Polymorphism of Age-Related Changes in the Antibody Response to the Hapten Phosphorylcholine

Aging is accompanied by changes in the immune system that occur at different levels and at different periods of time. We have studied age-related changes in isotype and idiotype of the antibody response to hapten phosphorylcholine (PC) in C57BL/6, and A mice and in the congenic MRL/Mp-+/+ and MRL/Mp-1pr/1pr strains. Three groups, representing young, middle and old age were immunized with PC-keyhole limpet hemocyanin. Total anti-PC antibody and the contribution of each isotype and of the T15 idiotype were assessed in the initial and late response. Some features of the antibody-response were similar in all the strains tested, e.g. the largest quantity of anti-PC antibody is formed in middle age and IgM is dominant in the initial response. However, remarkable differences occur in the isotype and idiotype predominance. Particularly, congenic MRL/Mp strains, prone to autoimmune disease, express the T15 idiotype only at low levels, even though IgM, which normally expresses this idiotype, is produced in large amounts. Furthermore, the late (memory) response of the MRL/Mp strains is dominated by IgG2b rather than IgG1, which is the predominant isotype in mice of long-lived strains. We conclude from these results that the number of T helper cells, involved in isotype regulation decreases with age and that there is a genetic variation, i.e., polymorphism in the ability to express T15-idiotype producing subtypes.     

Polymorphism of Age-Related Changes in the Antibody Response to the Hapten Phosphorylcholine

Aging is accompanied by changes in the immune system that occur at different levels and at different periods of time. We have studied age-related changes in isotype and idiotype of the antibody response to hapten phosphorylcholine (PC) in C57BL/6, and A mice and in the congenic MRL/Mp-+/+ and MRL/Mp-1pr/1pr strains. Three groups, representing young, middle and old age were immunized with PC-keyhole limpet hemocyanin. Total anti-PC antibody and the contribution of each isotype and of the T15 idiotype were assessed in the initial and late response. Some features of the antibody-response were similar in all the strains tested, e.g. the largest quantity of anti-PC antibody is formed in middle age and IgM is dominant in the initial response. However, remarkable differences occur in the isotype and idiotype predominance. Particularly, congenic MRL/Mp strains, prone to autoimmune disease, express the T15 idiotype only at low levels, even though IgM, which normally expresses this idiotype, is produced in large amounts. Furthermore, the late (memory) response of the MRL/Mp strains is dominated by IgG2b rather than IgG1, which is the predominant isotype in mice of long-lived strains. We conclude from these results that the number of T helper cells, involved in isotype regulation decreases with age and that there is a genetic variation, i.e., polymorphism in the ability to express T15-idiotype producing subtypes.     

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.     

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.     

Age- and strain-dependent polymorphism in IgE antibody against the phosphorylcholine hapten

The magnitude of the IgE antibody response against the phosphorylcholine (PC) hapten and the rate of age-related change of IgE formation is polymorphic in the three long-lived and six relatively short-lived strains of mice studied. Long-lived mice showed an early increase, followed by a decline in the levels of anti-PC IgE antibody. The rate of increase and decrease was strain dependent. Among short-lived strains, MRL/Mp-lpr and MRL/Mp-+ mice showed an early decline in IgE antibody. The extent and rate of decline with age was more rapid in MRL/Mp-lpr animals than in MRL/Mp-+ mice. In contrast, there was an early increase of IgE antibody in female SJL, NZB/BIN, BXSB/Mp and male BXSB/Mp. Thus, opposite age-related changes in IgE antibody production can occur in animals with a tendency to develop autoimmune disease. In hybrids of (SJL X BALB/c)F1 and (BALB/c X MRL/Mp-lpr)F1, the levels of IgE antibodies were higher than those observed in either parental strain, and declined steeply with advancing age. We suggest that this could be attributed to recessive inheritance.     

Suppression of phosphorylcholine-specific IgE antibody formation in BALB/c mice by isologous anti-T 15 antiserum

In order to study the regulation of IgE antibody formation, isologous anti-idiotypic antisera against the phosphoryl choline (PC)-specific BALB/c myeloma proteins T 15 and M 167 were passively administered to BALB/c in the course of an anti-PC IgE response. Isologous anti-T 15 antiserum had a long-lasting suppressive effect on the formation of IgE antibodies with PC specificity, whereas administration of anti-M 167 antiserum had no or only little effect, similar to that of normal BALB/c serum. This indicates that anti-PC IgE antibodies consist mainly of the T 15 idiotype or of cross-reacting idiotypes, and that IgE response is accessible to regulation with anti-idiotypic antibodies. This murine model may permit the study of regulation of an IgE response largely restricted to few defined idiotypes characterized as tumor proteins.     

