Mouse Vk gene classification by nucleic acid sequence similarity

Skewed primary Igκ repertoire and V-J joining in C57BL/6 mice: implications for recombination accessibility and receptor editing

Previous estimates of the diversity of the mouse Ab repertoire have been based on fragmentary data as a result of many technical limitations, in particular, the many samples necessary to provide adequate coverage. In this study, we used 5'-coding end amplification of Igκ mRNAs from bone marrow, splenic, and lymph node B cells of C57BL/6 mice combined with amplicon pyrosequencing to assess the functional and nonfunctional Vκ repertoire. To evaluate the potential effects of receptor editing, we also compared V/J associations and usage in bone marrows of mouse mutants under constitutive negative selection or an altered ability to undergo secondary recombination. To focus on preimmune B cells, our cell sorting strategy excluded memory B cells and plasma cells. Analysis of ~90 Mbp, representing >250,000 individual transcripts from 59 mice, revealed that 101 distinct functional Vκ genes are used but at frequencies ranging from ~0.001 to ~10%. Usage of seven Vκ genes made up >40% of the repertoire. A small class of transcripts from apparently nonfunctional Vκ genes was found, as were occasional transcripts from several apparently functional genes that carry aberrant recombination signals. Of 404 potential V-J combinations (101 Vκs × 4 Jκs), 398 (98.5%) were found at least once in our sample. For most Vκ transcripts, all Jκs were used, but V-J association biases were common. Usage patterns were remarkably stable in different selective conditions. Overall, the primary κ repertoire is highly skewed by preferred rearrangements, limiting Ab diversity, but potentially facilitating receptor editing.

Peripheral B cell receptor editing may promote the production of high-affinity autoantibodies in CD22-deficient mice

CD22-deficient mice are characterized by B cell hyperactivity and autoimmunity. We have constructed knock-in CD22-/- mice, expressing an anti-DNA heavy (H) chain (D42), alone or combined with Vkappa1-Jkappa1 or Vkappa8-Jkappa5 light (L) chains. The Ig-targeted mice produced a lupus-like serology that was age- and sex-dependent. High-affinity IgG autoantibodies were largely dependent on the selection of B cells with a particular H/L combination, in which a non-transgenic, endogenous L chain was assembled by secondary rearrangements through the mechanism of receptor editing. Moreover, we present evidence that these secondary rearrangements are very prominent in splenic peripheral B cells. Since CD22 is primarily expressed on the surface of peripheral B cells, we propose a model for the development of a lupus-like autoimmune disease by a combination of peripheral receptor editing and abnormal B cell activation.

Differences in potential for amino acid change after mutation reveals distinct strategies for kappa and lambda light-chain variation

B cells generate varied yet functional clones under high rates of mutation of their V genes. It has been proposed that as a result of the opposing demands of diversification and preservation of integrity, the V genes of heavy and light chains have evolved to overexpress codons prone to amino acid change in their complementarity determining regions (CDR) compared with the framework (FW) regions. We have analyzed the germ-line V genes of heavy and light chains (both kappa and lambda), comparing codons of CDR and FW of the germ-line V regions both to each other and to control regions. We found that in both germ-line heavy chains and lambda chains, CDR codons are prone to replacement mutations, whereas in the FW, the opposite is true. Furthermore, the difference between CDR and FW in heavy chains and lambda chains is based on codons that are prone to nonconservative changes of amino acid. In contrast, in germ-line kappa chains, the codons in both CDR and FW are more prone to replacement mutations. We also demonstrated that negative selection during immune responses is more sensitive to nonconservative amino acid substitutions than overall amino acid change, demonstrating the applicability of our analysis to real-time process of selection in the immune system. The differences in germ-line kappa and lambda light chains' potential reaction to mutation suggests that via these two differently evolved light-chain types, the B cell repertoire encompasses two different strategies to balance diversity and stability in an immune response.

Rapid specific amplification of rat antibody cDNA from nine hybridomas in the presence of myeloma light chains

Most monoclonal antibodies to mouse antigens have been derived from rat spleen-mouse myeloma fusions. Many resultant hybridomas express one of several myeloma kappa chain transcripts, even though the parent myeloma may have been ascribed as not expressing light chain protein. Previous reports have only differentiated against one of these mouse light chains. We have found at least three different myeloma kappa transcripts in the panel of nine hybridomas that were derived from four different myeloma parents. We have designed an amplification strategy that differentiates the rearranged rat kappa chain from all mouse light chains. Moreover, this method is expedient as it requires minimal downstream manipulation.

Attenuated liver fibrosis in the absence of B cells

Analysis of mononuclear cells in the adult mouse liver revealed that B cells represent as much as half of the intrahepatic lymphocyte population. Intrahepatic B cells (IHB cells) are phenotypically similar to splenic B2 cells but express lower levels of CD23 and CD21 and higher levels of CD5. IHB cells proliferate as well as splenic B cells in response to anti-IgM and LPS stimulation in vitro. VDJ gene rearrangements in IHB cells contain insertions of N,P region nucleotides characteristic of B cells maturing in the adult bone marrow rather than in the fetal liver. To evaluate whether B cells can have an impact on liver pathology, we compared CCl4-induced fibrosis development in B cell-deficient and wild-type mice. CCl4 caused similar acute liver injury in mutant and wild-type mice. However, following 6 weeks of CCl4 treatment, histochemical analyses showed markedly reduced collagen deposition in B cell-deficient as compared with wild-type mice. By analyzing mice that have normal numbers of B cells but lack either T cells or immunoglobulin in the serum, we established that B cells have an impact on fibrosis in an antibody- and T cell-independent manner.

CD19 regulates positive selection and maturation in B lymphopoiesis: lack of CD19 imposes developmental arrest of immature B cells and consequential stimulation of receptor editing

Ligand-independent signals that are produced by the B-cell antigen receptor (BCR) confer an important positive selection checkpoint for immature B cells. Generation of inappropriate signals imposes developmental arrest of immature B cells, though the fate of these cells has not been investigated. Studies have shown that the lack of CD19 results in inappropriate signaling. In immunoglobulin transgenic mice, this inappropriate signaling impairs positive selection and stimulates receptor editing. Here, we studied the extent and significance of receptor editing in CD19-regulated positive selection of normal, nontransgenic B lymphopoiesis, using our bone marrow culture system. We found that the lack of CD19 resulted in elevated tonic signaling and impaired maturation, as revealed by surface marker expression and by functional assays. Immature CD19-/- B cells did not suppress RAG and underwent intensive receptor editing attempts in culture. Finally, in vivo analysis of light-chain isotype expression and Jkappa use in CD19-/- mice validated our in vitro observations. Our results suggest that CD19 has an important function in regulating positive selection and maturation of nontransgenic B-cell precursors and that receptor editing is an important salvage mechanism for immature B cells that fail positive selection.

Specificity-Based Negative Selection of Autoreactive B Cells during Memory Formation

Autoreactive B cells are not completely purged from the primary B cell repertoire, and whether they can be prevented from maturation into memory B cells has been uncertain. We show here that a population of B cells that dominates primary immune responses of BALB/c mice to influenza virus A/PR/8/34 hemagglutinin (HA) are negatively selected in transgenic mice expressing PR8 HA as an abundant membrane-bound Ag (HACII mice). However, a separate population of B cells that contains precursors of memory B cells is activated by PR8 virus immunization and is subsequently negatively selected during the formation of the memory response. Negative selection of PR8 HA-specific B cells altered the specificity of the memory B cell response to a mutant virus containing a single amino acid substitution in a B cell epitope. Strikingly, this skewed reactivity resulted from an increase in the formation of memory B cells directed to non-self-epitopes on the mutant virus, which increased 8-fold in HACII mice relative to nontransgenic mice and precisely compensated for the absence of autoreactive PR8 HA-specific memory B cells. Negative selection of PR8 HA-specific B cells was a dominant process, since B cells from HACII mice could induce negative selection of PR8 HA-specific B cells from BALB/c mice. Lastly, HA-specific memory responses were unaffected by self-tolerance in another lineage of HA-transgenic mice (HA104 mice), indicating that the amount and/or cell type in which self-Ags are expressed can determine their ability to prevent autoreactive memory B cell formation.

