Idiotype expression and the inheritance of mouse antibody clones

Human Monoclonal Antibodies: The Benefits of Humanization

The major reasons for developing human monoclonal antibodies were to be able to efficiently manipulate their effector functions while avoiding immunogenicity seen with rodent antibodies. Those effector functions involve interactions with the complement system and naturally occurring Fc receptors on diverse blood white cells. Antibody immunogenicity results from the degree to which the host immune system can recognize and react to these therapeutic agents. Thus far, there is still no generally applicable technology guaranteed to render therapeutic antibodies antigenically silent. This is not to say that the task is impossible, but rather that we need to train the immune system to help us. This can be achieved if we take advantage of natural mechanisms by which an individual can be rendered tolerant of "foreign" antigens, and as a corollary minimize the potential immunogenicity of any contaminating protein aggregates, or "aggregates" arising from antibodies complexing with their antigen. I here summarize our efforts to engineer antibodies to harness optimal effector functions, while also minimizing their immunogenicity. Potential avenues to achieve the latte are predicted from classical work showing that monomeric "foreign" immunoglobulins are good tolerogens, while aggregates of immunoglobulins ate intrinsically immunogenic. Consequently, I argue that one solution to the immunogenicity problem lies in ensuring a temporal quantitative advantage of tolerogenic non-cell-bound monomer over the cell-binding immunogenic form.

Human monoclonal antibodies: the residual challenge of antibody immunogenicity

One of the major reasons for seeking human monoclonal antibodies has been to eliminate immunogenicity seen with rodent antibodies. Thus far, there has yet been no approach which absolutely abolishes that risk for cell-binding antibodies. In this short article, I draw attention to classical work which shows that monomeric immunoglobulins are intrinsically tolerogenic if they can be prevented from creating aggregates or immune complexes. Based on these classical studies two approaches for active tolerization to therapeutic antibodies are described.

Human immune response to group A streptococcal carbohydrate (A-CHO). I. Quantitative and qualitative analysis of the A-CHO-specific B cell population responding in vitro to polyclonal and specific activation

The immune response to the group-specific carbohydrate of group A streptococci (A-CHO) provides an informative in vitro model for the investigation of several aspects of human anticarbohydrate immune responses. A-CHO-specific B cells can be polyclonally activated by pokeweed mitogen (PWM), and, specifically, by in vitro immunization with streptococcal vaccine. High levels of A-CHO-specific antibodies, mainly directed to the immunodominant side chain N-acetyl-D-glucosamine (GlcNAc), occur in healthy adult individuals. Serum antibody levels are reflected in high frequencies of precursor B cells among peripheral blood lymphocytes. In one particular case, greater than 15% of all B cells activated by PWM for IgM production were found to produce IgM anti-A-CHO antibodies, as determined in limiting dilution experiments, as well as by analyzing Ig concentrations in bulk culture experiments. The case with the lowest proportion observed had 0.3% A-CHO-specific B cells among IgM-producing B cells. Preferential PWM activation of anti-A-CHO-producing B cells could be excluded. The comparison of the proportions of anti-A-CHO IgM produced in vivo, and of B cells producing antibodies of this specificity in peripheral blood, suggests a similar distribution of specific precursor B cells in the antibody-producing lymphoid tissue compartments and in peripheral blood. However, nearly all specific antibodies produced in vitro belong to the IgM isotype, whereas IgG anti-A-CHO in high amounts, mostly exceeding the specific IgM, was found only among anti-A-CHO antibodies produced in vivo. Low anti-A-CHO IgG production was seen in polyclonally activated as well as in antigen-activated cultures, whereas, in contrast, total IgG was produced in considerable amounts after polyclonal activation. This suggests a different distribution pattern, and/or diverse differentiation requirements for anti-A-CHO-producing B cells, compared with other B cell species.

Genetic control of the immune response to staphylococcal nuclease. X. Isoelectric focusing spectrotypes of antinuclease antibodies detected by labeling with antigen and with anti-idiotype

Antibody responses of inbred strains of mice to staphylococcal nuclease were studied by isoelectric focusing in polyacrylamide gels followed by in situ labeling of focused antibodies with radioactive antigen. All A/J mice examined produced antinuclease antibodies of limited heterogeneity, and although there was individual variation in the focusing patterns observed, a characteristic spectrotype produced by all of the animals could be discerned. In order to determine the possible relationship between this characteristic spectrotype and the cross-reactive idiotypes of A/J antinuclease antibodies previously described, focused antibodies were also examined with a radioactively labeled pig anti-(A/J antinuclease) anti-idiotypic antibody preparation. Using this reagent, similar spectrotypes to those observed for antigen binding were seen in all of the individual A/J sera, suggesting that cross-reactive idiotype expression is a reflection of the characteristic spectrotypes observed. The same labeled anti-idiotypic reagent revealed characteristic but different spectrotypes when used to develop focused antinuclease antibodies from individual mice of other strains, suggesting that the use of similar variable region structures may be a common feature of the antinuclease response in mice of different allotypes. These studies thus provide a structural basis for the genetics of idiotype expression defined previously by serologic analysis.

