DNA antibody idiotypes: an analysis of their clinical connections and origins

Approximately thirty common DNA antibody idiotypes have been described on hybridoma derived or affinity purified DNA-binding antibodies. There are associations between some idiotypes and the clinical manifestations of systemic lupus erythematosus although none are sufficiently firm to be clinically useful in identifying subsets of SLE or in assessing disease activity in individual patients. The expression of these idiotypes is not confined to DNA antibodies in SLE. They may be found in the serum from patients with a range of autoimmune rheumatic disorders, infectious disease and blood dyscrasias. In most cases the antigen binding specificity of the antibody bearing the idiotype is unknown. The precise relationship between the various idiotypes is becoming better understood with increasing availability of genetic and structural data. DNA antibody idiotype manipulation may provide a potential new therapeutic modality in SLE.     

Expression of an interspecies idiotype in sera of SLE patients and their first-degree relatives.

Sera from 29 SLE patients and 81 first-degree healthy family members were tested for quantitative expression of a cross-reactive idiotype present on a murine monoclonal anti-Sm autoantibody (Y2). Forty-one percent of SLE patients and 27% of all relatives showed increased serum levels of the Y2 idiotype compared to 6% in a normal, unrelated control group. In addition, female relatives of SLE patients showed slightly increased levels of anti-Sm antibodies compared to male relatives (15% vs 3%). In one of the 28 families and three unrelated SLE patients studied, there was a significant correlation between the Y2 idiotype expression and expression of another idiotype present on anti-DNA antibodies (1341d). Affinity column absorption studies showed that these two idiotypes were present on different antibody molecules. This study demonstrates: (1) a genetic predisposition for an anti-Sm antibody idiotype expression in humans; and (2) that two different idiotypes may be under parallel or coordinate regulation.     

Pathogenic anti-DNA antibodies in SLE: idiotypic families and genetic origins

We have adopted an idiotypic approach to study the double stranded DNA (dsDNA) binding antibodies of systemic lupus erythematosus (SLE). Three anti-idiotypic reagents, 8.12, 3I, and F4, identify cross reactive idiotypes that are each expressed on anti-dsDNA antibodies in the sera of many patients with SLE. These idiotypic antibodies are implicated in the pathogenesis of SLE as they are present in immune complex deposits in the kidneys of patients with SLE glomerulonephritis. The autoantibody associated idiotypes are also expressed on antibodies that do not bind DNA. We are investigating the origin of the pathogenic anti-dsDNA antibodies of SLE by comparing the autoantibodies, the antibodies to foreign antigens, and the myeloma proteins that express each SLE associated idiotype. In conjunction with serological analysis of these idiotypic systems, molecular genetic studies indicate that both the 8.12 and the 3I autoantibody associated idiotypes may be germline encoded, while the F4 idiotype is generated by somatic mutation. The data further suggest that the antigenic specificity of the pathogenic anti-DNA antibodies of SLE is acquired through somatic mutation of germline immunoglobulin genes. By studying the regulation of genes capable of encoding pathogenic autoantibodies, in both SLE patients and non-autoimmune individuals, we may be able to elucidate the pathogenesis of autoimmune disease and begin to design more effective therapeutic interventions.     

Pathogenic Anti-DNA Antibodies in SLE: Idiotypic Families and Genetic Origins

We have adopted an idiotypic approach to study the double stranded DNA (dsDNA) binding antibodies of systemic lupus erythematosus (SLE). Three anti-idiotypic reagents, 8.12, 31, and F4, identify cross reactive idiotypes that are each expressed on anti-dsDNA antibodies in the sera of many patients with SLE. These idiotypic antibodies are implicated in the pathogenesis of SLE as they are present in immune complex deposits in the kidneys of patients with SLE glomerulonephritis. The autoantibody associated idiotypes are also expressed on antibodies that do not bind DNA. We are investigating the origin of the pathogenic anti-dsDNA antibodies of SLE by comparing the autoantibodies, the antibodies to foreign antigens, and the myeloma proteins that express each SLE associated idiotype. In conjunction with serological analysis of these idiotypic systems, molecular genetic studies indicate that both the 8.12 and the 31 autoantibody associated idiotypes may be germline encoded, while the F4 idiotype is generated by somatic mutation. The data further suggest that the antigenic specificity of the pathogenic anti-DNA antibodies of SLE is acquired through somatic mutation of germline immunoglobulin genes. By studying the regulation of genes capable of encoding pathogenic autoantibodies, in both SLE patients and non-autoimmune individuals, we may be able to elucidate the pathogenesis of autoimmune disease and begin to design more effective therapeutic interventions.     

