cloning of mitogen- and antigen-reactive B lymphocytes on filter paper discs. I. A description of the technique and of methods for the analysis of colonies

A novel technique for establishing short term clones of antigen- or mitogen-activated splenic B lymphocytes is described. Spleen cells are plated onto the surface of filter paper discs and subsequently stimulated by antigen or mitogen in situ; activated B cells proliferate and differentiate into pure colonies of cells analogous to bacterial colonies growing on agar. These colonies of lymphocytes may be characterized in a series of replica hemolytic-plaque, autoradiographic, or immunoenzyme assays making possible a full characterization of the frequency of secreted idiotopes and paratopes and of the cells that produce them. Colony induction by either antigen or mitogen occurs under identical conditions, thus a rigorous comparison between the mitogen-selected and antigen-selected antibody repertoires may be made.

Idiotypic networks and other preconceived ideas

The preceding section implies that the immune system (like the brain) reflects first ourselves, then produces a reflection of this reflection, and that subsequently it reflects the outside world: a hall of mirrors. The second mirror images (i.e., stable anti-idiotypic elements) may well be more complex than the first images (i.e., anti-self). Both give rise to distortions (e.g., mutations, gene rearrangements) permitting the recognition of nonself. The mirror images of the outside world, however, do not have permanency in the genome. Every individual must start with self. Paraphrasing Nicolas Schöffer (Schöffer 1982): those who always seek exterior pressures (e.g., microbes) to account for the evolution of the sets of V genes, would do well to turn their vision towards the interiors of themselves, and there discover the mystery, perhaps never completely revealable, of the immune system.

Antibodies specific for different T15 idiotopes induce neonatal suppression of the T15 idiotype

The response of BALB/c mice to Pneumococcus pneumoniae is dominated by a single idiotype defined by the phosphorylcholine-binding myeloma protein TEPC 15 (T15). Injection of newborn BALB/c mice with antibodies to the T15 idiotype will lead to suppression of this idiotype. Such mice will respond to the antigen Pneumococcus, but with idiotypically different anti-phosphorylcholine antibodies. In an attempt to further characterize the effect of anti-idiotypic antibodies on induction of tolerance, three monoclonal antibodies specific for different T15 idiotopes were used. Although these antibodies belonged to the mouse immunoglobulin classes, IgG1 or IgG2 alpha, and were derived from different mouse strains, in all cases, a long lasting suppression could be induced. The data show that injection of idiotope-specific antibodies will suppress the T15 idiotype, but not necessarily the idiotope itself. The results are discussed in terms of the mechanism which will lead to the suppression of a dominating idiotype in the newborn mouse.

Induction of idiotype-specific suppressor T cells with antigen/antibody complexes

The effects of immune complexes on the antibody response of BALB/c mice to Streptococcus pneumoniae R36a (Pn) were investigated. The cell wall polysaccharide (PnC) extracted from Pn was used to form complexes with TEPC-15, a myeloma protein that binds to phosphorylcholine determinants on the PnC. Complexes formed at equivalence were cultured with splenic T cells from BALB/c mice for 2 d, and then the cells were added to fresh BALB/c spleen cell cultures to test their effect on the antibody response to Pn, a response dominated by the T15 idiotype family. The results indicate that TEPC-15/PnC complexes induced potent suppressor T cells (Ts) whereas cells cultured with free antigen or free antibody alone had no effect on the plaque-forming cell response to Pn. The suppression was specific since the response to control antigens such as sheep erythrocytes was unaffected. The suppression appears to be idiotype-specific since the Ts had a relatively weak (and in some cases no) effect on the anti-Pn response of BALB/c mice that had been suppressed for T15 idiotopes by neonatal injection of a monoclonal anti-T15 antibody, MaId 5-4. Furthermore, cells cultured with TEPC-15/PnC complexes were shown to express specific receptors for TEPC-15 idiotopes. The results indicate that antigen/antibody complexes may have important immunoregulatory effects because they are potent inducers of idiotype-specific Ts.