Influence of subclass-specific anti-idiotypic antibodies on the kinetics of the immune response to BCG

The role of anti-idiotypic subclass-specific antibodies was analysed in the regulation of the immune response to BCG in the guinea-pig. The idiotypes to BCG were separated into subclasses and anti-idiotypes were carried out by immunizing with the purified IgG1 and IgG2 anti-idiotypes. The in vivo T cell response was recorded by tuberculin skin testing, and the in vitro response by lymphocyte stimulation testing with tuberculin. A suppressive effect was detected in cases where the animals were preimmunized with anti-idiotypic IgG2 against anti-BCG IgG1. In the B cell response, the anti-BCG IgG1 and IgG2 subclasses were also quantified by a solid-phase radioimmunoassay. There were 10 times more IgG2 antibodies than IgG1 against BCG in the guinea-pig, and this major idiotypic subclass was suppressed by the IgG2 anti-idiotype raised against anti-BCG IgG2. The minor component anti-BCG IgG1 was slightly stimulated by both IgG2 anti-idiotypes.

Production of auto-anti-idiotypic antibody during the normal immune response. IX. Characteristics of the auto-anti-idiotype antibody and its production

Using hapten-reversible inhibition of plaque formation as an assay for auto-anti-idiotype antibody (anti-Id) and as a means for following idiotype (Id) expression, we have obtained evidence that following immunization with trinitrophenyl (TNP) conjugates (a) there are differences in Id expression in the anti-TNP antibody response to different TNP conjugates although there is some overlap; (b) different strains, although showing some differences in Id expression, tend to produce cross-reactive Ids, thus no obvious allotype linked inheritance of Id expression is observed in this heterogeneous immune response; (c) the auto-anti-Id produced following immunization with TNP-Brucella abortus or TNP-Ficoll tends to be of the IgG2a and IgG2b isotypes.

Genetic controls of T cell-independent Thy-1 alloantibody responses

Early and late primary IgM antibody responses of mice to Thy-1.1 antigens showed different antigenic and cellular requirements. We studied genetic controls of the early primary responses, which could be induced by subcellular thymocyte antigens independently of host T-cell activity. All Thy-1.2 mouse strains of Igha (BALB/c and BC8), Igh-VaCb (BAB14), Ighd (AKR/Cum), Ighj (CBA/J, C3H/HeN, C3H.SW, and C3H.JK), and Ighn (NZB) definitely responded early to Thy-1.1 antigens from AKR/J (Ighd), A.Thy-1.1 (Ighe), or B10.Thy-1.1 (Ighb) mice or SD rats, whereas all strains of Ighb (C57BL/6, C57BL/10, B10.D2, B10.BR, B10.A, CB20 and CWB), Ighc (DBA/2), Ighe (A/J), and Igho (C.AL20) responded poorly to the same antigens. This contrasts with the observation that both strains of Ighj (C3H/HeN) and Ighb (B10.BR) responded well at later times. As was the case for late responses, the matching of H-2 between donor and recipient resulted in early responses of exceptional quality in high-responder strains. It was concluded that under the influence of H-2, whose incompatibility between donor and recipient partially interferes with responses, early but not late primary Thy-1.1-specific antibody responses are selectively controlled by Igh-V or closely linked Ir gene(s) as a new VH marker.

Multiple VH gene segments encode murine antistreptococcal antibodies

Most mouse strains are able to mount a diverse antibody response against group A streptococcal carbohydrate (GAC). We have previously reported that murine anti-GAC antibodies are for the most part restricted to IgM and IgG3 subclasses. In addition, despite extensive heterogeneity in their isoelectric focusing patterns, greater than 50% of A/J anti-GAC antibodies share a common light chain defined by spectrotypic and idiotypic (VK1GAC) criteria. We have used protein and DNA sequencing strategies to examine the genetic basis of diversity in murine anti-GAC antibodies. In particular, we report that, (a) multiple, closely homologous VH gene segments contribute to the generation of anti-GAC antibodies, (b) a common framework sequence, related to the VK27 subgroup, probably defines VK1GAC, and (c) the A/J anti-GAC VH regions and BALB/c anti-inulin VH sequences are 95% homologous at the protein level and are likely encoded by overlapping VH gene families. Lastly, we discuss the genetic mechanisms that might permit the evolution of multiple, closely homologous germline VH gene segments in the context of highly divergent flanking region sequences.

Idiotypes of anti-major histocompatibility complex antibodies

Our studies to date indicate that treatment with anti-idiotype to monoclonal anti-MHC antibodies can markedly influence the repertoire of anti-MHC antibodies expressed. The antibodies discussed here appear to represent two classes, one of which is public, probably representing expression of a germ line gene, and the second of which probably represents either a somatic variant of a germ line gene or one of a very large number of germ line genes devoted to the same specificity. In either case, this class of idiotype arises only rarely following antigen, but is readily induced by anti-idiotype treatment. There may indeed exist a third class of anti-MHC monoclonal antibodies representing distant somatic diversification from a germ line gene. Our only indication of this so far is that certain idiotypes are only induced after multiple boosts with anti-idiotypes rather than a single treatment. This finding, however, may reflect again the enormous number of different ways in which anti-MHC antibodies to the same nominal specificity can be produced. Finally, our results in adoptive transfer systems indicate that manipulation of idiotype expression by anti-idiotype treatment probably involves a complex pathway of cellular interactions. If, as we expect, these intercellular interactions involve idiotype and/or anti-idiotypic receptors, they should provide a model for mechanistic studies of the in vivo immune network.

