Specific VDJ gene combinations contribute to the specificity of memory antibodies to the phosphorylcholine hapten.

Based on their fine specificity, two groups of antibodies against the phosphorylcholine (PC) hapten have been described. Group I antibodies react predominantly with the PC moiety of the hapten and group II are directed against the entire hapten including the azophenyl spacer to the protein carrier. We have analyzed the VH gene segment utilization of hybridomas from the memory response to PC by Southern blot analysis and nucleotide sequencing of the functional VDJ rearrangements. Three main specificities of anti-PC antibodies could be distinguished. Anti-PC hybridomas with group I fine specificity utilize the VH1-DFL 16.1-JH1 rearrangement. A major portion of group II antibodies recognized the phenyl-PC part and expressed the same VH1 gene in combination with a member of the SP2 family and JH1 or JH2. The other anti-PC antibodies either used the PJ14-DFL16-JH3 rearrangement in combination with a lambda 1 L chain or a member of the VGam3.8 VH family rearranged to the DFL16.1 and the JH3 gene segments. The PJ14 and VGam3.8 V gene expressing antibodies were directed to the phenyl group and were either not or barely inhibitable by PC chloride. Thus, specific VDJ gene combinations contribute to the fine specificity of antibodies in the memory response to the PC hapten. The use of the S107, Q52, and VGam3.8. VH gene families, together with FL16.1 or SP2 D segments and JH1, JH2, or JH3 results in different fine specificities to the PC, phenyl-PC, or the azophenyl moiety of the PC hapten. These fine specificities of the memory response use V, D, and J segments of the initial T15Id+ response in combination with gene segments usually related to phenyl specificity.     

Immunologic memory to PC-KLH: participation of the Q52 VH gene family

BALB/c mice immunized with phosphocholine-conjugated keyhole limpet hemocyanin respond with two major groups of antibodies that differ with respect to fine specificity and idiotype. Group I antibodies predominantly bear the T15 idiotype, and show appreciable affinity for the haptens PC and nitrophenyl PC (NPPC), whereas group II antibodies have appreciable affinity for NPPC only and are T15 idiotype negative. Previous studies indicated that group II binding characteristics may derive from the use of novel V gene segments not observed in group I antibodies. To determine the nature of VH gene usage in the group II antibody response, we examined the VH region of a prototype group II hybridoma, PCG1-1. The nucleotide sequence obtained from the VDJ region indicates that PCG1-1 utilizes a VH gene not observed in the group I response, one that belongs to the Q52 VH family. The PCG1-1 VH nucleotide sequence shares 97% identity with the myeloma M141 VH gene. In addition, PCG1-1 utilizes a D segment most closely related to DSP2.6 rearranged to JH-3. These data indicate that M141, a VH gene not seen in group I anti-PC antibodies is utilized by PCG1-1 to generate a PC-protein-binding group II antibody. PCG1-1 was previously shown to express the V kappa 1-3 light chain, a characteristic shared by several group II hybridomas. Furthermore, here we examined the VH gene rearrangements in four lambda 1-bearing group II hybridomas that share a common JH rearrangement with PCG1-1 by Southern blot analysis. A VH-specific probe that detects M141 VH rearrangements revealed that all four lambda 1 hybridomas as well as PCG1-1 share an identical VH gene rearrangement to JH-3. Thus the M141 VH gene product is able to utilize two distinct light chains to generate group II-like combining sites.     

Neonatal and adult primary B cells use the same germ-line VH and V kappa genes in their (T,G)-A-L-specific repertoire

Although there is a nonrandom usage of VH gene families by primary B cells early in ontogeny, at issue is whether the preferential rearrangement of 3' germ-line VH genes, e.g., VH7183 and VHQ52 family genes, influences the neonatal B cell repertoire that can be expressed in response to Ag. In order to address this issue, and to determine whether neonatal B cells can use the same germ-line VH and V kappa genes as adult B cells in their primary response, we have analyzed at the molecular level the neonatal antibody response to (T,G)-A-L and compared it with the adult primary response. Among the TGB5 Id+, GT+ antibodies, which dominate the neonatal response to (T,G)-A-L, two VH gene families were used: J558 (high frequency) and 36-60 (low frequency). The majority of Id+ neonatal hybridomas used the same germ-line VH gene (H10, from the VHJ558 family), but with enormous diversity in the D region, and one of two germ-line V kappa 1 genes (V kappa 1A, V kappa 1C). These are the same germ-line V-genes used by most primary adult Id+ hybridomas, and the frequency of expression of this germ-line V-gene combination appears equivalent in the neonatal and adult primary repertoires. Therefore, it is clear from this study that as early as day 5, neonatal B cells can use the same germ-line V-genes as adult primary B cells in their Ag-specific repertoire.     

