Expression of an idiotype (Id-460) during in vivo anti-dinitrophenyl antibody responses. I. Mapping of genes for Id-460 expression to the variable region of immunoglobulin heavy-chain locus and to the variable region of immunoglobulin kappa-light-chain locus

Diversity in the CDR3 region of V(H) is sufficient for most antibody specificities

All rearranging antigen receptor genes have one or two highly diverse complementarity determining regions (CDRs) among the six that typically form the ligand binding surface. We report here that, in the case of antibodies, diversity at one of these regions, CDR3 of the V(H) domain, is sufficient to permit otherwise identical IgM molecules to distinguish between a variety of hapten and protein antigens. Furthermore, we find that somatic mutation can allow such antibodies to achieve surprisingly high affinities. These results are consistent with a model in which the highly diverse CDR3 loops are the key determinant of specificity in antigen recognition in both T cell receptors (TCR) and antibodies, whereas the germline-encoded CDR1 and CDR2 sequences are much more cross-reactive.

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.

Complexity, polymorphism, and connectivity of mouse Vk gene families

To define the polymorphism and extent of the mouse immunoglobulin kappa (Igk) gene complex, we have analyzed restriction-enzyme digested genomic DNA from 33 inbred strains of mice with labeled DNA probes corresponding to 16 Vk protein groups (1 of them previously undescribed) and the Jk/Ck region (V, variable; J, joining; C, constant). These probes detected between 1 and 25 distinct restriction enzyme fragments (REF) that appeared in up to eight polymorphic patterns, thus defining eight mouse Igk haplotypes. The investigated portion of the Vk repertoire was estimated to encompass between 60 and 120 discernable Vk gene-containing REFs. In contrast to mouse VH gene families, several Vk gene families defined by these probes appeared to overlap. This observation has implications for Vk gene analyses by nucleic acid hybridization and raises the possibility that the Vk gene complex is a continuum of related sequences.

Effect of growth and differentiation stimuli on the development of antigen-responsive B cells in fetal liver

The development of the B cell immune repertoire was studied using an in vitro fetal organ culture system. In order to analyze the mechanism by which B cell precursors clonally expand and diversify, fetal lymphoid tissues were incubated in the presence of several factors known to influence B cell differentiation: IL-1, IL-2, WEHI-3 culture supernatant containing IL-3, and a factor from a cyclic neutropenia patient (CNF). By analyzing the effect of exogenous factors on the frequency of antigen-responsive B cells, the ability of the factor to either inhibit or enhance clonal expansion was determined. It was found that the addition of IL-1, WEHI-3 supernatant, or CNF increased the frequency of DNP-responsive B cells suggesting an enhancement of clonal expansion. IL-2, on the other hand, did not alter the frequency of antigen-responsive B cells. The effect of added factors on the kinetics of appearance of phosphorylcholine (PC)-responsive B cells, which are known to be acquired in ontogeny about 2 weeks later than DNP-responsive B cells, was also analyzed. The data indicate that CNF, unlike IL-1, IL-2, and WEHI-3 culture supernatant, results in an earlier appearance of PC-responsive B cells. These results suggest that soluble factors may play a role in the generation of the B cell repertoire.

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

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

Structural differences in a single gene encoding the V kappa Ser group of light chains explain the existence of two mouse light-chain genetic markers

Two phenotypic markers of mouse immunoglobulin kappa light chains, the IB-peptide marker and the Ef1a isoelectric focusing marker, are expressed by the C58/J, AKR/J, RF/J, and PL/J strains (called expressor strains) but not by BALB/c and most inbred strains. Expression is linked to the kappa light-chain locus and the Lyt-2/Lyt-3 genes on chromosome 6. Light chains bearing these markers belong to a group of variable region kappa chain (V kappa) regions called V kappa Ser, which has a serine amino terminus and a framework 1 region not observed to date among BALB/c light chains. Southern hybridization of genomic DNA with a V kappa Ser-specific cDNA probe has demonstrated a single strongly hybridizing DNA fragment in all strains of mice tested. Characteristic restriction enzyme polymorphisms define the V kappa Ser alleles of expressor (Igk-VSera) and nonexpressor (Igk-VSerb) strains. In the present study, the unrearranged V kappa Ser gene and its flanking regions from an expressor (C.C58) and nonexpressor (BALB/c) strain have been cloned and their nucleotide sequences determined. The C.C58 V kappa Ser gene isolated (the Igk-VSera allele) was shown to code for the two phenotypic markers described. While the nucleotide sequence of the BALB/c coding region (the Igk-VSerb allele) shows 97% identity with the C.C58 gene, single nucleotide substitutions lead to structural changes in the encoded protein which render it IB-negative and Ef1a-negative. These differences alone can explain the failure of strains containing the BALB/c allele to express these kappa-chain phenotypic markers. Also, the BALB/c gene contains a single substitution in a conserved octamer sequence approximately equal to 100 nucleotides upstream of the coding region, which could affect its expression. Finally, the C.C58 allele contains a BAM5/R repetitive DNA element approximately equal to 1200 nucleotides upstream of the coding regions that is not present in BALB/c. This element gives rise to the EcoRI and BamHI restriction enzyme polymorphisms, which distinguish the Igk-VSera and Igk-VSerb alleles.

