Studies of structure and immunosuppression of cross-reactive idiotype in strain A mice

On the nomenclature for V-region serological markers

A recent article in Immunology Today raised significant questions concerning the appropriate use of the terms 'idiotype' and 'V-region isotype'. An alternative approach to the usage of these terms, which emphasizes their functional aspects, is presented here by Alfred Nisonoff.

Transient dominance of the early primary immune response by a highly conserved B-cell clone that is distinguished by its lack of memory, high threshold of activation, and a high affinity

We establish here that the very early primary response to the hapten phthalate (Xmp) is distinguished by a restricted heterogeneity with over 80% of the anti-Xmp antibodies expressing a single well-defined cross-reactive idiotype (CRIXmp-1) associated with a previously described highly conserved clonotype that is expressed by most inbred strains of mice and many outbred mouse populations as well. The characteristic early dominance of this one clonotype in the primary response is transient. While the CRIXmp-1 clonotype is present later in the primary and throughout the secondary response, it represents only a very small proportion of the total anti-Xmp antibody population at these times. The early dominance of the single clonotype is rapidly replaced by a heterogeneous population of antibodies. Differential activation thresholds for the primary response clonotype (CRIXmp-1) and secondary response clonotypes, and the failure of the dominant primary response clonotype to expand in the secondary response (i.e., absence of memory) suggest the presence of two distinct B-cell lineages.

Comparison of the immune response to Ars-BGG in germfree or conventional piglets

Neonatal germfree (GF) colostrum-deprived and conventional (CV) colostrum-fed piglets were immunized IP with p-azo-phenyl-arsonate-bovine gamma globulin (Ars-BGG) in Freund's adjuvant to study the development of the immune response in the absence or presence of maternal antibodies and environmental antigens. Overall, the immune response varied greatly within each group but did not differ in GF from CV piglets statistically. Affinity immunoblot analysis suggested that anti-Ars antibody was more restricted in GF than CV piglets and clonotype shifts occurred more in GF than CV piglets after each antigenic stimulation. In contrast, the clonotype pattern of the anti-BGG antibody was similarly heterogeneous in the two groups. Based on the affinity immunoblot data the antibodies generated to the Ars-haptenic group in CV piglets are more heterogeneous than GF piglets and suggest that clonotype generation is influenced by maternal antibodies and environmental antigens.

The distinctive specificity of antigen-specific suppressor T cells

Although suppressor T cells have been cloned in only a few instances, the existence of a functional cadre of T cells that acts to downregulate the immune response is well documented. In this review Eli Sercarz and Urszula Krzych describe studies on suppressor T-cell (TS-cell) specificity that provide some support for the conclusion that the TS cell is a distinctive cell type with an expressed repertoire that is different from that expressed by helper T (TH) cells. They go on to explore the interaction between cells recognizing TS-cell-inducing determinants (SDs) and TH-cell-inducing determinants (HDs), and their relationship to immunogenicity and Ir gene effects.

Three-dimensional structure of Fab R19.9, a monoclonal murine antibody specific for the p-azobenzenearsonate group

The crystal structure of Fab R19.9, derived from an anti-p-azobenzenearsonate monoclonal antibody, has been determined and refined to 2.8-A resolution by x-ray crystallographic techniques. Monoclonal antibody R19.9 (IgG2b kappa) shares some idiotopes with a major idiotype (CRIA) associated with A/J anti-p-azobenzenearsonate antibodies. The amino acid sequences of the variable (V) parts of the heavy (VH) and light (VL) polypeptide chains of monoclonal antibody R19.9 were determined through nucleotide sequencing of their mRNAs. The VL region is very similar to that of CRIA-positive anti-p-azobenzenearsonate antibodies as is VH, except for its third complementarity-determining region, which is three amino acids longer; it makes a loop, unique to R19.9, that protrudes into the solvent. A large number of tyrosine residues in the complementarity-determining region of VH and VL, with their side chains pointing towards the solvent, may have an important function in antigen binding.