The complexity of expressed kappa light chains in egg-laying mammals

Complementary DNAs encoding immunoglobulin light chains were isolated from two monotreme species, Ornithorhynchus anatinus (duckbill platypus) and Tachyglossus aculeatus (echidna). The sequences of both the variable and constant regions of these clones had greater similarity to IGK than to other light chain classes and phylogenetic analyses place them squarely within the mammalian IGK group, establishing them as monotreme IGK homologues. The constant region sequences of all clones were essentially identical within each species and, along with Southern blot results, the data are consistent with a single IGKC in each species. The expressed IGKV repertoires from both platypus and echidna were randomly sampled and there appear to be at least four platypus and at least nine echidna IGKV subgroups. The IGKV subgroups are highly divergent within species, in some cases sharing as little as 57% nucleotide identity. Two of the IGKV subgroups are present in both species, so there is some degree of overlap in the germline repertoires of these two monotremes. Overall the complexity seen in platypus and echidna IGK light chains is comparable with that of other mammals considered to have high levels of germline diversity and is in contrast to what has been found so far for monotreme IGL.

The kinetics of V-J joining throughout 3.5 megabases of the mouse Ig kappa locus fit a constrained diffusion model of nuclear organization

To gain insight into the nuclear organization of the mouse Ig kappa locus and how it may relate to the formation of synapses during recombination, we have studied the kinetics of rearrangement of different V kappa gene families to J kappa gene segments in the pre-B cell line, 103bcl2. Remarkably, V kappa gene families separated by more than 3.5 Mb from J kappa gene segments rearranged with nearly identical kinetics to those as close as 18 kb to J kappa gene segments. These results fit a model of nuclear organization in which the entire V kappa J kappa region resides within a single nuclear subcompartment and is capable of exhibiting multiple reversible contacts through diffusion and Brownian motion.

Molecular identification of pathogenetic IdLNF+1 autoantibody idiotypes derived from the NZBxSWR F1 model for systemic lupus erythematosus

The acceleration of nephritis in SNF(1) mice by CD4(+) T-cell clones reactive with a nephritogenic idiotype, Id(LN)F(1) [1], as well as the ability of anti-Id(LN)F(1) antisera to down-regulate the production of Id(LN)F(+)(1) immunoglobulin (Ig) in vivo and delay nephritis [2], suggests that dysregulation of this idiotype may contribute to the development of SNF(1) nephritis. Herein, we show that a monoclonal Id(LN)F(1)-expressing antibody, 540, significantly (P< or = 0.01) stimulated Id(LN)F(1)-reactive T-cell clones B6 and D2 to proliferate, while other Id(LN)F+1 antibodies did not. Further, injection of 540-producing hybridoma cells into nonautoimmune (SWRxBalb/c)F(1) mice resulted in the deposition of Id(LN)F(+)(1) Ig in the kidneys, in a pattern indicative of early nephritis. To identify the pathogenetic Id(LN)F(1) epitope(s) at the molecular level, we compared the deduced amino acid sequences of the heavy and light chain variable regions of pathogenetic and non-pathogenetic Id(LN)F(1)-expressing Igs 540, 317, and 533. Two overlapping peptides derived from the V(H) sequence of 540 (aa 54-66 and 62-73), which both contain the triple basic amino acid motif K(X)K(X)K, stimulated SNF(1) T cells and T-cell clones B6 and D2. These results further support the involvement of a subset of Id(LN)F(1)-expressing Ig in SNF(1) nephritis.

Chromatin structural analyses of the mouse Igkappa gene locus reveal new hypersensitive sites specifying a transcriptional silencer and enhancer

To identify new regulatory elements within the mouse Igkappa locus, we have mapped DNase I hypersensitive sites (HSs) in the chromatin of B cell lines arrested at different stages of differentiation. We have focused on two regions encompassing 50 kilobases suspected to contain new regulatory elements based on our previous high level expression results with yeast artificial chromosome-based mouse Igkappa transgenes. This approach has revealed a cluster of HSs within the 18-kilobase intervening sequence, which we cloned and sequenced in its entirety, between the Vkappa gene closest to the Jkappa region. These HSs exhibit pro/pre-B cell-specific transcriptional silencing of a Vkappa gene promoter in transient transfection assays. We also identified a plasmacytoma cell-specific HS in the far downstream region of the locus, which in analogous transient transfection assays proved to be a powerful transcriptional enhancer. Deletional analyses reveal that for each element multiple DNA segments cooperate to achieve either silencing or enhancement. The enhancer sequence is conserved in the human Igkappa gene locus, including NF-kappaB and E-box sites that are important for the activity. In summary, our results pinpoint the locations of presumptive regulatory elements for future knockout studies to define their functional roles in the native locus.

Predominance of a novel splenic B cell population in mice expressing a transgene that encodes multireactive antibodies: support for additional heterogeneity of the B cell compartment

We generated IgHmudelta transgenic mice using a V(H) gene that in A/J mice encodes multireactive BCR in the preimmune B cell compartment and is predominantly expressed by a memory B cell subpopulation. Most primary splenic B cells in these mice have a size, cell-surface phenotype and in vitro response profile distinct from mature follicular (B2), marginal zone (MZ) or B1 B cells, but are long-lived and appear to be slowly cycling. They reside in conventional B cell areas of the spleen and mount robust foreign antigen-driven germinal center responses, but do not efficiently differentiate to secretory phenotype. We propose that these qualities result from ongoing, low-avidity BCR-self-ligand interactions and promote entry into the memory pathway. Given these data, and the enormous diversity and characteristic multireactivity of the preimmune antibody repertoire, we also suggest that it may be more appropriate to view the primary B cell compartment as a continuum of functional and phenotypic 'layers', rather than as a group of discrete B1, B2 and MZ subsets.

Transcription factor AP-4 is a ligand for immunoglobulin-kappa promoter E-box elements

Immunoglobulin (Ig)-kappa promoters from humans and mice share conserved sequences. The octamer element is common to all Ig promoters and pivotal for their function. However, other conserved sequence motifs, that differ between Ig variable gene families, are required for normal promoter function. These conserved motifs do not stimulate transcription in the absence of an octamer. One example is an E-box of the E47/E12 type (5'-CAGCTG-3'), which is found in all promoters of the human and murine Ig-kappa gene subgroups/families, with the exception of subgroups II and VI and their related murine families. In the present study we show that the ubiquitously expressed transcription factor AP-4, and not E47, interacts specifically with the kappa promoter E-boxes when tested in electrophoretic mobility-shift assays using nuclear extracts derived from human and murine B-cell lines. Furthermore, AP-4, unlike E47, did not act as a transactivator, which is in agreement with previous studies on intact kappa promoters, showing that transcription is absent when the octamer element has been mutated. Based on these data, and the conservation of the 5'-CAGCTG-3' motif among human and murine kappa promoters, we propose that AP-4 is the major ligand for Ig-kappa promoter E-boxes.