Structural polymorphism of V kappa 21 E and V kappa 21 D gene products in laboratory mice

The aim of the present work was to study structural polymorphism of V kappa genes products. To this end we isolated immunoglobulins expressing the V kappa 21 D and V kappa 21 E gene products from the normal sera of several inbred strains of mice using a monoclonal antibody that selectively recognizes V kappa 21 D and V kappa 21 E subgroups. Analysis of the isoelectric focusing pattern of the light chain of these immunoglobulins revealed the existence of 3 clearly different phenotypes. The first one is shared by most inbred strains of mice, the second one is expressed by C58/J, AKR and PL/J and the third one defines V kappa 21 D-E light chains of SJL and SJA mice. Genetic analysis revealed that the locus controlling V kappa 21 D-E chain structure is closely linked to the Ly2-3 and to the Ig Kappa-Ef1 loci. Finally, using recombinant mouse strains, we could also order V kappa 21 D-E genes with respect to the known loci affecting V kappa polymorphism. Taken together our data argue against the possibility that the polymorphism observed results from strain-specific expression of V kappa genes common to all mice, but rather suggest that different allelic form of the same V kappa gene subgroup exist in different strains.

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

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

Molecular genetic analysis of the V kappa Ser group associated with two mouse light chain genetic markers. Complementary DNA cloning and southern hybridization analysis

Previous studies (21) have shown that two mouse kappa light (L) chain variable (V) region polymorphisms, the IB-peptide and Efla markers, reflect expression of a characteristic group of V kappa regions, called V kappa Ser, by some inbred strains and not others. Expression of V kappa Ser is controlled by a locus on chromosome 6, the chromosome that contains the kappa locus. To further characterize this V kappa group and begin to analyze the basis for its strain-specific expression, full-length complementary DNA (cDNA) copies were produced of L chain mRNA from the M75 myeloma that had been induced in the C.C58 strain of mice, and which produces a V kappa Ser L chain. The C.C58 strain is congenic with BALB/cAn, differing in the region of chromosome 6 that controls expression of the V kappa polymorphisms and the Lyt-2 and Lyt-3 T cell alloantigens. The complete nucleotide sequence of this cloned cDNA was determined and compared with the nucleotide sequences the most closely related BALB/c myeloma L chains known. Results indicated significant differences throughout the variable region, but particularly toward the 5' portion of the sequence. A probe corresponding to 200 bp of the 5' end of the cloned V kappa Ser cDNA was used in Southern hybridizations of restriction digests of liver DNA from a number of inbred, recombinant, and recombinant inbred strains. Under stringent hybridization conditions, one strongly-hybridizing fragment was observed in Bam HI, Hind III, and Eco RI digests, and based on the size of the fragments, strains could be organized into two groups. The presence of strongly hybridizing Bam HI, Hind III, and Eco RI fragments of 3.2, 2.8, and 2.1 kb, respectively, was found to correlate completely with expression by the strain of the IB-peptide and Efla markers. All nonexpressor strains yielded hybridizing fragments of 7.8, 8.4, and 2.8 kb, respectively. Possible explanations for strain-specific expression of V kappa Ser-associated phenotypic markers are discussed.

