A simple method for estimating the probable numbers of different antibodies by examining the repeat frequencies of sequences or isoelectric focusing patterns

Pneumococcal surface protein A (PspA) is serologically highly variable and is expressed by all clinically important capsular serotypes of Streptococcus pneumoniae

Pneumococcal surface protein A (PspA) has been shown previously to elicit antibodies protective against pneumococcal infection and to be necessary for full pneumococcal virulence in mice. The protein was originally defined by the two mouse monoclonal antibodies Xi64 and Xi126, which together recognized PspA on 14% of pneumococcal isolates. Some PspA molecules reacted with both antibodies, but most reacted with only one or the other. In the present study we demonstrated that PspA is produced by all pneumococci, confirming our hypothesis that there are variants of PspA which are not detected by Xi64 and Xi126. We produced a rabbit antiserum and five additional monoclonal antibodies specific for PspA for these studies. The rabbit antiserum reacted with each of 95 pneumococcal isolated tested, comprising 16 capsular serotypes. One or more of the seven monoclonal anti-PspA antibodies reacted with 95% (53 of 57) of pneumococcal isolates tested. The specificity of the monoclonal and polyclonal antibodies to PspA was confirmed in two ways: (i) by detection of molecules on wild-type pneumococci that are identical in molecular weight to those detected in Western blots (immunoblots) with Xi64 and Xi126 and (ii) by the use of mutants of Streptococcus pneumoniae that fail to produce PspA or that produce a truncated form of PspA. By using the seven monoclonal antibodies, we observed 31 PspA types among the 57 isolates. When the 53 strains reactive with the monoclonal antibodies were analyzed by capsular type as well as by serologic type and molecular weight of PspA, we observed 50 different clonotypes of pneumococci.

The mouse immunoglobulin kappa light-chain genes are located in early- and late-replicating regions of chromosome 6

The murine immunoglobulin kappa (kappa) light-chain multigene family includes the constant region (C kappa), joining-region genes, and approximately 30 kappa-variable (V kappa) region families. The entire region occupies an estimated 1,000 to 3,000 kilobases, and some V kappa families have been linked by recombinant inbred mapping. The C kappa gene and 14 V kappa families replicated differently among cell lines of lymphoid and nonlymphoid origin. In nonlymphoid cells, the C kappa gene replicated earlier than the V kappa families. A transition from replication during the second third of S phase for the C kappa gene to later replication during S for V kappa families was observed. The V kappa family (V kappa 21) that maps closest to the C kappa gene, replicated during the first half of the S phase; most of the other V kappa families replicated during the second half of S, and some replicated during the last quarter of the S phase. In lymphoid cells, the kappa locus replicated earlier in the pre-B than in the B-cell lines. In one pre-B-cell line, 22D6, the kappa genes examined replicated at the beginning of the S phase. In the B-cell lines, the EcoRI segment containing the transcribed gene replicated near the beginning of the S phase. Other V kappa families replicated within the first two-thirds of S phase. Some linked V kappa families replicated at similar times. In the B-cell lines, a transition from replication at the beginning of S for the transcribed C kappa and V kappa genes and surrounding DNA sequences to later replication for the other V kappa families was observed. However, in contrast to the non-lymphoid cell lines, the replication of this locus occurred predominantly during the first half of S. The kappa locus contains both early- and late-replicating genes, and early replication is usually associated with transcriptional activity. The results are discussed with respect to the organization of transcriptionally active chromatin domains.

