Structural and serological relationships among different antibodies from the same rabbit antiserum. II. The idiotypes of ten antibody components from an anti-streptococcal serum.

In studies aimed at elucidation of the idiotypic relationships among antibodies produced by a single rabbit, ten antibodies were isolated from the serum of a rabbit immunized with streptococcal Group C vaccine. Four of these antibodies were obtained in amounts sufficient to prepare homologous (rabbit) anti-idiotype antisera. The antisera were used to test for cross-reactivities among all ten antibodies by binding and inhibition of binding assays. Idiotypic cross-reactions among the antibodies were detected by three of the four antisera, while the fourth antiserum reacted only with the antibody that was used as the immunogen for its preparation. Two antibodies demonstrating the highest degree of cross-reactivity had readily distinguishable VH allotypic (a1) subspecificities. The idiotypic reactions and cross-reactions could be inhibited by haptens prepared from the Group C carbohydrate. Bleedings taken from the three immunization periods of this rabbit indicated that the four idiotypes were expressed in approximately equal amounts in each immunization period and that all idiotypes dropped to undetectable levels between immunization periods.     

Anti-idiotypic sera against monoclonal anti-progesterone antibodies: production in rabbits and rats and characterization of specificity.

Antisera were raised in rabbits and rats against three mouse monoclonal anti-progesterone IgG1 antibodies. Anti-idiotypic antibodies were isolated from rabbit sera by successive passage over immunoadsorbent columns of normal mouse Ig and the specific immunizing monoclonal, with elution from the latter. Radioimmunoassays for anti-idiotype and free idiotype were established, enabling detection of idiotype in sera of mice immunized with progesterone-BSA conjugate. Binding of rabbit anti-idiotype to anti-progesterone monoclonals was partially inhibitable by free progesterone-hemisuccinate or progesterone-ovalbumin conjugate. While showing considerable specificity for their respective inducing monoclonals, the anti-idiotypes also cross-reacted in varying degrees with the other anti-progesterone monoclonals, demonstrating the presence of IdI and IdX determinants. The patterns of cross-reactivity showed some correlation with the relative isoelectric points and combining-site specificities of the anti-progesterones. The specificities of rat and rabbit anti-idiotypes were similar, but not identical.     

Induction of an immune response to the porin of Haemophilus influenzae type b by monoclonal anti-idiotypic antibodies.

Monoclonal anti-idiotypes were generated against monoclonal antibody (mAb) Hb-2 which recognized a highly conserved epitope on the outer membrane porin protein from Haemophilus influenzae type b (Hib). Four hybridomas reacting with F(ab') 2 fragments of Hb-2 were selected and characterized. Inhibition studies using syngeneic anti-anti-idiotypic antisera suggested that at least three different antigenic determinants on Hb-2 were recognized by these monoclonal anti-idiotypes. The binding of each anti-idiotype to Hb-2 was inhibited by Hb-2 whereas the reaction was not affected by any other anti-Hib mAb. Complete inhibition of the binding of anti-idiotype to the idiotype could be achieved with 10 micrograms of total outer membrane protein (OMP) from Hib suggesting that the anti-idiotypes might be directed against paratope-associated idiotypes. Outer membrane antigens not recognized by mAb Hb-2 did not inhibit the reaction. Furthermore, the pre-incubation of Hb-2 with each anti-idiotype specifically prevented the reaction of Hb-2 with its antigen. Antibodies with specificity for the porin were generated in guinea pigs immunized with anti-idiotypes AHb-22 and AHb-23. This study indicates that these particular monoclonal anti-idiotypes may be used as an antigen substitute for the porin of Hib in a xenogeneic species.     