Repertoire diversity of antibody response to bacterial antigens in aged mice. II. Phosphorylcholine-antibody in young and aged mice differ in both VH/VL gene repertoire and in specificity

Aging of mice is accompanied by both quantitative and qualitative changes in antibody responses to phosphorylcholine (PC), an immunodominant epitope of Streptococcus pneumoniae R36a strain (Pn). In order to study these changes at the molecular level, we generated PC-specific hybridomas from young (3 to 4 mo) and aged (20 to 24 mo) mice of different strains after primary immunization with S. pneumoniae R36a strain. These mAb were tested for Ig VH and VL gene family utilization, idiotopic repertoire, and cross-reactivity with unrelated Ag. Hybridomas from young mice (BALB/c, C57BL/6, and D1.LP) uniformly expressed the VH-S107 and V kappa-22 genes as well as most idiotopes of the T15 family, which were identified with different anti-T15 mAb. In contrast, the PC-reactive mAb from aged mice were quite heterogeneous: only 2 out of 13 utilized VHS107, 1 of 13 used VH7183, and 3 of 13 used VHJ558 gene family. Moreover, none of these mAb used L chain encoded by V kappa 22(0/13), but surprisingly they frequently expressed some of the T15 idiotope. In addition, the PC-binding mAb from aged mice showed broad cross-reactivity with various mouse and foreign proteins, whereas the mAb from young mice did not. These results demonstrate the genetic shift in antibody response of aging mice to PC, which is accompanied by a change in the antibody specificity. Interestingly, the qualitative repertoire change appears to be unrelated to the magnitude of antibody response, for the aged BALB/c mice maintain a very high reactivity to PC.     

A single VH gene is utilized predominantly in anti-BrMRBC hybridomas derived from purified Ly-1 B cells. Definition of the VH11 family

By establishing hybridomas from two distinct surface IgM+ splenic B cell populations, Ly-1 B cells and "conventional" (Ly-1-) B cells, we found that the Ly-1 B population includes a 30 to 70 times higher frequency (1 to 2%) of cells with specificity for bromelain treated autologous red blood cells (anti-BrMRBC) when compared with conventional B cells (0.03%). We cloned and sequenced the V genes encoding anti-BrMRBC antibody from two hybridomas made with Ly-1 B cells sorted from the spleen of SM/J mice. The VH sequence (for both) is identical with the previously reported sequence associated with this specificity and belongs to a new VH gene family. This gene family, defined here as VH11, has only two members and is the predominant VH rearranged in a collection of Ly-1 B derived anti-BrMRBC hybridomas, always in association with a single VL gene (a member of the V kappa 9 family). Furthermore, analysis of hybridomas made with Ly-1 B cells sorted from the peritoneum reveals a yet higher increased frequency of VH11-encoded anti-BrMRBC specificity (30%). This variation in frequency of anti-BrMRBC in the Ly-1 population depending on location, together with the repeated association of VH11 with a particular V kappa gene suggest that antigen driven selection is (at least in part) responsible for the biased V gene expression seen in this population. Furthermore, a mechanism that might contribute to biased expression, preferential rearrangement due to close proximity to J (as seen in pre-B lines), is excluded by localization of VH11 5' to several of the more J-proximal families (Q52, 7183).     