Antigen specific down regulation of murine collagen induced arthritis: T suppressor cell circuits in arthritis immunotherapy

The present article summarizes a series of experiments which have been performed to describe an antigen-specific suppressor cell pathway for the suppression of the erythema and edema associated with an animal model of rheumatoid arthritis, collagen induced arthritis (CIA). Initial studies utilized the adoptive transfer of splenic cell subpopulations to establish the presence of suppressor cells in lymphoid tissues of mice which were suppressed for collagen induced arthritis. Subsequent studies generated T cell hybridomas from animals which had been suppressed for collagen induced arthritis by a single injection of a large quantity of Type II collagen. The T cell hybridomas varied in their self surface expression of glycoproteins which are associated with genetically determined functions. The suppressor T cells generated, described a regulatory suppressor cell pathway comprised of at least afferent suppressor T cells and effector suppressor T cells. The cells act in an antigen-specific fashion with regard to the suppression of collagen induced arthritis but appear to be polymorphic in their recognition of the interstitial collagens. The studies, taken together, indicate that the use of antigen specific T suppressor cells in the form of T cell hybridomas can be utilized as a form of immunotherapy in experimental arthritis.

Regulation of immunity by anti-idiotypic antibodies

The immune system is under control by idiotypic-anti-idiotypic regulation. This control can operate according to dose of antigen, age of the individual, route of administration etc. and function as a specific stimulator or inhibitor of immune reactivity against a defined antigen. Data already exist to justify the statement that our immune system contains within itself all foreign structures against which it can react in the form of anti-idiotypic receptors. These "foreign" structures as displayed at the anti-idiotypic level may be more or less like their true counterparts outside the body and can serve as immunogen, for instance as vaccines. The regulation of immune reactivity via idiotypic interactions may also serve as a potent regulatory of fetal-neonatal immune reactivity causing it to resemble that of the mother. Potential clinical use of auto-anti-idiotypic immunity can thus be foreseen both with regard to elimination of unwanted immune reactivity as well as induction of wanted immunity.

Crossreactivity and inheritance of idiotypes restricted to human anti-tetanus toxoid antibodies

The presence of cross-reactive idiotypes on human IgG antibodies of tetanus toxoid (TT) antigen was assessed by examining the capacity of two anti-idiotypic (ID) antisera raised against IgG (Fab')2 anti-TT (idiotype) from two subjects to bind radiolabeled "idiotype" and to inhibit the binding of radiolabeled TT to IgG from unrelated subjects and from family members of the idiotype donors. Idiotypic crossreactivity with unrelated individuals was infrequent and weak but was frequent and stronger among siblings. The strongest idiotypic crossreactivity was seen between identical twins in studies using four anti-ID raised against the anti-TT idiotypes of two sets of twins. The results of the present study suggest that idiotypic determinants restricted to human anti-TT antibodies are, at least in part, encoded by inherited genes, which are infrequently shared among unrelated individuals.

The repertoire of anti-TNP antibodies in mice neonatally suppressed with anti-IgM

Previous studies have shown that mice immunized with TNP-Ficoll when young, adult, or aged expressed different repertoires of anti-TNP antibodies. The aim of the present study was to find out whether this age-related nonrandom progression was driven by antigen, and whether it was regulated by the immune network through surface-Ig receptors on B lymphocytes. The approach utilized was to block receptor expression on B lymphocytes of mice by the chronic administration of anti-IgM from birth for approximately 1 year, and then compare their subsequent antibody response to that of age-matched control animals. The results obtained have shown that the age-dependent shift in the anti-TNP repertoire expressed could take place in animals whose B lymphocytes were blind to antigen and anti-id for the greater part of their lives and thus suggest that the regulatory events responsible for this shift may be (surface Ig) receptor independent.

