VK Genes Research Articles

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.

Somatic Mutations in the Ig Variable Region Genes and Expression of Novel Cμ-Germline Transcripts in a B-lymphoma Cell Line (“Farage”) Not Producing Ig Polypeptide Chains

Non-Hodgkin's B-lymphomas (B-NHL) are a very heterogeneous group of B-cell neoplasias originating from the germinal centers of lymphatic follicles. Thus, they represent a suitable experimental model to study the molecular basis of certain key events which take place in the lymphatic follicles, including somatic hypermutation and heavy chain isotypic switch.An unusual B-NHL cell line (“Farage”) not producing Ig polypeptide chains was previously shown to rearrange its IgH and Ig genes and transcribe seemingly normal size μ and mRNAs. In an attempt to characterize the phenotype of Farage cells better and to elucidate the molecular basis of the failure of Farage cells to synthesize Ig chains, we sequenced its VH and VK rearranged gene segments by PCR and RT-PCR. It was found that both V genes are somatically, heavily mutated compared to their germline counterparts. In addition, this rearranged VDJ gene of the heavy chain is not transcribed. Instead, the Farage cells express a low level of a new family of germline transcripts starting with a VH like sequence, continuing with a small segment of the 3VH germline flanking region, and ending within the Cμ region. These transcripts lack D and J segments and do not contain the open reading frame of the full-length Cμ protein. Thus, Farage cells fail to produce μ heavy chains due to silencing of the expression of the conventional VDJCμ transcript and expression of unusual Cμ-germline transcripts. In contrast to the IgH genes, the rearranged VJ gene of Farage is transcribed and gives rise to a full-size -mRNA. This transcript, however, is not translated to a full-length -chain, as it contains a stop codon in its coding region. All the above show that Farage cells are unable to produce Ig polypeptide chains, due to somatic mutations altering the -chain gene, and mutations and/or regulatory events that shutoff the transcription of the IgH gene.The heavily mutated VK and VH genes found, support the conclusion that the Farage cell line originated either from germinal center cells or from the mantle zone of the lymphoid follicle.

The role of promoter-intron interactions in directing hypermutation.

Evolution is driven by a revolving process of mutation and natural selection during which the fittest individuals survive under harsh selective pressures in their environment. In a molecular recapitulation of this process, antibodies undergo a somatic evolution after antigen stimulation, resulting in a more protective defense of the host against the environment. Immunoglobulin genes undergo apparently random hypermutation of their rearranged variable regions followed by selection for the fittest (i.e., highest affinity) of the mutated antibodies. The first evidence of hypermutation and selection of immunoglobulin genes was the observation of increased mutations in the sequences of variable regions of heavy chains encoding anti-phosphorylcholine antibodies bearing IgG isotypes (Gearhart et al. 1981) and in their associated Vκ genes (Selsing and Storb 1981). Over the ensuing 16 years, we have delineated the pathway that B cells undergo to acquire somatic mutations in their rearranged immunoglobulin genes, in regards to the timing, location, and some extracellular requirements (Gearhart 1993). The advent of transgenic and polymerase chain reaction (PCR) technology brought especially powerful tools to cut and paste the immunoglobulin loci together to establish the minimal sequences required for targeting hypermutation, and gene targeting allows the targeting of proteins that may play a role in signaling the cell to begin mutating.

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.

The human immunoglobulin κ locus on yeast artificial chromosomes (YACs)

The human immunoglobulin κ locus is a duplicated structure. Contigs of 600 kb with 40 Vκ genes and 440 kb with 36 Vκ genes had been established for the Cκ proximal (p) and distal (d) copies, respectively. In addition the human genome contains more than 24 dispersed Vκ genes, called orphons. In the present study, 22 κ-locus derived YACs were analyzed in detail, while 30 orphon-derived YACs were characterized only with respect to some parameters. The κ-locus derived YACs allowed three gaps to be closed which previously could not be bridged by cosmid and phage λ cloning. At the 5′ side, the p contig was extended in the YACs by 50 kb and the d contig by 16 kb. At the 3′side, the d contig was extended by 11.5 kb. Beyond the 3′ end of the d contig a new Vκ gene was found, which is located, according to pulsed field gel electrophoresis (PFGE) experiments, at a distance of at least 140 kb from the last Vκ gene of the contig. This Vκ gene, which was termed Z0, occurred on three YACs, albeit at distances smaller than 140 kb; this was probably due to deletions in the YACs caused by abundant repetitive sequences at the borders of the locus. According to its sequence and to the restriction map of its surroundings, Z0 is an orphon gene of the so-called Z family, of which several members are known to be dispersed throughout the genome. The possibility that Z0 has been the parent of the other Z orphons is discussed.

