Regulation of azophenylarsonate-specific repertoire expression. 1. Frequency of cross-reactive idiotype-positive B cells in A/J and BALB/c mice

Cross-reactions and specificities of monoclonal antibodies against myelin basic protein and against the synthetic copolymer 1

Antibody cross-reactivity is here demonstrated between basic protein (BP), the encephalitogenic molecule of myelin, and copolymer 1 (Cop 1), the synthetic amino acid copolymer, which has a suppressive effect on experimental allergic encephalomyelitis and is effective in reducing the number of relapses in exacerbating-remitting multiple sclerosis. This cross-reactivity is conclusively established using mouse monoclonal antibodies (mAbs). About a third of anti-rat BP mAbs and most of anti-mouse BP mAbs cross-reacted with Cop 1. This cross-reactivity could be demonstrated with anti-BP mAbs of different specificities. In addition, several anti-Cop 1 hybridomas cross-reacted with BP. This cross-reactivity was verified in several assay systems, including competitive inhibition experiments. Moreover, some anti-BP mAbs and anti-Cop 1 mAbs reacted in a heteroclitic manner and favored the cross-reactive antigen over the immunogen. In contrast to the mAbs, no cross-reactivity could be demonstrated with the antisera of immunized mice. This observation may reflect the different B-cell populations expressed in the mAb response as compared to the polyclonal response. Thus, the use of mAbs has uncovered specificities that are not evident in antisera and has revealed pronounced cross-reactivity between BP and Cop 1 at the B-cell level. These results further establish the immunological interrelationships between Cop 1 and BP, demonstrated earlier at the T-cell level.

In vivo induction of A/J anti-ARS responses with different ranges of affinities: correlation between affinity and CRIA idiotype dominance

The anti-ARS immune response of A/J mice is characterized by the reproducible and dominant selection of CRIA bearing antibodies. In this report, we have investigated the role of affinity for the antigen in the selection of antibody repertoire during an immune response. A/J anti-ARS responses with different ranges of affinities for arsonate were elicited by the injection of differently arsanylated carrier proteins. The selection of higher affinity A/J anti-ARS responses was shown to be associated with the induction of higher levels of CRIA bearing anti-ARS antibodies. A detailed idiotopic analysis also showed a more precocious selection of the CRIA "canonical combination" in the higher affinity anti-ARS responses. These results strongly suggest an important role for affinity and clonal selection in the dominant expression of the CRIA idiotype in the A/J anti-ARS response.

Novel rearrangements at the immunoglobulin D locus. Inversions and fusions add to IgH somatic diversity

IgH rearrangements (VH-D, D-JH) are central to the generation of antibody diversity. The majority of the diversity seen in the third hypervariable region is generated by the D segment and at the joints formed by both junctional and N segment variation during D-JH and VH-D rearrangements. The mechanisms that regulate rearrangement are thought to obey the 12/23 rule, wherein D-D or VH-JH rearrangements are precluded. Here, we present evidence that D-D fusions do in fact occur, either as direct or inverted rearrangements. The fused D segments so generated may be fully capable of proceeding in subsequent D-JH and VH-D rearrangements. The resultant VH-D-D-JH recombinations add another dimension to the potential repertoire of IgH V regions by increasing the level of combinatorial diversity and by providing additional sites for N region variation.

Altered expression of the Salmonella typhimurium-specific B-cell repertoire in mice chronically treated with antibodies to immunoglobulin D

Using a modification of the splenic focus assay, we analyzed the Salmonella typhimurium-specific B-cell repertoire in salmonella-susceptible BALB/c mice. Although these mice normally succumbed to salmonella infection before antibody was produced, they appeared to have splenic S. typhimurium-specific B-cell precursors that could be activated to differentiate and secrete antibody in a manner which was quantitatively and qualitatively identical to that of salmonella-resistant mouse strains. We also analyzed the primary S. typhimurium-specific B-cell repertoire in BALB/c mice that had been chronically treated with antibodies to immunoglobulin D (IgD) and therefore had no surface IgD-positive B cells. Although the frequency of S. typhimurium-specific precursors in these mice was similar to that of control mice, there was an apparent alteration in the isotype distribution pattern in anti-IgD-treated mice. Control mice generated a significantly greater proportion of IgG-secreting clones than did anti-IgD-treated mice. In addition, a greater proportion of S. typhimurium-specific clones from control mice secreted IgG2 than secreted IgG1, and those clones that secreted IgG2 but not IgM, IgG3, or IgG1 were greater than 20-fold more common in control than in anti-IgD-treated mice. Finally, we analyzed the immune response of control and anti-IgD-treated mice to a live avirulent vaccine, S. typhimurium SL3235. Although both groups were protected after challenge with a live virulent S. typhimurium strain, only the control mice made serum antibodies to this vaccine. Taken together, these results show that (i) salmonella-susceptible BALB/c mice have S. typhimurium-specific B cells, (ii) the S. typhimurium-specific B cells in anti-IgD-treated mice may have a restricted capacity to switch heavy-chain classes, (iii) the similarity observed in the frequency of the S. typhimurium-specific precursors for these two groups of BALB/c mice is not reflected in the serum, and (iv) the failure of anti-IgD-treated mice to generate a serum antibody response to SL3235 in the face of complete protection suggests that this model may be used to study cell-mediated immune mechanisms in the apparent absence of humoral immunity.