Genetic basis for expression of the idiotypic network. One unique Ig VH germline gene accounts for the major family of Ab1 and Ab3 (Ab1') antibodies of the GAT system

Ig germline genes have been isolated from recombinant clones prepared in separate libraries constructed from adult BALB/c liver DNA either in pBR328 plasmid or in EMBL 3 phage. Three clones that gave a very strong positive hybridization signal with a VH anti-GAT-specific probe were completely characterized and sequenced. All three were greater than 95% homologous, with the exception of the 5' noncoding region, which was only 85% homologous but contained characteristic regulatory signals. One of these genes, H10, had a sequence that was completely identical to that of a cDNA derived from a GAT-specific BALB/c hybridoma. Southern blot analysis using Eco RI-digested DNA from rearranged GAT-specific hybridomas revealed that the same gene was used for other GAT-specific VH regions, including one differing from the H10 sequence by 12 nucleotides, which must have been generated by a somatic mechanism. The same H10 germline gene was also used, in most cases without any nucleotide substitution, in hybridomas of the Ab1' set of the GAT idiotypic cascade, suggesting that immunization with Ab2 (antiidiotypic) antibodies preferentially stimulates the direct expression of VH germline genes. Finally, the previous hypothesis that NPa and GAT VH genes were derived from the same germline gene was definitively confirmed, both from sequence data and Southern blot analysis.

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.

Molecular events during maturation of the immune response to oxazolone

Sequence analysis of the heavy- and light-chain messenger RNA of hybridomas immunized with a specific hapten yields important clues about the interplay between genetic and selective events during the onset and maturation of the immune response. The maturation of the primary response to the hapten 2-phenyl-5-oxazolone is characterized by a drift to higher-affinity somatic variants of a germline-encoded basic sequence, whereas hybridomas from the secondary response demonstrate a further maturation dominated by a shift to alternative germline combinations.

Surface expression and partial characterization of an arsonate hapten-specific idiotype-bearing T-cell receptor

Anti-idiotype antibodies raised against the arsonate hapten idiotype have been used to detect arsonate-binding receptors on the surface of peripheral T cells of A/J mice and to isolate this material after biosynthetic labeling for partial chemical characterization. It was found that 2-3% of splenic T cells from arsonate-immune mice specifically bound the hapten using immunofluorescent keyhole limpet hemocyanin as a carrier. In double-immunofluorescence labeling experiments, a high proportion (approximately equal to 70%) of these cells also bound the (Fab')2 fragment of rabbit anti-idiotype antibody in exactly the same patches on the cell as the arsonate hemocyanin antigen. In addition, the anti-idiotype antibody inhibited the binding of the hapten-carrier complex to T cells by approximately equal to 70%. In parallel experiments, fowl antibodies against mouse (Fab')2 fragments bound to 100% of arsonate-binding T cells in the same cell-surface patches as the hapten, and were capable of inhibiting 100% of the hapten-binding cells. Capping, shedding, and resynthesis experiments indicated that the T cells synthesized their antigen-binding idiotype-bearing receptors. Immunoblots of unreduced detergent extracts of purified splenic T cells developed with anti-idiotype antibodies showed bands at 150,000 and 94,000 Da. Equal amounts of protein extracted from liver and analyzed in the same gels as the T-cell material failed to show any reactivity with anti-idiotype antibodies. To confirm the biosynthetic origin of the idiotype-positive materials, detergent extracts from 75Se-methionine- or [3H]leucine-labeled Con A-treated splenic T cells were reacted with anti-idiotype antibodies and the bound material was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the presence of 2-mercaptoethanol the major band was at 68,000 Da, with variable minor levels of material at 45,000 Da, while when hapten was used to isolate the receptor a dominant 25,000- to 30,000-Da band was seen. We believe that the higher-molecular-weight materials are multimers of the 25,000-30,000 subunit.

Analysis and modulation of the immune response of mice to acetylcholine receptor by anti-idiotypes

Anti-idiotypes were raised in mice against three well-characterized anti-acetylcholine receptor (AChR) monoclonal antibodies (mcAbs), as well as against polyclonal mouse anti-AChR antibodies. In binding experiments, the anti-idiotypic antibodies inhibited the binding of AChR only to the immunizing idiotype. However, a less restricted specificity was found in in vivo experiments. Mice producing anti-idiotypes were challenged with AChR and the idiotypic composition of their anti-AChR response was analysed using specific rabbit anti-idiotypic antibodies. It was found that preimmunization with a certain idiotype leads to the preferential suppression of this particular idiotype in the polyclonal response to AChR. However, preimmunization with either polyclonal or monoclonal anti-AChR antibodies resulted in a reduction of the overall anti-Torpedo AChR and anti-muscle AChR titers. This reduction was greater than would be expected from the representation of each of the respective idiotypes in the polyclonal anti-AChR serum, and may imply that in addition to the immunizing idiotype other anti-AChR idiotypes are also suppressed. Our results suggest that anti-idiotypes may have a potential for the modulation of the autoimmune response directed against AChR in myasthenia.