Immunologic memory to phosphorylcholine. VI. Heterogeneity in light chain gene expression

BALB/c mice immunized with phosphorylcholine-conjugated keyhole limpet hemocyanin (PC-KLH) produce two types of anti-PC antibodies, designated group I and group II, which differ in their fine specificity and idiotype expression. Group II hybridomas can utilize VH genes and VL genes (in particular, V kappa 1-3) distinct from those expressed in the group I-like anti-PC myelomas. Here we have analyzed additional anti-PC hybridomas from BALB/c and (CBA/N X BALB/c)F1 male mice and also anti-PC antibodies purified from BALB/c and C57BL/6N antisera. Isoelectric focusing indicates that one of the group II hybridomas utilizes V kappa 1-3 and that related L chains are expressed in a major portion of group II serum antibodies. Other group II antibodies in antisera express different L chains, some of which are presently unidentified. However, isoelectric focusing analysis also indicates that the L chains of some group II hybridomas and serum antibodies are related to those found in the group I anti-PC myelomas and group I hybridoma and serum antibodies. In addition, one hybridoma was found to utilize lambda 2. Thus, it appears that the anti-PC antibodies with group II-like fine specificity can utilize a variety of VL genes related to, or distinct from, those expressed in group I antibodies.

BALB/c antiarsonate idiotypes: gene complementation necessary for expression

The expression of two idiotype (id) families (5AF6 and 3C6) associated with the BALB/c p-azophenylarsonate-specific antibody response was examined in 11 mouse strains. Eight strains produced some of one or the other of these two id families with the mean percent expression in the anti-Ar responses of id(+) strains ranging from 8 to 43% for the 5AF6 and from 2 to 10% for the 3C6 idiotype. Four strains of mice (C58, AKR, PL, and RF) thought to have Lyt-3.1-linked VL repertoire differences from other mouse strains (Lyt-3.2) were tested for their capacity to contribute to 5AF6 and 3C6 id expression. The RF strain was capable of producing 5AF6 id and small amounts of 3C6 id. Tests of Lyt-3.1 congenic strains C.AKR (AKR Lyt-3.1 on a BALB/c background) and C.C58 (C58 Lyt-3.1 on a BALB/c background) showed that C.AKR could produce 5AF6 id while C.C58 could not. 3C6 id expression was present but depressed in C.C58 mice compared with the high 3C6 id expression in C.AKR. Breeding studies mating C.C58 (bearing the required Igh-Ca-linked VH genes) to other 5AF6(-) strains showed that gene complementation could result in 5AF6 expression in F1 offspring. 5AF6(-) strains capable of complementation included CBA/J, C57BL/6J, AKR/J, and PL/J. C58/J (from which C.C58 were derived) was the only tested strain that failed to complement for 5AF6 id expression. Additional matings between C58/J[5AF6(-)] and CBA/J[5AF6(-)] showed F1 offspring could produce 5AF6 id, indicating that C58/J can contribute functional VH genes necessary for 5AF6 id expression. Depressed expression of 5AF6 and 3C6 id was noted in mice where the C58/J-derived Lyt-3.1 genotype was present. The possibility that the depression of 5AF6 and 3C6 id expression derived from C58/J mice was due to regulatory influences rather than a lack of the VL structural genes is discussed.

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.

A serologic marker for the Ars-C family of anti-arsonate antibodies

Attempts are being made to define, at the serologic, structural and genetic levels, the anti-arsonate repertoire. We previously identified three families of anti-arsonate antibodies based on the amino acid sequence of the heavy chain V regions. The present report establishes the serologic correlates of one of these families, the Ars-C family. The determinants defining this family are expressed by anti-Ar molecules displaying the A/J minor idiotype or the BALB/c major idiotype; these determinants are also expressed on molecules of different specificity, notably by the DNP-binding myelomas, MOPC-460 and MOPC-315. All strains tested employed the Ars-C family in the response to arsonate.

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

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

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

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

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

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

The selection and maintenance of the V region determinant repertoire is germ-line encoded and T cell-independent

The number of lipopolysaccharide-sensitive precursor cells synthesizing immunoglobulin (Ig) which reacts with the monoclonal anti-M460 antibody F6(51) has been determined in the spleen and in the bone marrow of different strains of mice. These precursor frequencies fall into two quantitatively different groups. The first group includes mice with the same Igh haplotype as BALB/c animals (Igha). In this group, spleen cells contained between 1:10(4) to 1:5 X 10(4) B cell precursors secreting Ig which bound F6(51). The second level of precursor was obtained with animals with allotypic haplotypes other than Igha. These values were too low to allow accurate frequency determinations. The frequency of these cells in mice of the latter group, however, increased dramatically when these animals were hyperimmunized with the monoclonal anti-M460 antibody. Similar results were obtained when the frequencies were determined using the Ig- fraction of bone marrow cells. Surprisingly, the numbers of lipopolysaccharide-sensitive B cell precursors secreting F6(51)-binding Ig in spleen cells of nude mice was found to be similar to the one in splenocytes of normal mice, and even in this case, the frequencies reflected the genetic background of the animals tested. Taken together these data support the notion that the establishment and the maintenance of the M460 idiotypic repertoire is germ-line encoded and independent of regulatory T cells.