Molecular Cloning of ANTI-SS-A/Ro 60-kDa Peptide Fab Fragments from Infiltrating Salivary Gland Lymphocytes of a Patient with Sjögren's Syndrome

Anti-SS-A/Ro antibodies are commonly found in systemic autoimmune diseases such as Sjögren's syndrome and systemic lupus erythematosus, and some of these antibodies appear to be responsible for certain pathological lesions including congenital heart block in neonatal lupus. In this study, we generated three human antibody Fab fragments that specifically bind to SS-A/Ro 60-kd peptide from salivary gland lymphocytes of a patient with Sjögren's syndrome by using a phage-display technique. Sequence analysis demonstrated that two of the three Fab clones (E-42 and E-60) used homologous heavy chains derived from the germline VH gene DP73 in combination with different light chains which were derived from germline Vκ gene L6 and Vλ gene DPL23. The third Fab clone (E-56) used another heavy chain derived from the germline VH gene DP31 in combination with the identical light chain as that of E-42. All three Fab clones revealed a high number of somatic mutations that likely occurred in the context of antigen selection. These findings suggest the restricted usage of VH and VL genes of anti-SS-A/Ro antibodies in salivary gland lymphocytes of the patient.

Characterization of a germline Vk gene encoding cationic anti-DNA antibody and role of receptor editing for development of the autoantibody in patients with systemic lupus erythematosus.

We found previously that cationic anti-DNA autoantibodies (autoAbs) have nephritogenic potential and usage of a specific germline Vk gene, A30, has major influences on cationic charge of the autoAb in human lupus nephritis. In the present study, we have characterized A30 germline Vk gene using cosmid cloning technique in patients with SLE. A30 gene locus locates in less than 250 kb from the Ck region, and the cationic anti-DNA mRNA used the upstream Jk2 gene, indicating that cationic anti-DNA mRNA is a product of primary gene rearrangement. By using PCR technique, we found that A30 gene locus in the genome was defective in eight out of nine SLE patients without nephritis. In contrast, all nine patients with lupus nephritis had intact A30 gene. The presence and absence of A30 gene was associated with the development of lupus nephritis or not (P < 0.01, by Fisher's exact test, two-sided). It was thus suggested that absence of functional A30 gene may rescue from developing lupus nephritis in the patients. A30 is reported to be a potentially functional but rarely expressed Vk gene in humans. It is possible that normal B cells edit primarily rearranged A30 gene with autoreactive potentials by receptor editing mechanism for changing the affinity of the B cell Ag receptor to avoid self-reactivity, whereas SLE B cells may have a defect in this mechanism. Indeed, we found that normal B cells edit A30-Jk2 gene in their genome possibly by inversion mechanism, whereas SLE B cells contain rearranged A30-Jk2-Ck gene in the genome and express A30-associated mRNA, suggesting that receptor editing mechanism is also defective in patients with SLE. Our study suggests that polymorphism of Ig Vk locus, and failure of receptor editing may contribute to the development of pathogenic anti-DNA responses in humans.

Construction and expression of single-chain Fv antibody against human bladder carcinoma.

We designed two sets of oligonucleotide primers to amplify the immunoglobulin heavy- and light-chain variable-region genes from genomic DNA by polymerase chain reaction (PCR). The genomic DNA was extracted from hybridoma BDI-1 cells, which secreted a monoclonal antibody (mAb) against human bladder carcinoma. The primers contained special restriction sites that allowed the variable-region genes to be easily cloned for sequencing and expression. The recombinants were sequenced by Sanger's method. It was proved that the full lengths of the VH and VK genes were 366 and 324 bp, respectively. Compared with other published sequences, the VH gene was a member of mouse heavy-chain VH subgroup II and originated from the rearrangement of VH, Dsp2.2 and JH4. The VK gene was VK subgroup IV and from VK and JK4. The VH and VK genes was inserted expression vector pWAI80. By inducement, the ScFv antibodies were expressed and secreted from Escherichia coli. Binding activities against the bladder carcinoma cells were detected. We suggest that ScFv antibody recognized the antigen specifically.

The B cell response to autologous type II collagen: biased V gene repertoire with V gene sharing and epitope shift.

Collagen-induced arthritis is an autoimmune model disease induced in the DBA/1 mouse immunized with type II collagen (CII). Both T and B cells play a critical role for the induction of arthritis. Draining lymph nodes from CII-immunized mice contain high numbers of CII-specific B cells, which are isotype switched and V gene selected. In the present study we analyze the V region gene usage and epitope specificity of CII-reactive B cell hybridomas, randomly isolated from the primary and the secondary response in mice immunized with rat CII we make the following conclusions. 1) There are major epitopes in the native CII molecule to which the B cells preferentially respond. 2) B cells specific for the same epitope show a preferential pairing of certain VH/VK genes or a biased usage of individual VH (VHJ558 and VHX24) or VK genes (VK21). 3) The V genes are germ line encoded in the primary response and somatically mutated in the secondary response. Somatic mutations give the Abs cross-reactivity between CII epitopes, and epitope shift, i.e., another epitope within the CII molecule is recognized. 4) There is a sharing of certain V genes in B cell clones specific for different epitopes, indicating structural similarities of the different CII epitopes.