Neonatal expression of a cross-reactive idiotype associated with anti-phenylarsonate antibodies in strain A mice

Data are presented which indicate that B cells expressing the cross-reactive idiotype associated with anti-p-azophenylarsonate antibodies of A/J or allotype-congenic C.AL-20 mice are present in neonatal mice. Data were obtained by direct immunization of neonatal mice or by adoptive transfer of cells from neonatal C.AL-20 mice into idiotype-negative BALB/c recipients. These findings, together with those previously reported for antibodies to phosphocholine in BALB/c mice, support the generalization that major cross-reactive idiotypes may usually be found early in the life-span of a mouse. The contrast between the frequency of appearance of the major cross-reactive idiotypes and “private” idiotypes with the same antigen-binding specificity, which are found after immunological suppression of the major idiotype, is consistent with the possibility that cross-reactive idiotypes are the product of germ line genes or minor somatic variants of germ line genes while private idiotypes arise through somatic diversification. Alternatively, regulatory mechanisms may account for the striking difference. The present results are therefore consistent with the early expression of germ line genes controlling the major idiotype or of corresponding regulatory genes. The average concentration of idiotype, per unit weight of anti-phenylarsonate antibody, is somewhat lower in neonatal than in adult A/J mice indicating that the major idiotype does not account for all of the antibody produced in response to this hapten in the neonate.     

Comparison of DNA antibody idiotypes in human sera: an international collaborative study of 19 idiotypes from 11 different laboratories

The distribution of and relationships between 18 anti-DNA antibody idiotypes and one anti-acetylcholine receptor antibody idiotype have been tested in an international collaborative study of human sera from 180 individuals. The main finding is that the serum levels of many of these idiotypes, whether of murine or human origin, show a high degree of statistical correlation. The studies in a wide range of autoimmune rheumatic diseases confirm that none of the idiotypes tested is disease specific, but 13 of 15 (87%) whose levels were recorded as OD units or cpm correlated strongly with anti-ssDNA antibody levels and 11 of 15 (73%) with total serum IgM. Expression of several idiotypes was found to fluctuate in parallel with disease activity in SLE; levels of others were also elevated in the healthy relatives of lupus patients whilst a few were also raised in the spouses of these patients. The data support the notion that there may be only a few groups of related DNA antibody idiotypes. The correlations between the idiotypes with regard to their quantities, association with disease activity, and wide distribution in different diseases and healthy individuals suggest at least two explanations. First, all of these idiotypes may be present in normal immunoglobulin repertoires and simply increase in response to poly- or oligoclonal B-cell activation in autoimmune diseases. Secondly, these idiotypes may be structurally linked to each other, so that their behaviour under conditions of specific antigenic stimulation is similar. Genetic and structural studies will be required to distinguish between these possibilities.     

SLE患者血清抗F(ab′)_2片段抗体的测定及其临床意义

用酶解法制备正常人 IgG-F(ab')_2片段及 SLE 患者血清抗 ds-DNA-F(ab')_2片段,ELISA 法检测同一组(46例)SLE 患者血清中抗 F(ab')_2片段抗体,两者检测结果呈高度相关性.同时发现,缓解期 SLE 患者血清中抗 F(ab')_2片段抗体水平明显高于活动期 SLE 患者,而抗 ds-DNA 抗体水平与之相反.提示,正常人 IgG-F(ab')_2片段与 SLE 患者血清抗 ds-DNA-F(ab')_2片段可能有共同的结构表位,其抗 F(ab')_2片段抗体测定可作为临床观察 SLE 活动性的一个指标.     