Functional activities and immunoglobulin variable regions of human and murine monoclonal antibodies specific for the P1.7 PorA protein loop of Neisseria meningitidis

The meningococcal PorA protein is considered a promising vaccine candidate. Although much is understood regarding the structure of PorA proteins, little is known about the structure-function relationships of PorA antibodies. The aim of this study was to compare the functional and molecular characteristics of a human monoclonal antibody (MAb) and three murine MAbs specific for the PorA P1.7 serosubtype. Murine MAbs 207,B-4 (immunoglobulin G2a [IgG2a]) and MN14C11.6 (IgG2a) were both bactericidal and opsonophagocytic for P1.7-expressing meningococci, whereas human MAb SS269 (IgG3) and murine MAb 208,D-5 (IgA) initiated neither effector function. Epitope mapping with synthetic peptides revealed that MAbs 207,B-4 and 208,D-5 recognized the sequence ASGQ, which is the same specificity motif that a previous study had established for SS269 and MN14C11.6. Nucleotide and amino acid sequence analyses of the variable regions of the four MAbs showed that the SS269 V(H) region belonged to the VH3 family and was approximately 70% homologous to those of the murine MAbs which were all from the 7183 family, whereas the SS269 V(L) region belonged to the Vlambda1-b family and was less than 40% homologous to those of the murine MAbs which were all members of the Vkappa1 family. The Fab fragment of SS269 was cloned and expressed in Escherichia coli and was shown by enzyme-linked immunosorbent assay analyses to bind as well as intact SS269 MAb to P1.7,16 serosubtype group B strain 44/76. We conclude that distinct differences exist in the effector function activities and variable region gene sequences of human and murine P1.7-specific MAbs despite their recognition of similar epitopes.

A B-cell receptor-specific selection step governs immature to mature B cell differentiation

Seventy percent of peripheral immature conventional (B2) B cells fail to develop into mature B cells. The nature of this cell loss has not been characterized; the process that governs which immature B cells develop into long-lived peripheral B cells could be either stochastic or selective. Here, we demonstrate that this step is in fact selective, in that the fate of an immature B cell is highly dependent on its Ig receptor specificity. A significant skewing of the B cell receptor repertoire occurs by the time cells enter the mature B cell fraction, which indicates that there is selection of only a minority of immature B cells to become mature B cells. Because only a few heavy-light chain pairs are enhanced of the diverse available repertoire, we favor the idea that selection is positive for these few heavy-light chain pairs rather than negative against nearly all others. Because most immature B cells are lost at this transition, this putative positive selection event is likely to be a major force shaping the mature B cell receptor repertoire available for adaptive immune responses.

High-level rearrangement and transcription of yeast artificial chromosome-based mouse Ig kappa transgenes containing distal regions of the contig

The mouse Ig kappa L chain gene locus has been extensively studied, but to date high-level expression of germline transgenes has not been achieved. Reasoning that each end of the locus may contain regulatory elements because these regions are not deleted upon V kappa-J kappa joining, we used yeast artificial chromosome-based techniques to fuse distal regions of the contig to create transgene miniloci. The largest minilocus (290 kb) possessed all members of the upstream V kappa 2 gene family including their entire 5' and 3' flanking sequences, along with one member of a downstream V kappa 21 gene family. In addition, again using yeast artificial chromosome-based technology, we created Ig kappa miniloci that contained differing lengths of sequences 5' of the most distal V kappa 2 gene family member. In transgenic mice, Ig kappa miniloci exhibited position-independent and copy number-dependent germline transcription. Ig kappa miniloci were rearranged in tissue and developmental stage-specific manners. The levels of rearrangement and transcription of the distal and proximal V kappa gene families were similar to their endogenous counterparts and appeared to be responsive to allelic exclusion, but were differentially sensitive to numerous position effects. The minilocus that contained the longest 5' region exhibited significantly greater recombination of the upstream V kappa 2 genes but not the downstream V kappa 21 gene, providing evidence for a local recombination stimulating element. These results provide evidence that our miniloci contain nearly all regulatory elements required for bona fide Ig kappa gene expression, making them useful substrates for functional analyses of cis-acting sequences in the future.

Murine immune response to Neisseria meningitidis group C capsular polysaccharide: analysis of monoclonal antibodies generated in response to a thymus-independent antigen and a thymus-dependent toxoid conjugate vaccine

Antibody (Ab) responses to polysaccharides (PSs) such as Neisseria meningitidis group C PS (MCPS) are characterized as being thymus independent (TI) and are restricted with regard to clonotype and isotype expression. PS conjugated to proteins, e.g., MCPS coupled to tetanus toxoid (MCPS-TT), elicits a thymus-dependent (TD) response. In order to understand the influence of the form of a vaccine (TI versus TD) on the Ab repertoire, we generated monoclonal antibody (MAb) panels from mice immunized and boosted with MCPS or MCPS-TT in different ways. The panels of MAbs were examined for isotype, fine specificity, affinity, and V(H) gene family usage. The use of MCPS-TT resulted in a shift in the isotype from immunoglobulin M (IgM) and IgG3 elicited in response to the MCPS to primarily IgG1. This isotype shift was accompanied by a change in the fine specificity of the response to the conjugate compared to that of PS. New fine specificities and increased affinity were observed in response to the TD antigen (Ag). Dot blot and Northern analyses of MCPS MAbs revealed that V(H) gene family usage is dominated by V(H)J558, used by 23 of 39 MAbs. V(H)3609 was seen in three MAbs of restricted fine specificity. V(H)Q52, V(H)7183, and V(H)VGAM3-8 were seen in more than one MAb across these panels, while V(H)10 and V(H)X24 were detected only once in response to the TI-2 Ag. All MAbs in the panels utilized kappa light chains, and all functional J(kappa) genes were expressed.

Variability of the immunoglobulin light chain in the Siberian sturgeon, Acipenser baeri

All sturgeon VL segments isolated in this study belong to a single family, VLI, which can be divided into two subfamilies. Of the 79 cDNA clones isolated, 76 belong to the larger subfamily, VLIa, and only 3 clones constitute the smaller subfamily, VLIb. To evaluate variability, the Shannon entropy was estimated for each individual amino acid position, and to facilitate comparisons of variability between species the mean entropy of the CDR regions was calculated. In such a comparison, the sturgeon was found to have CDR1 and CDR3 variability approaching those found in mouse and clawed frog, but showed very low variability for CDR2. Amino acid position 50 does however display variability in the range of mouse and clawed frog. It is further confirmed that the sturgeon has numerous J segments, but that the junctional diversity does not contribute greatly to the diversity of the light chain. Comparisons of cDNA clones and a genomic VL segment indicate that the VL undergoes changes, particularly in the CDR regions, in a manner that can be explained by somatic hypermutation and/or gene conversion.

The IgG2a/IgA produced by the murine T560 B lymphoma that arose during a graft-versus-host reaction is polyreactive and somatically mutated

In mice undergoing a graft-versus-host (GVH) reaction, donor T cells responding to the host's MHC antigens induce polyclonal activation of the host's B cells and secretion of their antibodies and autoantibodies. T560, a CD5- B lymphoma that arose in the gut-associated lymphoid tissue (GALT) of a (B10 x B10.H2aH4(b)pWts) F1 hybrid mouse that had been injected with parental B10.H2aH4b splenocytes, is of particular interest because it produces switched, heavily mutated, but, nevertheless, polyreactive immunoglobulin. T560 bears and contains IgG2a but switches to IgA spontaneously. The T560 Ig variable region is encoded by a V186.2-related VH gene, juxtaposed to DFL 16 and J(H)1, and by a Vkappa gene of the Vkappa 4/5 group juxtaposed to Jkappa1. Both VH and VK are heavily mutated. The IgA binds to polystyrene, to p-azophenyl-phosphorylcholine (PC)-conjugated keyhole limpet hemocyanin (KLH) (PC-KLH), to 2,4,6 trinitrophenylated (TNP)-KLH and to human TNF-beta but not to KLH, human TNF-alpha, or any of several other Ags tested. Hapten inhibition experiments indicate that the polystyrene, PC- and TNP-binding sites do not overlap. The switched isotypes and heavy load of somatic mutations found in the T560 IgG2a/IgA suggest that T cell-dependant somatic selection of the T560 precursor B cell may have been superimposed on polyclonal B cell activation originally associated with the GVH.