Grouping of haemolytic streptococci by monoclonal antibodies: determinant specificity, cross-reactivity and affinity

Streptococcal group polysaccharide (CHO), A-, A-variant-, B-, C-, D- and G-specific monoclonal antibodies were prepared by the hybridoma technique employing spleen cells of several inbred mouse strains which are either high or low responders to the group A-CHO. The isotypes of these reagents were restricted to the class mu and IgG subclasses gamma 3 and--in small numbers--gamma 1. Two distinct categories of antibodies were identified for all but group D specificity: those which agglutinate suspended bacteria but do not precipitate purified soluble antigen, and those which show both agglutinating and precipitating properties. The group D antibodies described here were only of the latter category. The reactions were inhibitable by haptens in as far as these were known. Cross-reactions were observed in group-A-specific antibodies with E and L polysaccharides. Most G-CHO-specific antibodies cross-reacted with B-CHO. Association constants determined by fluorescence quenching measurements were for binding of complete A and C polysaccharides in the range of 10(6) to greater than 10(8) M-1, and for hapten binding by A-, Av- and C-CHO-specific antibodies in the range of 10(3) to 10(4) M-1. These results support a model of steric arrangements of antigenic determinants on A-variant bacteria and solubilized antigen [42] and allow its extension to streptococcal groups A, B, C and G. This model explains the observed functional differences by postulating single, terminal determinants which interact with the prevailing non-precipitating antibodies and internal repeating determinants which react with precipitins, respectively. No significant differences were found in the reactivity patterns to these streptococcal group antigens between strains of mice in terms of their ability to respond with high or low serum antibody titres to group A-CHO. On the other hand, within high and low responder strains, different kinetics of the optimal timing of fusion after initiation of the secondary immune reaction by boosting was observed. Low responders were most efficiently used for fusion 1.5 days later than high-responder spleen cells. This feature is interpreted to indicate an earlier proliferation of B lymphocytes in high responders, due to either an improved responsiveness to T-lymphocyte help or a reduced reactivity with T suppressor cells in comparison to low-responder B lymphocytes.

Evidence of unique idiotypic determinants and similar idiotypic determinants on human antithyroglobulin antibodies

This is a report on the production of heterologous anti-idiotypic antisera against human anti-thyroglobulin antibodies and on the detection of cross-reactivities among human anti-thyroglobulin antibodies by means of anti-idiotypic antisera. The results are evidence of the existence of unique idiotypic determinant on that anti-thyroglobulin antibody used for immunization and similar idiotypic determinants on all anti-thyroglobulin antibodies.

The immune response against anti-idiotope antibodies. I. Induction of idiotope-bearing antibodies and analysis of the idiotope repertoire

In the present analysis we dissect the idiotype repertoire, independently of hapten-binding specificity, by immunizing different strains of mice with cross-linked monoclonal anti-idiotope antibodies against antibody B1-8. B1-8 is a monoclonal antibody with specificity for the hapten (4-hydroxy-3-nitro-phenyl)acetyl (NP) and carries a germ line gene-encoded variable region. The results demonstrate that the expression of B1-8 idiotopes and their association with each other and with NP-binding specificity are strain-specific. Certain idiotopes are expressed on antibodies differing in antigen-binding specificity, whereas one of the idiotopes appears strictly associated with NP-binding antibodies. The genetic analysis provides strong evidence that the strain specificity of the idiotope repertoire is a result of V region polymorphism in the mouse.

Cross-reactivity of the NPa and NPb idiotypic responses of BALB/c and C57BL/6 mice to (4-hydroxy-3-nitrophenyl)acetyl (NP)

A comparative antigenic analysis was carried out to determine whether cross-reactivity exists between the major idiotypic responses to (4-hydroxy-3-nitrophenyl)acetyl (NP) in BALB/c and C57BL/6 mice. Extensive cross-reactivity exists between the NPa (BALB/c) and NPb (C57BL/6) allotype-linked idiotypic responses to NP. The cross-reactive determinants of the NPb idiotype are confined to one particular group of NPb-positive monoclonal antibodies. The extent of cross-reactivity between this group of C57BL/6 antibodies and idiotype-positive monoclonal antibodies of BALB/c is so great that they cannot be readily distinguished as NPb- or NPa-positive antibodies with polyclonal anti-idiotypic reagents. That this cross-reactivity is not unique to monoclonal antibodies was confirmed by the demonstration of these cross-reactive determinants in the immunesera of individual BALB/c and C57BL/6 mice. Additionally, evidence was obtained from these experiments and from earlier ones from this laboratory which suggests that the BALB/c idiotypic response to NP-protein conjugate is more homogeneous than the C57BL/6 idiotypic responses.