Induction of anti-DNA autoanti-idiotypic antibodies in (NZB X NZW)F1 mice: possible role for specific immune suppression

(NZB X NZW)F1 (B/W) mice spontaneously produce anti-deoxyribonucleic (DNA) acid antibodies. PME77 anti-DNA monoclonal antibody (MoAb) is a syngeneic antibody bearing idiotype present in most B/W sera. In the present investigation the effect of immunization of B/W mice with the PME77 MoAb on the production of PME77 idiotypes and anti-DNA antibodies in B/W mouse sera was investigated. PME77 MoAb immunization regimen induced the production of autoanti-idiotypic antibodies and abrogated the expression of PME77 idiotype in B/W treated mice. In contrast, untreated mice and control B/W mice, receiving NZB polyclonal IgG2b which lacked detectable DNA binding capacity, expressed PME77 idiotopes. These results demonstrate that the expression of idiotype borne by autoantibodies may be modified through the induction of autoanti-idiotypic antibodies.     

Shared idiotypes are expressed on mouse and human anti-DNA autoantibodies.

The expression of common idiotypes on human and mouse anti-DNA monoclonal autoantibodies made by hybridomas was examined by their competitive binding to anti-idiotype antibodies. Some murine autoantibodies inhibited the binding of a human anti-DNA autoantibody 16/6 to monoclonal or polyclonal anti-idiotypic antibodies. Another human antibody (134) was not inhibited in its binding to homologous anti-idiotypic antibodies. The expression of the human 16/6 idiotype on mouse antibodies was restricted to those that had a specificity similar to the 16/6 antibody itself, their major properties being that they reacted more strongly with single stranded DNA (ssDNA) than double stranded DNA (dsDNA). One mouse antibody expressing the 16/6 idiotype also bound weakly to RNA. The results imply structural similarities between the binding sites of the antibodies in the two species, and are consistent with evolutionary conservation of V genes coding for primitive ancestral antibodies that react with DNA and become diversified through somatic mutation.     

An unusual mouse myeloma protein binding native DNA.

SP 104 is an IgA-kappa myeloma protein produced by a lymphoid tumour of CA F1 mice. It arose originally in mice injected intraperitoneally with cell-free extract of spleen from a dog with systemic lupus erythematosus. The monoclonal nature of the IgA was shown by characteristic appearance on immunoelectrophoresis, restriction to a single light chain type and ability to induce anti-idiotypic antiserum. This protein has antibody activity against native (double-stranded) DNA and its specificity is similar to the antibodies against DNA found in the sera of humans with SLE and NZB/NZW F1 mice. Its idiotype does not cross-react with idiotypes of other mouse myeloma proteins known to bind DNA.     

A common anti-DNA idiotype and other autoantibodies in sera of offspring of mothers with systemic lupus erythematosus.

Since the immune response in fetuses of mothers with systemic lupus erythematosus (SLE) is unknown, we investigated sera from six mothers and their paired offspring by enzyme-linked immunosorbent assay (ELISA) for the presence of a common anti-DNA idiotype (16/6 Id) and, as control, for the presence of an unrelated public idiotype of antibody to hepatitis B surface antigen (HBsAg). In addition, maternal as well as fetal sera were evaluated for the presence of antibodies to ssDNA, dsDNA, poly(I), poly (dT), RNA, cardiolipin, total histones and the presence of lupus anticoagulant. Clinically active SLE mothers showed in general increased IgG and, to a lesser extent, IgM autoantibody activity. Circulating lupus anticoagulant was detectable in clinically active mothers only. All offspring of clinically active SLE mothers showed increased IgG autoantibodies to a variety of antigens, while IgM antibodies were detected in only one fetus. In contrast, fetuses of clinically inactive mothers showed only minor IgG activity. Common anti-DNA-idiotype (16/6 Id) activity also correlated with disease activity in both maternal and fetal compartments. One clinically active mother was 16/6-negative; her offspring was, however, positive, indicating de novo production of the idiotype by the fetus. In contrast, a control anti-HBsAg idiotype was not detected in either maternal or fetal sera. It therefore appears that offspring of clinically active SLE mothers serologically reflect maternal disease activity. Furthermore, autoantibodies and common idiotype of autoantibodies can be found within the fetal compartment even in the absence of such antibodies in the maternal serum. Discrepancies between mothers and offspring in IgM-autoantibody levels and the presence of new idiotypes in fetuses are indicative of fetal de novo autoantibody production.     