Monoclonal vs. heterogeneous anti-H-8 antibodies in the analysis of the anti-phosphorylcholine response in BALB/c mice

Biological activities of monoclonal A/J antibodies to the T15 idiotype in BALB/c mice were compared to heterogeneous antibodies raised by conventional immunization procedures. Two monoclonal antibodies, AB1-2 and GB4-10, which are of the γ₁,? class, appeared to have identical specificities by binding criteria and reacted similarly to conventional antibodies in their abilities to induce neonatal suppression, inhibit plaque-forming cell induction by phosphorylcholine (PC) antigens and to inhibit specifically, anti-PC plaque-forming cells. However, in functional analyses of anti-PC responses in various strains of mice, discrepancies were noted in the T15 responses as defined by monoclonal antibodies and conventional antisera. This heterogeneity was also observed in adult mice suppressed with the GB4-10 monoclonal antibody. These animals eventually produced an anti-PC response of AB1-2 idiotype but lacking the GB4-10 marker. These results show that the T15 IgM anti-PC response in BALB/c and other strains of mice is heterogeneous and probably consists of a family of clones. Particular clones can be precisely eliminated by the use of appropriate monoclonal antibodies, and the anti-PC response that eventually recovers is still T15⁺ but lacking the suppressed clones.     

Induction and characterization of "autologous" anti-isiotypic antibodies.

Upon immunization with phosphorylcholine (PC), conventional BALB/c mice produce anti-PC antibodies bearing predominantly the idiotype characteristic of the BALB/c PC-binding myeloma protein TEPC 15 (T15). To investigate whether BALB/c mice are able to produce antibodies to the autologous T15 idiotype, conventional (T15-positive) and neonatally suppressed (T15-negative) BALB/c mice were immunized with purcific for the T15 idiotype. However, anti-T15 antibodies were more readily induced in neonatally suppressed mice which in turn produced higher anti-T15 titers than conventional mice. Such "autologous" anti-T15 antibodies are able to (a) change the idiotypic pattern of the anti-PC response of conventional BALB/c mice in situ and, (b) inhibit the induction of an anti-PC response in vitro by spleen cells from T15-positive but not T15-negative BALB/mice. Thus, BALB/c mice are capable of producing anti-T15 antibodies upon immunization with an isologous myeloma protein which bears the autologous T15 isiotype. We suggest that isiotypes should not be strictly considered as "self-antigens" since the dramatic increase in their concentration, subsequent to antigen stimulation, might confer upon them immunogenic properties not shared by self-antigens.     

Fine specificity and idiotype expression of anti-phosphorylcholine IgE and IgG antibodies

The immune response to the phosphorylcholine (PC) hapten elicited in BALB/c mice by PC-keyhole limpet hemocyanin (KLH) is composed of 2 groups of antibodies with specificity to PC and phenyl-PC, respectively. They were designated as group I and group II anti-PC antibodies. In this report we demonstrate that anti-PC IgE antibodies elicited by PC-KLH or PC-ovalbumin belong to the group II and do not express the T15 idiotype. Anti-PC IgG1, IgG2a and IgG2b antibodies express group I characteristics in the primary response and bear the T15 idiotype. Later, after 5 weeks and 3 injections of PC-KLH or PC-ovalbumin, a change in these isotypes to group II antibodies is observed. In contrast, anti-PC IgE is a group II antibody throughout progression of the immune response. The regulation of group I and group II antibody expression in serum is independent of the genetic background of the animals.     

Phosphorylcholine-binding hybridoma proteins of normal and idiotypically suppressed BALB/c mice. I. Characterization and idiotypic analysis