Clonal analysis of a human lymphoblastoid cell line (B17) secreting antibody to N-acetyl-D-glucosamine

In this paper we analyse the clonal composition of a human lymphoblastoid B-cell line secreting IgM/k antibody to N-acetyl-D-glucosamine, the immunodominant sugar of Group-A-streptococcal carbohydrate. Besides non-antibody secreting cells, the line consists of two clonotypes of antibody-secreting cells: B17 cells producing over 90% and F6 cells producing less than 10% of the antibody in the supernatant. The proportions of B17 and F6 cells in the cell line seem to be similar to the proportion of antibodies in the supernatant. F6 cells can be isolated by cloning and maintained as stable lines, whereas this is more difficult with B17 cells. The results suggest that upon establishment of the line, at least two N-acetyl-D-glucosamine-specific B cells were immortalized and coexist together as independent clonotypes. Although F6 cells seem to have a slight tissue culture advantage, they represent the minor clonotype in the B17 cell line.

An immunoglobulin V gene polymorphism in the rat

Anti-phenyloxazolone (phOx) antibodies of different AVN rats (primary response) share several isoelectric focusing bands. These bands were not shared by antibodies of some other rat strains, including DA. An anti-idiotype reagent was prepared (in rabbits) that bound radioactive anti-phOx antibodies of AVN rats but not normal AVN immunoglobulin. This binding was strongly inhibited by AVN anti-phOx antisera, but not by AVN anti-BOC-p-azobenzene arsonate-tyrosine antisera or DA anti-phOx antisera. Anti-phOx antisera of (AVN X DA)F1 rats were also strongly inhibitory indicating the presence of the idiotype (Ox-r1). Antisera of backcross rats (AVN X DA) X DA either resembled F1 hybrid sera (31 rats) or DA sera (23 rats). The data suggest that the presence of idiotype Ox-r1 is controlled by one gene, or genes linked to each other. The gene(s) is not linked to the Ig kappa chain locus. It may be a V gene of the Ig H chain.

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

After immunization of mice with 2,4-dinitrophenyl-ovalbumin (DNP-OVA), it was shown previously that strains having Igh-Va genes and able to express light chains of the Vk1 group produce high levels of anti-DNP antibody bearing an idiotype (Id-460) associated with the combining site of the BALB/c DNP-binding myeloma protein MOPC 460. Expression of Id-460 in serum is transient; Id-460 levels peak early in the response and are regulated independently of total anti-DNP antibody. In this paper, the transient dominance of Id-460 expression has been confirmed at the cellular level by inhibition of splenic anti-DNP plaque-forming cells (PFC) with rabbit anti-Id-460 antiserum. Id-460+ PFC can account for 52-91% of anti-DNP PFC early after secondary challenge with DNP-OVA. Furthermore, Id-460 is represented at these high levels in IgM, IgG, and IgG1, and IgG2a, the three isotypes tested in the PFC assay, as well as in IgE, as tested by passive cutaneous anaphylaxis. Thus, there is no preferential association of Id-460 with a given isotype. We conclude from these studies that Id-460 is a dominant idiotype in the anti-DNP antibody response of BALB/c mice to DNP-OVA. This dominance is expressed transiently and is independent of isotype. A further conclusion from these studies is that regulation of isotype expression is independent of the regulation of idiotype expression in this system. We would suggest that regulation of Id-460 expression involves Ig-dependent helper T cells specific for Id-460 that induce Id-460+ B cells and also activate suppressor T cells, both events occurring via idiotype-anti-idiotype interactions.

Characterization of the NPa idiotype through the analysis of monoclonal BALB/c anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) antibodies

Spleen cells from BALB/c mice were fused with the nonsecreting myeloma line X63.Ag8.6.5.3 seven days after immunization with NP-CG (4-hydroxy-3-nitrophenyl) acetyl-chicken gamma-globulin. The hybrid cell lines obtained were analyzed for heavy and light chain distribution, fine specificity, and idiotype. The majority of monoclonal antibodies possessed either gamma 1 or mu chains. The distribution of L chains among these antibodies was approximately half lambda and half kappa . Thirteen monoclonal antibodies were grown as ascites tumors in mice. Examination of their fine specificity patterns showed that all of the lambda antibodies are heteroclitic and have similar fine specificity patterns. Five of the seven kappa antibodies are also heteroclitic, but their fine specificity patterns are more heterogeneous than those of the lambda antibodies. Polyspecific anti-idiotypic sera directed against pooled primary serum antibody (R a-NPa) or against individual monoclonals were used for idiotypic characterization of the monoclonal antibodies. The Ra-NP bound all of the lambda antibodies but none of the kappa antibodies suggesting that the kappa antibodies may be much more heterogeneous and were therefore not recognized in the presence of the more homogeneous lambda antibodies. Further idiotypic analysis demonstrated that the lambda antibodies, although no two are identical, are a very homogeneous group of antibodies which cross-react with one another but not with the kappa antibodies. Some, but not all, of the kappa antibodies cross-react with each other although none are cross-reactive with the lambda antibodies. Because the lambda-associated idiotype is recognized by the R a-NPa and its characteristics are similar to that of the C57BL/6 major idiotype (NPb), it is referred to as NPa. There may be a second major idiotype associated with at least some of the kappa antibodies.