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.

Association of placental transfer of anti- Haemophilus influenzae type b polysaccharide antibodies with their V regions

Immunization of mothers during pregnancy may be an effective means of providing protection to infants during the first months of life against many pathogens. Previous studies have identified factors that influence the transfer of immunoglobulin across the placenta, including the time of vaccination during pregnancy and isotypes of specific immunoglobulins. By studying antibodies to Haemophilus influenzae type b polysaccharide (Hib-PS) in 26 pairs of maternal-cord sera obtained from unimmunized healthy women and 22 pairs of maternal-cord sera from women immunized with one of three different Hib vaccines, we have found that the immunoglobulin transfer is also dependent on the V region of antibodies. Anti-Hib-PS derived from the VϰII gene “A2” was transferred about ten times more efficiently to the fetus than other anti-Hib-PS antibodies (20% vs 1–2%). It was found that antibodies derived from the A2 Vϰ gene are primarily IgG whereas other antibodies are preferentially associated with the IgM isotype. The potential association between the antibody V region with preferential placental transfer should be considered for future studies involving maternal immunization.

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.

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.

Human and Mouse Monoclonal Antibodies to Blood Group A Substance, Which Are Nearly Identical Immunochemically, Use Radically Different Primary Sequences

A human monoclonal antibody (HuA) specific for blood group A substance with two fucose groups was found to be immunochemically almost identical with that of a previously characterized mouse monoclonal anti-A, AC-1001. The VH and VL chain cDNAs of HuA were sequenced and compared with those of AC-1001. The human and mouse antibodies used VH and Vk genes that came from different families and shared minimal nucleotide and amino acid sequence identity. Thus, two antibodies from two different species can use evolutionarily unrelated sequences to bind the same carbohydrate epitope. The cloned HuA VH and VL genes were then transfected into a mouse myeloma cell line and re-expressed, together, and each separately with an irrelevant VH or VL. Only the original HuA VH and Vk had anti-A activity, demonstrating that both the heavy and light chains contributed to specificity.

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.

Variant translocation of the BCL6 gene to immunoglobulin kappa light chain gene in B-cell lymphoma.

A lymphoma cell line with a variant type of translocation, t(2;3)(pll;q27), was established from a patient who had received liver transplantation. To elucidate the molecular mechanism of the t(2;3)(pll;q27) chromosomal translocation, we compared the structures of both derivative (der) chromosomal breakpoints with those of their germline predecessors. We noted that the BCL6 gene on chromosome 3 was juxtaposed with the immunoglobulin k light chain (Igk) gene on chromosome 2 in a head‐to‐head configuration. The breakpoint of the BCL6 gene was within a previously reported breakpoint cluster region. The breakpoint on chromosome 2 was within the intron between the leader (L) and variable (V) sequences of one of the Vk genes, which was fused to the Jk3 (J=joining) segment. At chromosomal junctures, a direct repeat duplication of chromosome 3 sequences and a deletion of chromosome 2 sequences were discovered. These results are consistent with a translocation model with illegitimate pairing of staggered double‐stranded DNA breaks at 3q27 and 2pll, repair, and ligation to generate der(3) and der(2) chromosomes.

Construction and Functional Characterization of a Single Chain Fv Antibody Binding to the Plant Hormone Abscisic Acid

Summary The VH and VK genes coding for the variable regions of the monoclonal antibody 15-I-C5 to abscisic acid were isolated by molecular cloning and connected by a linker to allow translation of the single chain Fv fusion protein gene. This was expressed in E. coli either as a free peptide secreted into the periplasmic space or as a fusion protein with protein g3 of the single strand phage. Binding to abscisic acid, either by free scFv or by an anti-ABA scFv displaying fd phage, was shown by ELISA. Specificity to ABA comparable to the binding properties of the complete antibody was verified by competition ELISA. A comparison of the relative affinity to ABA of the scFv and the complete antibody was carried out using competition ELISA with anti-ABA scFv display phage.

Immunoglobulin V region sequences of two human antiplatelet monoclonal autoantibodies derived from B cells of normal origin.

