Expression of an idiotype (Id-460) during in vivo anti-dinitrophenyl antibody responses. II. Transient idiotypic dominance

In vivo IgE levels in exogenous antigen stimulated responses: measurement of total IgE as a valid, simple surrogate for Ag-specific IgE

Due to its dependence on IL-4 and IL-13 production, IgE production is frequently used to assess the type 2 character of an immune effector response. It is particularly relevant to measure IgE in murine models of immediate hypersensitivity, as allergen specific IgE is a critical effector molecule in this process. Given the complexity of developing ELISAs to measure specific IgE, total IgE levels are often reported with the implicit assumption that this provides an accurate gauge of specific IgE responses. Here, we rigorously test this assumption by examining the relationship between total and Ag-specific IgE levels in mice immunized to elicit a wide range of serum IgE responses. We identify a strong, consistent relationship between total and Ag-specific IgE, regardless of the phenotype of the immune response (type 1 vs. type 2 biased), the nature of the immune response (primary vs. recall), the genetic background of mouse strain examined (C57Bl/6, BALB/c or outbred CD1 mice), or the intensity of the initial immunological stimulus (0.2, 2.0 or 100 microg OVA). These findings indicate that measurement of total IgE levels through straightforward, easy to develop, total IgE ELISAs offers an appropriate surrogate for measurement of Ag-specific IgE levels, usually measured through the use of subjective PCA assays or Ag-specific IgE ELISAs.

Frequency of clonal dominance in the specific antibody response to DNP-HSA in CBA and C57BL mice reflects their susceptibility to age-associated development of monoclonal gammopathies

The effects of age, genetic background, and neonatal thymectomy on the levels and the heterogeneity of the specific antibody response were investigated in an experimental mouse model. Both intact and neonatally thymectomized (NTx) C57BL/KaLwRij (C57BL) and CBA/BrARij (CBA) mice were immunized at the age of 3 ("young") or 22 months ("old"). Highly sensitive antigen-specific immunoblotting techniques (ABL), in combination with agar-electrophoresis and isoelectric focusing (IEF), were used to investigate total specific antibody levels, the number of responding antigen-specific clonotypes, and the dominance of responding B cell clones in the antibody response against dinitrophenylated human serum albumin. After immunization, the specific antibody levels progressively increased in all experimental groups with the exception of old C57BL mice. All mice responded with a specific polyclonal heterogeneous response. In addition, some mice showed a clonal dominance of antibody-producing cells, as is reflected in the appearance of distinct homogeneous antibody components (H-Ab) in the sera. This clonal dominance was scarce in CBA mice but frequent in C57BL mice. Age at time of immunization and NTx had little if any additive effect on the incidence of H-Ab in either mouse strain. All dominant clones showed different electrophoretic mobility, indicating the proliferation of various clonotypes and not a strain-specific dominance of one clone. In old C57BL mice the specific antibody response was more restricted in heterogeneity, as is illustrated by more visible spectrotype bands in IEF and subsequent ABL. Hence, in old C57BL mice smaller amounts of specific antibodies were produced by fewer clones. Still, the incidence of H-Ab in this group was the same as that in the group of young C57BL mice. This indicates that at old age the responding B cell clones are more prone to becoming clonally dominant in C57BL mice. This tendency correlates with the high incidence of spontaneously developing monoclonal gammopathies in aging C57BL mice.

Moloney leukemia virus-induced cell surface antigen mimicry by monoclonal antibodies

We have investigated antigen-independent modulation of immune responses by monoclonal antibodies directed against both viral and nonviral antigens. BALB/c mice were immunized with monoclonal IgM (i.e. Ab1) specific for either Moloney murine leukemia virus-induced cell surface antigen (MCSA) or the hapten 2,4-dinitrophenyl (DNP). Injection with either Ab1 activated a functional idiotypic (Id) network as evidenced by production of both anti-Id (Ab2) antibodies and anti-anti-Id (Ab3) antibodies. A subset of induced Ab3 (designated Ab1'), exhibited specificity for antigen (virus or DNP). In mice immunized with anti-Id antibodies (Ab2), production of Ab3 and Ab1' was also observed. In the MCSA system, antibody-induced Ab1' responses were effective in protecting mice from tumor development upon subsequent challenge with live virus. Furthermore, antigen-independent modulation of immunity to both viral and nonviral antigens was found to be thymus-dependent. Similar findings in other viral systems suggest that antibody-induced activation of Id networks may prove a viable alternative vaccine strategy that can elicit antigen-specific responses, and in some cases protection, in the apparent absence of exposure to antigen.