The immune response of BALB/c mice to phosphorylcholine (PC) is dominated by an antibody bearing the idiotype of the myeloma protein TEPC 15 (MP T15). Anti-PC antibody of a different idiotype can be elicited in BALB/c mice by neonatal suppression with an anti-T15 idiotypic antiserum (anti-Id-T15). In an attempt to further characterize the immune response to PC, spleen cells of normal and idiotypically suppressed mice have been fused with the myeloma line X63-Ag8, and hybrid lines secreting anti-PC antibodies have been isolated. The antibodies were characterized by two-dimensional gel electrophoresis and their affinity for Pneumococcus pneumoniae was measured. Using both an A/J and a rabbit anti-Id-T15 serum, we could show that 4 out of 5 hybridomas obtained from normal BALB/c spleen cells secreted antibodies which, within the limits of the analysis, were idiotypically and structurally indistinguishable from MP T15 (T15⁺). Hybridomas obtained from suppressed BALB/c mice, on the other hand, secreted anti-PC antibodies which differed idiotypically from MP T 15: of the six lines, two were negative for T15 idiotopes (T15^?), while four showed some cross-reactivity with the T15 idiotype (T15^cr). All six, however, showed structural differences in one or more immunoglobulin chains. Inhibition of anti-PC plaque-forming cells induced in neonatally suppressed mice revealed that the idiotypic spectrum of the hybridoma proteins was representative of clones arising under such conditions in BALB/c mice. The majority of the anti-PC antibodies in idiotypically suppressed mice still bear idiotopes resembling MP T15. Only a minority, less than 20%, are truly T15^?.     

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.     

Regulatory effects of isologous anti-idiotypic antibodies on the formation of different immunoglobulin classes in the immune response to phosphorylcholine in BALB/c mice

BALB/c mice were immunized with purified phosphorylcholine (PC)-specific myeloma protein of the TEPC-15 tumor, which bears the major idiotype of the anti-PC response (T15 Id) in this mouse strain. Four months after establishing the anti-idiotypic response, animals were immunized with PC-keyhole limpet hemocyanin under conditions which normally lead to IgE antibody formation. The expression of anti-PC antibodies of each immunoglobulin class was compared to a group of matched control mice not immunized with T15. In BALB/c mice producing anti-idiotypic antibodies the formation of anti-PC IgM, IgG1, IgG2, IgG3 and IgE was suppressed to various extents and for different lengths of time. An exception to this observation was the formation of anti-PC IgA antibodies, in that no significant difference was measured between the two groups of mice. BALB/c mice immunized in the same way with the PC-specific myeloma proteins of the MOPC-167, MOPC-511 and MOPC-603 tumors produced normal levels of anti-PC IgE and IgG antibodies. These results suggest that T15 idiotype-positive antibodies are probably formed within all classes of specific antibodies expressed during an immune response to PC. The possibility of extending the phenomena of anti-idiotype-induced suppression to the level of various classes of specific antibodies, including IgE, might be of interest in the treatment of some allergic diseases.     

Immunologic memory to phosphorylcholine (PC). VIII. Expression of the VH-12 gene product in the response to PC-keyhole limpet hemocyanin

Three murine anti-phosphorylcholine (PC) hybridomas with group II-like fine specificity patterns isolated during a memory response to PC-keyhole limpet hemocyanin (KLH) are examined at the molecular level to determine the origins of the VH and VL used by these antibodies. Southern blots of Hind III cut DNA were hybridized with a probe specific for the V1 gene of the T15 VH family. The V1 germ-line configuration is retained in these hybridomas indicating that this gene which encodes the VH gene product expressed by most group I anti-PC hybridomas is not used for antibody production. Southern blots of Eco RI cut DNA hybridized to a probe specific for JH1-JH4 indicated that all three hybridomas PCG1-2, PCG1-3 and PCM-23 share a 5.2-kb rearranged JH band, suggesting utilization of a common VH gene segment. N-terminal amino acid sequence analysis of the heavy chains of two of the hybridoma proteins PCG1-2 and PCG1-3 indicates that they belong to mouse heavy chain subgroup II and are closest in sequence to a VH-12 isotype anti-PC hybridoma protein, HPC-104, derived from BALB/c mice suppressed for the T15 idiotype; PCG1-2 and PCG1-3 each differed from HPC-104 at only 1/20 residues. In addition, these proteins have in common a lysine at position 1 which has not been found previously in 203 other heavy chain sequences reported. N-terminal sequences of the light chains of PCG1-2 and PCG1-3 are each shown to differ at only 1/22 residues from V kappa 24, and PCM-23 had previously been shown to use V kappa 8; both of these have been associated previously with heavy chains derived from the V1 gene in anti-PC antibodies. These results indicate that the VH-12 isotype can be used during a normal antibody response to PC and thus that heavy chains derived from both subgroup II and subgroup III (the T15 heavy chain) contribute to the molecular heterogeneity observed in memory responses to PC-KLH.     