Autoimmune thrombocytopenia has been attributed to the presence of antiplatelet autoantibodies which mediate platelet destruction. The derivation of these autoantibodies is presently unknown. While normal B cells do not produce these autoantibodies in vivo, it has been demonstrated in vitro by somatic cell hybridization that the B lymphocytes of nonthrombocytopenic individuals have the potential to produce antiplatelet autoantibodies. Antigen specificities of these antibodies are similar to those seen in autoimmune thrombocytopenic purpura and the lupus anticoagulant syndrome. The immunoglobulin V region genes encoding two such human monoclonal antiplatelet antibodies, an anti-GP IIb (STO 171) and an anti-phospholipid antibody (STO 103) derived from tonsillar lymphocytes of a non-thrombocytopenic male, have now been sequenced. These antiplatelet antibodies were found to be encoded by unmutated germline VH and VK genes. The third complementarity determining region (CDR3) of the genes encoding both of these antibodies have unique D regions with evidence of N-nucleotide additions, and the light chain genes show VK-JK junctional diversity. STO 103 is encoded by the VH4 V71-2 germline gene and a truncated JH4 gene. The light chain gene showed closest homology with the VK4 Humk18 gene and JK2 gene. STO 171 showed closest homology with the VH4.18 germline gene and had a complete germline JH6 gene. The light chain of STO 171 is encoded by the VK3 Humkv325 germline gene, which is also used by some rheumatoid factors and cold agglutinins, and a JK4 gene. Although these antibodies were not derived from circulating B cells or found to be actively producing antibody at the time they were harvested, it is possible that naturally occurring antibody producing B cells, similar to those represented here, are recruited for the development of pathogenic autoantibodies in immune thrombocytopenia.

Structure-function studies of anti-3-fucosyllactosamine (Le(x)) and galactosylgloboside antibodies.

We are studying murine mAbs against two carbohydrate epitopes, 3-fucosyllactosamine (Le(x), CD15) and galactosylgloboside. The VH domains of both panels of Ab are encoded by VH441, a member of the X24 family of Ig genes. To evaluate the contribution of the heavy chain CDR3 to the affinity of the anti-3-fucosyllactosamine Ab, CDR3-H of PMN6, a low affinity Ab, was replaced by the CDR3 of PM81, a higher affinity Ab. The affinity of the chimeric 6/81 Ab was increased when the heavy chain was paired with the PM81 light chain, but not when paired with another light chain (M5), which differs from PM81 light chain by three amino acids. To evaluate the contribution of somatic mutations to the binding of GalGb4, the 3A9 VH sequence, which contains three amino acid substitutions, was replaced by a germ-line sequence encoded by either VH441 or VHX24. The chimeric Ab, 441/3A9 and X24/3A9, bound Ag as well as the wild-type 3A9 Ab. Computer models of the Fv fragments of PM81 and 3A9 were compared with the crystal structure of the Fv fragment of J539, a galactan-binding myeloma protein that is encoded by the same VH and VK genes as 3A9. The surfaces of 3A9 and J539 have shallow pockets that are potential Ag-binding sites. Replacement of CDR3-H Tyr99, which is a prominent component of the pocket, by Ala abolished the binding of Ag. In contrast, the Fv surface of PM81 contains a large cleft rather than a pocket. These models indicate how the same VH gene segment can be used to encode Abs that exhibit different specificities.

Biased utilization of immunoglobulin variable region heavy- and light-chain genes by the malignant CD5- B lymphocytes from patients with Burkitt's lymphoma.

Twenty-six established Burkitt's lymphoma (BL) cell lines from endemic or sporadic groups of patients were examined for the expression of cross-reactive idiotypes (CRI) associated with VHI, VHIII, VHIV, VHVI, VKIIIa and VKIIIb heavy- and light-chain gene products, using a panel of anti-CRI and anti-subgroup monoclonal antibodies (MAbs). Membrane, cytoplasmic and secreted immunoglobulins (Ig) were analysed by immunofluorescence, immunoperoxidase and ELISA respectively. While 35% of the lines expressed either of the VHIV-associated CRI, recognised by the MAbs 9G4 or LCI, none expressed the other VH-associated CRI included in our study. Of the kappa light chain expressing BL lines 54% and 46% belonged to the VKIII subgroup and VKIIIb sub-subgroups respectively. None, however, was found to express the VKIIIa or VKIIIb-associated CRI, recognised by the 6B6.6 and 17-109 MAbs. A significant association has been observed between the expression of the VHIV-associated CRI and the VKIII subgroup within the BL lines derived from the sporadic group of patients as compared with their endemic counterparts. Our results suggest that the expressed repertoire of Ig variable region genes within the malignant B lymphocytes of BL is not random and that a highly selective mechanism(s) may operate on this subset of B lymphocytes, as evidenced by the expression of the VH and VK gene products.