Lambda Gene Segments Research Articles

Analysis of human immunoglobulin gene repertoire in NOD/scid IL2Rγ null mice engrafted with human cord blood derived hematopoietic stem cells (36.14)

Abstract The humanized NOD/scid IL2rg-/- (hNSG) and similar mouse models hold promise as testing platforms for preclinical studies. Here, we analyzed the human immunoglobulin (IG) variable heavy and light chain gene repertoire from sorted single B-cells of hNSG mice engrafted with cord blood derived hematopoietic stem cells. Unique IGHV (339) and IGLV (364, kappa and lambda) gene segments were derived from major B cell subsets identified in a largely normal B cell development pathway. However, the hNSG mice expressed elevated CD5+ mature B-1-like cells in the periphery. In mice and humans, B-1 cells are the major source of autoantibodies. Although the hNSG mice expressed a highly diverse repertoire comparable to humans, detailed genetic analysis of IG gene segments from the mature B cell subset revealed the presence of long IGH-CDR3 regions with positive charges—a hallmark for auto/polyreactivity. For functional tests, several in vitro expressed scFv-Fc IG candidates, derived from cloned heavy and light chain cognate pairs of single B cells, tested positive in an anti-nuclear antibody assay for auto/polyreactivity and/or bound to HIVgp120 in ELISA assays. The natural induction during HIV-1 infection of broadly neutralizing antibodies (BnAbs) which display autoantibody-like characteristics may be curtailed by the checkpoint control mechanisms during B cell ontogeny. We propose the hNSG mouse can be a model platform to test this hypothesis and interrogate how BnAbs are formed.

Unraveling of the polymorphic C lambda 2-C lambda 3 amplification and the Ke+Oz- polymorphism in the human Ig lambda locus.

Two polymorphisms of the human Ig(lambda) (IGL) locus have been described. The first polymorphism concerns a single, 2- or 3-fold amplification of 5.4 kb of DNA in the C(lambda)2-C(lambda)3 region. The second polymorphism is the Mcg(-)Ke(+)Oz(-) isotype, which has only been defined via serological analyses in Bence-Jones proteins of multiple myeloma patients and was assumed to be encoded by a polymorphic C(lambda)2 segment because of its high homology with the Mcg(-)Ke(-)Oz(-) C(lambda)2 isotype. It has been speculated that the Mcg(-)Ke(+)Oz(-) isotype might be encoded by a C(lambda) gene segment of the amplified C(lambda)2-C(lambda)3 region. We now unraveled both IGL gene polymorphisms. The amplification polymorphism appeared to result from a duplication, triplication, or quadruplication of a functional J-C(lambda)2 region and is likely to have originated from unequal crossing over of the J-C(lambda)2 and J-C(lambda)3 region via a 2.2-kb homologous repeat. The amplification polymorphism was found to result in the presence of one to five extra functional J-C(lambda)2 per genome regions, leading to decreased Ig(kappa):Ig(lambda) ratios on normal peripheral blood B cells. Via sequence analysis, we demonstrated that the Mcg(-)Ke(+)Oz(-) isotype is encoded by a polymorphic C(lambda)2 segment that differs from the normal C(lambda)2 gene segment at a single nucleotide position. This polymorphism was identified in only 1.5% (2 of 134) of individuals without J-C(lambda)2 amplification polymorphism and was not found in the J-C(lambda)2 amplification polymorphism of 44 individuals, indicating that the two IGL gene polymorphisms are not linked.

Primary Central Nervous System Lymphomas Are Derived from Germinal-Center B Cells and Show a Preferential Usage of the V4–34 Gene Segment

Primary central nervous system lymphomas (PCNSLs) have recently received considerable clinical attention due to their increasing incidence. To clarify the histogenetic origin of these intriguing neoplasms, PCNSLs from 10 HIV-negative patients were analyzed for immunoglobulin (Ig) gene rearrangements. All tumors exhibited clonal IgH gene rearrangements. Of the 10 cases, 5 used the V4-34 gene segment, and all of these lymphomas shared an amino acid exchange from glycine to aspartate due to a mutation in the first codon of the complementarity-determining region 1. No preferential usage of D(H), J(H), V(kappa), J(kappa), V(lambda), or J(lambda) gene segments was observed. All potentially functional rearrangements exhibited somatic mutations. The pattern of somatic mutations indicated selection of the tumor cells (or their precursors) for expression of a functional antibody. Mean mutation frequencies of 13. 2% and 8.3% were detected for the heavy and light chains, respectively, thereby exceeding other lymphoma entities. Cloning experiments of three tumors showed ongoing mutation in at least one case. These data suggest that PCNSLs are derived from highly mutated germinal-center B cells. The frequent usage of the V4-34 gene and the presence of a shared replacement mutation may indicate that the tumor precursors recognized a shared (super) antigen.