Intrastrain recurrent idiotypes among anti-DNA antibodies of (NZB X NZW)F1 hybrid mice

Immunization of NZB and A/J mice against an anti-DNA hybridoma antibody (F227) derived from (NZB x NZW)F₁ (B/W) mice allowed the preparation of two anti-idiotype antisera. These two reagents were shown to recognize different idiotopes of the F227 monoclonal antibody. NZB anti-idiotypic antibodies recognized non-ligand-modifiable idiotypic determinants. These idiotopes were private or present at undetectable level in BW mouse sera since it was found that only two of the 24 B/W mouse sera tested were recognized by these antibodies. Conversely, A/J anti-idiotypic antibodies recognized partially ligand-modifiable idiotopes which were found in all B/W mouse sera tested. These results demonstrate that anti-DNA antibodies share similar idiotypic specificities and suggest that these autoantibodies occur as families of structurally related proteins.     

Comparative idiotype network interactions: antigen mimicry by an anti-bovine idiotype monoclonal antibody in rats and cattle

Idiotype/anti-idiotype networks have been extensively investigated in such conventional animal models as the mouse and the rabbit. However, systems of veterinary interest have remained largely unexplored. A monoclonal target idiotype, with which to begin such studies in cattle was provided by LHRB 19.17 an interspecific bovine x mouse hybridoma. This hybridoma was constructed by the fusion of supramammary lymph node cells from S. agalactiae-immunized lactating Holsteins with the Ig synthesis-permissive established cell line, SP 2/0. Two collections of monoclonal anti-idiotype antibodies were generated by fusion of spleen cells from LHRB 19.17-immunized Balb/c or A/J mice immunized with the monoclonal bovine idiotype, LHRB 19.17. Many of the anti-idiotypes inhibited binding of LHRB 19.17 to S. agalactiae, but only one, LHRAID 2.71, proved to be an internal image of a S. agalactiae epitope. Immunization of C/D outbred rats by priming with 100-300 micrograms of LHRAID 2.71 emulsified in CFA followed by a 300 micrograms boost at day 32 elicited anti- S. agalactiae antibody in 4/4 animals tested. Similarly, the injection of two lactating Holsteins with the anti-id resulted in the production of anti- S. agalactiae antibody in serum and milk. In both rats and cattle, the administration of the antigen-mimicking anti-idiotype induces the appearance of S. agalactiae-reactive horseradish peroxidase-streptavidin conjugate; LHRBs, interspecific bovine x mouse hybridomas secreting bovine Ig; LHRAID.X, monoclonal anti-bovine idiotype antibodies derived against LHRB 19.17; PBS, phosphate buffered saline; PBS/BSA, PBS containing 0.1% bovine serum albumin: antibody [AB3] that competes with LHRB 19.17 [AB1] for binding to LHRAID 2.71 [AB2]. It should also be noted that the immunization of C/D rats with S. agalactiae does not result in the appearance of idiotypes which compete with LHRB 19.17 for binding to LHRAID 2.71. We have concluded that immunization of two widely divergent species with the antigen mimicking LHRAID 2.71 induced a S. agalactiae-reactive idiotype which was not detectable in the immune response of rats to S. agalactiae.     

The common occurrence of internal image type anti-idiotypic antibodies in rabbits immunized with monoclonal and polyclonal human IgM rheumatoid factors.

We have previously reported that rabbits immunized with a polyclonal human rheumatoid factor (RF) autoantibody preparation could induce anti-idiotypic antibodies bearing the 'internal image' of the Fc fragments of human IgG. The 'internal image' anti-idiotype have been shown to react with both the RF molecules as well as with the RF receptors on B lymphocytes. Under what conditions these anti-idiotypes occur is not known. Presently, we report that these anti-idiotypic antibodies occur more frequently than previously thought and could be isolated in sera of rabbits immunized with either monoclonal paraproteins with RF activity or other purified human polyclonal serum RFs. Immunization of rabbits with a peptide corresponding to the second complementarity-determining regions of a monoclonal RF did not induce this anti-idiotype. Immunization of goats with human RF similarly did not result in induction of such anti-idiotype. Induction of these anti-idiotypes thus depended upon immunization with the intact RF antigen as well as the species of animal immunized. The repeated isolation of 'internal image' anti-idiotypic antibodies from RF immunized rabbits suggests that the antigenic conformations recognized by human RF autoantibodies are restricted, and that 'internal image' anti-idiotypic species to RF may pre-exist within the rabbit immune network. Such broadly cross-reactive anti-idiotypic reagents provide unique reagents for studying the regulation of RF autoantibody synthesis.     