Association of CSF IgG concentration and immunoglobulin allotype in multiple sclerosis and optic neuritis

The cerebrospinal fluid (CSF) and serum from 64 patients with multiple sclerosis (MS) and 47 patients with monosymptomatic optic neuritis (ON) were analyzed for the distribution of allotypic determinants on IgG and compared to similar samples from 51 patients with other neurological diseases (OND) as well as to serum samples from 97 healthy controls. The results indicate a significantly increased frequency of the haplotypes Gm a;g and Gm a,x;g among MS patients (P = 0.024) with an associated increase in relative risk for MS among individuals with the Gm a,(x);g haplotypes compared to those individuals without them (P = 0.014). Among MS patients, those with the Gm a,(x);g haplotypes had significantly higher CSF levels of IgG than those without (P = 0.016); levels of serum IgG did not covary with Gm haplotype. Two-way analysis of variance indicates that familial cases have significantly higher levels of CSF IgG than nonfamilial cases (P less than 0.001) and that familial cases with the Gm a,(x);g haplotypes have the highest CSF IgG levels (P less than 0.005). There was no correlation between Gm haplotype and CSF or serum IgG levels in patients with ON or OND. The allotype effects were independent of age at onset and duration of disease. In all patients, regardless of disease classification, the phenotypes found in serum samples were identical to those found in CSF samples. The data presented support the hypothesis that the etiology of MS has as one of its parameters an immunoregulatory/immunogenetic factor. The successful analysis of these various parameters will provide useful information not only about MS but also about general principles of human immune responsiveness.

Depletion of murine anti-azobenzenearsonate plaque-forming cells by derivatized polyacrylamide beads

The depletion of secondary p-azobenzenearsonate plaque-forming cells (ABA-PFC) by affinity columns substituted with ABA was dependent on the primary dose, times elapsed after priming, and the nature of the side-arm on the columns. Thus, higher priming doses of ABA coupled to keyhole limpet haemocyanin (50-500 micrograms of ABA-KLH in complete Freund's adjuvant (CFA] favoured depletion of ABA-PFC by ABA coupled to a 6- aminocaproyltyrosine side-arm (SAC-TYR-ABA beads), whereas ABA-PFC from mice primed with 1 microgram of ABA-KLH in CFA were never depleted; this latter population were only depleted by ABA coupled to a histamine side-arm (HIST-ABA beads) 7 months after priming. These data are consistent with the notion that two specificities, HIST-ABA and TYR-ABA, appear to emerge independently, lower priming doses inducing the preferential appearance of the HIST-ABA specificity.

Induction of idiotope suppression in the anti-azophenylarsonate response of T-depleted A/J mice

The homologous, monoclonal antiidiotope, MB, induced idiotope suppression that was remarkably stable and could be transferred by B lymphocytes. Marked depletion of T cell function, confirmed by limiting diluting analysis, did not affect the ability of MB to suppress the corresponding idiotope. Suppression induced by MB appears to result from direct interaction with idiotope-positive B cells, without the intervention of idiotope-specific T suppressor cells.

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

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

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

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

Monoclonal antibodies reveal the structural basis of antibody diversity

Hybridoma technology has made it possible to introduce into continuous culture normal antibody-forming cells and to obtain large amounts of the immunoglobulin produced by each of these cells. Examination of the structure of a number of monoclonal antibodies that react with a single antigen has provided new information on the structural basis of the specificity and affinity of antibodies. Comparisons of families of monoclonal antibodies derived from a single germ line gene revealed the importance of somatic mutation in generating antibody diversity. Monoclonal antibodies that react with variable regions of other monoclonals allow the further dissection and modulation of the immune response. Finally, the continued somatic instability of immunoglobulin genes in cultured antibody-forming cells makes it possible to determine the rate of somatic mutation and to generate mutant monoclonal antibodies that may be more effective serological reagents.