High frequency expression of S107 VH genes by peritoneal B cells of B10.H-2aH-4bP/WTS mice

Our previous analyses of peritoneal Ly-1 B cells indicate that a high percentage express VH genes of the VH11 and VH12 families, and that this bias is due to clonal selection. The antibodies encoded by these genes bind the same hapten, phosphatidyl choline (PtC). Twenty-one of 73 hybridomas generated from fusions with peritoneal Ly-1 and Ly-1 sister population B cells of B10.H-2aH-4bp/Wts mice produce anti-PtC specific antibodies. We show here that 19 of these express VH11 and VH12 family genes and two express VH36-60 family genes. To assess whether there is a bias in VH gene use among non-PtC-specific hybridomas we analyzed the remaining 52 hybridomas for VH family expression by using VH family-specific probes in an RNA dot blot assay and by Ig mRNA sequencing. We find a seven-fold increase in the expression of the VHS107 family genes, and only slight differences in the expression of VH genes of other families relative to splenic B cells. We attribute the increase in VHS107 gene expression to clonal selection inasmuch as five of the seven VHS107+ hybridomas express the same VH gene (V11) and VL association is nonrandom. The bias in VH gene use among the entire panel of 73 peritoneal hybridomas is to the extent that approximately one-third express one of three genes: the V11 gene of the S107 family, the CH34 gene of the VH11 family, and the VH12 family gene.     

Restricted Ig variable region gene expression among Ly-1+ B cell lymphomas

The majority of the characterized Ly-1+ B cell lymphomas of B10.H-2aH-4bp/Wts origin (the CH series) bear surface Ig related by Ag specificity or idiotype or both. To determine the genetic basis for these structural similarities, we have sequenced the VH and VL region genes expressed by 10 CH lymphomas, and have compared their VH and V kappa gene rearrangements by Southern blot analysis to one another and to those of four other CH lymphomas. Sequence analysis identified only five different VH, and seven different VL genes, and indicated that these V genes are essentially unmutated. CH lymphomas which express the identical VH gene share at least one idiotope. Thus, the basis for shared idiotype and specificity is due in most cases to the use of the same V gene. This restriction in V gene expression is not due to the preferential use of V genes of any particular VH family or VL group, as the expressed V genes belong to four different VH families and four V kappa groups, and include V lambda 1 and V lambda 2. We hypothesize that Ag selection accounts for the restriction in V gene usage among CH lymphomas.     

Immunologic memory to phosphocholine. IV. Hybridomas representative of Group I (T15-like) and Group II (non-T15-like) antibodies utilize distinct VH genes

The anti-phosphocholine (PC) memory response elicited in BALB/c mice by phosphocholine-keyhole limpet hemocyanin (PC-KLH) contains two groups of antibodies distinguished by their fine specificity for PC and p-nitrophenylphosphocholine (NPPC). Group I antibodies are inhibited by both PC and NPPC, while Group II antibodies are inhibited appreciably only by NPPC; only Group I antibodies are dominated by the T15 idiotype. Anti-PC hybridomas representative of the memory response to PC-KLH were produced to examine the variable region genes expressed by memory B cells. Two IgM hybridomas were of the Group I type, because they were inhibited by both PC and NPPC and they bound to the pneumococcus R36A. However, only one of these antibodies (PCM-2) expressed a T15 idiotope, while the other (PCM-1) did not express any of three T15 idiotopes. Despite its negative T15 idiotype profile, N-terminal amino acid sequencing of PCM-1 purified heavy chain and Southern blots of the hybridoma DNA indicated that it utilizes the T15 VH and JH1 genes. Three hybridomas, IgG1, IgM, and IgE, typical of Group II antibodies, were examined; these were negative for three T15 idiotopes and displayed measurable avidity only for NPPC in a PC-protein binding inhibition assay. These three hybridoma antibodies, like serum Group II IgG1, did not measurably bind to the bacterium R36A. The heavy chain amino termini of all three of these antibodies were inaccessible for Edman degradation. Southern blots of DNA from the IgG1 hybridoma revealed the T15 VH gene to be in the germ line configuration only and unassociated with any JH segment, indicating that this Group II antibody utilizes a VH gene different from the T15 family. These results signify that, whereas some diversity of the (anti-PC) memory response may be generated by somatic diversification of variable regions important in the primary response, a significant contribution to the overall heterogeneity of memory antibodies originates in the expression of additional variable region genes.     