Autoregulation of immune responses via idiotype network interactions

Images

Late clonal selection and expansion of the TEPC-15 germ-line specificity

The maturation of the antibody response to phosphorylcholine (PC) in neonatal BALB/c mice was studied. A T cell-independent class 1 1 PC-antigen, 3-(p-azophenyl phosphorylcholine)-N-acetyl-L-tyrosylglycylglycine lipopolysaccharide, was synthesized and used to immunize neonatal mice of different ages. The earliest anti-PC hemolytic plaque-forming response could be induced in 1-d-old neonates. Idiotype analysis on these early anti-PC antibodies showed that the response was not TEPC-15 dominant although TEPC-15-positive plaque-forming cells were detected. However, idiotype analysis of the anti-PC-LPS response in 7 d or older animals indicated that clonal dominance had been established. Similar results were obtained in splenic fragment culture with cells from neonatal livers and spleens. PC-specific precursors were detected in the liver of 1-d-old neonates, whereas the spleen of those animals contained no precursors for PC. Precursors for PC residing in the neonatal liver are not TEPC-15 dominant, whereas the splenic PC precursors of 5- to 6-day-old animals express the TEPC-15 idiotype dominatly. These findings demonstrate that during ontogeny PC-specific B cells appear before the TEPC-15 clone becomes dominant. Thus clonal dominance in the adult anti-PC response and late acquisition of the TEPC-15 specificity during ontogeny do not signify a particularly unique or direct relationship to the expression of genes encoded in the germline.

A gene of the immunoglobulin H-chain cluster controls the murine antibody response to pneumococcal polysaccharide type 14

Mice of various strains were immunized with pneumococcal polysaccharide type 14 (pneumo-14), and their anti-pneumo-14 antibodies were measured by the Farr test. Mice of strains BALB/c, ST/b, NZB and CBA (Ig allotypes a, e or j) had 300-1700 ng of antibody nitrogen per millilitre of serum on day 7. The corresponding values for C57BL/Ka, RF or AKR mice (allotypes b, c or d) were 40-300 ng/ml. Two families of congenic strains were tested, one with the C57BL and the other with the BALB/c background genome. Their response was either high or low depending on the VH genes, and other gene loci had little effect on the concentration of anti-pneumo-14 antibodies.

Immunoglobulin diversity in the phylogenetically primitive shark, Heterodontus francisci. Suggested lack of structural variation between light chains isolated from different animals

A two-step procedure employing gel filtration and anion exchange chromatography has been utilized to isolate LMW immunoglobulin from the horned shark, Heterodontus francisci. Light chains obtained by complete reduction and alkylation of the parent protein have been compared by several analytical techniques. Amino acid composition data implies a limited degree of variation in the light chains isolated from individual animals. Polyacrylamide gel electrophoresis of the CNBr digests of the light chains reveal indistinguishable banding profiles of the major peptides. Isoelectric focusing indicates limited heterogeneity in the light chain spectrotype and identity in the pI of the majority of bands detectable by staining. The suggested degree of structural similarity in the light chains of this phylogenetically primitive shark is discussed in terms of the evolutionary position of the species and current theories concerning the origins of structural diversity in immunoglobulins.

Regulation of the anti-inulin antibody response by a nonallotype-linked gene

The antibody response to the inulin [(In), beta-(2 leads to 1) fructosan] determinant of bacterial levan [(BL), a beta-(2 leads to 6) polyfructosan that contains beta-(2 leads to 1) branch points] requires the presence of the a haplotype of the Igh gene complex. BALB/c (Igh a) mice immunized with BL produce IgG anti-In antibodies of a single spectrotype by isoelectric focusing analysis. C57BL/6 mice, which possess the b haplotype of the Igh gene complex and which fail to produce anti-In antibodies, nevertheless possess a gene, spectrotype regulation gene 1 (Sr-1), that regulates the isoelectric focusing (IEF) pattern of anti-In antibodies in mice of the a haplotype. Thus, the IEF patterns of anti-In antibodies of (BALB/c x C57BL/6)F1 mice and of B.C8 mice (C57BL/Ka . Igh-Ca) are considerably more complex than those of BALB/c. Backcross analysis indicates that Sr-1 is not linked to the Igh complex, the major histocompatibility complex, or to the genes that code for coat color. Studies of the heterogeneity of anti-In antibodies in recombinant inbred lines and their progeny from matings to BALB/c and C.B20 (BALB/c . Igh-Cb) suggest the existence of other regulatory genes.

Subclass restriction of murine antibodies. II. The IgG plaque-forming cell response to thymus-independent type 1 and type 2 antigens in normal mice and mice expressing an X-linked immunodeficiency

Antigens have been classified previously into three categories, thymus-dependent (TD), thymus-independent type (TI) 1, and TI-2, based upon thymic dependence and ability to stimulate an immunodeficient strain of mouse, CBA/N. Here we demonstrate that the different antigen classes elicit IgG antibodies of different subclasses. TD antigens stimulate predominantly IgG1 antibodies, with smaller amounts of IgG2 and IgG3 being expressed. TI-1 antigens stimulate almost no IgG1 antibodies and equal amounts of IgG2 and IgG3. TI-2 antigens elicit predominantly IgG3 antibodies. Mice expressing the CBA/N phenotype are known to be nonresponsive to TI-2 antigens. This was confirmed in this study. In addition, we demonstrate that the IgG3 component of the response to TI-1 antigens is virtually absent in mice expressing the CBA/N phenotype, which supports our previous finding that the CBA/N defect may be restricted to a B-lymphocyte subpopulation containing most of the precursors of IgG3-secreting cells.