Thymus-independent induction and antigen-dependent recovery of idiotype-specific suppression

BALB/c nude (nu/nu) mice and euthymic (nu/+) littermates were treated as neonates with anti-T15 antibody and challenged at various ages with either a thymus-independent, PC-Brucella abortus (PC-BA), or thymus-dependent, PC-keyhole limpet hemocyanin (PC-KLH), form of phosphorylcholine (PC). Nu/nu mice challenged with PC-KLH received KLH-primed splenic T cells prior to immunization. Neither neonatally anti-idiotype-treated nu/+ nor nu/nu mice responded with the production of T15-positive anti-PC antibodies after challenge with either form of PC antigen. It is concluded that neither induction nor maintenance of a state of T15-specific suppression requires thymus-matured T cells. Recovery of anti-PC responsiveness in suppressed nu/+ or nu/nu mice was similar and was found to be related to the form of antigen used to elicit the response. Immunization with PC-KLH revealed a long-lasting unresponsiveness (up to 16 weeks). In contrast, immunization with PC-BA elicited a full anti-PC response as early as at 6.5 weeks of age.

Immunoglobulin idiotopes expressed by T cells. I. Expression of distinct idiotopes detected by monoclonal antibodies on antigen-specific suppressor T cells

The idiotopic repertoire expressed by antigen-specific suppressor T cells (Ts) generated by Streptococcus pneumoniae strain R36a (Pn) in BALB/c strain mice was investigated using a panel of five monoclonal anti-idiotopic antibodies against TEPC-15/HOPC-8 myeloma proteins. Previous studies suggested that the anti-idiotopic antibodies recognize distinct idiotopic determinants within the T15 idiotype, and that Pn-reactive B cells express all of those idiotopes as shown by a specific inhibitory effect of the anti-idiotopic antibodies on induction of anti-Pn response in vitro as well as on the mature antibody plaque-forming cells. In this study we asked the question of whether anti-idiotopic (Id) can block the inductive and/or effector phases of generation of Ts which act on the Pn-reactive B cells. The presence of anti-Id during the activation of T cells with Pn did not prevent the generation of Ts. However, suppression mediated by Ts on responder lymphocytes (cultures of spleen cells or B cels) was inhibited (reversed) by four out of five anti-Id. Some of the antibodies recognize hapten (phosphorylcholine)-inhibitable Id in the paratope of Ig whereas others are directed against nonparatopic Id. These data indicate that the antigen receptor on Ts includes VH sequences both within and without the immunoglobulin in paratope, and that the Id repertoir of Ts overlaps with that of B cells.

Expression of a distinct B cell clonotype profile after recovery from antigen-induced unresponsiveness

The purpose of these experiments was to determine whether the B cell clonotype profile expressed in mice which have recovered from antigen-induced unresponsiveness is similar to that of nontolerized mice. Unresponsiveness to phosphorylcholine (PC) was initiated by injection of neonatal mice with PC-coupled human gamma globulin, resulting in the inability to respond to challenge with PC-lipopolysaccharide at 1.5 months of age. By 3 months of age, pretreated mice were 50% responsive while by 5 and 7.5 months of age, full responsiveness was observed. At each time point two differences distinguished the anti-PC antibody from nonpretreated mice. First, whereas nonpretreated mice displayed T15 dominance, pretreated mice did not. Second, the average avidity of T15-negative antibody produced in pretreated mice was greater than that in nonpretreated mice and similar to that of T15-positive antibody. Possible mechanisms for this "permanent" alteration of the antibody profile are discussed.

Idiotypic characterization of antibody-induced antibody responses

Anti-idiotypic antisera were produced in syngeneic (C57BL/6) mice against a monoclonal anti-Dextran B512 (Dex) antibody (38-13). In radioimmunoassays, anti-idiotypic antibodies were shown to react with the homologous idiotype, while failing to recognize another monoclonal anti-Dex antibody, independently derived from C57BL/6 mice (D-16). Plaque inhibition tests confirmed the specificity of the anti-idiotypic antibodies and revealed that the 38-13 idiotype is expressed by about half of all anti-Dex antibodies produced in C57BL/6, but not in CBA mice. Injection of normal (but not athymic) C57BL/6 mice with low doses of 38-13 monoclonal antibodies, contained culture supernatants or ascitic fluids, resulted in a 10-20 fold increase in the numbers of anti-Dex PFC detected in the spleen 5 days later, the majority of which carried the 38-13 idiotype.