Analysis of a major rat idiotype associated with Anti-GAT antibodies

An anti-idiotypic antiserum was raised in a rabbit against a pool of purified F.344 rat anti-GAT antibodies. GAT-13, the idiotype defined by this serum, is present in all F.344 anti-GAT sera from primary and secondary anti-GAT responses. Anti-GAT sera of 13 inbred rat strains, with different RT1 haplotypes and with different heavy- and light-chain allotypes, all express idiotypic determinants cross-reacting with GAT-13. Thus, like in mice anti-GAT antibodies from rats express public idiotypic determinants. The anti-idiotypic serum also recognizes a highly conserved idiotypic specificity present on mouse and guinea-pig anti-GAT antibodies. The mouse, rat and guinea-pig express a similar highly conserved idiotypic specificity after immunization with GAT. All anti-GAT antibodies from the mouse and guinea-pig bear this idiotypic specificity. These results confirm the existence in the anti-GAT response of interspecies cross-reactive idiotypic determinants.     

Monoclonal 'internal image' anti-idiotypic antibodies of hepatitis B surface antigen.

The hypervariable regions of the immunoglobulin molecule which function as the antigen-combining site are, themselves, capable of provoking an antibody response. These antigenic determinants on the immunoglobulin are termed the 'idiotype', and antibodies directed against them 'anti-idiotype'. In circumstances where there is a close complementarity of shape between antigen and idiotype, and subsequently between idiotype and anti-idiotype, it would be predicted that anti-idiotype would be like an 'internal image' of the antigen. Starting with a monoclonal antibody (idiotype) to the protective a determinant of the hepatitis B surface antigen (HBsAg), we have succeeded in raising two monoclonal anti-idiotypes which mimic HBsAg in their ability to bind polyclonal antibodies to HBsAg produced in a variety of species. These internal image anti-idiotypes may provide a strategy for immunization without the need for antigen.     

Studies of hyperimmune restricted and partially restricted anti-pneumococcal polysaccharide antibodies from allotype-defined pedigreed rabbits. II. Allotypes and idiotypes in sera and electrofocused fractions

The expression of allelic forms of immunoglobulin during immunization of heterozygotes with pneumococcal vaccines was monitored using anti-allotype antisera specific for the genetically different forms of rabbit kappa chains (b-locus allotypes). We also used the a-locus (V_H) allotypic markers of rabbit heavy chains and idiotypic determinants associated with a restricted subpopulation of anti-polysaccharide antibodies of an individual rabbit. Analysis of fractions obtained by preparative liquid isoelectric focusing (IEF) of antisera from heterozygous rabbits exhibiting restricted antibody responses to type 3 or type 8 pneumococcal polysaccharides, indicated an enrichment for one a or b locus allotype. Enrichment of a specific idiotype from ～ 11 % in the starting serum up to as high as 65 % in a focused fraction was also obtained. The method of preparative liquid IEF can thus be used to isolate antibodies restricted in allotype and idiotype from antisera. The quantities obtained are sufficient for further chemical and immunological study.     

Anti-idiotypes against anti-H-2 antibodies VI. Detection of shared idiotypes among monoclonal anti-H-2 antibodies

Anti-idiotypes produced against monoclonal anti-H-2 antibodies have been used to examine idiotope sharing among a panel of anti-major histocompatibility complex (MHC) antibodies detecting the same and different specificities. Both xenogeneic anti-100-30 and anti-3-83, which did not react with predominant idiotypes in conventional alloantisera, detected idiotopes on 3-83 and 100-30 as well as on 2 other monoclonal anti-H-2Kk antibodies. All 4 monoclonal antibodies recognized the same epitope cluster on the Kk molecule and detected the same serological specificity. H-2.5. In contrast, syngeneic and allogeneic anti-idiotype produced against the same monoclonal antibodies did not detect these cross-reactive determinants. In several instances, xenogeneic anti-idiotype reacted with anti-MHC antibodies which recognized distinct H-2 determinants, suggesting that anti-MHC antibodies detecting the same or different specificities may share idiotypic determinants. These reagents may be useful probes of the anti-MHC immune repertoire.     