Frequent N Addition and Clonal Relatedness among Immunoglobulin Lambda Light Chains Expressed in Rheumatoid Arthritis Synovia and PBL, and the Influence of Vλ Gene Segment Utilization on CDR3 Length

In rheumatoid arthritis (RA), B-lineage cells in the synovial membrane secrete large amounts of immunoglobulin that contribute to tissue destruction. The CDR3 of an immunoglobulin light chain is formed by rearrangements of VL and JL gene segments. Addition of non-germline-encoded (N) nucleotides at V(D)J joins by the enzyme terminal deoxynucleotidyl transferase (TdT) enhances antibody diversity. TdT was previously thought to be active in B cells only during heavy chain rearrangement, but we and others reported unexpectedly high levels of N addition in kappa light chains. We also found clonally related kappa chains bearing unusually long CDR3 intervals in RA synovium, suggesting oligoclonal expansion of a set of atypical B lymphocytes. In this study, we analyzed lambda light chain expression to determine if N addition occurs throughout immunoglobulin gene rearrangement and to compare CDR3 lengths of lambda and kappa light chains in RA patients and normal individuals. Reverse transcription-polymerase chain reaction (RT-PCR) amplification of V lambda III transcripts was performed on RA synovia and peripheral blood lymphocytes (PBL) and normal PBL for which kappa repertoires were previously analyzed. Representative lambda + PCR products were cloned and sequenced. Analysis of 161 cDNA clones revealed that N addition occurs in lambda light chains of RA patients and normal controls. The lambda light chain repertoires in RA were enriched for long CDR3 intervals. In both RA and controls, CDR3 lengths were strongly influenced by which V lambda gene segment was present in the rearrangement. Five sets of clonally related sequences were found in RA synovia and PBL; one set was found in normal PBL. In humans, unlike mice, N addition enhances antibody diversity at all stages of immunoglobulin assembly, and the structural diversity of lambda CDR3 intervals is greater than that of kappa light chains. Clonally related V lambda gene segments in RA support an antigen-driven B-cell response.

One-megabase sequence analysis of the human immunoglobulin lambda gene locus.

A total of 1,025,415 bases of nucleotide sequence, including the entire human immunoglobulin lambda gene locus has been determined. This is the largest contiguous human DNA sequence ever published. The sequence data revealed the organization of 36 potentially active V lambda gene segments, 33 pseudogene segments, and seven J lambda-C lambda gene segments. Among these 69 functional or nonfunctional V lambda gene segments, 32 were newly discovered. These V lambda gene segments are located within five gene-rich clusters and are divided into five clans based on sequence identity. Five potentially active nonimmunoglobulin genes were also detected within the lambda gene locus, and two other genes were observed in the upstream region. Sequence organization suggests that large DNA duplications diversified the germ-line repertoire of the V lambda gene segments.

The organization of the human immunoglobulin lambda gene locus.

To elucidate the complex structure of the human immunoglobulin lambda gene locus, a 1020-kb contig was constructed using 184 cosmid clones and one bacterial artificial chromosome (BAC) clone. A high-resolution physical map of this contig revealed that the entire lambda gene locus is 911 kb in length. It contains seven constant region (C lambda) gene segments and 69 unique EcoRI-HindIII segments that hybridize to variable region gene (V lambda) probes. The VpreB gene, BCRL4, and gamma-glutamyl transpeptidase gene (GGT)-like sequences are also located within the lambda gene locus. Hybridization analysis suggested that the lambda gene locus has undergone extensive amplification events in evolution.

A mutated promoter of a human Ig V lambda gene segment is associated with reduced germ-line transcription and a low frequency of rearrangement.