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.

Somatically mutated forms of a major anti-p-azophenylarsonate antibody variable region with drastically reduced affinity for p-azophenylarsonate. By-products of an antigen-driven immune response?

The pivotal role played by antigen in the clonal selection of B cells for initial participation in an immune response is well established. Antigen selective mechanisms ensure that antigen-binding antibodies are produced during all stages of the immune response. However, antibodies that lack specificity for the immunogen might also be produced during the course of an antigen-driven immune response . It has been suggested that, through idiotype-antiidiotype network interactions within the immune system, production of antibodies that lack specificity for the immunogen but that share idiotopes with antigen-binding antibodies could result (1). In addition, data obtained by a number of investigators suggest that somatic mutation of antibody V region genes occurs at a rate of 10(-3)/basepair/cell division in B cells participating in an immune response (2, 3). One outcome of such V region structural alteration could be antibodies that lack, or have drastically reduced affinity for the immunogen . We sought to identify and characterize some of the antibody by-products of the antigen-driven immune response that are expected to be created by the mechanisms described above.

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.

Influence of helper T cells on the expression of a murine intrastrain crossreactive idiotype

The requirement for idiotype-specific helper T (Th) cells in the generation of a major intrastrain crossreactive idiotype was investigated. This idiotype, designated CRIA, is associated with a large proportion of anti-p-azobenzenearsonate (anti-Ar) antibodies in A/J mice. Secondary in vitro responses were studied. Using carrier-primed heterogeneous Th-cell populations, it was found that CRIA expression is determined by the mouse strain that provides the responding B cells and is independent of the strain of the Th cells functioning in vitro. Thus, A/J or A.BY (Ighe) B-plus-accessory-cell populations, primed in vivo to keyhole limpet hemocyanin-Ar (KLH-Ar), generated CRIA-dominant responses in vitro in the presence of KLH-Ar regardless of whether the KLH-primed Th cells were derived from CRIA+ strains (A/J or A.BY, Ighe) or CRIA- strains (B10.A or C57BL/10, Ighb). Further, when major histocompatibility complex-restricted, KLH-specific Th-cell clones were used, the CRIA dominance of the Ar-specific responses was again determined by the strain providing B plus accessory cells. Similar levels of expression of CRIA in Ar-specific antibodies were generated in the presence of heterogeneous or cloned Th cells. The results suggest that there is no absolute requirement for idiotype-specific Th cells in generating an Ar-specific secondary antibody response in vitro.

Strain-specific silencing of a predominant antidextran clonotype family

The immune response to dextran is characterized by marked phenotypic differences among murine strains. In particular, Igha strains, as opposed to strains of other Igh haplotypes, respond relatively vigorously to dextran B1355 fraction S (DEX), producing predominantly antibodies bearing the lambda light chain, and specific for the alpha(1----3) glucose linkage. We have investigated this disparity in BALB/c (Igha) vs. C.B20 (Ighb) mice at the individual precursor cell level. Consistent with previous findings (7-9, 35, 40, 42, 43), there was a 10-fold higher frequency of lambda-bearing splenic B cells specific for the alpha(1----3) linkage in Igha mice. As with previously studied (25-27) predominant specificities, the origin of this high frequency of lambda-bearing alpha(1----3) DEX-specific B cells appears to be a reflection of a high expression of this specificity in surface Ig (sIg)-negative cells emerging from the bone marrow generative cell pool. Surprisingly, although C.B20 mice (Ighb) have a low frequency of lambda-bearing alpha(1----3) DEX-specific B cells in their mature primary splenic population, the frequency of precursor cells of this clonotype in their sIg- bone marrow cell population is equivalent to that of BALB/c sIg- cells. These cells could only be stimulated in allotype allogeneic (Igha), as opposed to allotype syngeneic (Ighb), carrier-primed irradiated recipients. This finding was confirmed by the finding that a high proportion of antidextran hybridoma cell lines derived from C.B20 bone marrow cells produced lambda-bearing alpha(1----3) DEX-specific antibodies that were IdX+. These findings have led us to conclude that the well-established phenotypic difference between Igha and Ighb mice with respect to the expression of lambda-bearing alpha(1----3) DEX-specific antibody responses is not, as previously assumed, the result of an inability of Ighb mice to generate B cells of this clonotype, but rather, is the product of environmental, possibly antiidiotypic, silencing of cells of this clonotype as they mature in Ighb mice.