Comparative study of idiotypes on monoclonal antibodies derived from patients with lupus and leprosy and from normal individuals

A collaborative study was performed to compare the expression of a series of idiotypes defined on human anti-DNA and other autoantibodies. Three panels of human monoclonal antibodies were tested: eight derived from patients with systemic lupus erythematosus (SLE); 13 from an individual with lepromatous leprosy; and 38 from normal subjects. The following rabbit anti-idiotype sera were used: one (RId16/6) raised against the lupus-derived monoclonal anti-DNA antibody 16/6, four (RId8E7, RId4G7, RId4D5 and RIdTH9) against leprosy-derived monoclonal antibodies of various specificities, and one (anti-4.6.3) against a normal-derived anti-DNA monoclonal (KIM 4.6). In addition, two other anti-idiotypes were used--one a murine monoclonal (3I), the other a rabbit polyclonal (RIdD)--which had been raised against polyclonal anti-DNA antibodies from lupus serum. Further experiments were performed with immunoabsorbed fractions of RId8E7. Direct-binding and competition assays were used. All of the anti-idiotypes produced different patterns of positivity among the three panels of human monoclonal antibodies, with the exception of RId8E7 and RId4G7, which showed considerable concordance. There was a tendency towards anti-idiotypes being disease- or group-specific: thus anti-4.6.3 failed to bind to any of the lupus or leprosy-derived monoclonals, while RId16/6 and RId8E7 bound most strongly to the lupus- and leprosy-derived antibodies respectively. KIM 4.6 itself was bound only weakly by RId16/6, while 16/6 was not recognized by anti-4.6.3; 16/6 was, however, bound by 3I, while KIM 4.6 was not. 3I bound to several other monoclonals but RIdD, which has been shown to be specific for the anti-DNA fraction of lupus serum, did not bind to any of them. These results indicate that the majority of these anti-idiotype preparations recognize largely separate sets of determinants. The monoclonal antibodies which bind to DNA may be only partly representative of anti-DNA antibodies in the serum of lupus patients.     

Studies of Monoclonal Antibodies Specific for Major Histocompatibility Complex Products of the Rat

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

Idiotypic heterogeneity of VKIII autoantibodies to red blood cell antigens.

VKIII light (L) chains are commonly expressed by human autoantibodies with diverse binding specificities, including red blood cell antigens. To better understand the physiologic and pathologic expression of these L chain variable region genes, we have created a panel of murine monoclonal anti-idiotypic antibodies by immunization with a human lymphoblastoid B cell line that secretes an IgM VKIII autoantibody specific for the I red blood cell carbohydrate determinant. The binding specificities of these nine murine monoclonal antibodies, termed IV.1-IV.9, were evaluated against a large panel of monoclonal Ig proteins and compared to two previously well-characterized monoclonal anti-idiotypes, 6B6.6 and 17.109; these two anti-idiotypes have been shown to primarily identify VKIII rheumatoid factors derived from the kv328 (VKIIIa) and kv325 (VKIIIb) genes, respectively. In contrast, our anti-idiotypic antibodies identified (public) cross-reactive idiotypes present on many VKIII proteins that included both anti-erythrocyte and rheumatoid factor autoantibodies. Certain anti-idiotypic antibodies (IV.2 and IV.6) were restricted to VKIIIa L chains but differed from the 6B6.6 anti-idiotype by binding to a larger subset of VKIIIa proteins representing the products of at least two VKIIIa genes. One antibody of our panel (IV.5) recognized a private idiotope expressed only by the immunizing antibody. Using the panel of anti-idiotypic antibodies to evaluate erythrocyte autoantibodies with different serologic specificities, we found striking heterogeneity of L chain idiotype expression, even among known VKIII anti-i/I autoantibodies. These findings differ from the recently described structural and idiotypic conservation associated with the H chain of anti-i/I autoantibodies. From correlations of idiotypic reactivity with L chains of known sequence, it is postulated that the observed heterogeneity of L chain idiotype expression is due to differences in the genetic origin and/or somatic diversification of L chain variable region genes. Furthermore, subtle variability of L chain structure may contribute in part to the differences in fine binding specificity among anti-I and anti-i autoantibodies.     