Recombinant single-chain Fv antibody fragment-alkaline phosphatase conjugate for one-step immunodetection in molecular hybridization

Using phage-display technology, a recombinant single-chain Fv antibody fragment (scFv) was rapidly generated from the K16-16 hybridoma secreting mouse monoclonal antibody (MAb) that binds to acetylaminofluorene-labeled DNA (AAF-DNA). The selected A4 phage-scFv specifically bound to AAF-DNA. The anti-AAF scFv gene was then recloned into a fusion vector for the production of a hybrid protein comprising the antibody fragment fused to a potent bacterial alkaline phosphatase variant (PhoAv). The anti-AAF scFv-PhoAv hybrid protein was bifunctional and possessed both antigen binding capacity and PhoA activity. The recombinant conjugate was directly used, without further purification, for one-step immunodetection in dot-blot hybridization. The detection limit was identical and the test was quicker than the conventional two-step procedure with the purified anti-AAF MAb revealed with a secondary enzyme-labeled antibody. To assess the value of this new reagent for the immunodetection of genomic nucleic acids, genomic DNAs of Campylobacter jejuni and Campylobacter coli were then one-step immunodetected with non-purified recombinant scFv-PhoAv conjugate in a Southern-blot hybridization experiment. The present study shows that the genetic fusion with PhoAv provides a new tool for immunodetection which presents easier and quicker production and use with the same sensitivity and specificity as classical reagents. The recombinant anti-AAF scFv-PhoAv conjugate is a promising alternative reagent for applications involving the immunodetection of specific DNA or RNA sequences, such as the detection and characterization of microorganisms.

The variable genes and gene families of the mouse immunoglobulin kappa locus

In this report 118 mouse Vkappa genes are described which, together with the 22 Vkappa genes reported previously (T. Kirschbaum et al., Eur. J. Immunol. 1998. 28: 1458-1466) amount to 140 genes that had been cloned and sequenced in our laboratory. For 73 of them cDNAs are known, i. e. they have to be considered functional genes, although 10 genes of this group have 1-bp deviations from the canonical promoter, splice site or heptanucleotide recombination signal sequences. Twenty Vkappa genes have been defined as only potentially functional since they do not contain any defect, but no cDNAs have been found (yet) for them. Of the 140 Vkappa genes 47 are pseudogenes. There are indications that two to five Vkappa genes or pseudogenes exist in the kappa locus which we have not yet been able to clone. The 140 Vkappa genes and pseudogenes were assigned to 18 gene families, 4 of them being one-member families. This differs from previous enumerations of the families only by the combination of the Vkappa9 and Vkappa10 families and by the addition of the Vkappa dv gene as a new separate family. Sequence identity usually was 80% or above within the gene families and 55-80% between genes of different families. Many of the mouse Vkappa gene families show significant homologies to the human ones, indicating that in evolution Vkappa gene diversification predated the divergence of the primate and rodent clades.

Efficient amplification and direct sequencing of mouse variable regions from any immunoglobulin gene family

We have designed two original sets of oligonucleotide primers hybridizing the relatively conserved motifs within the immunoglobulin signal sequences of each of the 15 heavy chain and 18 kappa light chain gene families. Comparison of these 5' primers with the immunoglobulin signal sequences referenced in the Kabat database suggests that these oligonucleotide primers should hybridize with 89.4% of the 428 mouse heavy chain signal sequences and with 91.8% of the 320 kappa light chain signal sequences with no mismatch. Following PCR amplification using the designed primers and direct sequencing of the amplified products, we obtained full-length variable sequences belonging to major (V(H)1, V(H)2, V(H)3, Vkappa1 and Vkappa21) but also small-sized (V(H)9, V(H)14, Vkappa2, Vkappa9A/9B, Vkappa12/13, Vkappa23 and Vkappa33/34) gene families, from nine murine monoclonal antibodies. This strategy could be a powerful tool for antibody sequence assessment whatever the V gene family before humanization of mouse monoclonal antibody or identification of paratope-derived peptides.

Increased junctional diversity in fetal B cells results in a loss of protective anti-phosphorylcholine antibodies in adult mice

Fetal Igs are less diverse than adult Igs, largely because of the lack of N addition in the absence of Tdt. To test whether the absence of Tdt is essential, we generated Tg mice that express Tdt and add N regions in fetal B cells. When challenged as adults with PC-containing Streptococcus pneumoniae, these mice fail to make the hallmark T15 anti-PC Ab encoded by canonical rearrangements of Ig H and L chain genes. The anti-PC Abs from these mice are altered by premature N addition and do not protect against death from virulent pneumococcal infection. These results show that maintenance of lower Ig diversity in early life is essential for the acquisition of a complete functional adult repertoire.

Production of High Affinity Autoantibodies in Autoimmune New Zealand Black/New Zealand White F1 Mice Targeted with an Anti-DNA Heavy Chain

Lupus-prone, anti-DNA, heavy (H) chain “knock-in” mice were obtained by backcrossing C57BL/6 mice, targeted with a rearranged H chain from a VH11(S107)-encoded anti-DNA hybridoma (D42), onto the autoimmune genetic background of New Zealand Black/New Zealand White (NZB/NZW) F1 mice. The targeted female mice developed typical lupus serologic manifestations, with the appearance of transgenic IgM anti-DNA autoantibodies at a young age (2–3 mo) and high affinity, somatically mutated IgM and IgG anti-DNA Abs at a later age (6–7 mo). However, they did not develop clinical, lupus-associated glomerulonephritis and survived to at least 18 mo of age. L chain analysis of transgenic anti-DNA Abs derived from diseased NZB/NZW mouse hybridomas showed a very restricted repertoire of Vκ utilization, different from that of nonautoimmune (C57BL/6 × BALB/c)F1 transgenic anti-DNA Abs. Strikingly, a single L chain was repetitively selected by most anti-DNA, transgenic NZB/NZW B cells to pair with the targeted H chain. This L chain had the same Vκ-Jκ rearrangement as that expressed by the original anti-DNA D42 hybridoma. These findings indicate that the kinetics of the autoimmune serologic manifestations are similar in wild-type and transgenic lupus-prone NZB/NZW F1 mice and suggest that the breakdown of immunologic tolerance in these mice is associated with the preferential expansion and activation of B cell clones expressing high affinity anti-DNA H/L receptor combinations.

Rearrangement and expression of immunoglobulin light chain genes can precede heavy chain expression during normal B cell development in mice

In mouse mutants incapable of expressing mu chains, VkappaJkappa joints are detected in the CD43(+) B cell progenitors. In agreement with these earlier results, we show by a molecular single cell analysis that 4-7% of CD43(+) B cell progenitors in wild-type mice rearrange immunoglobulin (Ig)kappa genes before the assembly of a productive VHDHJH joint. Thus, mu chain expression is not a prerequisite to Igkappa light chain gene rearrangements in normal development. Overall, approximately 15% of the total CD43(+) B cell progenitor population carry Igkappa gene rearrangements in wild-type mice. Together with the results obtained in the mouse mutants, these data fit a model in which CD43(+) progenitors rearrange IgH and Igkappa loci independently, with a seven times higher frequency in the former. In addition, we show that in B cell progenitors VkappaJkappa joining rapidly initiates kappa chain expression, irrespective of the presence of a mu chain.