Feedback suppression of the immune response in vitro. II. IgVH-restricted antibody-dependent suppression

Feedback suppression of the primary humoral immune response to sheep erythrocytes (SRBC) in vitro was induced with cell-free supernate material derived from antigen-(SRBC) activated B (sIg+) cells. This soluble products bears Ig determinants and binds to the eliciting antigen (SRBC). The activity of this antibody in suppressing anti-SRBC plaque-forming cell responses is restricted to spleen cell cultures containing B cells sharing VH genes with the B cells producing the suppressive antibody. The anti-hapten (trinitrophenyl) response to derivatized SRBC is not affected by antigen-primed B cells or their products. These data are compatible with suppression being mediated by anti-antigen antibody, either (a) via blockade of different SRBC epitopes recognized by a limited set of B cell clones in each mouse strain, (b) via triggering of an anti-idiotypic response, either antibody or suppressor T cell in nature, restricted to activity in cultures containing B cells sharing VH structures with the original antibody, or (c) via interference by preformed antibody with T cell help directed at idiotype bearing B cells.

Correlated expression of VH framework and VH idiotypic determinants on T helper cells and on functionally undefined T cells binding group A streptococcal carbohydrate

Antibodies to framework determinants of the VH and V lambda fragments of MOPC 315 and antisera to the VH idiotype determinants of the A 5 A antibody were used to analyze the antigen receptors of mouse T (and B) cells. This was done by using the antibodies as inhibitors in (a) an assay in which the binding of radiolabeled streptococcal carbohydrate (A-CHO) antigen by primed and unprimed T and B cells is determined and (b) an assay in which the helper activity of group A streptococcal vaccine-primed T cells is determined. The results suggest that the major proportion of primed and unprimed T cells binding A-CHO (70-90%) exhibit VH framework and VH idiotypic determinants. This population appears to include the helper T cells. A minor proportion of T cells (10-30%) express V lambda-related framework determinants and lack VH framework and VH idiotypic determinants. This population does not include T helper cells. Taken together, the data suggest that a subpopulation of T cells, including the helper cells, uses entire Ig VH regions as part of their antigen receptor system.

Production of auto-anti-idiotypic antibody during the normal immune response to TNP-Ficoll. II. Hapten-reversible inhibition of anti-TNP plaque-forming cells by immune serum as an assay for auto-anti-idiotypic antibody

Sera taken from AKR/J mice 7 d after the intravenous injection of 2,4,6-trinitrophenyl-lys-Ficoll (TNP-F) caused a specific inhibition of anti- trinitrophenol (TNP) plaque-forming cells (PFC) in vitro. This inhibition was reversed by the incorporation of 10(-8)-10(-7) M 2,4,6-trinitrophenyl- epsilon-amino-n-caproic acid (TNP-EACA) into the agar during the PFC assay. The factor responsible for the hapten-reversible PFC inhibition was removed from serum by passage through an anti-immunoglobulin column or through a 2,4,-dinitrophenyl-human-serum-albumin-bromoacetylcellulose plus anti-TNP- antibody column, but not by DNP-HSA-BAC alone. It was concluded that this immunoglobulin-like substance, lacking anti-TNP activity but reacting with anti-TNP antibody of AKR/J origin, was most likely an auto-anti-idiotypie antibody that had been produced during the normal course of the response of AKR/J mice to TNP-F. Pools of anti-idiotypic-antibody-containing antisera inhibited anti-TNP plaque formation to varying degrees when tested on d-4 PFC from different mice of the same inbred strain, suggesting a variability in idiotype expression. 4 d after transfer of immune (7 d after 10 mug TNP-F, administered intravenously) AKR/J spleen cells plus 10 mug TNP-F into syngeneic mice, the number of PFC detectable in the recipients' spleens could be markedly augmented by the inclusion of TNP-EACA in the agar during the PFC assay. Incubation of spleen cells containing such hapten-augmentable PFC with TNP- EACA yielded a factor in the supernate that caused a specific, in vitro, hapten-reversible inhibition of anti-TNP PFC. Studies with immunoadsorbents indicated that this PFC-inhibiting factor was antigenically immunoglobulin- like, lacked anti-TNP-antibody activity, but reacted with anti-TNP antibody of AKR/J origin. The results are consistent with the view that this PFC inhibitor is auto-anti-idiotypic antibody that is involved in the normal regulation of the immune response. It is proposed that hapten-reversible inhibition of plaque formation can be employed as an assay for anti-idiotypic antibody and the conditions for such an assay are described. It is further proposed that the detection of hapten-augmentable PFC suggests the presence of auto-anti-idiotypic antibody.