Anti-idiotypic IgM antibodies to anti-HLA class I antibodies in habitual abortion.

In order to investigate the role of the idiotypic network in miscarriages, sera from 28 habitually aborting women undergoing paternal leukocyte immunization were studied for the presence of HLA antibodies and related anti-idiotypes. Sixty-eight percent of sera from preimmunized patients which did not contain anti-lymphocyte antibodies inhibited the activity of antibodies to the HLA class I antigens expressed by the spouse. This inhibitory activity could be assigned to IgM antibodies, which cross-inhibit antibodies of similar specificity. This suggests that they are anti-idiotypes for the binding site of HLA antibodies. Immune sera of successfully treated patients exhibited both cytotoxic IgG anti-HLA antibodies and inhibitory IgM anti-idiotypic antibodies. A possible role for an intact idiotypic network in maintaining pregnancy is suggested.     

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.     

The idiotypy of the MOPC 173 (IgG2a) mouse myeloma protein: characterization of syngeneic, allogeneic and xenogeneic anti-idiotypic antibodies. Contribution of the H and L chains to the idiotypic determinants.

Anti-idiotypic antibodies were raised against the mouse (γ_2a, κ) myeloma protein MOPC 173 in syngeneic, allogeneic and xenogeneic conditions. Syngeneic immunization resulted in individual hemagglutination titers ranging from 1:40 to 1:160000 with about 30% of nonresponders, whereas upon allogeneic immunization (in A/J mice) almost all animals responded, with titers ranging from 1:1250 to 1:320000. Anti-idiotypic antisera were also obtained in the rabbit. Inhibition of a radioimmunoassay using ¹²⁵I-labeled MOPC 173 Fab fragments as the reference antigen indicated that the native Ig and the Fab competed on a similar molar basis. No inhibition was observed with the Fc or with other mouse monoclonal Ig, of the same or different classes or subclasses. Standard BALB/c serum did not inhibit either. Whatever the anti-idiotypic antiserum used, idiotypic determinants were not found on isolated heavy (H) and light (L) chains provided they were carefully purified. Reoccurrence of idiotypic determinants was obtained in high yield whenever Ig molecules were reformed from the homologous H and L chains, whereas no potentiation of the low inhibition of isolated chains was observed when hybrid molecules were formed using heterologous complementary chains isolated from the MOPC 21A (γl, ?) or the LPC 1 (γ_2a, ?) protein. These results suggest that MOPC 173 idiotypic determinants rely on the specific H-L interaction and that they must be largely conformational in nature. Heterogeneity of the anti-idiotypic antibodies was analyzed by isoelectric focusing. A major pattern was observed for the A/J antisera, whereas, in the case of BALB/c, expression of a few clones, characteristic of each “high responder” animal, was strongly suggested, superimposed to faint production of antibodies by clones that were common to all mice.     

Lack of inter-animal cross-reaction of anti-acetylcholine receptor antibodies at the receptor-binding site as demonstrated by heterologous anti-idiotype antisera: implications for immunotherapy of myasthenia gravis.

Anti-idiotype antisera were raised in rabbits by immunization with purified sheep anti-Torpedo receptor antibodies. The antisera were able specifically to block the binding of receptor to the inducing antibodies but not anti-Torpedo antibodies from other animals of the same, or other, species. Rabbits producing the anti-idiotype sera were not protected from experimental autoimmune myasthenia gravis (EAMG). The implications of these observations for the potential use of anti-idiotype antisera in the treatment of myasthenia gravis are discussed.     