The mouse immunoglobulin kappa light-chain genes are located in early- and late-replicating regions of chromosome 6

The murine immunoglobulin kappa (kappa) light-chain multigene family includes the constant region (C kappa), joining-region genes, and approximately 30 kappa-variable (V kappa) region families. The entire region occupies an estimated 1,000 to 3,000 kilobases, and some V kappa families have been linked by recombinant inbred mapping. The C kappa gene and 14 V kappa families replicated differently among cell lines of lymphoid and nonlymphoid origin. In nonlymphoid cells, the C kappa gene replicated earlier than the V kappa families. A transition from replication during the second third of S phase for the C kappa gene to later replication during S for V kappa families was observed. The V kappa family (V kappa 21) that maps closest to the C kappa gene, replicated during the first half of the S phase; most of the other V kappa families replicated during the second half of S, and some replicated during the last quarter of the S phase. In lymphoid cells, the kappa locus replicated earlier in the pre-B than in the B-cell lines. In one pre-B-cell line, 22D6, the kappa genes examined replicated at the beginning of the S phase. In the B-cell lines, the EcoRI segment containing the transcribed gene replicated near the beginning of the S phase. Other V kappa families replicated within the first two-thirds of S phase. Some linked V kappa families replicated at similar times. In the B-cell lines, a transition from replication at the beginning of S for the transcribed C kappa and V kappa genes and surrounding DNA sequences to later replication for the other V kappa families was observed. However, in contrast to the non-lymphoid cell lines, the replication of this locus occurred predominantly during the first half of S. The kappa locus contains both early- and late-replicating genes, and early replication is usually associated with transcriptional activity. The results are discussed with respect to the organization of transcriptionally active chromatin domains.

Mapping of Igk-V genes using backcrossed laboratory and wild mice

In the mouse, the genes coding for the Ly-2 antigen, the beta chain of the T-cell receptor, and the immunoglobulin kappa light chain have been located on chromosome 6. Although a tentative order has been proposed for these genes, very few data have been reported concerning their genetic distance. To address this question, we have produced backcross mice between SJL and MAI (a wild-derived strain belonging to the Mus musculus), since these mice segregate for the Ly-2 and Igk-C proteins and for the Igk-V24, Igk-V21, Igk-V10, Igk-V8, and Igk-V4 genes. Twelve recombinants were obtained from 163 backcross mice studied. Two mice showed a recombination between the (Igk-V24, Igk-V10, Igk-V8, Igk-V4) and the (Ly-2, Igk-C, Igk-V21) groups, and ten mice displayed a recombination between the (Igk-V24, Igk-V10, Igk-V8, Igk-V4) group and the Tcrb-C loci. These data imply the following gene order: Tcrb-C .... (Igk-V24, Igk-V10, Igk-V8, Igk-V4) .... (Igk-V21, Igk-C, Ly-2). They indicate a distance of 6.1 cM between Tcrb-C and (Igk-V24, Igk-V10, Igk-V8, Igk-V4) and 1.2 cM between Igk-V24, Igk-V10, Igk-V8, Igk-V4 and the (Igk-V21, Igk-C, Ly-2) groups.

Clonotypic heterogeneity in experimental interstitial nephritis. Restricted specificity of the anti-tubular basement membrane B cell repertoire is associated with a disease-modifying crossreactive idiotype

Experimental anti-tubular basement membrane (anti-TBM) disease is an autoimmune interstitial nephritis elicited in susceptible rodents after immunization with renal tubular antigen. The nephritogenic antigen in the immunizing preparation is 3M-1, a 48,000 Mr noncollagenous glycoprotein. The hallmarks of the renal lesion are the presence of anti-TBM antibodies (anti-TBM-Ab) and a dense mononuclear cell infiltrate. The anti-TBM B cell repertoire in this disease was analyzed using a library of 22 anti-TBM mAbs generated in a prototypically susceptible Brown Norway rat. These anti-TBM mAbs were all demonstrated to be 3M-1 specific and their characterization formed the basis for the following observations: (a) The size of the anti-TBM B cell population is estimated at 58 distinct clones; (b) by competitive inhibition criteria, all anti-TBM mAbs recognize the same (or spatially close) epitope(s) on 3M-1. This focused recognition was maintained in spite of considerable variability in affinity. Epitopic dominance could also be demonstrated in human polyclonal anti-TBM antisera from a patient with anti-TBM disease; and (c) a crossreactive idiotype was documented, and antisera directed toward this set of variable region determinants was shown to be effective as a prophylactic regimen to abrogate disease, and as a therapeutic modality to arrest the progression of disease; (d) analysis of VH gene families suggested biased usage of Q52- and 7183-like families, although at least three gene families are used in the anti-TBM-Ab response. Thus, the anti-TBM B cell compartment in BN rats is moderately large, but is primarily focused to a single epitope on the nephritogenic antigen and is associated with a disease-modifying crossreactive idiotype.