Germline V genes encode viable motheaten mouse autoantibodies against thymocytes and red blood cells

Autoantibodies against thymocytes and RBC may contribute to the pathophysiology of homozygous viable motheaten (mev) autoimmune disease. Whether the production of these autoantibodies in mev mouse results from polyclonal nonspecific B cell activation or specific Ag-driven stimulation is not known. To understand the mechanisms involved in the induction of antithymocyte autoantibody response in mev mouse, we have studied the fine antigenic specificity, structure, and origin of three antithymocyte autoantibodies derived from mev splenic B cell hybridomas. Western blot analysis showed that these mAb bind to polypeptides of 33 and 105 kDa present in RBC and thymocytes, respectively. Additional specificities for the epitopes present in other polypeptides distinguished these three autoantibodies. Northern hybridization and flow microfluorimetry analysis indicated that these hybridomas are derived from the Ly1+ B cell subset. These autoreactive Ly-1 B cell hybridomas, chosen on the basis of their specificity, expressed L chain V genes from a single VK family (VK9) and VH genes from J606 and S107 families. Hybridomas UN34.11 and UN42.5 expressed the VK9 gene identical to that used by peritoneal Ly1+ B cells from various mouse strains and malignant B lymphoma cells secreting anti-mouse RBC treated with proteolytic enzyme bromelin and anti-SRBC antibodies. The third hybridoma, S2-14.2, used a VK9 gene identical to that expressed by MOPC41. None of the VK genes encoding these autoantibodies showed any somatic mutations. In the case of VH genes, the two hybridomas UN42.5 and S2-14.2 derived from two separate fusions, used identical VH genes from the J606 family. The third hybridoma UN34.11 used unmutated V11 germline VH gene, a member of the S107 family. Southern hybridizations, using oligonucleotide probes specific for CDR1 and CDR2, showed that the VH genes encoding the J606 autoantibodies were derived from a germline gene found in the 6.7-kb fragment of EcoRI-digested germline DNA. This germline VH gene is distinct from VH22.1 germline gene that codes for antigalactan antibodies. Sequence analysis of this gene showed perfect homology with the rearranged VH genes confirming the lack of somatic mutations. Thus, our data demonstrate that antithymocyte antibody response occurring in mev mouse is polyclonal and it involves Ly-1 B cells expressing unmutated germline VH and VK genes. These results indicate that antigen driven stimulation may not play an important role in the induction of anti-thymocyte antibody response in mev mouse.     

Nucleotide sequence of messenger RNA encoding VHDJH and VKJK of a highly conserved idiotype-defined primary response anti-hapten antibody.

The primary humoral immune response of mice to the hapten phthalate (Xmp) is focused upon two adjacent immunodominant negatively charged carboxyl groups on a benzene ring that are in positions meta and para to the azolinkage (i.e., Xmp) to the protein carrier keyhole limpet hemocyanin. A significant fraction of the anti-Xmp antibodies raised in several different inbred mouse strains (BALB/c, DBA/2, A/HeHa; C3H, and SM/J), and many wild mouse populations express a cross-reactive Id, CRIXmp-1. This CRIXmp-1 is conspicuously absent in C57BL/6 mice. In order to obtain a better understanding of the events and parameters that influence the selection and regulation of the primary response B cell repertoire, and to explore the structural basis of Ag binding, we have determined the nucleotide sequence of the entire V region gene complexes, which encode the H and L chains of these highly conserved and dominant CRIXmp-1+ antibodies. Our data establish that the H chain gene complex consists of a single VH germ-line gene that is identical to VH Oxazolone-1, encoding the H chain of another highly conserved and dominant cross-reactive Id family associated with the primary response to Oxazolone. In CRIXmp-1+ Xmp-specific hybridomas this gene is joined to a limited set of D region sequences that express a conserved amino acid motif-GLR. At least three of the five D regions examined are coded for by DFL16.2. This VHD complex can be utilized with one of three different JH region genes (JH1, JH2, and JH4) without any significant effect upon antibody fine specificity or Id. In spite of this lack of JH fidelity all of the CRIXmp-1+ hybridomas have precisely maintained the same length in the H chain CDR3 and FRW4 by altering either the length of the D segment or the length of JH. Nucleotide sequence analysis of the VL gene complex of CRIXmp-1+ anti-Xmp antibodies indicates that the L chain V region is also encoded by a single germ-line gene. The amino acid sequence predicted from the nucleotide sequence of the VKJK from Xmp-specific CRIXmp-1+ hybridomas is identical to the sequence of the anti-arsonate antibody 1210.7, which is the prototype of another Id family (CRI) that is conserved and dominant in BALB/c mice.     