Idiotypic manipulations: hierarchy in idiotype expression in rabbits immunized against Micrococcus luteus

Idiotypic cross-reactions were analyzed among three series of anti-peptidoglycan antibodies of the Micrococcus luteus system. The reference idiotype Ab1 was an antibody fraction isolated from an isoelectric focusing preparative column. Cross-reactive idiotypes, Ab1', were induced through the immunization chain (Ab1-Ab2-Ab3). Idiotypic antibodies of Ab1-F1 type were obtained from offspring of female rabbits, actively producing Ab3 during pregnancy. Finally, Ab1 CRI were cross-reactive idiotypes with Ab1 found in a random population of rabbits immunized with M. luteus. Three idiotopes could be characterized within Ab1 antibody. Ab1' usually expressed two of these idiotopes, but never the third specificity which is "private" to Ab1. Ab1-F1 shared one or two idiotopes with Ab1 and Ab1' antibodies. Only one common idiotope appeared to be present on Ab1 CRI. Finally, this idiotope, IdX, could be detected by radioimmunoassay in 20% of rabbits immunized with micrococcal vaccine. It appears that a recurrent idiotype of anti-peptidoglycan antibodies can be preferentially amplified through idiotypic manipulations. On the other side, cascade immunizations lead to the expression on Ab1' and on some Ab1-F1 of a second idiotypic specificity, shared with Ab1. This hierarchy of idiotype expression may well be important in the regulation of antibody synthesis through idiotypes.     

Characterization and idiotypic analysis of an anti-RNP monoclonal antibody

To investigate mechanisms of anti-RNP antibody expression in autoimmune disease, idiotypes of a monoclonal anti-RNP of murine origin were analysed. This antibody, designated 4L1, was obtained from a MRL-lpr/lpr mouse and shown to have anti-RNP specificity by gel analysis of radiolabelled cellular RNA. An anti-idiotypic antiserum was prepared in a rabbit to 4L1 and rendered specific for idiotype by absorption with IgG from B6 mice and two BALB/c myelomas of the same chain composition as 4L1 (IgM kappa). In competition ELISA assays, this antiserum detected idiotypes commonly expressed in sera of MRL-lpr/lpr mice irrespective of the presence of anti-RNP. These idiotypes were not exclusive to this autoimmune strain, however, and could also be identified in normal mice. To identify other antibodies with this idiotype, a panel of MRL hybridomas was tested. This analysis demonstrated idiotypic cross-reactivity between 4L1 and two anti-Sm monoclonal antibodies derived from another animal. These results suggest that 4L1 belongs to a larger idiotype bearing family only some of whose members may have aberrant expression.     

Common lupus anti-DNA antibody idiotypes in chronic liver diseases

Chronic liver diseases may be associated with the appearance of antinuclear antibodies. To further analyze the relationship between connective tissue and liver diseases the sera of 88 patients with chronic liver disorders were examined for the presence of common lupus anti-DNA idiotypes (16/6-id, 134-id, and 32/15-id), using an enzyme-linked immunosorbent assay. The 16/6-id was found in 58 (65.9%), the 134-id in 43 (48.9%), and the 32/15-id in 13 (14.8%) of the patients' sera. Distinct diagnostic groups displayed different lupus anti-DNA idiotype profiles. Patients with primary biliary cirrhosis (PBC) and chronic active hepatitis (CAH) had mainly the 16/6 idiotype, while in alcoholic (AC) and in cryptogenic cirrhosis (CC) the 16/6-id and 134-id were the main idiotypes recorded. There was considerable correlation among the different anti-DNA idiotypes but not between any of these idiotypes and an unrelated common anti-HBsAg idiotype. The occurrence of the various idiotypes was not found to be correlated with increased serum immunoglobulin levels. It can be concluded that the similarities between chronic liver diseases and connective tissue diseases are extended also to the presence of specific common anti-DNA antibody idiotypes.     

The role of anti-idiotypic antibodies in the induction of experimental systemic lupus erythematosus in mice

We have recently reported the induction of experimental systemic lupus erythematosus (SLE) in mice by a human anti-DNA monoclonal antibody (mAb) that bears a common idiotype, the 16/6 Id. In the present report we investigated the role of the idiotypic network in the induction of experimental SLE by using a murine anti-idiotypic mAb specific for the 16/6 Id. This anti-idiotypic mAb induced experimental SLE similarly to the 16/6 Id. Thus, following immunization, in addition to 16/6 Id+ antibodies, the mice produced antibodies to various nuclear antigens: single-stranded DNA, double-stranded DNA, poly(I), poly(G), Ro, La, Sm and ribonucleoproteins. Similarly to the 16/6 Id-immunized mice, the mice injected with the anti-16/6 Id mAb exhibited elevated erythrocyte sedimentation rate and leukopenia. The murine anti-16/6 Id mAb was found to be more effective than the 16/6 Id, in causing earlier onset of proteinuria and renal damage. These results suggest that the idiotypic network and particularly anti-idiotypic antibodies specific for anti-DNA common idiotypes found in SLE, play an important role in the induction of SLE in mice.     