Regulation of idiotype expression. II. The phenotypic diversity of T15 idiotype-bearing antibody to phosphorylcholine in response to T-dependent and T-independent antigens

The idiotypic (Id) diversity of the immune response to phosphorylcholine (PC) was studied by immunization of mice with thymus-dependent (PC-keyhole limpet haemocyanin; PC-KLH) and thymus-independent (S. pneumoniae R36a; Pn) forms of the antigen. Mice with the BALB/c genetic background (BALB/c, C.B20, and BALB.B) were used because their response to PC is dominated by immunoglobulins encoded in VH-1 and V kappa 22 genes, which uniformly express the T15 idiotype. The actual repertoire of the antibody was determined by idiotypic markers (Id) defined with monoclonal antibodies designated AB1-2, B36-82, MaId5-4, and B24-44. Previous studies from our laboratory have shown that these Id are present on T15 (VS107-1/V kappa 22) immunoglobulins only, but that they differentiate between somatic variants of the antibody molecules. We have measured the serum concentrations of these four Id after primary (1 degree), secondary (2 degree), and tertiary (3 degree) immunization; all of the Id activity was associated with the PC-binding antibody, as shown by specific immunoadsorbents. However, the levels of the Id-bearing (Id+) antibody did not correlate with each other. After immunization with PC-KLH, the AB1-2+ antibody declined precipitously, whereas the levels of B24-44 and B36-82 remained steady. A similar pattern of Id heterogeneity was seen at the level of direct antibody-plaque-forming cells from the spleen, suggesting that the idiotopic (clonal) diversification occurred already during the early IgM response. A significant portion of anti-PC antibody after the 3 degrees PC-KLH immunization was negative for all four Id, implying that the late response to the antigen involved distinct, T15-negative clones.

Comparison of the fetal and adult functional B cell repertoires by analysis of VH gene family expression

The functional B cell repertoire in BALB/c mice was assessed at various stages in ontogeny. This was done by analyzing VH gene family expression using the sensitive technique of in situ hybridization. The B cell repertoire was probed with the mitogen, LPS, and the antigen DNP. DNP was chosen because B cells responsive to this hapten appear very early in ontogeny. The APCs that developed after stimulation with LPS or DNP were analyzed for VH gene expression by in situ hybridization of individual cells using radiolabeled VH gene family probes. The results indicated that VH gene expression in fetal B cells after stimulation was distinct from adult B cells in that there was a biased expression of D proximal families. The results indicated that this bias was associated with developmental age and not a given differentiation stage in the B cell lineage. In addition, stimulation of fetal B cells with DNP resulted in a large increase in expression of member(s) of VH 36-60, suggesting that the early appearance of DNP-responsive B cells is not strictly correlated with preferential rearrangement of D proximal families, VH 7183 and VH Q52. However, the results suggested that a large proportion of pre-B cells that preferentially rearrange D proximal families early in ontogeny become part of the functional developing repertoire.

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.

Immune response to diphtheria toxin and to different CNBr fragments: evidence for different B and T cell reactivities

The antigenic structure of the diphtheria toxin has been studied in man. B and T cell responses to diphtheria toxoid and to different fragments of the toxin molecule were analyzed in 4 individuals one month after booster immunization. Studies on the B cell response showed that: part of the response was directed against assembled topographic sites; 80% of the response was directed against determinants present on fragment A; the few determinants present on the CNBr peptides of B cross-react with determinants present on A; and reduction of the second disulfide bridge of fragment B diminishes the response. In contrast to the antibody response, most of the T cell reactivity was directed against the B fragment or CNBr peptides from this fragment. Analysis of the fine specificity of T lymphocyte clones revealed that some CNBr fragments share common T cell determinants. These studies indicate that T and B cell determinants are differently distributed on the molecule and that large cross-reactivities that are not explained by the analysis of the amino acid sequence could be found at the B and T cell level.