Recombination between kappa chain genetic markers and the Lyt-3 locus

Recombination has been detected for the first time between chromosome 6 loci controlling kappa chain expression in normal mouse serum immunoglobulin and the Lyt-3 locus. The recombination event occurred at the 26th or 27th backcross generation during the derivation of the Lyt-2a, Lyt-3a-congenic line B6.PL(85NS). The line is now homozygous for the Lyt-2a, Lyt-3a allele(s) at N30F13 and homozygous animals express the Igk-Ef1b allele derived from C57BL/6. The frequency of recombination has been estimated to be 0.30% based on the present results and previous studies in which no recombination was detected. The results rule out the hypothesis that the Lyt-3 locus itself controls the light chain phenotype observed in normal serum immunoglobulin.

Idiotype regulation: evidence for the involvement of Igh-C-restricted T cells in the M-460 idiotype suppressive pathway

Allotypic restriction of idiotype suppression has been shown in several idiotypic systems. It has also been demonstrated that naive BALB/c mice contain naturally occurring suppressor T cells capable of inhibiting the M-460 idiotype expressed on BALB/c B cells, and that T cells from allotype-congenic mice have no effect on this expression. Since we have previously shown that upon polyclonal activation B cells of all mice tested are capable of secreting M-460-positive anti-2,4,6-trinitrophenyl (TNP) antibodies, we postulated that idiotype suppressor cells may recognize idiotypes in conjugation with products of the Igh loci. In the present study we tested this hypothesis. The data clearly showed that regardless of their allotypic haplotype all strains of mice do possess suppressor cells capable of recognizing the M-460 idiotype. However, mixing experiments indicated that the functional potential of these suppressor cells can only be expressed when T and B lymphocytes come from allotype-matched animals. Efficient suppression in those cultures containing allotype-matched but incompatible B and T cells at the I-J region of the H-2 locus could be detected. Finally, using allotypic recombinant strains of mice, we found evidence that the restrictive elements in idiotypic suppression are the product of genes mapping in the Igh-C locus, or closely linked to it.

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.

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.

Unique V kappa group associated with two mouse L chain genetic markers

The C.C58 and C.AKR congeneic strains of mice differ from BALB/c at loci on chromosome 6 which govern kappa light chain variable region (V kappa) polymorphisms and the Lyt-2 and Lyt-3 alloantigens. Amino acid sequence analysis of light chains of myelomas induced in these strains revealed one light chain, C.C58 M75, that had an NH2-terminal serine and differed sufficiently from published V kappa sequences to define a new V kappa group, V kappa (Ser), apparently not expressed by BALB/c mice. Peptide map analysis indicated that the M75 light chain contained the IB-peptide marker, a V kappa polymorphism expressed by C.C58 but not BALB/c mice, which is determined by the IgK-Trpa allele present on chromosome 6. This same light chain was found by isoelectric focussing to correspond to IgK-Ef1a, another V kappa genetic marker of C.C58 and C.AKR. Isoelectric focussing of approximately 200 C.C58 and C.AKR myeloma light chains revealed three additional C.C58 and four C.AKR light chains that corresponded to IgK-Ef1a-specific light chains. All three additional C.C58 light chains belonged to the V kappa (Ser) group and contained the IB-peptide marker. Thus, the differences in V kappa repertoires represented by the IB-peptide and IgK-Ef1a markers and controlled by genes on chromosome 6 appear to reflect expression (or failure of expression) of a distinct group of V kappa regions.

Role and strain distribution of genes controlling light chains needed for the expression of an intrastrain cross-reactive idiotype

Several strains of mice were tested for their capacity to provide immunoglobulin L chains required for the expression of the major cross-reactive idiotype (CRIA) associated with p-azophenylarsonate-specific antibodies of strain A mice. To facilitate testing, mice were bred that were homozygous for Igh-Ce and Lyt-2a, 3a, i.e., they possessed genes controlling H chains but not L chains required for expression of the CRIA. Such male mice were mated to females of various strains and their offspring were tested; expression of CRIA indicated the presence in the female parent of genes controlling the appropriate L chains. All females bearing the Lyt-2a, 3b or Lyt-2b, 3b genotype yielded offspring, most of which were CRIA+, whereas all the offspring of females that were Lyt-2a, 3a were CRIA-. The female parents included mice of several strains that are congenic for Lyt-2a, 3a, Lyt-2b, 3b or Lyt-2a, 3b, thus demonstrating very close linkage between the Lyt loci and the expression of CRIA. In addition, doubly congenic strains of mice with the heavy chain allotype of the CRIA+ AL/N strain and the Lyt-2a, 3a genotype on a BALB/c background failed to express CRIA. The data provide further evidence for the similarity of repertoires of L chains in Lyt-3b mice of various strains. When genes were present controlling A/J H chains and L chains of C57BL/6 or BALB/c origin, the quantitative expression of CRIA was only slightly lower than that observed in A/J mice. Mice possessing genes controlling the H or L chains required for CRIA expression, but not both, did not express CRIA but synthesized Ar-specific antibodies which contained low but significant concentrations of the idiotype-associated chain.