Functional relationship between T15 and J558 idiotypes in BALB/c mice.

In inbred strains of mice, antiphosphorylcholine (PC) and anti-alpha 1,3 dextran (DEX) antibodies are structurally distinct from each other and have been shown to exhibit noncross-reactive antigen binding and idiotypic specificities. However, the prototype anti-PC and anti-DEX antibodies, TEPC15 and J558, respectively, were shown to be connected via a common autoantiidiotypic monoclonal antibody isolated from newborn BALB/c mice. The capacity of various monoclonal anti-PC and anti-DEX antibodies as well as the antigens PC and DEX to modulate T15 and J558 idiotypes in BALB/c mice was tested by their administration to newborn mice. Anti-PC antibodies of the T15 idiotype injected into 2-4-day-old mice, at a time when T15+ anti-PC precursors develop in BALB/c mice, suppressed the anti-PC response of these mice at 6 weeks of age. Similarly, J558 antibodies injected into 8-12-day-old mice, at a time when J558 precursors normally develop, suppressed the response to DEX. As a further demonstration of this connectivity, the injection of J558 into 4-day-old mice led to a down modulation of T15 idiotype, whereas both T15 and a minor idiotype-expressing antibody M167 when injected into 8-12-day-old mice caused a reduction in expression of the J558 idiotype. As predicted from in vitro analysis, injection of anti-PC antibodies of the M167 idiotype 2 to 4 days after birth enhanced the subsequent response to PC. However, anti-PC antibodies expressing another minor M603 idiotype did not affect the PC response. The results parallel the in vitro enhancement of M167 antibodies but not M603 on T15 binding to antiidiotype in vitro. Similarly, anti-DEX antibodies expressing the M104E idiotype had no detectable effects on the capacity to respond to PC or DEX or on the expression of T15 and J558 idiotypes as adults. Exposure of newborn mice to PC led to a dramatic reduction in the response to DEX as adults, whereas exposure to DEX at this stage of development had no effect on response to PC as adults. Collectively, these observations provide evidence for a complex functional connectivity between T15 and J558 idiotype-bearing B cells during ontogeny and extend our previous observations that development of these idiotypes is regulated by idiotype-directed interactions between B cells or their immunoglobulin products.     

Idiotypic cross-reaction between MRL autoantibodies and a BALB/c myeloma

Y2, a monoclonal anti-Sm antibody of MRL origin, demonstrates an idiotype commonly expressed in autoimmune MRL mice, although not necessarily associated with anti-Sm activity. To identify non-anti-Sm antibodies with this common idiotype, a rabbit anti-Y2 anti-idiotypic antiserum was tested for activity with other MRL hybridoma products (HP) as well as BALB/c myelomas. Idiotypic cross-reactivity was thus demonstrated for Y2 and the product of the BALB/c fusing cell line 45.6TG1.7 (M45), an antibody without known antigen binding activity. This determinant was denoted the Y2-M45 idiotype and its presence in serum and other antibodies tested by an inhibition ELISA. The idiotype was demonstrated on some, but not all, MRL HP's tested and was not confined to antibodies of a unique specificity. The idiotype was also present in sera of some normal as well as autoimmune strains of mice with highest levels in two strains bearing the lpr gene. These results indicate that idiotypes of anti-Sm antibodies are not exclusive to the pathologic setting but may be found commonly expressed in mice with antibodies of a variety of binding activity.     

A human fetal monoclonal DNA-binding antibody shares idiotypes with fetal and adult murine monoclonal DNA-binding antibodies.