Molecular characterization of antibodies bearing Id-460. II. Molecular basis for Id-460 expression

Id-460+ immunoglobulins can be induced in vivo by immunization with dinitrophenyl (DNP) or P. pneumotropica and form two nonoverlapping groups of antibodies with respect to antigen binding specificity. In this study, using Id-460+ antibodies of differing antigen binding specificities, we compared on the molecular genetic level the five gene segment combinations (VH, DH, JH, VL, and JL) that encode the variable regions of these idiotype-positive immunoglobulins. The Id-460 determinant appears to be a conformational or combinatorial determinant encoded by VH460 and VK1 crosshybridizing genes. DH, JH, and JK gene segments appear to have no measurable effect upon expression of Id-460. Finally, antigen binding specificity does not appear to simply localize to any particular gene segment but may in part be the result of somatic mutation and/or VDJH junctional sequences, whose length correlates roughly with antigen binding specificity.

Idiotypic properties of the murine anti-arsonate antibody response: B- and T-cell influences

In a previous report characterizing the arsonate (ABA)-specific plaque-forming cell (PFC) responses of A/J mice induced by ABA-KLH, two interesting characteristics of the idiotypic (Id) profile were noted: (1) an apparent Id selectivity in the isotype switch since the earliest appearing IgG PFC in the primary response were significantly more "cross-reactive Id" (CRI)-dominant than the IgM PFC population, and, (2) a temporal waning of CRI dominance with time among IgG PFC, from 75-100% CRI+ PFC to about 25-45% CRI+ PFC in secondary responses. Experiments were performed to determine whether these effects are largely attributable to T or to B cells. Mice were immunized with a T-independent (TI) form of ABA (ABA-Brucella abortus) and apparent Id selectivity was observed; the earliest IgG PFC averaged 75% CRI+ while IgM PFC were only 39% CRI+. Due to the TI nature of the Ag, this provides suggestive, but not conclusive, evidence that the Id asymmetry in the isotype switch may be attributable to the direct interaction of Ag with B cells. Other studies addressed the temporal shift in CRI dominance. First, it was found that preexposure of mice to either KLH or to ABA (on an irrelevant carrier) resulted in diminished CRI dominance in subsequent "primary" responses to ABA-KLH. Secondly, adoptive transfer experiments with B and T cells from virgin mice (Bv, Tv) or ABA-KLH-primed mice (Bp, Tp) showed that recipients of Bv + Tp or Bp + Tv generated anti-ABA PFC responses with intermediate CRI levels. The Tv cells had some preferential tendency to activate CRI+ clones in the Bp population. The results demonstrate that CRI levels are jointly determined by the immune status of both B and T cells. A simple model is offered which accounts for early Id dominance and its gradual decline and has as its central postulate the assumption that CRI+ B cells in the virgin ABA-specific repertoire have an affinity advantage over CRI- clones.

Immunodominant protein epitopes. II. The primary antibody response to hen egg white lysozyme requires and focuses upon a unique N-terminal epitope

The antibody response to a defined protein antigen, hen egg white lysozyme (HEL) has been investigated using an aminopeptidase-treated HEL molecule, des-1,2,3-HEL (AP-HEL). Surprisingly, removal of these three N-terminal residues eliminates an epitope which is a dominant B cell determinant recognized in the primary antibody response to HEL. Thus, the initial antibody response focuses on a very small region of the molecule. Even more striking is the observation that removal of this epitope markedly reduces the immunogenicity of HEL. Therefore, the epitope is not only the focus of the primary antibody response, but is essential for the initiation of the response. This report demonstrates that a selective mechanism must be activated during the response to this protein antigen. Of the multitude of B cell determinants present on HEL, only a limited number are focused upon by the immune system.