Distinct functions of monoclonal IgG antibody depend on antigen-site specificities

Intraveneous hyperimmunization of selectivity bred rabbits with streptococcal group A-variant vaccines elicits antibody responses of restricted heterogeneity at high antibody levels. All antisera contain two functionally distinct antibody populations, which can be isolated in single-band purity upon analytical isoelectric focusing. Typical examples of these two kinds of single-band antibodies were investigated in great detail for several parameters by a variety of methods. 85--99% of the streptococcal group A-variant polysaccharide (Av-CHO)-specific antibody in the antisera does not precipitate the isolated 5,000 daltons poly-L-rhamnose antigen, neither agglutinates nor lyses in the presence of complement Av-CHO-coated sheep erythrocytes (SRBC), binds the radio-labeled Av-CHO with an association constant in the ragne of 10(5)--10(6) M-1, and is of terminal specificity (nonreducing end) for the linear Av-CHO. In contrast, the minor fraction of Av-CHO-specific antibody (1--15%) does precipitate the linear Av-CHO, both agglutinates and lyses Av-CHO-coated SRBC in the presence of complement, has an affinity range of 10(8)--10(9) M-1, and is of internal specificity for the Av-CHO. The antigenic determinants of the Av-CHO for the antibodies are nonoverlapping, only one Fab of the low affinity antibody can be bound whereas four Fab of the high affinity antibody are accommodated. Hence, the determinant specificity explains the functional differences observed, for there is no indication of subclass differences. A mechanistic model of the A-variant carbohydrate presentation on the vaccine appears to account best for the unbalanced levels of low and high affinity antibody.

Recognition of idiotypes in lymphocyte interactions. I. Idiotypic selectivity in the cooperation between T and B lymphocytes

Idiotypic restrictions are demonstrated in vitro for the cooperation between T and B lymphocytes with specificity for Group A streptococcal carbohydrate. T helper cells which have been primed in vivo with anti-idiotypic antibodies to the A5A idiotype and which are therefore essentially A5A idiotype-positive, cooperate only with A5A idiotype-positive B cells, even when mixtures of A5A idiotype-positive and A5A idiotype-negative B cells are present. Essentially A5A idiotype-negative T helper cells that have been primed in vivo with Group A streptococcal vaccine after in vivo suppression with anti-A5A idiotypic antibody are unable to cooperate with B cells which have been primed with anti-A5A idiotype antibody and which are therefore essentially A5A idiotype-positive. Mixtures of A5A idiotype-negative and A5A idiotype-positive T cells cooperate with both A5A idiotype-negative and A5A idiotype-positive B cells. Idiotypic restrictions could not be demonstrated for T and B cells recognizing carrier and hapten determinants, respectively, in experiments in which the cooperation of genetically VH-identical T and B cells was compared to the cooperation of genetically VH-different T and B cells. The data are discussed with respect to various models for the communication between T and B cells. It is proposed that for successful T-B cooperation, ordinarily two types of T helper cells are required, one recognizing the antigen and the other recognizing the idiotype of the B cell.

Inheritance of antibody specificity V. Anti-2-phenyloxazolone in the mouse

Antibodies to hapten 2-phenyloxazolone (phOx) of all BALB/c and DBA/2 mice have the same idiotype and the same major (public) isoelectric focusing pattern whose main spectrotype is called Ox-1. Neither of these characteristics could be readily demonstrated in anti-phOx antibodies of C57BL, C3H or LP mice; these antibodies were heterogeneous, and lacked public spectrotypes. Also, a fine specificty difference could be demonstrated between anti-phOx antibodies of BALB/c and C5MBL mice; the latter have a higher relative affinity than the former for a structural analogue of phOx (2-o-iodophenyloxazolone). The three BALB/c characteristics were inherited in congenic and recombinant inbred strains as an allotype-linked block, defining a new VH marker, VHphOx. Murine anti-phOx antibodies were found to exhibit three types of conservatism: (a) Every individual mouse of strains BALB/c, DBA/2 or BAB-14 had an almost indistinguishable IEF pattern. (b) These patterns (and the cross-reactive idiotype) remained virtually unchanged during an immunization course of 70 days. (c) An identical idiotype (and in some cases IEF pattern) was present in mouse strains of five different allogroups.

Antibody diversity in amphibians: inheritance of isoelectric focusing antibody patterns in isogenic frogs

Anti-sheep red cell, anti-dinitrophenyl, anti-phosphorylcholine antibody responses have been followed in isogenic frogs of the genus Xenopus. Isoelectric focusing antibody patterns show a high degree of overlap for all antigens studied, and a heterogeneity that is lower than in mammals for the same antigens. Inheritance of antibody isoelectric focusing spectrotypes was demonstrated for sheep red cells and dinitrophenyl in two clones of isogenic animals. Outbred frogs show a higher frequency of spectrotype sharing than outbred mammals. It is therefore suggested that antibody diversity is lower in frogs than in mammals.