B Cell Deletion, Anergy, and Receptor Editing in “Knock In” Mice Targeted with a Germline-Encoded or Somatically Mutated Anti-DNA Heavy Chain

To study the relative contributions of clonal deletion, clonal anergy, and receptor editing to tolerance induction in autoreactive B cells and their dependence on B cell receptor affinity, we have constructed “knock in” mice in which germline encoded or somatically mutated, rearranged anti-DNA heavy (H) chains were targeted to the H chain locus of the mouse. The targeted H chains were expressed on the vast majority of bone marrow (BM) and splenic B cells and were capable of Ig class switching and the acquisition of somatic mutations. A quantitative analysis of B cell populations in the BM as well as of Jκ utilization and DNA binding of hybridoma Abs suggested that immature B cell deletion and light (L) chain editing were the major mechanisms affecting tolerance. Unexpectedly, these mechanisms were less effective in targeted mice expressing the somatically mutated, anti-DNA H chain than in mice expressing the germline-encoded H chain, possibly due to the greater abundance of high affinity, anti-DNA immature B cells in the BM. Consequently, autoreactive B cells that showed features of clonal anergy could be recovered in the periphery of these mice. Our results suggest that clonal deletion and receptor editing are interrelated mechanisms that act in concert to eliminate autoreactive B cells from the immune system. Clonal anergy may serve as a back-up mechanism for central tolerance, or it may represent an intermediate step in clonal deletion.

Receptor editing occurs frequently during normal B cell development

Allelic exclusion is established in development through a feedback mechanism in which the assembled immunoglobulin (Ig) suppresses further V(D)J rearrangement. But Ig expression sometimes fails to prevent further rearrangement. In autoantibody transgenic mice, reactivity of immature B cells with autoantigen can induce receptor editing, in which allelic exclusion is transiently prevented or reversed through nested light chain gene rearrangement, often resulting in altered B cell receptor specificity. To determine the extent of receptor editing in a normal, non-Ig transgenic immune system, we took advantage of the fact that lambda light chain genes usually rearrange after kappa genes. This allowed us to analyze kappa loci in IgMlambda+ cells to determine how frequently in-frame kappa genes fail to suppress lambda gene rearrangements. To do this, we analyzed recombined VkappaJkappa genes inactivated by subsequent recombining sequence (RS) rearrangement. RS rearrangements delete portions of the kappa locus by a V(D)J recombinase-dependent mechanism, suggesting that they play a role in receptor editing. We show that RS recombination is frequently induced by, and inactivates, functionally rearranged kappa loci, as nearly half (47%) of the RS-inactivated VkappaJkappa joins were in-frame. These findings suggest that receptor editing occurs at a surprisingly high frequency in normal B cells.

Asymmetric Contribution to Ig Repertoire Diversity by Vκ Exons: Differences in the Utilization of Vκ10 Exons

The mouse has approximately 140 germline Vκ genes, and functional Vκ exons are expressed at roughly equivalent levels in the preimmune repertoire. We have examined the expression of individual members of the Vκ10 family. Vκ10A and Vκ10B genes have been utilized in numerous hybridomas and myelomas, while Vκ10C has not. In this study, we have cloned the Vκ10C gene and shown that it is structurally functional, has the expected promoter elements and recombination signal sequences, and that it is capable of recombination. Vκ10C mRNA, however, is present at levels at least 1000-fold lower than Vκ10A and Vκ10B in adult spleens. While there are no sequence differences in the octamer or TATA box between Vκ10C and Vκ10A, there are three nucleotide changes in the promoter region. These promoters equally drive the expression of a reporter gene in B cells or plasma cells, but the Vκ10A promoter is able to drive expression in pre-B cell lines significantly better than the Vκ10C promoter (p &lt; 0.05). Vκ10C rearrangements can be detected in bone marrow and splenic DNA. Therefore, the lack of Vκ10C expression may reflect the inability of Vκ10C-rearranged cells to undergo positive or negative selection. Our results suggest that the available Ab repertoire is shaped not only by the number of structurally functional genes, but also by the ability of assembled genes to be expressed at critical points during B cell maturation.

Comparison of the frequencies of arginines in heavy chain CDR3 of antibodies expressed in the primary B-cell repertoires of autoimmune-prone and normal mice

Because the pathogenesis of anti-DNA Ab in SLE is correlated to Ab specificity for native DNA (dsDNA), understanding how such specificity is generated is important. The VH structures of most autoimmune anti-DNA antibodies include at least one arginine in VH-CDR3; moreover, antibody specificity for dsDNA can be correlated to the relative position of arginines in VH-CDR3. The coding sequences for most VH-CDR3 arginines among the anti-DNA MoAbs we have studied to date appeared to have been encoded by sequences generated during V-D-J recombination and would have been expressed in the primary B-cell repertoire. The frequency at which arginine codons are generated during V-D-J recombination therefore could potentially influence the frequency at which DNA-specific B cells are generated in the primary B-cell repertoire. The present study was undertaken to determine whether a higher percentage of B cells in the primary, preautoimmune repertoire of autoimmune-prone (NZB x NZW)F1 mice have immunoglobulin heavy chains with at least one VH-CDR3 arginine compared to B cells in the primary, preimmune repertoire of non-autoimmune-prone BALB/c mice. The present results indicate that mature B cells in preautoimmune (NZB x NZW)F1 mice, whether specific for DNA or not, are no more likely to have heavy chains with VH-CDR3 arginines than are B cells in BALB/c mice. The high frequency of recurrence of VH-CDR3 arginines among autoimmune anti-DNA in (NZB x NZW)F1 mice would appear to derive from the selective oligoclonal expansion of selected B cells that express such structures.

Only Selected Light Chains Combine with a Given Heavy Chain to Confer Specificity for a Model Glycopeptide Antigen

The M and N human blood group glycopeptide Ags are carried on RBCs by glycophorin A. Previous results suggested that the murine humoral immune response against the N, but not the M, Ag is restricted. In addition, these results suggested that particular highly homologous heavy chains might be able to combine promiscuously with various light chains to yield anti-N specificity. To examine this, the current study used Fab phage methodology to couple an array of light chains, obtained from cDNA libraries isolated from immunized mice, to single Fd obtained from N61, N92, and 425/2B hybridomas. Interestingly, for the chimeric Fab to retain M or N specificity, the new light chains needed to belong to the same Vk gene family as the light chain from the parental, hybridoma-derived mAb. In some cases the new light chains modified the Fab affinity and fine specificity. For example, library-derived light chains coupled with the N92 Fd yielded chimeric Fab with increased affinity. In particular, the affinity of these univalent chimeric Fab for the N Ag was equivalent to that of the bivalent parental IgG mAb. Taken together, these results demonstrate that particular structures formed by the light chain V region are required to cooperate with a particular heavy chain V region to create a functional binding site for these glycopeptide Ags. They also demonstrate a lack of heavy chain promiscuity in the formation of murine anti-M and anti-N Abs.

Differentiation-Specific, Octamer-Dependent Costimulation of κ Transcription

By mutational analysis of the octamer-TATA box intervening region in the mouse SP6 κ promoter, we have mapped two octamer-dependent, costimulatory regions, A and B. The A region was active in late B cells only, while the B region was active throughout B cell differentiation. The B region was TATA proximal and contained a heptamer and an E box of the E2A type that is common in Vκ promoters. Mutation of the heptamer element did not decrease transcriptional stimulation from this region, but mutations in, or immediately 5′ of, the E box core sequence did. A protein binding to this region could be detected in nuclear extracts. The complex could only partially be competed with a μE5 binding site and could not be supershifted with Abs raised to E2A gene products, indicating that it may represent a novel E-box binding complex. The A region was located proximal to the octamer and contained a CCCT element that is conserved both with regard to position and sequence in human VκII promoters. By mutational analysis, the transcriptional stimulatory activity was mapped to the CCCT element that also is part of an early B cell factor (EBF) binding site. In late B cells, a novel protein (FA), which did not bind to the EBF binding site in the mb1 promoter, interacted with the A region. This protein was found to be expressed at lower levels in early B cells as well as in HeLa cells. Thus, the octamer-flanking sequence contains positive control elements that may act independently but that differ in the stage of B cell differentiation at which they are active. One of these factors is an example of an ubiquitously expressed transcription factor that participate in differentiation-specific transcriptional activation.