Several explanations for skewed variable (V) gene usage in the expressed Ig repertoire have been put forth, ranging from cellular selection to differences in the actual rearrangement frequencies of individual V gene segments. In this report we study V gene usage in human Ig lambda rearrangements in an in vitro system, thus largely avoiding selective forces. We find a significant bias in V lambda gene usage in these rearrangements. Through deletional mapping on Southern blots, the relative chromosomal organization of members of the V lambda I, V lambda V, V lambda VI, and V lambda X families was established, which revealed that the bias in V lambda gene usage cannot be readily explained by chromosomal location. We further found that the qualities of the recombination signal sequences, nucleotide sequence/regions of homology of the coding ends or the CpG methylation patterns, do not explain this bias either. We do, however, find a direct correlation between a low frequency of rearrangement and a reduced level of germ-line transcription of a particular V gene segment. We were able to identify three mutations in the octamer motif of the promoter region of this V gene segment. This is the first report showing that mutations in important transcriptional control motifs of individual V gene segments are associated with reduced levels of transcription in the germ line, which in turn may influence the frequency of rearrangement and the shaping of the expressed Ig repertoire.

Heterogeneous expression of human antibody lambda chains by concanavalin A-resistant hybridomas lead to changed antigen binding.

Human HB4C5 hybridoma cells produce a lung cancer-specific human monoclonal antibody that possesses a lambda light chain on which a N-linked carbohydrate chain is attached at the first complementary determining region. Up to six light chains of various sizes are secreted by the original and concanavalin A (ConA)-resistant HB4C5 clones. Two of these six light chains are derived directly from the HB4C5 original and are 30 and 32 kDa in size. The structural difference between these two light chains has been shown to be a N-linked carbohydrate located at a single site. The other four variants, which are derived from ConA-resistant variants, have light chain sizes ranging from about 26 to 29 kDa. No changes in the secretory forms were observed when glycosylation was inhibited by the addition of tunicamycin, indicating that the heterogeneous light chain forms produced by these ConA-resistant variants resulted from the size differences of core polypeptides and not from N-glycosylation. Sequence analysis from one of the variant light chains revealed that its V lambda gene segment differs markedly from identified human V lambda gene segments (at most, 60% homology with known human V lambda subgroups) and, furthermore, the variant light chain shares 80% homology with the rabbit V lambda gene. In addition, the antigen binding ability of these variant antibodies changed significantly in both specificity and affinity. These results suggest that heterogeneous light chains expression by ConA-resistant variants may provide a new way for developing an antigen-specific human monoclonal antibody repertoire.

Identification of a new human V lambda gene family--V lambda X.

Although approximately 40% of Ig light chains in human sera are of the Ig lambda isotype, until recently very little was known about the human Ig lambda gene locus. The genomic structure of the Ig lambda C region has been determined and consists of seven tandemly organized J-C lambda segments. The structure of the region containing the Ig lambda V gene segments is less well defined. Based on amino acid and nucleotide sequence homologies, the V lambda gene segments isolated have been grouped into nine families. Here we report on the isolation of a V lambda gene from the functional rearrangement of a human B lymphoma cell line that has less than 71% nucleotide sequence and 57% deduced amino acid sequence homology to any known V lambda gene. According to the current classification schemes, this gene does not belong to any existing V lambda family. Thus we suggest that this gene belongs to a new V lambda family, V lambda X. The genomic counterpart of the rearranged V lambda gene, and a second member of the family were isolated. The second member is a pseudogene. Southern analysis suggests that the V lambda X family is a small family. The functional V lambda X gene has a consensus heptamer and a nonamer that differs at two sites from the consensus recombination signal sequence. The promoter region contains a consensus TATA box and an octamer that diverge from the consensus sequence by two base pairs.

Transcription and diversity of immunoglobulin lambda chain variable genes in the rat.