An antigen-specific signal is required for the activation of second-order suppressor T cells in the regulation of delayed-type hypersensitivity to 2,4,6-trinitrobenzene sulfonic acid

Suppressor T cells (Ts-1) induced with trinitrophenyl (TNP)-conjugated syngeneic spleen cells (TNP-SC) can be enriched on antigen-coated plates and are afferent suppressors. In addition, these suppressor cells produced soluble suppressor factors (TsF) that were active in vivo. Therefore, the Ts-1 cells in the TNP system are very similar to the Ts-1 cells in other systems we have studied earlier. Further characterization of these TsF-1 revealed that TsF-1 obtained from TNP-SC-induced Ts-1 is major histocompatibility complex restricted in its activity. Injection of TNP-specific TsF-1 into naive mice did not induce Ts-2 unless additional corresponding antigen was provided. Moreover, the Ts-2 cells induced by administration of both TsF-1 and trinitrobenzene sulfonic acid were antigen specific rather than antiidiotypic.

A bi-directional immune network mechanism: simultaneous induction of idiotype and anti-anti-idiotype in rabbits immunized with antibody to a common idiotypic specificity of anti-VHa2-allotype antibodies

Recently, we identified a common idiotypic specificity (IdC) present on all of the allo and auto anti-VHa2-allotype antibodies tested. In this report, we immunized allotype-matched rabbits with anti-IdC Ab. When an a1a1 homozygote was immunized with anti-IdC Ab (also from an a1a1 rabbit), two distinct Ab populations were induced which were isolated through the use of immunoadsorbent column chromatography. One of these Ab populations, adsorbed to and eluted from an insolubilized a2 IgG column, was anti-VHa2-allotype Ab (Ab 1), which reacted with a2 Ig and inhibited the reaction between the a2 allotype and anti-VHa2-allotype Ab. The other Ab population, adsorbed to and eluted from an insolubilized immunogen anti-IdC column, was anti-anti-IdC Ab (Ab 3), which was specific for the immunogen anti-IdC Ab. In another experiment, when an a1a2 heterozygous rabbit was immunized with anti-IdC Ab, only the Ab 3 was induced, which appeared to be identical to the Ab 3 induced in the a1a1 rabbit. However, when the expression of the a2 allotype in an a1a2 heterozygous rabbit was suppressed and then this rabbit was immunized with anti-IdC Ab, both Ab 1 and Ab 3 were induced. These data indicate the occurrence of a bi-directional immune response within our immune network system. According to Jerne's network theory, Ab 3 appeared to be induced through a stimulation by the idiotope of the immunogen Ab 2, whereas Ab 1 appeared to be induced through a reverse stimulation by the paratope of the immunogen Ab 2. Furthermore, the production of Ab 1 in these rabbits exhibiting the bi-directional immune response was at least 3-5 times greater than that of Ab 3 production indicating that the response through the reverse stimulation appeared to be dominant. The importance of this bi-directional immune response is discussed in this paper.

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.

ABA-specific helper T cells in A/J mice bear the major cross-reactive idiotype

Attempts were made to induce azobenzenearsonate (ABA)-specific helper cell responses in A/J mice. These were measured by an increase in TNP plaque-forming cells following administration of the double hapten conjugate ABA-bovine serum albumin-TNP. Immunization with ABA coupled homologous immunoglobulin or spleen cells produced ABA-specific help only when the same carrier was used to boost. Hapten-specific help was achieved by two injections of ABA-N-acetyltyrosine in complete Freund's adjuvant 5 weeks apart. This help was passively transferable by T cells as shown by its elimination with anti-Thy 1.2 serum and complement treatment. The presence of the major ABA cross-reactive idiotype (CRI) on these T helper cells could be similarly shown by the elimination of help when the cells were treated with rabbit anti-CRI antibody and complement prior to passive transfer. The same treatment did not effect ABA-specific helper activity of CBA/J mice.