Age-dependent changes of isotype and idiotype expression in the antibody response to the phosphorylcholine hapten in BALB/c mice

The distribution of antibodies among different isotypes in an immune response to a given antigen reflects the immunoregulatory linkage of T and B cell compartments, the genetic background of an individual and the functional state of its immune system. In addition, idiotypes are markers for the clonal origin of antibodies and their genetic relationship. Therefore, we have analyzed the isotype patterns and development of the major idiotype (T15) in BALB/c mice of different ages, immunized with a T-cell-dependent phosphorylcholine conjugate. The response was dominated by mu, gamma 3 and gamma 1 isotypes. The proportion of these antibodies changed in the progress of immunization but not with age in the primary response. An age-dependent change of the isotype distribution was observed only in the memory response. The T15 idiotype was dominantly expressed in the primary response and decreased in the memory response by 80-95% independently of the age of the mice. The results demonstrate that 2 populations of anti-phosphorylcholine antibodies which both prefer particular isotypes are expressed according to the functional state of the T and B cell compartments with age.     

Expression of new idiotypes following neonatal idiotypic suppression of a dominant clone.

The anti-PC antibodies of BALB/c origin bear predominantly the idiotype characteristic of the phosphorylcholine (PC)-binding T15 idiotype than sera from adult mice, and, unlike the latter, they also contain detectable amounts of anti-T15 antibodies. By 2 weeks of age the anti-T15 antibodies are no longer detectable while the T15 idiotype has reached adult levels. Injection of neonatal mice with anti-idiotypic antibodies renders them unresponsive to PC until the 15th week of life. Furthermore, this treatment induces a chronic suppression of the T15 idiotype, since on recovery from unresponsiveness, the neonatally suppressed mice produce anti-PC antibodies which are predominantly T15-negative. In contrast, treatment of adult mice with anti-idiotypic antibodies induces only a transient state of unresponsiveness to PC, and the antibodies produced upon recovery bear the T15 idiotype. These findings are discussed in the context of idiotype anti-idiotype interactions and their possible role in immuno-regulation.     

Characterization of the group I and group II antibody response against PC-KLH in normal and T15 idiotype-suppressed BALB/c mice.

The memory response of BALB/c mice to phosphocholine-keyhole limpet haemocyanin (PC-KLH) consists of two antibody populations, designated Group I and Group II, that differ in their fine specificity, as determined by hapten inhibition using phosphocholine (PC) and p-nitrophenylphosphocholine (NPPC). It is known that Group I response is dominated by T15 idiotype-positive antibodies that utilize the VH1 heavy-chain gene in combination with V kappa 22 light-chain gene. In this paper we show that Group II serum antibodies of BALB/c mice are also highly restricted in their heterogeneity, as determined by N-terminal amino acid sequence analysis. Furthermore, we demonstrate that the Group II response is not affected by neonatally induced T15 suppression, whereas the Group I response in these mice consists of T15-negative antibodies. This suggests that the expression of the two antibody populations is regulated independently. Finally, we show that the isotype distributions within a fine specificity are the same in normal and T15-suppressed mice. Interestingly this is true not only for the Group II but also for the Group I antibodies. Because the isolated Group I antibodies from normal mice differ in structure from those of T15-suppressed mice, i.e. different light chains, our data indicate that the isotype distribution of these two populations is associated with their fine specificity in addition to their clonal origin.     

Specificities of IgM and IgG anti-histone H1 autoantibodies in autoimmune mice.

Autoantibodies to histone H1 represent the most common specificity among anti-histone autoantibodies in systemic autoimmune diseases. Here we analyse anti-H1 autoantibodies in mice from the following autoimmune strains: MRL/Mp-lpr/lpr, NZB and NZB x NZW/F1. Autoantibodies of the IgM isotype bind predominantly to epitopes located in the COOH-terminal domain of the H1 molecule, whereas IgG autoantibodies in the MRL/Mp-lpr/lpr and NZB strains also recognize epitopes requiring the integrity of both the COOH-terminal and the central globular domains of H1. In both of these strains, the titre of these IgG anti-H1 antibodies rises during the course of the disease. The importance of three-dimensional structure of histone H1 was attested by a significant decrease in IgG binding after cleavage of the H1 molecule within the folded globular domain. The binding of these sera to H1 variants from various species was also investigated and a strong binding of MRL/Mp-lpr/lpr sera to certain phylogenetically distant histone H1 variant molecules (sea-urchin sperm H1 and chicken erythrocyte H5) was observed. This cross-reacting binding can be explained by the presence in MRL/Mp-lpr/lpr sera of autoantibodies to H1(0), a variant found in non-dividing cells and exhibiting sequence homologies to the above mentioned variants. The significance and the possible implications of these data for the pathogenesis of autoimmunity are discussed.     