In order to determine the extent of the repertoire of the immunoglobulin light chain V-region locus (Igl-V) in the laboratory rat (Rattus norvegicus), we constructed a specifically primed cDNA library from lipopolysaccharide-stimulated DA strain rat spleens. The library was screened with a rat Igl-C2-specific probe, and 33 clones containing identifiable V regions were sequenced, of which 19 sequences are presented here. In addition to one sequence (Igl-V1) which was already known, and is closely related to the two known mouse V lambda gene segments, clones encoding representatives of three new, distantly related, rat Igl-V subfamilies were found, namely Igl-V2, Igl-V3, and Igl-V4. At least two of these sub-families, Igl-V2 and Igl-V3, contain multiple members as well as restriction fragment length polymorphism variants, indicating the presence of at least 10-15 Igl-V gene segments (including some pseudogenes) in the rat genome. An additional ten clones contained no rearranged V region, although they showed a correct J-C splice, suggesting the presence of cryptic transcriptional promoters between J lambda and the 3'-most Igl-V gene segment. Phylogenetic tree reconstruction based on amino acid sequence alignments showed at least three of the four rat Igl-V sequences clustering with distinct human Igl-V genes. Thus, although rats express lambda-bearing Ig at levels no higher than mice, the rat Igl-V locus is considerably more complex than that of laboratory mice, and its diversity reflects the products of gene duplications which predate the time of primate/rodent divergence.

Vλ and Jλ‐Cλ gene segments of the human immunoglobulin λ light chain locus are separated by 14 kb and rearrange by a deletion mechanism

We have cloned a region of 124 kb of the human immunoglobulin lambda light chain locus on chromosome 22 encompassing seven V lambda and seven J-C lambda gene segments. No further C lambda gene segment was found in a region of 35 kb downstream of C lambda 7, which encodes the Ke+Oz- isotype. The C lambda proximal V lambda gene segment V lambda III. 1 is located 14.5 kb upstream of C lambda 1. The five sequenced V lambda genes have the same transcriptional orientation as the J-C lambda gene segments which is likely to be true for the majority of the V lambda gene segments in the human lambda locus and which suggests a deletion mechanism for DNA rearrangement. This is supported by hybridization of V lambda gene probes to germ-line and rearranged DNA from lambda light chain-producing cell lines. Sequences of 23 cDNA clones allow to establish a V lambda subgroup classification based on nucleic acid sequence data and an estimate of the J-C lambda usage.

Rheumatoid factors isolated from patients with autoimmune disorders are derived from germline genes distinct from those encoding the Wa, Po, and Bla cross-reactive idiotypes.

To better understand the structural basis for rheumatoid factor activity, the nucleotide sequence of the light chain variable regions of nine human monospecific IgM rheumatoid factors were analyzed. Rheumatoid factors were isolated from three patients with rheumatoid arthritis, a patient with systemic lupus erythematosus, and a normal individual. The VL gene segments used by these rheumatoid factors are not as restricted as previous work on mixed cryoglobulin rheumatoid factors had suggested. Each of the different VK families is represented and there are two examples where a V lambda gene segment is used. Molecules with structures similar to those of the Wa and Po CRI, characteristic of mixed cryoglobulin rheumatoid factors, are not common among these rheumatoid factors isolated from patients with rheumatoid arthritis. While there are clear examples of rheumatoid factors that are direct copies of germline genes, most of the sequence data suggest that the processes of antigenic selection and somatic mutation contribute significantly to the generation of monospecific rheumatoid factors in patients with autoimmune disease.

The human lambda L chain Ig locus. Recharacterization of JC lambda 6 and identification of a functional JC lambda 7.

The human lambda L chain Ig gene complex consists of multiple JC gene segments. A seventh human lambda C region gene segment, C lambda 7, was found 2.7 kb downstream of C lambda 6 in this gene complex. A J lambda gene segment, J lambda 7, was found 1.2 kb upstream of C lambda 7 and contains potentially functional nonamer and heptamer recombination sites, an RNA splice site and J coding region. C lambda 7 maintains an open reading frame and encodes a new lambda isotype. C lambda 7 encodes Kern+ and Oz- determinants, but does not encode any of the Kern+Oz- myeloma proteins published to date. Nevertheless, we present evidence that JC lambda 7 is transcribed in normal lymphocytes and is functional. In contrast, we present new data that the C lambda 6 gene segment, reported by others to encode the Kern+Oz- protein, is non-functional due to a 4-bp insertion in our cosmid clone. The 4-bp insertion was characterized further in 32 genomic DNA samples by producing a distinctive restriction fragment length and verified by the DNA sequences of the polymerase chain reaction products of two different cell lines. We discuss the possibility that the Kern+Oz- myeloma proteins do not define an isotype and are not encoded by JC lambda 7 nor other non-allelic genes, and we discuss the level of expression of JC lamba 7 as compared to that of JC lambda 2 and JC lambda 3.