Variable region cDNA sequences and antigen binding specificity of mouse monoclonal antibodies to isomaltosyl oligosaccharides coupled to proteins. T-dependent analogues of alpha(1----6)dextran

Four mouse hybridomas specific for alpha(1----6)dextran, 16.4.12E (IgA kappa, C57BL/6), 28.4.10A (IgM kappa, BALB/c), 35.8.2H (IgG1 kappa, BALB/c), and 36.1.2D (IgM kappa, BALB/c) were obtained by immunization with the T-dependent Ag isomaltohexaose or isomaltotriose coupled to keyhole limpet hemocyanin or to BSA. Immunochemical characterization of the hybridoma antibodies showed that 16.4.12E and 36.1.2D had cavity-type combining sites, recognizing the terminal non-reducing end of alpha(1----6)dextran, whereas 28.4.10A and 35.8.2H had groove-type sites, recognizing internal linear segments of the dextran. The V region cDNA of the H and L chains of the antibodies were cloned and sequenced. VH of 16.4.12E and VH of 36.1.2D belonged to the X24 and Q52 germ-line gene families, respectively. The VH and V kappa sequences of 16.4.12E and V kappa sequence of 36.1.2D were highly homologous to those of W3129, the only anti-alpha(1----6)dextran mAb with a cavity-type site thus far sequenced; 16.4.12E differed from W3129 in the D, JH, and J kappa. VH genes of 28.4.10A and 35.8.2H were homologous to those of several anti-alpha(1----6)dextrans with groove-type sites, but belonged to the J558 germ-line gene family, differed from the other J558 anti-alpha(1----6)dextrans, probably representing a different germ-line subfamily. The L chain sequence of 28.4.10A encoded by V kappa-Ars and J kappa 2 was almost identical to other groove-type anti-alpha(1----6)dextrans obtained by immunizing with the T-independent glycolipid Ag, stearyl-isomaltotetraose. Use of T-dependent Ag such as isomaltosyl oligosaccharide-protein conjugates provides an additional parameter for probing the fine structure of antibody combining sites and evaluating the V-gene repertoire of anti-alpha(1----6)dextrans.     

Variable region sequence analysis of anti-DNA antibodies: evidence for a family of closely related germ-line VH genes encoding lupus autoantibodies.

Cloning and sequencing of the V regions of the anti-DNA monoclonal antibodies (mAbs), H438 and H130, indicate that H438 is encoded by a J558 VH gene, a single D region nucleotide, and unmutated JH1, V kappa-1C and J kappa 1 genes, and the H130 L chain is encoded by a V kappa-21 subgroup gene J kappa 1 gene. Identification of VH438, which shared VH hybridization pattern with 6% of a panel of 352 MRL/lpr hybridomas, suggests that the frequency of J558 use among spontaneously activated B cells in MRL/lpr mice is greater than previously reported. The VHH438 J558 family gene is identical to VHPAR, which encodes the independently derived MRL/lpr autoantibody, MRP-2, and is highly homologous to the previously reported VHH130, which is identical to a BALB/c germ-line VH gene. Comparison of consensus sequences of homologous autoantibodies and previously reported restriction mapping suggest that a minimum of three highly related J558 germ-line genes encode lupus autoantibodies.     

The developmental patterns of B cell precursors distinguishing between environmental and nonenvironmental forms of phosphocholine.