A cross-reacting human idiotype (B17) associated with antibodies to N-acetyl-D-glucosamine. Specificity, immunoglobulin class association, and distribution in the population

This report describes the study of the expression of an idiotype in the human population which is associated with antibodies to N-acetyl-D-glucosamine (GlcNAc) present in most human sera presumably due to streptococcal infections. The idiotype is identified with antisera and monoclonal antibodies prepared against the IgM (kappa) antibody secreted by the Epstein-Barr virus-transformed human B cell line B17. At least 90% of 207 individuals tested had immunoglobulin with B17 idiotypic determinants in their sera, as demonstrated with conventional and one monoclonal anti-idiotypic antibody. Another monoclonal anti-idiotypic antibody reacted with antibodies in only a few of the sera. No correlation was found between the level of expression of different idiotopes in individual human sera, suggesting molecular heterogeneity of the B17-positive antibody population. B17-positive immunoglobulins are to a large extent specific for GlcNAc but represent only a minor population of all GlcNAc-specific antibodies in human sera. B17 determinants are on IgM (kappa) in all human sera and on IgG and IgA in some. In addition, some lambda-bearing Ig was found to react with anti-B17 antisera, suggesting the detection of VH-associated idiotypic determinants in this experimental system.

Production of auto-anti-idiotypic antibody during the normal immune response. VI. Hapten augmentation of plaque formation and hapten-reversible inhibition of plaque formation as assays for anti-idiotype antibody

(1) Evidence has been presented that the detection of hapten-augmentable plaques indicates cells whose secretion of antibody had been blocked by the binding of auto-anti-id to cell surface idiotypes. Because of the dependence of the assay on the affinities of the various species for one another, the number of hapten-augmentable plaques detected should be regarded as a minimal estimate of the number of cells whose secretion of antibody is inhibited by auto-anti-id. For confirmation that hapten-augmentable PFC are due to auto-anti-id 2 principal controls are important: (a) incubation of the spleen cell population with hapten prior to plaquing should remove the hapten-augmentable PFC; (b) the dialyzed supernate from hapten incubated cells should inhibit plaque formation in a hapten-reversible manner. (2) Evidence has been presented that hapten-reversible inhibition of plaque formation can serve as an assay for anti-id. Apparent false positive assays can result from the presence of anti-hapten antibody or antigen-antibody complexes; however, these apparent false positives are rarely reversed by hapten. Removal of anti-hapten antibody, by passage over an antigen immunoadsorbent, will eliminate this source of false positives and the procedure is recommended. False negative results can arise from mismatching of the anti-ids in the sample to be assayed and the idiotypes of the target cells used in the assay. This can result from shifts in idiotype expression related to age and time after antigen injection. False negatives can also result from the presence of idiotype-anti-id complexes in the sample to be assayed. This source of false negatives can sometimes be eliminated by passage of the sample through an antigen immunoadsorbent.

Affinity analysis of idiotype-positive and idiotype-negative Ars-binding hybridoma proteins and Ars-immune sera

The possibility that idiotype dominance may be associated with increased affinity for hapten was investigated in the murine A/J anti-p-azophenylarsonate (Ars) response. Fluorescence quenching of 14 Ars-binding hybridoma proteins by Ars-tyrosine was measured and Ka calculated using computer-assisted curve fitting. There was a 200-fold range in Ka for idiotype-positive hybridoma proteins, with 2 IgM hybridoma proteins being near the median. No clear difference in Ka was apparent between idiotype-positive (Id+) and idiotype-negative (Id-) hybridoma proteins. Ka was measured by fluorescence quenching on affinity-purified anti-Ars antibodies from 6 conventional antisera; there was no difference between Id+ and Id- (idiotype suppressed) sera. The affinities of the hybridoma proteins were correlated with the ratio of binding to Ars36-BSA and Ars10-BSA by direct radioimmunoassay. With this calibration, functional affinities of Ars-immune sera could be determined from relative binding ratios without the need for prior affinity purification. This was done for 18 Ars-immune sera, and again there was no clear difference between Id+ and Id- sera. Studies from this laboratory have identified the amino acid sequence of a hybridoma protein which corresponds to the germ line DNA sequence for the cross-reactive idiotype family. The present study shows that the protein directly encoded by the germ line gene has low affinity for hapten suggesting that somatic diversification operating on the germ line sequence can produce antibodies with increased affinity for hapten within the cross-reactive idiotype family. The present study also suggests that affinity is not the driving force behind idiotype dominance of the Ars-immune response.