A linkage map of the mouse immunoglobulin lambda light chain locus

The mouse immunoglobulin lambda light chain locus has been linked using field inversion gel electrophoresis. The lambda light chain locus classically contains two V and four J-C gene segments in inbred mouse strains, and was physically mapped in the BALB/c cell line Wehi-3 which contains unrearranged lambda light chain gene segments. The locus is relatively small and spans 300 kb, as defined by a variety of single and double digests using methylation-sensitive restriction enzymes. The order of the lambda gene segments is V2-J2C2J4C4-V1-J3C3J1C1, as was originally proposed. No evidence for nonmethylated CpG rich areas (HTF islands) within the region was found. Fine mapping using the lambda 1, lambda 3 rearranged cell line J558 mapped the gap between the V and J-C gene segments in the lambda 1 gene cluster (V1-J3C3J1C1) to approximately 70 kb. The similar distance (60-100 kb) found in the lambda 2 gene cluster (V2-J2C2J4C4) is further evidence that duplication of an ancestral locus occurred.

The human Vpre B gene is located on chromosome 22 near a cluster of V lambda gene segments.

The chromosomal location of the human VpreB gene was determined by Southern blotting analysis of restriction enzyme-digested DNAs from a panel of 17 mouse-human somatic cell hybrids. The pattern of hybridization of a Vpre B-specific probe in conjunction with earlier analysis of several marker genes allowed the following conclusions: 1) Vpre B is on human chromosome 22 within band 22q11.2 distal to the bcr-like gene, bcr-2 and proximal to the bcr-like gene, bcr-4. 2) Vpre B has been localized relative to several constitutional and tumor-specific breakpoints within 22q11.2, segregates in hybrids retaining 22q- chromosomes with some but not with all members of the V lambda 1 subgroup of the V lambda genes, and is amplified with these genes in K562 cells. 3) The order of the loci on chromosome 22 is centromere----bcr-2, Vpre B, V lambda 1----bcr-4----C lambda----bcr-1----bcr-3----sis.

A rabbit Ig lambda L chain C region gene encoding C21 allotopes.

Southern blot analyses of germ-line DNA obtained from rabbits expressing lambda chains of C7 and/or C21 allotypes were performed with a rabbit C lambda region-specific probe; a 12-kbp EcoRI- and a 2-kbp BamHI-hybridizing fragment were detected only in the DNA from rabbits expressing the C21 allotype. The 12-kbp EcoRI fragment was cloned and shown to contain two C lambda region-encoding genes in the same orientation. Each is preceded by a J lambda gene segment. Nonamer-12-bp spacer-heptamer recombination signal sequences were found 5' of each J lambda segment, and splicing signals were identified at the 3' ends of the J lambda segments and the 5' ends of the corresponding C lambda genes. The C lambda 5 gene, which exhibits a sequence identical with that found in several cDNA clones, is carried by the 2-kbp BamHI fragment missing from the genomic DNA of rabbits which do not express the C21 allotype. The second C lambda gene, C lambda 6, lies 3' of C lambda 5, in a 1.6-kbp BamHI fragment which is present in genomic DNAs of all tested rabbits, irrespective of their phenotype. Its sequence is identical with that found in one cDNA clone and differs from that of C lambda 5 in 17 base positions resulting in four amino acid substitutions. A fragment of a cDNA, with a J-C region sequence identical with that encoded by the J lambda 5-C lambda 5 gene pair, was subcloned into a plasmid expression vector. The resulting polypeptide product could be specifically immunoprecipitated by anti-C21 but not anti-C7 alloantisera, showing that some, if not all, C21 allotopes are encoded by the C lambda 5 gene. In contrast, the C lambda 6 gene product was not precipitable, either by anti-C7 or by anti-C21 alloantisera, although it was readily immunoprecipitated by a goat anti-rabbit lambda chain antiserum.

Structure of a third murine immunoglobulin lambda light chain variable region that is expressed in laboratory mice.