A human DNA-binding monoclonal antibody was produced by fusing the hepatocytes from a 12-week-old human fetus with the lymphoblastoid cell line GM 4672 using polyethylene glycol. This antibody, designated BEG 2, binds to single-stranded (ss) DNA but also binds to double-stranded (ds) DNA, poly(dT), polyI and poly(ADP-ribose), but not to RNA, cardiolipin or K-30. The binding of BEG 2 to these polynucleotides can be inhibited by incubation with polynucleotides in the fluid phase. A rabbit polyclonal anti-idiotype was raised, and using this reagent it was shown that the BEG 2 idiotype is present in normal human serum (7%), systemic lupus erythematosus (SLE) sera (8%) and rheumatoid arthritis sera (23%). The extent of idiotypic sharing between BEG 2 and murine monoclonal DNA-binding antibodies, in particular monoclonal antibody (mAb) 423 (derived from a 15-day-old fetal MRL/Mp-lpr/lpr mouse) and mAb 402 (derived from an adult MRL/lpr mouse), was also investigated. Using a competition ELISA, it was shown that preincubation of BEG 2 with rabbit anti-423 and rabbit anti-402 inhibits the binding of BEG 2 to DNA, and the binding of 402 to DNA by anti-BEG 2 and anti-423. These data suggest that mAb BEG 2, 423 and 402 share common idiotypes, that autoreactivity is present in early fetal life, and that autoantibodies may be encoded for by germline genes, which have been conserved through evolution.     

Heterogeneity of anti-idiotypic antibodies to anti-DNA antibodies in humans.

Serum antibodies in some patients with systemic lupus erythematosus (SLE) were found to have specificity to idiotypes (Id) of 0-81 (human monoclonal anti-single-stranded DNA (ssDNA) antibody) but not to Id of NE-1 (human monoclonal anti-double-stranded DNA (dsDNA) antibody) or pooled human IgM. The interaction of the antibodies and 0-81 was blocked by the co-existence of free ssDNA. Some of SLE sera also showed preferential binding to Id determinants of NE-1, which included the antigen-binding sites of the dsDNA antibody. Some other SLE sera reacted with both Id of 0-81 and NE-13. Thus, there was heterogeneous population among human anti-Id autoantibodies to anti-DNA antibodies. The anti-Id activity was commonly detected in inactive SLE sera, and less frequently in normal controls, suggesting some regulatory role for anti-Id antibodies in the production of autoantibodies.     

Functional Relationship Between T15 and J558 Idiotypes in BALB/c Mice

In inbred strains of mice, antiphosphorylcholine (PC) and anti-α1,3 dextran (DEX). antibodies are structurally distinct from each other and have been shown to exhibit noncrossreactive antigen binding and idiotypic specificities. However, the prototype anti-PC and anti-DEX antibodies, TEPC15 and J558, respectively, were shown to be connected via a common autoantiidiotypic monoclonal antibody isolated from newborn BALB/c mice. The capacity of various monoclonal anti-PC and anti-DEX antibodies as well as the antigens PC and DEX to modulate T15 and J558 idiotypes in BALB/c mice was tested by their administration to newborn mice. Anti-PC antibodies of the .T15 idiotype injected into 2-4-day-old mice, at a time when T15 anti-PC precursors develop in BALB/c mice, suppressed the anti- PC response of these mice at 6 weeks of age. Similarly, J558 antibodies injected into 8-12-day-old mice, at a time when J558 precursors normally develop, suppressed the response to DEX. As a further demonstration of this connectivity, the injection of J558 into 4-day-old mice led to a down modulation of T15 idiotype, whereas both T15 and a minor idiotypeexpressing antibody M167 when injected into 8-12-day-old mice caused a reduction in expression of the J558 idiotype. As predicted from in vitro analysis, injection of anti-PC antibodies of the M167 idiotype 2 to 4 days after birth enhanced the subsequent response to PC. However, anti-PC antibodies expressing another minor M603 idiotype did not affect the PC. response. The results parallel the in vitro enhancement of M167 antibodies but not M603 on T15 binding to antiidiotype in vitro. Similarly, anti-DEX antibodies expressing the M104E idiotype had no detectable effects on the capacity to respond to PC or DEX or on the expression of T15 and J558 idiotypes as adults. Exposure of newborn mice to PC led to a dramatic reduction in the response to DEX as adults, whereas exposure to DEX at this stage of development had no effect on response to PC as adults. Collectively, these observations provide evidence for a complex functional connectivity between T15 and J558 idiotype-bearing B cells during ontogeny and extend our previous observations that development of these idiotypes is regulated by idiotype-directed interactions between B cells or their immunoglobulin products.