Fine specificity of idiotope suppression in the A/J anti-azophenylarsonate response

Two hapten-inhibitable murine monoclonal antiidiotopic antibodies identified two idiotopes expressed by the heavy chain of hybridoma protein 36-65, whose amino acid sequence is encoded in the germ line of A/J mice. Among cross-reactive idiotype-positive hybridoma proteins and p-azophenylarsonate-immune antibodies, the two idiotopes were not always expressed together; some diversified antibodies expressed one idiotope without the other. Suppression that was induced by the two antiidiotopes was idiotope specific and corresponded to the fine specificities of these two reagents.

The genetic basis of antibody production: the dominant anti-arsonate idiotype response of the strain A mouse

Immunization of the A strain of mice with the hapten p-azophenylarsonate (Ars) results in an immune response in which approximately 50% of the anti-Ars antibodies share cross-reactive idiotypic determinants (IdCR). A gene or genes linked to the heavy chain constant region locus is required for the production of this idiotype. The expressed VH gene from a hybridoma cell line which expresses the IdCR has been cloned. DNA hybridization studies utilizing the VH gene have revealed that there are many related genes in both idiotype-producing and idiotype-nonproducing strains of mice. However, under stringent hybridization conditions, only a single band of 6.4 kb is present in Eco R1-digested A strain DNA. Strains of mice which are phenotypically idiotype-negative either lack this band completely or possess a much weaker one at this position. Utilizing DNA from Igh recombinant strains of mice, it has been shown that the VH locus controlling idiotype expression contains the structural gene information for the idiotype-positive heavy chains. It has also been shown that DNA at this locus appears to be sufficient for the production of the cross-reactive idiotype. Utilizing a DNA probe derived from regions flanking the structural gene has confirmed the relatedness of V genes in a variety of mouse strains and revealed a significant degree of polymorphism at the Igh locus.

Degree of heterogeneity of binding specificities of antibodies to the phenylarsonate group that share a common idiotype

We have investigated the microheterogeneity of hybridoma products (HP) expressing the major idiotype (CRIA) associated with A/J antibodies to the p-azophenylarsonate (Ar) hapten group. The properties investigated were affinity for a phenylarsonate derivative and the fine specificity of the combining sites of the various HP. The fine specificity was approached by measuring relative affinities for a series of related haptens. It was found that, although variations exist, there are strong similarities in affinities and fine specificities of the antigen-binding sites of CRI+A HP. The range of affinities for (p-azobenzenearsonic acid)-N-3H-acetyl-L-tyrosine was 0.41 x 10(6)-2.2 x 10(6) M-1. In all cases the addition of a second ring structure (benzene or histidine) and an azo group greatly increased the binding affinity. Some differences in fine specificity among the HP were seen with respect to affinities for o-arsanilate or the arsanilate derivative of histidine. However, the two HP which are the strongest inhibitors in the conventional assay for CRIA were virtually identical to one another and to induced A/J anti-Ar antibodies in their fine specificities. Together with previous data on amino acid sequences and serological properties, the results indicate that, despite their microheterogeneity, members of the CRIA family are closely related in structure and hapten-binding specificity.