Fine specificity and VJ usage of light chains in antibodies to the phosphorylcholine hapten

In the memory response to the phosphorylcholine hapten (PC) two major groups of anti-PC antibodies with different fine specificities are elicited. Group I antibodies are mainly PC specific, whereas Group II antibodies are comprised of two specificities directed against the phenyl-PC and the phenyl moiety of the PC hapten. The V_L gene usage of 17 monoclonal memory anti-PC antibodies were investigated by Southern blot analysis and nucleotide sequencing. Six out of eight Group I memory PC-specific antibodies used the same V_K22-J_K5 rearrangement as the major T15 primary response idiotype. One expressed a mutated J_KI and one employed another V_K22 gene family member. A shift in specificity from PC (Group I) towards phenyl-PC (Group II) was accompanied with the usage of either V_K1C-J_K1 or V_K1A-J_K5 rearrangements. The phenyl-specific Group II antibodies expressed the V_λl-J_λ L chain rearrangement in combination with V_H M141 expressing H chains. In this specific segment of Group II antibodies most mutations were found. Thus four different V_L genes were found to contribute to the fine specificity of memory response antibodies to the PC hapten in a clear structure-function relationship. The diversified fine specificity in the memory response derives mainly from the usage of different L chains with particular VJ rearrangements in combination with V_H of the dominant initial response clonotype and is not primarily due to mutational events.     

Autologous anti-idiotypic antibody response is regulated by the level of circulating complementary idiotype.

BALB/c mice injected with lyophilized vaccine from Streptococcus pneumoniae R36a (Pn) predominantly responded with antibody molecules the vast majority of which expressed the public idiotype T15 and were directed to the immunodominant epitope phosphorylcholine (PC). However, after a single immunization with Pn vaccine young (3-month-old) BALB/c mice did not produce any specific anti-T15 antibody response. In contrast, young D1.LP mice were able to mount a specific anti-T15 response upon primary immunization with pneumococcal vaccine. The anti-PC response in the two mouse strains differed in that the proportion of antibody molecules that expressed the T15 idiotype for Pn-primed D1.LP mice showed a smaller proportion of PC-specific antibody expressing the T15 idiotype. Neonatal injection of anti-T15 monoclonal antibodies led to a long-term suppression of the PC-specific T15+ B-cell clones but at young/adult age these mice maintained the ability to produce a normal amount of PC-specific antibody. Interestingly, the idiotypically-suppressed BALB/c mice mounted a significant anti-T15 response during the primary response to Pn. We interpreted these data as showing that the level of circulating idiotype may regulate the production of the complementary anti-idiotypic antibody. In addition, in vitro experiments demonstrated that the lack of the anti-T15 response during primary antibody response in BALB/c mice is probably because of a state of tolerance that is regulated by T cells.     

Identification and characterization of a hapten-modifiable TEPC 15 cross-reactive idiotype in swine

Rabbits and swine immunized with TEPC 15 IgA, goats immunized with T15-positive IgM and swine immunized with affinity-pure swine anti-phosphorylcholine (PC) all produce antibodies which recognize a hapten-inhibitable idiotypic determinant on swine anti-PC. The similarity in reactivity and order of inhibitability with various PC analogs of the heterologous (swine anti-TEPC 15) and isologous (swine anti-swine anti-PC) reagents indicates that they recognize a related idiotype and suggest it may be the predominant idiotype expressed on swine anti-PC antibodies. The heterologous and isologous anti-idiotypic reagents generated in this study recognize swine and mouse anti-PC but not normal swine IgM, IgG or MOPC 460. Only reactions with swine anti-PC and mouse T15-positive anti-PC proteins are hapten-inhibitable. The greater inhibitory capacity of trimethylammonium and acetylcholine than PC suggests that the idiotope(s) recognized on swine anti-PC by the anti-idiotypic reagents is integral rather than peripheral to the anti-PC binding site. The nearly exclusive IgM anti-PC response of swine to Streptococcus pneumoniae R36A and PC-Brucella have so far hindered attempts to study the isotypic distribution of the idiotype.