Molecular dissection of the murine antibody response to streptococcal group A carbohydrate

Monoclonal antibodies (mAb) to streptococcal group A carbohydrate (GAC) are encoded by a minimum of two VH, four JH, four V kappa, three J kappa, one V lambda, and one J lambda gene segments. The IdX, IdI-1, and Id5 idiotypic determinants are expressed by anti-GAC mAb and are found on free kappa chains. Each pattern of these determinants is encoded by a distinct V kappa gene segment, apparently without the requirement for a particular J kappa, VH, or JH gene segment, or somatic mutation. In contrast, the binding site-associated idiotypic determinant IdI-3a does not correlate with any single V or J gene segment.

The organization of immunoglobulin variable kappa chain genes on mouse chromosome 6

One mouse with a known recombination (NAK) at the Igk locus on chromosome 6 and two new recombinants [B6.PL (75NS) and B6.PL (85NS)] were examined using a series of probes, each of which is specific for a set of immunoglobulin (Ig) Vk genes. Under high stringency conditions, each probe detects from 1 to 19 Bam HI restriction endonuclease fragments (REFs) in genomic DNA by Southern transfer hybridization techniques. Analysis of the REF patterns indicate that the NAK recombination event occurred within the variable region of Igk. The REF patterns of the two B6.PL congenic mice provided two additional recombination events which could be examined. Although some of the REFs had shared mobility among the parental strains, at least 1 and up to 13 polymorphic REFs were present for a given probe among the NZB and AKR parental strains. The results from the NAK mouse indicate that at least some members of Vk4, Vk8, Vk10, and Vk21 were on one side of the recombination event linked to the Lyt-2 alpha and Igk-Ef1 alpha alleles of AKR, while the Vk9, Vk11, and Vk24 REF patterns came from the NZB parental strain linked to the Igk-Ef2 beta (Vk1) allele. The two B6.PL congenics produced a refined map on the Lyt-2, Lyt-3 side of the Vk region. The B6.PL (85NS) mice retained the Vk21 REF pattern of the Lyt-2 alpha, Lyt-3 alpha donor strain PL/J, while displaying the C57BL/6 REF pattern for the other Vk gene groups tested. The B6.PL (75NS) mice retained the REF patterns of PL/J for Vk21 and Ef-1, indicating a third recombination. This indicates the Vk gene order is (Lyt-2; Vk21); Ef-1; (Vk4; Vk8; Vk10); and (Vk9; Vk11; Vk24; Ef-2).

Evidence for 65 electrophoretically distinct groups of light chains in BALB/c and NZB myelomas

Light chains of 426 randomly selected myelomas from BALB/c and NZB mice were characterized by isoelectric focusing (IF) and electrophoresis at pH 3. Approximately 50% of the light chains in each strain were found to have unique electrophoretic properties. The remaining 50% of light chains fell into groups of two or more proteins showing apparent identity. A total of 49 groups of light chains were identified in this way. On the basis of repeat frequencies, the total number of such groups has been estimated to be around 65. Analysis of light chains of known amino acid sequence suggests that many of the "IF-groups" may represent light chains belonging to single V-region subgroups. The large number of unique light chains could represent somatic mutants bearing charge differences from the germ-line-coded sequences or products of a subset of V-genes which are infrequently expressed in myeloma proteins. Comparison of the light chains of BALB/c and NZB myelomas indicated extensive overlap of IF-subgroups in the two strains. One clear difference between the two samples was the presence of three groups of light chains at an unexpectedly high frequency in the BALB/c myelomas. In contrast, no light chains belonging to these groups were found in the NZB myelomas. One of the anomalous groups corresponded to Vk-1A light chains, a subgroup previously shown to be absent in NZB serum light chain IF-profiles. A second group represented at an elevated level included MOPC467, a light chain closely related in sequence to Vk-1A. The third group included ADJPC5 and LPC1. The overrepresentation of these light chain groups in the BALB/c myelomas is not understood. Two light chain-like polypeptides were observed in approximately 3-5% of myelomas in the two mouse strains. It seems likely that in many instances this may be explained by the presence of two cell lines in early generation tumors.