Antigen-specific helper T cells required for dominant production of an idiotype (THId) are not under immune response (Ir) gene control

Responder and nonresponder mice primed with poly-(L-glutamic acid,L-lysine,L-phenylalanine) (GLPhe), the response to which is under the control of immune response (Ir) genes, were used as a source of both types of helper T cells required for a T15 idiotype dominated T-dependent anti-phosphorylcholine (PC) response. It was found that the activity of one of the helper T cells needed for an anti-PC response was under major histocompatibility complex (MHC)-linked Ir gene control, and only GLPhe-primed responder mice could be used as a source of these cells. These T cells (ThMHC) whose presence is required for in vivo T-B collaboration are found in normal and anti-mu-treated mice, and their activity depends on the hapten being physically linked to the carrier molecule. By contrast, the activity of the second helper T cell (ThId) required for a T15-dominated anti-PC response was present in both GLPhe-primed responder and nonresponder mice. The ThId cell set that is missing or deficient in anti-mu treated mice can be restored by the addition of T cells from normal, carrier-primed donors and restimulating with the priming carrier. When T cells from GLPhe-primed donors are used as a source of ThId cells, both responder and nonresponder donors provide helper cells capable of inducing syngeneic B cells to produce a T15 dominated anti-Pc response. These results are interpreted to suggest that idiotype recognizing helper T cells (ThId) recognize antigen independent of known Ir gene products.

A major group of mouse kappa chains controlled by the chromosome 6 locus, IgK-Ef2

We previously demonstrated that loci closely linked to the Ly-3 locus control the expression of distinct sets of light chains in normal mouse serum immunoglobulin. One of these loci, IgK-Ef2, was shown to control two major bands in normal light chain isoelectric focusing (IF) profiles. Strains possessing the marker bands were designated IgK-Ef2a. Screening of myeloma proteins from the strains BALB/c (IgK-Ef2a) and NZB (IgK-Ef2b) led to the identification of eight proteins in the BALB/c collection having light chains that cofocus precisely with the polymorphic IF bands observed in normal serum light chains. Partial sequence analysis of 3 of the light chains has shown that they are all identical in the first 30 positions, which indicates that they constitute a single variable region of the kappa light chain (VK) group (VK1). The frequency of occurrence of the group within the BALB/c myeloma collections (8 out of 277) suggests that the number of such groups may be closer to 50 than to 100. The finding supports an interpretation of the genetic polymorphism as being in part a result of the absence of genes related to VK1 in IgK-Ef2b strains of mice.

Genetic polymorphism at the mouse immunoglobulin J kappa locus (Igk-J) as demonstrated by Southern hybridization and nucleotide sequence analysis

Comparison of the nucleotide sequences of the C.C58 M75 myeloma kappa chain gene and the BALB/c germ-line J kappa segments suggested that the J kappa regions of C.C58 and BALB/c might be distinguished by restriction enzyme polymorphisms. This was shown to be the case in Southern hybridizations of Hinf I and Acc I digests of liver DNA from these and other strains with a J kappa-specific probe. Tests of a wide variety of inbred, congenic, recombinant, and recombinant-inbred strains provided evidence for three alleles, Igk-Ja, Igk-Jb, and Igk-Jc, the type strains for which are C58/J, BALB/c, and SJL/J, respectively. Analysis of the B6.PL(85NS) congenic strain suggests that the Igk-J locus lies in the neighborhood of the Lyt-2/Lyt-3 loci, approximately 0.30 cM from the V gene segment determining the Igk-VSer and Igk-Efl polymorphisms. Finally, nucleotide substitutions lead to amino acid sequence differences between the C.C58 M 75 kappa gene and the BALB/c germ line in J kappa 2 and J kappa 4. Two of these substitutions reflect true germ-line differences, raising the possibility that idiotype differences observed among strains could reflect J kappa as well as V kappa differences.