T cell development in B cell-deficient mice. II. Serological characterization of suppressor T cell factors (TsF1) produced in normal mice and in mice treated chronically with rabbit anti-mouse IgM antibodies

Serological analysis of idiotypic specificities present in azobenzenearsonate (ABA)-specific first-order suppressor T cell factors (TsF1) from C.AL-20 and BALB/c mice revealed a significant difference between TsF from these two strains of mice. The idiotypic composition of TsF1 from BALB/c mice appears to be more heterogeneous, and at least two different fractions can be readily identified. One bears the characteristic BALB/c-associated CRI(C) (crossreactive idiotype) determinants, and the other is non-CRI(C)-bearing. Analysis of ABA-specific TsF1 from animals lacking B cells uncovered a fundamental change in the expression of their idiotypic specificities. TsF from rabbit anti-mouse IgM (anti-mu)-treated C.AL-20 mice failed to express the characteristic CRI(A) determinants. Instead, they express CRI(C) specificities. Similarly, TsF1 from anti-mu-treated BALB/c mice did not express their characteristic CRI(C) specificities, but rather express CRI(A) determinants. These experiments provide strong evidence that the Igh restriction specificity of TsF is dictated by the particular idiotypic specificities expressed. They also clearly demonstrate that B cells and their products play an important role in establishing the idiotypic composition and repertoire of suppressor T cells.

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.

Spontaneous in vitro production of anti-DNA and anti-RNA by systemic lupus erythematosus and normal peripheral blood mononuclear cells

The spontaneous in vitro production of anti-DNA and anti-RNA by peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE) and from normal subjects was evaluated employing sensitive solid-phase assays that are specific for these antibodies. PBMC from SLE patients produced more IgG anti-DNA and anti-RNA than did normal PBMC (P less than 0.01). In vitro production of IgG anti-DNA appeared to correlate with serum DNA bindings (r = 0.72, P less than 0.005). Similar amounts of IgM anti-DNA and anti-RNA were produced by both SLE and normal PBMC. However, IgM anti-DNA antibodies always appeared to be directed against determinants on denatured DNA. Only PBMC from SLE patients produced IgG antibodies to native DNA.

Idiotype connectance in the immune system. II. A heavy chain variable region idiotope that dominates the antibody response to the p-azobenzenearsonate group is a minor idiotope in the response to trinitrophenyl group

We describe the recurrence of a cross-reactive idiotope (CRIAD8) in antibody responses to different epitopes, and explore factors leading to its dominance in some responses, but not others. Serological and genomic DNA analyses showed that CRIAD8 is a marker of the CRIa heavy chain variable region (VH) that encodes the majority of anti-p-azobenzenearsonate (anti-ABA) antibodies. The independence of CRIAD8 from any particular light chain or antigen specificity was underscored by the fact that we could isolate hybridomas that secrete antitrinitrophenyl (TNP) antibodies expressing CRIAD8, with lambda 1 light chains. CRIAD8 is dominant in anti-ABA responses, recurrent but nondominant in anti-TNP and anti-chicken gammaglobulin responses, and is virtually absent in other antihapten responses, including that to p-azobenzenephosphonate (ABP), which contains an ABA-cross-reactive component (approximately 5-40%). Dominance in the anti-TNP response could not be achieved by immunization with doubly haptenated TNP-ABA-KLH (keyhole limpet hemocyanin), where the anti-ABA response was dominated by CRIAD8. These observations suggest that, while the CRIAD8 VH region is necessary for idiotypic dominance, it is not sufficient. Apparently, an additional specificity is required. Since immunization with ABA calls up anti-ABP antibodies that express CRIAD8, but not vice versa, it is possible that the additional specificity is ABA itself. This possibility imposes a new constraint on the specificity of the putative idiotype-specific regulation that may establish dominance in the CRIa system.