A Shannon entropy analysis of immunoglobulin and T cell receptor

In 1970, before any antigen-bound immunoglobulin structure had been solved, Elvin Kabat proposed that regions of high amino acid diversity would be the antigen binding sites of immunoglobulin (Kabat, 1970). Conversely, sites of low variability were proposed to be structural, framework regions. This variability was defined by Wu and Kabat as the number of different amino acids found at a site divided by the relative frequency of the most common amino acid at that site (Wu and Kabat, 1970). Several groups have subsequently devised improvements of Kabat-Wu variability analysis (Litwin and Jores, 1992). While these methods are somewhat better than Kabat-Wu, they still suffer from Kabat-Wu's basic limitation: they account for only the most common one or two amino acids in estimating diversity. This leads to underestimates of low diversities and exaggerations of high diversities. Shannon information analysis eliminates serious bias and is more stable than Kabat-Wu and second generation measures of diversity (Jores et al. 1990; Wu and Kabat, 1970). Statistical reliability can be measured using Shannon analysis, and Shannon measurements can be provided with error estimates. Here we use Shannon's method to analyze the amino acid diversity at each site of T cell receptor Valpha and Vbeta to identify complementarity determining regions and framework sites. Our results reveal that the T cell receptor is significantly more diverse than immunoglobulin-suggesting T cell receptor has more than the previously-discovered four complementarity determining regions. These new complementarity determining regions may represent a larger antigen combining site, additional combining sites, or an evolutionary strategy to avoid inappropriate interaction with other molecules.

Variable region gene segments of nine monoclonal antibodies specific to disialogangliosides (GD2, GD3) and their O-acetylated derivatives

Despite the weak immunogenicity of gangliosides, a limited number of highly specific murine monoclonal antibodies (MAbs) were elicited. This study investigated the reactivity and the structure of the VH and V kappa genes of nine hybridomas obtained from independent fusions producing antibodies against disialogangliosides GD2 and GD3 and their O-acetylated derivatives. These antibodies depended on four types of V kappa genes. They were also encoded by VH genes of the J558 family (5 out of 9) and occasionally by VH genes of the S107, 7183, and 3609 families, rearranged with a variety of DH and JH genes. The 8B6 and 7H2 MAbs specific for GD2-O-acetylated, respectively, used the VH gene of the S107 and 7183 families. The length of H chain CDR3 ranged from 8 to 11 amino acids. A set of S107 and 3609 germline genes closed from A/J murine fetal liver and matched with the VH segment of hybridomas 8B6 and 10B8 revealed somatic mutations. Although the relative number of sequences does not preclude any formal conclusions regarding the preferential use of V genes in the immune recognition of carbohydrate structures, our results clearly indicate that MAbs directed to very similar structures as GD2 and GD3 were encoded by different VH and V kappa genes.

Expanding the 43C9 class of catalytic antibodies using a chain-shuffling approach

We employed a chain-shuffling technique to determine if the light chain of the catalytic antibody, 43C9, provides the best partner for the 43C9 heavy chain. Previously, we reported construction and screening of a 43C9 HC CROSS library, where the 43C9 heavy-chain gene was crossed with a library of light-chain genes in a lambda bacteriophage system. The library contained a high frequency of reconstituted antibodies recognizing the transition-state analogue. Here, we report the isolation and characterization of four of these clones. Recovered light-chain proteins share 92-96% sequence identity to the 43C9 light-chain protein. Somatic mutations of these light chains occur randomly at positions distant from the active site. Residues required for binding and catalysis were conserved. Mutations affected the topology of the binding site. Nevertheless, catalysis was not affected. Isolation of these light chains suggests the best partner for the 43C9 heavy chain is the original light chain. These clones attempt to broaden a class of 43C9-like antibodies, where the catalytic residues, His91 and Arg96, have been reproducibly selected. Similar catalytic properties between the 43C9-like antibodies suggests binding has been optimized, thus further maturation of the light chain would not lead to a better catalyst. To improve catalysis, other approaches must be considered.

Differences in V kappa gene utilization and VH CDR3 sequence among anti-DNA from C3H-lpr mice and lupus mice with nephritis

To investigate the molecular properties of anti-DNA from lpr mice that express high levels of anti-DNA without immune-mediated nephritis, the sequences of VH and V kappa genes encoding 11 monoclonal anti-DNA antibodies derived from C3H-lpr/lpr (C3H-lpr) mice were studied. All of the C3H-lpr monoclonal anti-DNA bound single-stranded DNA while five also bound double-stranded DNA. Two of the hybridomas were clonally related as determined by Southern analysis and sequencing. Sequence analysis of C3H-lpr anti-DNA revealed the use of VH genes that encode anti-DNA from the MRL-lpr/lpr and (NZB X NZW) F1 mouse models of lupus, although differences occurred in the VH CDR3 amino acid content. In contrast, the V kappa genes from C3H-lpr mice lacked significant identity with previously reported V kappa genes for anti-DNA from lupus models. These results indicate that anti-DNA from C3H-lpr mice differ from anti-DNA from lupus mice with nephritis in patterns of V gene expression and suggest a molecular basis for the lack of pathogenicity of anti-DNA in these mice.

The mouse immunoglobulin kappa locus contains about 140 variable gene segments

In continuation of our efforts to elucidate the immunoglobulin kappa locus of the mouse we analyzed 46 yeast artificial chromosomes (YACs) containing V kappa, J kappa and C kappa genes. The YACs, which were derived from DNA of C57BL/6 and C3H mice, ranged from 0.3-1.9 Mb in size. On the basis of hybridization with probes specific for the V kappa gene families a group of 13 YACs was selected for detailed analysis. The V kappa genes of the YACs were then characterized by hybridization to the family-specific probes and by the sizes of the EcoRI fragments on which they were found. This way evidence was obtained for 140 different V kappa gene signals on the YACs. Of these 63 had been characterized before on clones from a cosmid library of total mouse DNA (I. Zocher et al., Eur. J. Immunol. 1995. 25: 3326-3331) and 22 others were found now on cosmid clones derived from the YACs. Six V kappa genes of the previous study which were not found on the YACs are probably located outside of the kappa locus. The YACs were arrayed in a unique order establishing a YACs panel which most likely contains the whole kappa locus. The cosmid contigs and solitary cosmid clones which contain the 63 plus 22 V kappa gene signals mentioned above comprise about 2.0 Mb. Assuming that the remaining 55 V kappa genes are spaced at the same average distance of 24 kb, one may extrapolate to a locus size of 3.3 Mb.

Structural diversity of monoclonal CD4 antibodies and their capacity to block the HIV gp120/CD4 interaction

A number of monoclonal antibodies have been raised against CD4, the receptor on T cells for the HIV envelope glycoprotein gp120. In the present paper we describe biological activities and sequence analysis of seven CD4 MAb. Five of these MAb preparations compete with HIV/gp120 for CD4 binding. The sequences of the variable regions for these MAb were determined in order to ascertain any correlation with selective V gene usage. A relationship was found between the expressed variable region genes and the CD4 recognition pattern. The VH genes that are used can be subdivided into two major groups expressing either a VH gene belonging to the J558 family or to the VGam family. The usage of the VL genes varies, indicating that the epitope specificity is predominantly determined by the rearranged VH genes. The distinct cross-reactivity pattern of these MAb also correlates with their capacity to block binding of recombinant gp120 to CD4 in vitro. Although five of these MAb were able to block gp120 binding none of the CDR sequences shows a relevant homology to the gp120 sequence. This indicates a steric hinderence mechanism for blocking gp120 binding and not a direct interaction with the receptor binding site on CD4. The data also confirm the failure of these MAb as a potential target for receptor mimicry.