Non-dinitrophenyl-binding immunoglobulin that bears a dominant idiotype (Id460) associated with antidinitrophenyl antibody is specific for an antigen on Pasteurella pneumotropica

We have previously described an idiotype (Id460) that transiently dominates anti-2,4-dinitrophenyl (DNP) antibody responses of mice that possess the appropriate Igh-V and V kappa genotypes. Normal serum has significant levels of Id460 that does not bind DNP, and hybridomas derived from spleen cell fusions that produce monoclonal antibodies with these characteristics have been generated. Many of these monoclonal, Id460-positive antibodies bind the opportunistic mouse pathogen Pasteurella pneumotropica. P. pneumotropica induces a marked increase in serum Id460 titers without significantly increasing serum anti-DNP titers. Both normal serum and P. pneumotropica-induced Ig460-positive immunoglobulin specifically bind to P. pneumotropica. These results suggest that the normal serum Id460-positive immunoglobulin is induced by environmentally encountered antigens on P. pneumotropica. We propose that this naturally occurring Id460 activates antiidiotypic regulatory cells that in turn promote production of Id460-positive anti-DNP antibody following DNP-ovalbumin immunization. These data are compatible with those obtained in several other idiotypic systems that suggest that dominant idiotypes may be associated with antibodies that have been evolutionarily selected for expression because of their specificity for antigens on environmentally encountered pathogens.

Allotypic restriction of the expression of MOPC460 idiotope after immunization with either anti-2,4-dinitrophenyl (DNP) or anti-idiotypic antibodies

The MOPC460 idiotype is expressed in mice with the IghCa allotypic haplotype after anti-2,4-dinitrophenyl (DNP) immunization. We have previously shown that two monoclonal syngeneic anti-idiotypic antibodies (IDM 92-13 and IDM 41-27) define two distinct idiotopes (the 460.92 and the 460.41) on the M460 idiotype. The current study demonstrates that only one idiotope (460.92) is recurrently expressed after antigen immunization in IghCa positive mice and also that, immunization against the monoclonal anti-idiotypic molecules induces the synthesis of 460.92 idiotope positive anti-DNP antibodies. However, the detection of such molecules is only possible when animals with the IghCa allotypic haplotype are immunized with the IDM 92-13 molecules. Immunization of mice with either of the two monoclonal anti-idiotypic antibodies never results in the synthesis 460.41 positive molecules. Therefore, whatever protocol of immunization used, the expression of 460.92 was allotypic restricted.

Incomplete expression of the MOPC 460 idiotype in the sera of BALB/c mice immunized either with DNP antigen or with anti-idiotypic antibodies

The MOPC 460 idiotype, as defined by polyclonal probes, has been described as a recurrent marker among the anti-DNP antibodies synthetized by IghCa mice. In this paper, we demonstrate, using syngeneic monoclonal anti-idiotypic probes, that only a part of the idiotopes of this idiotype are indeed recurrently expressed in BALB/c mice (IghCa) after immunization with DNP antigen. We will also show that the immunization of BALB/c mice with monoclonal anti-idiotypic antibody specific for the recurrent determinant results firstly in the synthesis of anti-DNP antibodies and secondly in the expression of the same recurrent M460 idiotope present on a part of induced anti-DNP molecules. Contrary to this, the immunization with the monoclonal anti-idiotypic antibody specific for the private idiotope never resulted in the synthesis of anti-DNP antibodies. These results clearly suggest that, after DNP or anti-idiotypic immunization, the M460 idiotype is not expressed in its entirety.

Expression of defined idiotypes throughout the BALB/c anti-fluorescyl antibody response: affinity and idiotype analyses of heterogeneous antibodies