Multiple VH gene segments encode murine antistreptococcal antibodies

Most mouse strains are able to mount a diverse antibody response against group A streptococcal carbohydrate (GAC). We have previously reported that murine anti-GAC antibodies are for the most part restricted to IgM and IgG3 subclasses. In addition, despite extensive heterogeneity in their isoelectric focusing patterns, greater than 50% of A/J anti-GAC antibodies share a common light chain defined by spectrotypic and idiotypic (VK1GAC) criteria. We have used protein and DNA sequencing strategies to examine the genetic basis of diversity in murine anti-GAC antibodies. In particular, we report that, (a) multiple, closely homologous VH gene segments contribute to the generation of anti-GAC antibodies, (b) a common framework sequence, related to the VK27 subgroup, probably defines VK1GAC, and (c) the A/J anti-GAC VH regions and BALB/c anti-inulin VH sequences are 95% homologous at the protein level and are likely encoded by overlapping VH gene families. Lastly, we discuss the genetic mechanisms that might permit the evolution of multiple, closely homologous germline VH gene segments in the context of highly divergent flanking region sequences.

B cell repertoire diversification precedes immunoglobulin receptor expression

68 monoclonal antibodies specific for the hemagglutinin (HA) of the influenza virus, PR8, were obtained from sIg- bone marrow B cell precursors stimulated in splenic fragment cultures. Reactivity pattern (RP) analysis demonstrated that these anti-HA antibody responses included at least 29 distinguishable clonotypes. Comparison of the specificities of anti-HA antibodies obtained from sIg- bone marrow cells with those obtained from adult spleen cells indicates that the anti-HA repertoires of the two populations are comparable in diversity. Since the sIg- bone marrow B cell precursor pool presumably has not encountered V region-specific regulatory mechanisms in vivo, our data suggest that substantial diversification of the B cell repertoire precedes surface immunoglobulin (sIg) expression and subsequent interaction with environmental regulatory processes.

Mapping epitopes on the insulin molecule using monoclonal antibodies

A panel of 18 monoclonal antibodies (mAb) delta to insulin have been prepared and used to begin to map antigenic determinants on the insulin molecule. All 18 mAb were of the IgG class, with 14 IgG1, 2 IgG2a and 2 IgG2b. The affinities of these mAb for their immunizing insulin ranged from 1 X 10(6) to 3 X 10(8) 1/M. The epitope recognized by three of the mAb, 1, 7 and 16 involves the three residues of the A chain, A 8-10, the so called A chain-loop determinant. This A chain loop is one of the most evolutionarily diverse regions of insulins from different species. Another mAb, 10, has been hypothesized to recognize a nearby epitope composed of the A chain residues, A4 and A8 and a B chain residue, B29, that are adjacent on the surface of the insulin molecule. Four of the mAb bind to synthetic B chain. The epitopes recognized by these 4 mAb and the last 10 mAb are unknown but the mAb are grouped according to their ability to bind to different species of insulin or proinsulin. The results of an 18 X 18 matrix analysis of pairs of mAb binding simultaneously to insulin indicate that, despite the finding that some mAb see similar antigenic sites on the insulin molecule, each of the mAb recognizes a unique site on the insulin molecule. Finally, a lower estimate of the number of possible antibodies made to insulin has been calculated to be greater than or equal to 115, a number only 10-fold lower than the lower limit of antibodies made to dinitrophenyl (DNP) or (4-hydroxy-5-iodo-3-nitrophenyl)acetyl (NIP), following hapten protein immunization.