Antibodies to RNA from autoimmune NZB/NZW mice recognize a similar antigenic determinant and show a large idiotypic diversity

We have identified two RNA-specific hybridoma autoantibodies in fusions of spleen cells from unimmunized NZB/NZW female mice with BALB/c myeloma cells. The two fusion experiments were carried out 2 years apart with different myeloma partners. Specificity analyses showed that the two monoclonal antibodies and the total RNA-binding IgG in NZB/NZW serum recognize a G,C-rich sequence of ribonucleotides. The isolated heavy and light chains of the two antibodies and their papain Fab fragments could be distinguished by NaDodSO4/polyacrylamide gel electrophoresis. Rabbit anti-idiotypic antibodies prepared against the two monoclonal proteins showed unique specificities for the antigen-binding sites of their cognate auto-antibodies. Moreover, the anti-idiotypic antisera had little effect on the RNA-binding capacity of the total IgG from NZB/NZW serum. These results suggest that a wide range of different idiotypes is involved in the autoimmune response to a similar antigenic determinant.

Somatic mutation in genes for the variable portion of the immunoglobulin heavy chain

The size of the gene pool potentially encoding antibodies to p-azophenyl arsonate has been examined. A heavy chain-specific full-length complementary DNA clone has been constructed with the use of messenger RNA from a hybridoma that produces antibodies to the arsonate hapten and bears nearly a full complement of the determinants comprising the cross-reactive idiotype (CRI). The sequences of both the complementary DNA clone and the corresponding immunoglobulin heavy chain have been independently determined. A probe for the variable region gene was prepared from the original heavy chain complementary DNA clone and used to analyze, by Southern filter hybridization, genomic DNA from both A/J (CRI positive) and BALB/c (CRI negative) mice. Approximately 20 to 25 restriction fragments containing "germline" variable region gene segments were detected in both strains, and many are shared by both, Since 35 CRI-positive heavy chains have been partially sequenced thus far and 31 are different, the results of the hybridization analysis suggest that somatic mutation events involving the variable region gene segments of the heavy chain play a role in the origin of the amino acid sequence diversity seen in this system.

T suppressor cells activated by anti-Tsud serum are Igh-V-restricted

T suppressor (Ts) cells can be activated by alloantiserum directed against Tsud, a cell surface marker associated with the Ts cell receptor for antigen. These cells are restricted in their ability to transfer suppression in allotype-congenic mice. Transfer of suppression requires matching of donor recipient mice at Igh-V loci, but recipient mice need not share the Tsud allele nor the same allotype as the activated Ts cells. Genes linked to the kappa light chain locus apparently do not affect this transfer.

Tthyd, a new thymocyte alloantigen linked to Igh-1. Implications for a switch mechanism for T cell antigen receptors

Tthyd is an alloantigen coded for by a gene(s) near the immunoglobulin locus on chromosome 12 in the mouse. This T cell-specific antigen may be the third member of a family of antigen receptors on T cells encoded by a cluster of genes in the IgT-C region. This antigen is preferentially expressed on thymocytes in contrast to Tindd or Tsud that are expressed on peripheral T cells. The hypothesis that T cell receptors undergo a switch in surface isotype upon maturation is discussed.

Anti-idiotypes to monoclonal anti-H-2 antibodies. II. Expression of anti-H-2Kk idiotypes on antibodies induced by anti-idiotype or H-2Kk antigen

Anti-idiotypic antibodies were prepared against two monoclonal anti-H-2Kk antibodies, 11-4.1 and 3-83P. These reagents were used to examine idiotype (Id) expression on anti-H-2Kk antibodies induced by the in vivo administration of the anti-idiotypic antibodies and/or H-2Kk antigen. Treatment of BALB/c mice with anti-Id induced both antigen-binding and nonantigen-binding Id-positive molecules in the absence of antigen. The level of production of anti-Id-induced Id (Id') has been shown to be linked to VH genes using allotype congenic mice and backcross analyses. The idiotypes expressed on the Id' induced in anti-Id-treated mice were closely related or identical to those of the original monoclonal anti-H-2Kk antibody. However, the idiotopes were present on immunoglobulins of different subclasses and in some cases were not all expressed on the same molecules, as reflected by differences in their antigen specificities and isoelectric focusing patterns. In vivo administration of anti-Id had a marked influence on the subsequent humoral response to immunization with H-2 antigen.

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

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