We have analyzed the developmental patterns of two groups of B cell precursors in nonimmunized BALB/c mice with respect to their relative proportions, absolute frequencies, V gene usage, fine specificity, and avidity for antigen. One group of B cells (group I) secretes antibodies specific for PC and PC-containing bacteria, whereas the other group (group II) produces antibodies recognizing only nonenvironmental PC-protein conjugates. A marked shift in the proportions of group I and group II occurs during ontogeny: while the group I B cells dominate (greater than 85%) the adult antibody repertoire, the group II B cells have equal representation in neonatal mice from Days 1 to 7, and remain as a significant portion until 2 weeks of age. Examination of the absolute frequencies of group I and group II B cells revealed that the frequency of group II B cells remained relatively stable throughout ontogeny, whereas group I B cells expanded rapidly after 7 days of age to predominate in the adult. Genetic analysis indicated that early group I antibodies were encoded by VH and VL genes different from adult group I antibodies which are mostly encoded by a single VH (S107) and VL (V kappa 22) gene combination (the T15 idiotype). On the other hand, early group II antibodies used VH genes comparable to their adult counterparts. The majority of early group I antibodies have lower avidity for PC than adult T15+ antibodies, whereas the avidity of neonatal group II antibodies varies considerably and is comparable with that of the adult group II antibodies. Our results suggest that the ontogeny of phosphocholine-specific B cells may be regulated according to their fine specificity rather than to their avidity or V gene usage.     

Germ Line Variable Regions That Match Hypermutated Sequences in Genes Encoding Murine anti-Hapten Antibodies

We asked whether there are germ line immunoglobulin variable (V) segments that match sites of hypermutation in V regions encoding murine antibodies. Murine germ line DNA was probed with a panel of short deoxyoligonucleotides identical in sequence to segments of hypermutated V regions from hybridomas generated in the BALB/c response to the hapten 2-phenyloxazolone (Ox). Germ line sequences that match mutations in both heavy and kappa light chain V regions were identified, and clones of some of these germ line V segments were obtained. Comparison of these clones with hypermutated V regions revealed regions of identity ranging in size from 7 to over 50 nucleotides. In an effort to separate the effects of antigen selection from the mutagenic process, we also searched for matches to a panel of silent mutations in VH regions from germinal center B cells. Fourteen silent mutations occur among a collection of 36 hypermutated VH regions from two separate germinal centers of C57BL/6 mice stimulated with the hapten 4-hydroxy-3-nitrophenyl. Matches to nine of these silent mutations can be found among published sequences of C57BL/6 VH regions of the J558 family. Taken together, these data are consistent with the possibility that a template-dependent mutational process, like gene conversion, may contribute to somatic hypermutation.     

Many variable region genes are utilized in the antibody response of BALB/c mice to the influenza virus A/PR/8/34 hemagglutinin

We have examined how many different H chain variable (VH) and kappa-chain variable (Vk) germ-line genes are used in the antibody response to the influenza virus A/PR/8/34 hemagglutinin (PR8 HA), and have assessed how the expression of individual VH and/or Vk genes contributes to the generation of specificity for the HA. A panel of 51 hybridoma antibodies that recognize two antigenic regions on the HA were compared for the sequence of their Ig H and L chain V regions. The hybridomas were obtained from 28 individual BALB/c mice that had been immunized with PR8 under a variety of primary and secondary response immunization protocols. The degree and pattern of sequence similarity suggests that 29 different VH genes drawn from seven different VH gene families, and 25 different Vk genes drawn from 12 different Vk gene families were used in this panel. Based on current estimates of the total numbers of VH and Vk genes in the mouse, this suggests that between 2.5 and 10% of the entire VH and Vk germ-line repertoires were used by these hybridomas. Despite this extensive diversity, some V genes were repetitively identified among these hybridomas, and were most often expressed in the context of specific VH/Vk combinations. Because antibodies that used identical VH/Vk combinations also usually displayed similar reactivity patterns with a panel of mutant viruses, this indicates that VH/Vk pairing can be important in establishing the specificity of antibodies for the HA.     

Natural auto- and polyreactive antibodies differing from antigen-induced antibodies in the H chain CDR3

We describe three sets of natural (preimmune) polyreactive antibodies and Ag-induced antibodies that share the same VH-VL combinations. The amino acid homology in the VH and VL segments averaged 92%. These sets were found among 49 neonatal and adult natural mAb that were compared with 35 Ag-induced monoclonals produced during the memory response to phosphocholine (PC)-keyhole limpet hemocyanin. Both groups of monoclonals had been selected on the basis of a restricted fine specificity pattern, namely the ability to recognize PC-protein and p-nitrophenyl phosphocholine but not PC. All of the antibodies were tested for reactivity against a panel of 15 self and foreign Ag. Despite their common fine specificity as the basis for selection, 33/49 natural antibodies were poly/auto reactive whereas 0/35 Ag-induced antibodies had such poly/auto reactive properties. The natural antibodies were encoded by genes representing nine different VH families and several V kappa and V lambda families. There were a few replacement substitutions distinguishing the Ag-induced antibodies from the natural antibodies in each set; however, the most noteworthy difference was the extreme variability of CDR3 in the natural antibodies that differed in both length and amino acid sequence from each other and from Ag-induced antibodies. The results suggest that CDR3 of the H chain may play a critical role in distinguishing poly- from monospecific combining sites in natural and Ag-induced antibodies.     