Monoclonal Anti-Azobenzenearsonate Antibodies Expressing the Cross-reactive Idiotype: Immunochemical Studies Show that All Idiotypic Determinants Reside on a Single Molecule

Cell lines that secreted antibodies to the hapten azobenzenearsonate (ABA) were established by hybridization of immune A/J spleen cells to the non-secreting myeloma, NS-I. Solid-phase radioimmunoassays (RIA) were developed for rapid screening of hybridoma supernatants to detect antibodies to ABA and lo detect antibodies bearing the ABA cross-reactive idiotype (CRI). Hybrid clones secreting both CRI⁺ and CRI⁻ anti-ABA antibodies were obtained. The supernatant from one clone (7-1-3) strongly inhibited binding of iodinated anti-idiotype serum in a competitive RIA. This clone expressing the CRI produced immunoglobulin of the IgG2a subclass. Solid-phase absorption of anti-idiotype serum followed by competitive radioimmunoassay analyses revealed that all the idiotypic determinants recognized by anti-idiotype scrum reside on this monoclonal antibody.     

Preparation of rabbit anti-IgE for use in radioimmunoassays of total IgE and specific IgE antibodies

Detailed methodology for preparing and testing isolated rabbit anti-human IgE suitable for radioimmunoassays of total IgE and specific IgE antibodies is presented in a single article for the first time. A method for obtaining a product free of anti-idiotype antibodies is also described.IgE was isolated from E-myeloma serum (PS) by 40 and 50% saturated ammonium sulfate fractional precipitation, followed by DEAE Sephadex ion-exchange chromatography. The purified product was digested with papain, and the Fc fragments were separated from the Fab fragments by G-150 gel filtration and ion-exchange chromatography. Rabbits were immunized with IgE (Fc), and the antisera with the highest precipitin titers were pooled. A globulin fraction was prepared from the pooled antiserum by 50% saturated ammonium sulfate precipitation and the fraction was absorbed using an immunosorbent prepared from whole human serum having a very low IgE level and with immunosorbents prepared from D-myeloma protein and from IgE (Fab). Following absorption, the antibodies were demonstrated by micro-Ouchterlony technique to have no cross-reaction with IgG, IgA, IgM, IgD or any serum protein other than IgE. More than 200 mg of isolated anti-IgE (Fc) was prepared from antiserum globulin by consecutive affinity chromatography on columns of insolubilized IgE. Elution peaks appeared following the application of 0.1 M glycine—HCl, 1.0 M NaCl buffer, pH 2.5, as well as following a subsequent flush with 0.1 M phosphate, 1.0 M NaCl buffer, pH 7.4. The eluates were tested, pooled, radiolabelled with iodine-125 and demonstrated to be effective in RAST analyses. Antibodies to idiotypic determinants of the IgE molecule were eliminated by preparing the affinity chromatography column from a second E-myeloma protein (HL) rather than the E-myeloma protein (PS) used for immunization of the rabbits. Anti-IgE preparations which were free of anti-idiotype antibodies displayed less non-specific binding to IgD and IgG coated discs than preparations containing such antibodies.     

Induction and characterization of isogeneic anti-idiotypic antibodies to BALB/c myeloma S117: lack of reactivity with major idiotypic determinants.

Isogeneic anti-idiotypic antibodies were induced by immunization of BALB/c mice with the BALB/c-derived myeloma protein S117 which binds N-acetylglucosamine-containing antigens including Group A streptococcal carbohydrate (A-CHO). Most BALB/c mice produced anti-S 117 idiotypic antibodies, as shown by various different immunization protocols. The antibodies of individual mice were of intermediate to high affinity (2.8 x 10(6) M-1 to 1.4 x 10(8) M-1). In isoelectric focusing, most individual antibodies were shown to consist of a small number of clonotypes, but each mouse produced its own unique set of clones so that the potential clonal repertoire of strain BALB/c is rather large. Most importantly, all isogeneic anti-idiotypic antibodies were directed against idiotypic determinants of S117 that are not shared with induced anti-A-CHO antibodies, whereas it has been shown previously that allogeneic and xenogeneic anti-S 117 idiotypic antibodies react with idiotypic determinants unique to S 117 as well as with those that are shared with anti-A-CHO antibodies. The data suggest that the expression of S 117 idiotypic determinants in strain BALB/c is not under antibody-mediated, anti-idiotypic feedback control.