Heterogeneous BALB/c anti-fluorescyl antibodies were shown to display increases (greater than 50-fold) in binding affinity from the primary through the tertiary responses. The structural basis of such affinity maturation and the diversity exhibited by anti-fluorescyl antibodies was examined by idiotypic analysis using a panel of anti-idiotype reagents specific for seven different monoclonal antifluorescyl antibodies. Because these clones exhibited binding affinities characteristic of a secondary or hyperimmune response, it was possible to examine the mechanism of affinity maturation by determining the prevalence of the seven idiotypes (Id-4-4-20, Id-20-19-1, Id-20-20-3, Id-6-10-6, Id-20-4-4, Id-4-6-10 and Id-6-19-1) in specifically purified heterogeneous preparations with low (i.e. primary response) or high (i.e. secondary and tertiary responses) binding affinities. Four of the idiotypes were not detected in heterogeneous preparations and thus each represented less than 0.1% of the total anti-fluorescein repertoire. Although results indicated that each of three other clones expressed unique or private idiotypic determinants not present in the heterogeneous population, these idiotypes (Id-4-4-20, Id-6-10-6, Id-6-19-1) were detected and ranged from approximately 0.2 to 2.0% of the repertoire. However, results indicated that each clone expressed unique or private idiotypic determinants not present in the heterogeneous population. Determinants expressed by such high-affinity monoclonal antibodies were expressed equally in all heterogeneous preparations examined. Because those determinants which were expressed were found in either low- or high-affinity heterogeneous antibodies, it is likely that the higher affinities exhibited by monoclonal antibodies derived from a secondary response are associated with unique idiotypic determinants which were not detected in polyclonal preparations. Hence, the process of affinity maturation may find as its structural correlate a mechanism such as somatic mutation which generates individual or unique idiotypes.

Use of anti-idiotype immunosorbents to isolate circulating antigen-specific T cell-derived molecules from hyperimmune sera

We immunized four different sheep with antigen-binding material found in the serum of BALB/c mice 4 days after primary immunization with sheep erythrocytes (SRBC). The resultant antibodies made by the sheep contained a specificity(ies) that appeared to react with a dominant idiotype present on SRBC-specific Lyt-2+ T cells. The antiserum made by the sheep markedly inhibited the formation of antigen-specific rosettes by SRBC educated T cells but did not inhibit T cells educated to other heterologous erythrocytes from forming crossreacting rosettes with SRBC or specific rosettes with the homologous erythrocytes. The "anti-Id serum" was depleted of all activity against known immunoglobulin isotypes and light chains and then was used to isolate antigen-binding molecules from mice that were hyperimmunized with SRBC. The ShId+ material so isolated could be divided into two main groups--one that expressed immunoglobulin determinants, and one that did not. The former represented 15-25% of the ShId+ protein isolated and comprised a minority of the anti-SRBC antibody in the anti-SRBC serum; the latter group of proteins bound sheep glycophorin specifically and expressed constant region determinants found on a number of other antigen-specific T cell factors. These experiments suggest that antigen-binding molecules made by T cells display much less heterogeneity than do antibodies and also show that the serum of hyperimmune mice contains significant amounts of T cell-derived antigen-specific immunoregulatory molecules.

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 an idiotype (Id-460) during in vivo anti-dinitrophenyl antibody responses. III. Detection of Id-460 in normal serum that does not bind dinitrophenyl

Using an anti-idiotypic antibody previously characterized as specific for the hapten binding site of the 2,4-dinitrophenyl (DNP)-binding BALB/c myeloma protein MOPC-460, we have detected substantial amounts of this idiotype (Id-460) in the serum of normal mice. Whereas the idiotypic material in DNP-immune serum binds to DNP, the Id-460-positive material in normal mouse serum is not specific for DNP. The material in normal serum appears to be immunoglobulin. Furthermore, Id-460-positive, non-DNP-binding monoclonal immunoglobulins that completely inhibit our assay for Id-460 are repeatedly isolated when hybridomas are prepared from LPS-activated normal spleen cells. These data are interpreted in the context of Jerne's network hypothesis. It is our conclusion that the non-DNP-binding form of Id-460 is the inherited form and that this form establishes an idiotypic network favoring the production of anti-DNP bearing Id-460. Thus, the paradox of finding an inherited idiotype in the antibody response to the nonpathogen DNP may be resolved by proposing that the true form of Id-460 is specific for an environmental pathogen and that Id-460 dominance in the anti-DNP response is simply a consequence of idiotype-specific regulatory events preconditioned by Id-460-bearing immunoglobulin specific for antigenic determinants unrelated to DNP.