Genetics of the phosphocholine-specific antibody response to Streptococcus pneumoniae. Germ-line but not mutated T15 antibodies are dominantly selected

The role that somatic mutations play in the phosphocholine-specific, antibody response to Streptococcus pneumoniae was examined by studying sets of hybridomas from different individual mice. As expected most of the cell lines were from the T15 anti-phosphocholine family and were not encoded by the v1 gene of the T15 VH family and V kappa 22. A minority of antibodies were from the M603 (v1/V kappa 8) and M511 (v1/V kappa 24) families. Three additional antibodies were encoded by the v11 gene of the T15 family; two were paired with a V lambda and the other with a V kappa 1 gene. In vitro binding studies showed that T15- and M603-like antibodies had the highest affinity for S. pneumoniae. Complete sequencing of the VH and VL mRNA from 25 of the hybridomas revealed somatic mutations in 11 of the antibodies. A total of 17 independently derived T15 positive cell lines were studied in detail, six of these were mutated. These mutations were scattered throughout the V regions and the replacement to silent ratio was typical of that for framework regions. Statistical evaluation of the placement of mutations showed that there was a slight but significantly decreased frequency of mutations in complementarity determining regions. Comparisons of mutated and unmutated T15-related antibodies showed that mutations caused a decrease in binding to S. pneumoniae in every case. These results argue that the optimal specificity for this molecular form of phosphocholine is encoded in the germline and that Ag-driven events favor selection of B cells expressing these germ-line encoded antibodies.     

V kappa gene usage, idiotype expression, and antigen binding among clones expressing the VHX24 gene family derived from naive and anti-idiotype immune BALB/c mice

The BALB/c myeloma protein ABPC48 binds beta(2-6)-linked fructosans and expresses genes derived from the VHX24 and V kappa 10 gene families. We have selected 30 hybridomas expressing the VHX24 gene family derived from mitogen-stimulated spleen cells of naive BALB/c mice and mice injected at birth with the syngeneic monoclonal anti-ABPC48Id, IDA10. The majority of mAb with kappa L chains uses V kappa 1. Antibodies reacting with IDA10 use both V kappa 10 and V kappa 1. Most of these VHX24+ mAb reacted with one or more members of a limited panel of predominantly polysaccharide Ag that have been previously observed to interact with antibodies expressing the VHX24 gene family. Nucleotide sequencing of selected VH and V kappa genes shows a very low frequency of somatic mutation. The effect of neonatal anti-Id injection on VHX24-V kappa pairing and Id expression is discussed.     

Cloning and sequence analysis of the VH and VL regions of an anti-myelin/DNA antibody from a patient with peripheral neuropathy and chronic lymphocytic leukemia

We have cloned and determined the nucleotide sequence of the Ig VH and VL region genes of an IgM kappa mAb that binds to denatured DNA and myelin from a patient (POP) with chronic lymphocytic leukemia and peripheral neuropathy. Sequence analysis indicates that the V region of the kappa L chain gene (PopVK) has 99% homology to a V kappa IIIa germ-line gene and the V region of the mu H chain gene (PopVH) has 96% homology to the VH26 germ-line gene that is a member of the VH3 gene family. It is likely the V kappa and VH genes arose from these respective germ-line genes via somatic mutation or from closely related genes. V kappa III genes have frequently been used by other IgMk mAb especially those with rheumatoid factor activity, and the VH26 gene with no somatic mutation has been used by several anti-DNA antibodies, suggesting the possibility of preferential association of these or related germ-line genes with autoantibodies. The minor differences between the sequences of POP's VH and V kappa genes and sequences used by other autoantibodies, may be responsible for this antibody's crossreactivity with myelin and, as a result, the autoimmune neuropathy.