Influence of clonal selection on the expression of immunoglobulin variable region genes

The humoral immune response of the mouse to certain antigens is characterized by the dominant expression of a single or limited number of related, immunoglobulin variable region (V) structures by antibody-secreting lymphocytes. Such dominance could be due to preferred expression of these V regions in the B cell population prior to the immune response or could result from the action of selective or regulatory mechanisms during the immune response. Expression of a heavy chain variable region (VH) gene segment that partially encodes a V region structure that dominates the immune response to para-azophenylarsonate (Ars) in strain A mice was examined in the B cell population of Ars nonimmune mice. This VH gene segment participates in encoding several hundred thousand different V region structures expressed in this B cell population. The immune system is therefore capable of recurrently selecting a single V region structure from such a repertoire for dominant expression by antibody-secreting lymphocytes during an immune response.

Complete amino acid sequence of heavy chain variable regions derived from two monoclonal anti-p-azophenylarsonate antibodies of BALB/c mice expressing the major cross-reactive idiotype of the A/J strain

The primary structure of A/J anti-p-azophenylarsonate (anti-Ars) antibodies expressing the major A-strain cross-reactive idiotype (CRIA) has provided important insights into issues of antibody diversity and the molecular basis of idiotypy in this important model system. Until recently, this idiotype was thought to be rarely, if ever, expressed in BALB/c mice. Indeed, it has been reported that BALB/c mice lack the heavy chain variable segment (VH) gene that is utilized by the entire family of anti-Ars antibodies expressing the A/J CRI. Recently, however, it has been possible to elicit CRIA+, Ars binding antibodies in the BALB/c strain by immunizing first with anti-CRI and then with antigen. Such BALB/c, CRIA+ anti-Ars antibodies can be induced occasionally with antigen alone. VH region amino acid sequences are described for two CRIA+ hybridoma products derived from BALB/c mice. While remarkably similar to each other, their VH segments (1-98) differ from the VH segments of A/J CRIA+, anti-Ars antibodies in over 40 positions. Rather than the usual JH2 gene segment used by most A/J CRIA+ anti-Ars antibodies, one BALB/c CRIA+ hybridoma utilizes a JH1 gene segment, while the other uses a JH4. However, the D segments of both of the BALB/c antibodies are remarkably homologous to the D segments of several A/J CRIA+ antibodies sequenced previously, as are the amino terminal amino acid sequences of their light chains. These data imply that BALB/c mice express the A/J CRIA by producing antibodies with very similar, if not identical, light chain and heavy chain D segments, but in the context of different VH and JH gene segments than their A/J counterparts. The results document that molecules that share serologic specificities can have vastly different primary structures.

Idiotypic analysis of potential and available repertoires in the arsonate system

We have shown that, by suitable idiotypic manipulation, BALB/c mice can express the major cross-reactive idiotype (CRI) of A/J mice in response to azophenylarsonate (Ars). In order to know if the CRIA idiotype is present in the potential repertoire of BALB/c before any intentional selection, we used polyclonal activation in vitro and limiting dilution analysis. The readout was done with two monoclonal anti-CRIA antibodies that recognize distinct idiotopes on a CRIA+ A/J germline-encoded monoclonal antibody. We studied the frequency of CRIA+ lipopolysaccharide (LPS)-reactive cells in the spleens of nonimmune and immune A/J mice and in the spleens of naive and manipulated (i.e., producing CRIA+ antibodies) BALB/c mice. A/J and BALB/c naive individuals presented very high frequencies of Ars-specific B cells while the frequency of CRIA+ B cells was only a minor subset (0.5%) of the total Ars-specific subset in the two strains. When A/J mice were immunized with Ars-keyhole limpet hemocyanin, a clear preferential expansion of the CRIA+ minor subset of A/J mice was observed (100x). No such enhancement was observed in BALB/c mice similarly treated. Manipulated BALB/c mice presented a higher frequency of CRIA+ anti-Ars B cells than naive or antigen-immunized BALB/c individuals.

Expression and rearrangement of homologous immunoglobulin VH genes in two mouse strains

A family of murine anti-p-azophenylarsonate (Ars) antibodies share a variable (V) region serologically defined marker, the 36-60 idiotype (Id36-60). Most mouse strains possess five genes highly homologous to the gene encoding the heavy (H) chain V region of antibodies bearing Id36-60 (VH36-60); however, only one of these genes is ever utilized by hybridomas whose antibodies bind Ars and bear Id36-60. The relevant VH genes were cloned from A/J and BALB/c mouse DNA libraries. Their DNA sequences were found to differ at only two positions. Southern blot analysis, protein sequence determination, and nucleic acid sequence determination indicate that the above hybridomas utilize the same joining (JH3), diversity (D), and VH gene segments regardless of BALB/c or A/J strain origin. Despite this virtual identity, BALB/c and A/J mouse strains express quite different serum levels of Id36-60-bearing antibodies when immunized with Ars. The basis of this regulatory process is discussed.