Antigen-independent, IgM-induced antibody responses: requirement for "recurrent" idiotypes

Anti-idiotypic antibodies (a-Id) were produced in syngeneic mice against two monoclonal IgM antibodies of BALB/c origin, TNP. 11 and SP/603. In plaque inhibition tests, using IgM-secreting hybridoma cells and anti-idiotypic antibodies, these two IgM proteins, as well as the anti-TNP myeloma protein MOPC 460 (IgA) were found to carry non-cross-reactive idiotypes. Analysis of the anti-trinitrophenyl (TNP) plaque-forming cells (PFC) in BALB/c mice, either normal or immunized with TNP-horse red blood cells, revealed that in addition to the MOPC 460 Id, also the SP/603 Id is recurrent and expressed by a fraction of the anti-TNP antibody-secreting cells in all individuals tested. In contrast, the TNP. 11 Id could not be detected in any BALB/c mouse studied. TNP. 11 and SP/603 antibodies were then characterized by their ability to induce an antigen-independent anti-TNP response in normal BALB/c mice. While TNP. 11 was found to be inactive, the same titers of SP/603 IgM induced antigen-specific PFC all of which expressed the SP/603 Id, and increased titers of circulating IgM molecules carrying the same Id, suggesting that "recurrent" but not "nonrecurrent" Id are competent in this respect. A fraction of these SP/603-induced, SP/603-positive anti-TNP antibodies also carried MOPC 460 Id, suggesting expression on the same molecule of idiotypic determinants found on independent non-cross-reactive "recurrent" idiotypes.

Generation of idiotype-specific T cell help through network perturbation

Different manipulations of BALB/c mice were used to generate idiotype-specific help: neonatally induced suppression of the T 15 idiotype and low-dose priming with anti-T15 antibody. The splenic foci culture system was used to study T15-idiotype-recognizing helper T cells under limiting-cell-dose conditions. These treatments induced T15 idiotype-specific help for B cells responding to TNP-T15. Normal or hemocyanin-primed BALB/c mice did not supply T15 idiotype-specific help. The helper cells were sensitive to anti-Thy-1.2 and complement treatment and can distinguish T15 from an idiotype-different, PC-binding myeloma protein, M167, and the TNP binding myeloma protein, M460. These data show that idiotype-specific T helper cells can be induced by at least two different manipulations of the idiotype network. These manipulations presumably do not act directly on the T15-recognizing T cells, but must involve complementary idiotypic circuits that stimulate anti-T15 specific T cells. Furthermore, this study demonstrates that the splenic-fragment culture technique provides a general method to investigate, at the single cell level, idiotypic T-B cell interactions induced by perturbations of the immune network.

Alteration of clonal profile. II. Studies on the capacity of BALB/c splenic B cells to perpetuate responsiveness to phosphorylcholine and T 15 idiotypic dominance

(CBA/N x BALB/c)F1 hybrid male mice are unable to mount anti-phosphorylcholine (PC) plaque-forming cell (PFC) responses because they carry the CBA/N X-linked immune defect of B lymphocyte differentiation. Transplantation of splenic B cells from BALB/c mice restores responsiveness to thymus-dependent and thymus-independent PC antigens up to 8 months after cell transfer. Cytotoxicity studies demonstrate the donor origin of PFC generated in reconstituted (CBA/N x BALB/c)F1 mice. Although responsiveness to PC is restored permanently, a shift in idiotype expression that leads to the loss of T 15 idiotypic dominance 3 months after cell transfer can be detected. This shift originates from Ig- cells because Ig+ splenic cells purified in a fluorescence-activated cell sorter maintain T 15 dominance. Therefore, the Ig+ cells have a remarkable capacity to maintain responsiveness to antigens and can perpetuate idiotypic dominance if the stem cell pool is removed.

Antiphosphocholine antibodies found in normal mouse serum are protective against intravenous infection with type 3 streptococcus pneumoniae

The antiphosphocholine (PC) antibody in normal mouse sera (NMS) provides protection against intravenous infection with encapsulated strain WU2 of type 3 Streptococcus pneumoniae. Mice unable to make anti-PC antibody, as a result of suppression with anti-T-15 idiotype or inheritance of the xid gene of CAB/N mice, are highly susceptible to infection with strain WU2. Mice inheriting the xid gene can be protected with NMS from immunologically normal mice or with IgM hybridoma anti-PC antibody. The protective effect of NMS can be removed with PC-containing immunoabsorbents.

Autoregulation of immune responses via idiotype network interactions

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