Specificities and genetic characteristics of nucleosome-reactive antibodies from autoimmune mice

Antinuclear antibodies are present in the serum of individuals with systemic autoimmune diseases such as SLE. Most autoantibodies characterized to date are directed against isolated nuclear molecules such as DNA or histones. We have obtained from spontaneously autoimmune mice six IgG mAb that recognize conformational nucleosome epitopes, but do not react with individual histones or DNA. For three of these mAb, the epitope is at least partially present in the H2A-H2B-DNA nucleosome subparticle, although their binding characteristics differ from those of conventional anti-H2A-H2B-DNA antibodies. All six mAb use VH or Vkappa genes which are recurrently utilized in anti-DNA and other antinuclear antibodies. The V regions of the nucleosome-reactive mAb also contain charged (mostly cationic) residues at sites that are likely to be critical for interaction with nucleosomal antigens. These results suggest that the usage of certain V gene segments in conjunction with suitable V(D)J rearrangements may confer reactivity to nucleosomal antigens. B cells producing such autoantibodies are probably expanded early during the autoimmune process. Somatic mutations in the V regions of nucleosome-reactive mAb may modulate their specificities and result in the acquisition of binding patterns restricted to individual chromatin components such as DNA.

Rapid cloning of any rearranged mouse immunoglobulin variable genes

Immunoglobulins (Ig) have been the focus of extensive study for several decades and have become an important research area for immunologists and molecular biologists. The use of polymerase chain reaction (PCR) technology has accelerated the cloning, sequencing, and characterization of genes of the immune system. However, cloning and sequencing the Ig variable (V) genes using the PCR technology has been a challenging task, primarily due to the very diverse nature of Ig V region genes. We have developed a simple, rapid, and reproducible PCR-based technique to clone any rearranged mouse Ig heavy or light chain genes. A close examination of all Ig heavy and light chain V gene families has resulted in the design of 5' and 3' universal primers from regions that are highly conserved across all heavy or light chain V gene families, and the joining or constant regions, respectively. We present our strategy for designing universal primers for Ig V gene families. These primers were able to rapidly amplify the rearranged Ig V genes, belonging to diverse Ig V gene families from very different cell lines, i.e., J558, MOPC-21, 36-60, and a chicken ovalbumin specific B-cell hybridoma. In addition, the present study provides the complete alignment of nucleotide sequences of all heavy and light chain variable gene families. This powerful method of cloning Ig V genes, therefore, allows rapid and precise analysis of B-cell hybridomas, B-cell repertoire, and B-cell ontogeny.

Activation and negative selection of functionally distinct subsets of antibody-secreting cells by influenza hemagglutinin as a viral and a neo-self antigen

We have compared transgenic mice that express the influenza virus PR8 hemagglutinin (PR8 HA) as a membrane-bound neo-self antigen (HA104 mice) with nontransgenic (non-Tg) mice for their ability to generate HA-specific B cell responses after primary immunization with PR8 virus. HA-specific, IgM-secreting B cells were induced with similar frequencies in HA104 and non-Tg mice. In addition, a B cell clonotype (C4) that is characteristic of anti-HA immune responses of BALB/c mice was identified among HA-specific IgM hybridomas from HA104 mice. A subset of HA-specific, IgG-secreting B cells that arises rapidly after primary virus immunization in non-Tg mice, however, was substantially reduced in HA104 mice. Likewise, a B cell clonotype (C12) that dominates HA-specific IgG hybridomas generated after primary immunization of non-Tg mice was present at greatly reduced frequencies among hybridomas from HA104 mice. Because HA-specific, IgG-secreting B cells were generated by HA104 mice in response to a mutant HA containing an amino acid interchange in a B cell antigenic site, we conclude that these PR8 HA-specific, IgG-secreting B cells are negatively selected in HA104 mice as a result of their specificity for the neo-self PR8 HA. The findings demonstrate that HA-specific B cells that display distinct phenotypic potentials in non-Tg mice also differ in their susceptibility to negative selection from the primary B cell repertoire of HA104 mice: a subset of B cells that undergo rapid differentiation to become HA-specific IgG antibody-secreting cells (ASC) after activation in non-Tg mice is negatively selected in HA104 mice. By contrast, a subset that gives rise to HA-specific, IgM-secreting ASC persists in the primary repertoire of HA104 mice and can be activated by virus immunization.

Yeast artificial chromosome contigs reveal that distal variable-region genes reside at least 3 megabases from the joining regions in the murine immunoglobulin kappa locus

The immunoglobulin kappa gene locus encodes 95% of the light chains of murine antibody molecules and is thought to contain up to 300 variable (V kappa)-region genes generally considered to comprise 20 families. To delineate the locus we have isolated 29 yeast artificial chromosome genomic clones that form two contigs, span > 3.5 megabases, and contain two known non-immunoglobulin kappa markers. Using PCR primers specific for 19 V kappa gene families and Southern analysis, we have refined the genetically defined order of these V kappa gene families. Of these, V kappa 2 maps at least 3.0 Mb from the joining (J kappa) region and appears to be the most distal V kappa gene segment.

Clustered and interspersed gene families in the mouse immunoglobulin kappa locus

Although numerous solitary germ-line V kappa genes and two small V kappa contiguously cloned gene regions (contigs) are known, no attempts to systematically elucidate the structure of the kappa locus of the mouse have been reported so far. As a first step to this aim we screened a cosmid library of C57BL/6J mouse DNA with 18 probes that are more or less specific for the different V kappa gene families. Ninety-one V kappa gene-containing cosmid clones were characterized by detailed restriction mapping and hybridizations. Several contigs were constructed from overlapping clones. The contigs and the still unlinked cosmid clones cover 1.6 Mb. Many of the cosmid clones were localized on chromosome 6 where the kappa locus is known to reside; no evidence for the existence of dispersed V kappa genes (orphons) was obtained. Eighty-five strong hybridization signals were assigned to distinct V kappa gene families, while for 11 weak signals the assignment was less definite. As to the distribution of gene families within the locus the following situation emerged: there are both, groups of genes which belong to one V kappa gene family ("clusters") and groups in which genes of different families are interspersed. The interspersion of gene families seems to be more pronounced than has been assumed so far. Additional V kappa genes which are known to exist will have to be isolated from other gene libraries of the same mouse Ig kappa haplotype.

Molecular characterization of mouse monoclonal antibody BIII.136 and the epitope recognized by the antibody in human band 3 protein

The monoclonal antibody BIII.136, which recognizes the cytoplasmic part of the band 3 protein from human erythrocytes, also detects products of proteolytic degradation of that protein caused by endogeneous proteases in erythrocytes. Now we extend and confirm these observations by finding that in very young erythrocytes from patients with hemolytic anemias the band 3 protein is almost intact, which suggests that proteolytic degradation of that protein proceeds in vivo during the life span f the erythrocyte. Interesting properties and applicability of this antibody for following the band 3 degradation in vivo and for detection of the band 3 variant forms have prompted us to characterize its primary structure and the epitope recognized in band 3. A set of solid phase-synthesized peptides allowed us to establish that MAb BIII.136 is directed against sequence EDPDIP, which corresponds to amino acid residues 22-27 in band 3 protein. Replacement analysis revealed that only E22 and P24 can be replaced by several other amino acids without a significant loss of reactivity, while the remaining four amino acids seem to be an essential part of the epitope. No reactivity of the antibody with band 3 from several other species was found. Analysis of the heavy and light chain variable region cDNAs revealed that the VH is encoded by a member of VH8(VH3609) family, while the VL is encoded by a member of the Vk12/13 family.