Idiotype profile of an immune response. II. Reversal of the relative dominance of major and minor cross-reactive idiotypes in arsonate-specific T-independent responses

Two different cross-reactive idiotype (CRI) groups are distinguishable in the Ab response of A/J mice to the p-azobenzenearsonate (ABA) hapten: CRIA and CRIm. These two groups showed distinct patterns of relative dominance in the ensuing response depending on whether the inducing Ag was a T cell-dependent (TD) form of ABA, such as ABA-KLH or ABA-CGG, or a T-independent type 1 (TI-1) form, such as ABA-Brucella abortus or ABA-lipopolysaccharide (LPS), and on whether the response was elicited in vivo or in vitro. The CRI+ component of primary in vivo plaque-forming cell (PFC) responses to TD ABA Ags was largely (greater than 90%) CRIA+ as was, to a slightly lesser extent (greater than 75%) the CRI+ portion of secondary or hyperimmune serum Ab or PFC responses to the same Ags. In contrast, in vivo primary and hyperimmune PFC responses to ABA-Bru or ABA-LPS showed a significantly lower CRIA/CRI ratio, averaging 0.5-0.6, with some individual mice giving figures as low as 0.2, indicating predominance of CRIm over CRIA. Serological analysis of hyperimmune anti-ABA Abs from a group of 5 A/J mice immunized with ABA-Bru gave a figure of less than 0.5 for the CRIA/CRI ratio. The most striking disparity from the TD pattern was seen in primary in vitro PFC responses to the TI ABA Ags; here ratios of less than 0.2 were generally seen. Since T cell removal did not alter the Id pattern in the TI responses, CRIA-specific Ts cells do not account for the weak expression of CRIA in such responses. We propose a model that explains these results on the basis of differential expression of IdX dominance by two distinct B cell subpopulations--equatable to the Lyb-5+ and Lyb-5- B cell subsets--along with differential relative activation of these subsets in different types of responses. Examination of anti-ABA PFC responses of F1 progeny of CBA/N and A/J mice to ABA-Bru lends support to this hypothesis since CRIA expression was significantly lower in mice with the xid defect.

Restricted adult clonal profiles induced by neonatal immunization. Influence of suppressor T cells

The effects of neonatal antigen exposure on the adult B cell repertoire have been examined by characterizing the influenza hemagglutinin (HA)-specific response of adult BALB/c mice given antigen soon after birth. Ligand exposure during early life exerts a profound and lasting effect upon the B cell repertoire, characterized by the expansion and preservation of particular antigen-reactive clones and the apparent loss of others. The precise subset of clonotypes selectively preserved depends upon the age at which antigen is first encountered; and is predictable given a knowledge of the emerging primary pool's dynamics and composition. The preserved (secondary) B cells differ from their unprimed precursors with respect to (a) expression of the surface marker detected by the monoclonal antibody J11d, and (b) susceptibility to T cell-mediated suppression. These studies thus demonstrate a strong relationship between the heritable dynamics of the emerging primary B cell repertoire and the effect of ligand-driven events upon repertoire phenotype. In addition, they provide a mechanistic model for certain forms of antigen-induced oligoclonal dominance, especially the phenomenon of original antigenic sin.

Idiotypic manipulation in mice: BALB/c mice can express the crossreactive idiotype of A/J mice

The response of A/J mice to arsonate-coupled keyhole limpet hemocyanin is characterized by a crossreactive idiotype (CRIA). CRIA+ antibodies are restricted to the Igh-Ic haplotype and are never expressed in BALB/c mice after immunization with antigen. Studies at the DNA level suggest that the gene encoding the CRIA heavy chain in A/J mice is probably absent in the genome of BALB/c mice. Despite this, using the immunization cascade tool, we have been able to induce the expression of CRIA+ antibodies in BALB/c mice. These studies led to an apparent paradox, whose understanding will provide new insights into the regulatory mechanisms of the immune system. We suggest that clones secreting CRIA-like Igs in BALB/c mice are "somatic variants" that could arise from gene conversion events.

Normal mice express idiotypes related to autoantibody idiotypes of lupus mice

Spleen and fetal liver B cells of normal mice synthesized idiotypes shared by anti-DNA autoantibodies of genetically autoimmune mice. Some of the idiotypes were specific for DNA; the majority, however, were not. The findings indicate that the autoantibody idiotypes are related to a conserved family of antibody variable regions that are present in normal animals.