Recently, we reported evidence for the existence of an immunoglobulin lambda light chain (lambda x) whose variable region differs from those encoded by the known V lambda gene segments V lambda 1 and V lambda 2. Expression of lambda x was detected in some hybridomas elicited by treatment of a BALB/c mouse with rabbit anti-lambda 2 antibodies coupled to bacterial lipopolysaccharide [Sanchez, P. & Cazenave, P.-A. (1987) J. Exp. Med. 166, 265-270]. We constructed a cDNA clone from one hybridoma (B6) that expresses the lambda x chain and determined the complete nucleotide sequence. The deduced amino acid sequence of V lambda x is 30-33% identical with those encoded by V lambda 1 and V lambda 2 and by V kappa gene segments. The third hypervariable region of V lambda x is four codons longer than those of the other murine variable gene segments. The expression of lambda x requires a genomic rearrangement that juxtaposes the V lambda x gene with the J lambda 2-C lambda 2 joining-constant gene pair. Rabbit anti-V lambda x antibodies detected the lambda x light chain in the normal sera of all laboratory mice tested. Lambda x expression seems to be independent of lambda 1 expression, since both SJL and SJA strains, which are defective in lambda 1 production, express normal levels of lambda x chain.

Active lambda and kappa antibody gene rearrangement in Abelson murine leukemia virus-transformed pre-B cell lines.

The two Abelson murine leukemia virus (A-MuLV)-transformed cell lines, BM18-4 and ABC-1, undergo immunoglobulin L-chain gene recombination during passage in tissue culture. BM18-4 cells are capable of kappa gene recombination, whereas ABC-1 cells are capable of both kappa and lambda gene recombination. The expression of H chains is apparently not necessary for continuing L chain gene recombination in either of these cells, although H-chain expression may have been involved in the initiation of L-chain gene recombination. All ABC-1 cells that have lambda gene rearrangements also display recombined kappa alleles, supporting the hypothesis that kappa and lambda gene recombination are initiated in an ordered, developmentally regulated manner in maturing B cells. However, analyses of the ABC-1 line indicate that pre-B cells that have initiated lambda gene recombination do not terminate kappa gene rearrangement. The lambda gene recombinations that occur in the ABC-1 cell line indicate that the germline order of lambda gene segments is: 5' ... V lambda 2 ... J lambda 2C lambda 2-J lambda 4C lambda 4 ... V lambda 1 ... J lambda 3C lambda 3-J lambda 1C lambda 1 ... 3'. In addition, the frequencies of lambda 1, lambda 2, and lambda 3 gene recombinations among ABC-1 cells are quite different than the frequencies of B cells producing lambda 1, lambda 2, and lambda 3 L-chains in the mouse. RS DNA recombinations also occur in the BM18-4 and ABC-1 cell lines, supporting the notion that Ig gene recombinases are involved in RS rearrangement. Recombined RS segments are infrequent among BM 18-4 cells but common among ABC-1 cells, suggesting that RS recombinational events often occur in maturing pre-B cells just before initiation of lambda gene rearrangements. This developmental timing is consistent with the hypothesis that RS recombination may be involved in the initiation of lambda gene assembly.

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.

Human ? light chain locus: Organization and DNA sequences of three genomicJ regions

Evidence for the genomic organization of human lambda light chain joining (J) region gene segments is presented. A mouse J lambda probe was used in Southern hybridizations to localize joining region sequences in a cosmid clone containing the genomic cluster of six human lambda constant (C) region gene segments. The results of these hybridizations suggest the presence of at least one J gene segment upstream from each constant region gene segment. The DNA sequences indicate that the human J lambda 1, J lambda 2, and J lambda 3 gene segments have consensus nonamer and heptamer sequences, proposed to be involved in V-J joining, are capable of encoding the known amino acid sequences for the respective J peptides, and have a sequence which could give a functional RNA splice site at the end of their coding regions. Our data show that a single functional J is located 1.3 or 1.6 kb upstream of each of the C lambda gene segments known to encode the Mcg, Kern- Oz-, and Kern- Oz+ isotypes. Therefore, the gene organization of this region of the human lambda locus is J1C1-J2C2-J3C3. The DNA sequences of J lambda 1, J lambda 2, and J lambda 3 presented in this paper establish that a single J lambda gene segment precedes each expressed C lambda gene segment, and support a model for the evolution of the human lambda JC clusters where J1C1 and J2C2-J3C3 arose from different ancestral JC units.