The diversity of the influenza-specific primary B-cell repertoire in BALB/c mice

The primary immune response of BALB/c mice to influenza (PR8) hemagglutinin (HA), a complex protein antigen, has been examined by the splenic focus assay, and the resulting monoclonal anti-HA antibodies have been characterized by their reactivity with heterologous viruses. The analysis of the primary B-cell response to HA revealed marked differences from responses previously defined for haptenic determinants. There were following differences: (a) the frequency of HA-specific B cells in both conventional and germ-free BALB/c mice was 1 in 1.0-1.5 X 10(5) splenic B cells, which is substantially lower than the frequency of B cells responsive to various simple haptenic determinants; (b) monoclonal anti-HA antibodies were predominantly of the IgA or IgM isotypes instead of IgG, which dominates antihapten responses; and (c) after immunization, the frequency of anti-HA-specific B cells increases by 10- to 50-fold, which is much greater increase than that observed after immunization with haptenic determinants. Fine specificity analysis of primary monoclonal HA-specific antibodies revealed extensive diversity and a considerable overlap with the specificities obtained from immune mice. Given the low overall frequency of HA-specific B cells, it could be calculated that the representation of most HA-specific clonotypes within the B-cell repertoire could not exceed 1 in 10(7) B cells. These findings indicate that the primary B-cell clonotype repertoire is extremely diverse and largely antigen independent in its generation.

Differential expression of an equivalent clonotype among BALB/c and C57BL/6 mice

The primary anti-phosphorylcholine (PC) response in BALB/c, C57BL/6, and congenic and recombinant inbred strains of these parental types has been examined in the splenic focus system. The frequencies of PC-specific precursors were shown to vary among these strains from 2 to 20 precursors per 10(6) splenic B cells. The distribution of these frequencies suggests that elements closely linked to or within the major histocompatibility complex may play a role in the determination of this parameter, although additional experiments are necessary to adequately assess this possibility. Moreover, all strains tested, regardless of immunoglobulin allotype, expressed monoclonal antibodies indistinguishable from the TEPC 15 myeloma protein (T15) clonotype. Further, the frequency of this clonotype in a given strain did not appear related to allotype, since both high and low T15 frequencies were found among strains of either the BALB/c (a(1)) or C57BL/6 (a(2)) allotype. The examination of normal serum for the T15 idiotype, however, revealed that only mice of the BALB/c allotype (a(1)) expressed the T15 idiotype in detectable quantities. After immunization with Diplococcus pneumoniae, sera from mice of the a(1) allotype consistently contained large quantities of the T15 idiotype, whereas sera from mice of the a(2) allotype exhibited various degrees of cross-reactivity with anti-T15 antibody. These results suggest that: (a) the allotype of an individual, although closely related to serum levels of an idiotype, is unrelated to the proportion of the precursor population which expresses that idiotype and; (b) the serum expression of a given idiotype may reflect regulatory processes, which act either during or before antigenic stimulation, rather than the actual clonotype representation in the repertoire. These findings indicate that distinctions must be made between the expression of idiotypic determinants within precursor B-cell populations and elements which regulate the subsequent appearance of those idiotypes in serum antibodies.

Two str1cturally similar haptens each induce a different inherited idiotype

When mice of the A/J strain were immunized with azobenzenearsonate (ABA) directly coupled to a protein, they produced antibodies that share an inherited cross-reactive idiotype (CRI). In the antigenic determinant that induces CRI, ABA is very probably coupled to tyrosine, and the structure that protrudes from the polypeptide backbone has two benzene rings and a molecular weight of 419. When this same structure is separated from the polypeptide backbone by a spacer of 99 daltons, it induces a different inherited idiotype (ABA-HOP-e) in the same strain of mice. Our data suggest that antibodies with the idiotype CRI recognize the terminal benzene ring and the azo group, but do not fit closely around the second ring structure. Antibodies with the idiotype ABA-HOP-e have fine specificity for both benzene rings. Both idiotypes are inherited and both are linked to genes controlling constant regions of the heavy chains.

Absolute frequencies of lipopolysaccharide-reactive B cells producing A5A idiotype in unprimed, streptococcal A carbohydrate-primed, anti-A5A idiotype-sensitized and anti-A5A idiotype-suppressed A/J mice

The absolute frequencies of B cells-producing A5A idiotype have been determined in vitro by limiting dilution analysis in a culture system in which every LPS-reactive B cell grows into a clone of IgM-secreting cells. Spleen cells from normal A/J mice contain 1 A5A-idiotype-producing B-cell precursor in 2.5 X 10(3) LPS-reactive B cells. Approximately a 10-20-fold increase in frequencies of precursor cells from antigen priming with Strep A-CHO (1 in 2.8 X 10(2)) or from sensitization with IgG1 anti-A5A idiotype (1 in 1.3 X 10(2)). Injection of IgG2 anti-A5A idiotype which has been shown to suppress A5A idiotype in vivo results in only a marginal and maybe insignificant decrease in precursor frequencies (1 in 6.7 X 10(3)). On the other hand, priming does not result in a detectable qualitative difference in the specific precursor cells, since each clone of B cells secretes 30 ng of A5A-bearing Ig within 8 days of culture, regardless of being unprimed or primed. Nearly half of all A5A idiotype-producing clones, both from unprimed as well as from primed mice, show antigen specificity in binding A-CHO. Priming by antigen, therefore, also results in a 10-fold increase in the frequency of idiotype positive B cells without antigen specificity. This result is a prediction of the network hypothesis.