Idiotypic diversity and variable region gene usage by mouse anti-HLA-DQ3 mAb

The anti-HLA-DQ3 monoclonal antibodies (mAb) KS13, SO1, SO2, SO3, SO4, and SO5 recognize spatially close but distinct antigenic determinants, since they crossinhibit each other in their binding to HLA-DQ3 antigens, but do not share idiotopes recognized in their antigen combining site by syngeneic and anti-id antisera and mAb. Furthermore, mAb SO1, SO3, SO4, and SO5 react also with HLA-DQ allospecificities other than HLA-DQ3. Sequence analysis of the heavy (VH) and light (VL) chain variable region of the six mAb revealed preferential usage of VH 36-60 and VK 12/13 gene families. However, the individual VH and VL germline gene usage by the six mAb is diverse and the utilization of D, JH, and JL gene segments is heterogeneous. The diverse usage of VH and VL gene segments and heterogeneous amino acid sequences of VH and VL CDR, together with the heterogeneous idiotypic profile, may reflect the complexity of the determinants recognized by the six mAb on HLA-DQ3 antigens. The results we have presented provide for the first time information about the structural basis of the diversity of antibodies recognizing human histocompatibility antigens.

Universal cloning and direct sequencing of rearranged antibody V genes using C region primers, biotin-captured cDNA and one-side PCR

Polymerase chain reaction (PCR) cloning has greatly facilitated the cloning of heavy and light chain genes from B cells and hybridomas and has been critical for the generation of natural antibody gene libraries for expression in bacteria and on filamentous phages. There remain difficulties, however, in cloning VH and VL genes from a number of mouse and rat hybridoma lines and from B cells from several other species due to insufficient sequence information. Here we describe a rapid and 'universal' strategy for cloning rearranged antibody genes from any species for which the sequence of the C segment(s) are known. First strand synthesis is primed with a biotinylated C region primer and full length cDNA is captured on streptavidin-coated magnetic beads for tailing with dGTP and terminal deoxynucleotidyl transferase. After tailing, the cDNA is captured again, amplified using polyC primers and used for direct sequencing or cloning. The use of C region primers and cDNA capture ensures that this one-side PCR procedure is efficient and rapid as well as being entirely independent of the sequence of the V segment. We demonstrate its application to the direct sequencing or cloning of the H and L chain genes from six mouse and rat hybridomas and propose that the method described will find applications in three areas: (i) cloning rearranged antibody genes in all cases in which cloning with V-J primers is not possible; (ii) repertoire studies in which an unbiased cloning procedure is required for accurate estimate of gene usage; and (iii) generation of VH and VL gene libraries from immunised animals.

Structural profile of idiotype, anti-idiotype and anti-anti-idiotype monoclonal antibodies in the HLA-DQ3 antigenic system

Interest in the characterization of idiotype cascades in the HLA antigenic system has been stimulated by their potential role in the immune response to mismatched HLA allospecificities and in the survival of kidney allografts. Since no information is available about the structural organization of idiotypic cascades in the HLA system, we have sequenced the variable regions of the heavy (VH) and light (VL) chains of mouse anti-HLA-DQ3 monoclonal antibody (mAb) KS13 elicited by cell membrane-bound antigens, of syngeneic anti-HLA-DQ3 mAb S2B154 elicited by anti-idiotypic (anti-id) mAb K03-34 and of five syngeneic anti-id mAb elicited by mAb KS13. mAb KS13 and S2B154, which have been previously shown to be very similar in their specificity and idiotypic profile, share several structural characteristics. Their VH and VL regions are encoded by the same VH, VK and JH genes, display relatively similar V(D)J rearrangements and differ only through a few amino acid substitutions. Among the five anti-id mAb elicited by mAb KS13, mAb R1-38 and R18-9 utilize multiple genetic elements that are different from those used by anti-id mAb KO3-34, K03-256 and K03-335. These results indicate that diverse V region combinations can confer an anti-id specificity in the antigenic system analyzed. mAb K03-34, K03-256 and K03-335 originate from the same B cell clone, since they use the same V, D and J genes and possess identical V(D)J rearrangements. The latter three anti-id mAb differ only by point mutations, which have dramatic effects on the HLA-DQ3 antigen mimicry properties of the three anti-id mAb. mAb K03-34 is the only one to induce anti-HLA-DQ3 antibodies both in syngeneic and xenogeneic hosts. The antigen mimicry properties of anti-id mAb K03-34 depend upon its three-dimensional conformation, since no significant amino acid sequence homology has been found between its VH and VL regions and alpha 1 and beta 1 domains of HLA-DQ3 antigens.

The anti-La response of a single MRL/Mp-lpr/lpr mouse: specificity for DNA and VH gene usage

Autoantibodies to ribonucleoproteins (RNP) occur prominently in human systemic lupus erythematosus and murine lupus models. In previous studies we demonstrated a relationship in MRL/Mp-lpr/lpr (MRL/lpr) mice between antibodies to Sm, an RNP autoantigen, and antibodies to DNA. Thus, many anti-Sm monoclonals bound DNA and expressed the same V region genes as anti-DNA. In addition, many had multiple VHCDR3 Arg residues suggestive of selection by DNA, and some had somatic mutations suggesting selection for mutant B cells by DNA. To determine whether autoantibodies to other RNP antigens are also associated with the anti-DNA response, we have analyzed the response to the La RNP. Six anti-La B cell hybridomas were generated from a single MRL/lpr mouse. Southern blot analysis of Ig V gene rearrangements and V gene sequences indicated two clonally related pairs, suggesting an oligoclonal response. Antibodies from all six hybridomas bound single-stranded DNA, while antibodies from five hybridomas bound double-stranded DNA. Two hybridomas expressed a VH7183 gene which is used by members of two previously reported anti-DNA clones and two anti-Sm/DNA clones of MRL/lpr origin. These data demonstrate an association between the anti-La and anti-DNA responses in MRL/lpr mice, suggesting that cross-reactive anti-RNP and anti-DNA responses are a general feature of autoimmunity in this lupus model.

D-penicillamine- and quinidine-induced antinuclear antibodies in A.SW (H-2s) mice: similarities with autoantibodies in spontaneous and heavy metal-induced autoimmunity

Ten percent of human lupus syndromes occur in patients as a result of treatment with certain medications. H-2s mice can produce autoantibodies following treatment with various drugs or heavy metals and they are a potential animal model of drug-induced lupus. We have examined nine anti-chromatin monoclonal antibodies (mAb) from A.SW mice that had been treated with either D-penicillamine or quinidine, two lupus-inducing drugs in humans. These mAb are specific either for DNA or histone-DNA complexes corresponding to nucleo-specific either for DNA or histone-DNA complexes corresponding to nucleosomes or subnucleosome particles. Only one mAb reacts with an unknown chromatin antigen. The V region sequences of six of these mAb were studied and are notable by several features. As previously observed in spontaneous autoantibodies to DNA or histone-DNA complexes, arginine or asparagine residues are found at critical locations throughout the V regions. Many of these residues, potentially important for binding to DNA or DNA-histone complexes, result either from somatic mutations or atypical VH-D-JH rearrangements. Another significant characteristic is that the VH genes of several D-penicillamine- or quinidine-induced mAb are most similar to those of anti-nucleolar mAb obtained from mercury-injected A.SW mice. The implications of these findings for the pathogenesis of spontaneous or induced autoimmunity are discussed.

Restricted VH gene usage by murine hybridomas directed against the human N, but not M, blood group antigen

The M and N human blood group antigens are complex glycopeptide determinants at the amino terminus of the red blood cell membrane glycoprotein, glycophorin A. The heavy and light chain variable region cDNA sequences were determined for seven murine monoclonal antibodies recognizing glycophorin A. Three of the antibodies were anti-M and four were anti-N. Each of the anti-M antibodies was composed of VH and VL regions derived from distinct germline gene families (VH1 (J558), VH4 (X24), VH5 (7183), VK5, VK8, and VK19). In contrast, all four anti-N heavy chains were composed of VH regions derived from the VH2 (Q52) germline gene family and all used the same J4 gene segment. In addition, two of the anti-N light chains were composed of VK regions from the VK8 germline gene family and used the J1 gene segment. Since each anti-N hybridoma was derived from different mice immunized by different protocols, these results suggest that the murine immune response to the N, but not the M, human blood group antigen is restricted.