The Igh-V locus of MRL mice: restriction fragment length polymorphism in eleven strains of mice as determined with VH and D gene probes

The MRL strain of mice is a model system that closely parallels the human autoimmune disease systemic lupus erythematosus. Our analysis of the variable region genes of MRL mice showed that the MRL/lpr D genes were similar to those of the C3H mouse (Igh-C allotype j). This result was unexpected, because previous studies of the MRL/lpr and MRL/+ substrains suggested that they are allotype a at the Igh-1 (gamma 2a) locus of the constant region. The Igh-V (heavy chain variable region) locus of the MRL/lpr and MRL/+ strains of mice and their parents were therefore examined by restriction fragment length polymorphism with probes for the DSP2 and DFL16 gene families and with two cloned VH probes. Five other strains of mice were also included because the heavy chain locus of the LG mouse, which is the major progenitor of the MRL strains, has not been studied. The MRL substrains and the LG and C3H parents were indistinguishable at all the Igh-V loci studied. These results suggest that the MRL substrains and their LG parent are haplotype j at the Igh-V locus. The results obtained with D gene probes show that the DSP2 gene family is more polymorphic than the DFL16 gene family, which is relatively conserved. We have assigned Igh-V haplotypes for the four VH loci to the 11 strains of mice studied.     

Genetic control of the immune response to staphylococcal nuclease. IX. Recombination between genes determining BALB/c antinuclease idiotypes and the heavy chain allotype locus.

The genetic linkage relationship of two antinuclease idiotypes produced by the BALB/c strain was investigated in the backcross (BALB/c x CB.20) X CB.20. These two idiotypes were detected by Lewis rat anti-idiotypic antisera prepared against affinity-purified A/J and SJL antinuclease antibodies, termed the A/J and SJL idiotypes, respectively. Both idiotypes were found to be linked to the IgCHa immunoglobulin heavy chain allotype locus. There was, however, a high frequency of recombination observed between both markers and the IgCHa locus, with eight of 83 backcross animals recombinant for the A/J idiotype and five of 83 recombinant for the SJL idiotype. All such recombinant animals were IgCHb/b homozygotes that had gained one or both idiotypes. These results are consistent with a genetic map of VHr region genes in the BALB/c strain in which genes determining the SJL idiotype are closer to the IgCHa allotype locus than are genes determining the A/J idiotype. This high frequency of recombination may indicate that the chromosome segment containing VH region genes is very large or that it has structural features that promote recombination.     

A new cross-reactive idiotype-defined family in the phthalate humoral immune response of mice. I. Linkage of VH-Xmp to IgCH allotype locus and mapping with respect to other known VH genes

A cross-reactive idiotype family was previously identified from a very large library of phthalate-specific hybridoma clones. The prototype of this idiotype family is the hybridoma, 2E9, secreting an IgM antibody with phthalate specificity. A portion of both primary and secondary anti-phthalate antibodies elicited in all BALB/c mice tested expresses the 2E9 cross-reactive idiotype. This idiotype has now been found in the anti-phthalate antibodies of several other inbred strains of mice (A/HeHa, DBA/2, and C3Hf/HeHa) tested but not in C57BL/6 mice. Anti-phthalate antibodies elicited from congenic mice BC.8, which express the same IgCH allotype as BALB/c mice but possess C57BL/6 genetic background, contain the 2E9 cross-reactive idiotype, whereas this idiotype is not expressed on the anti-phthalate antibodies derived from another congenic mouse CB.20, which expresses a C57BL/6 IgCH allotype and a genetic background of the BALB/c strain. These results indicate that the gene controlling the 2E9 idiotype is closely linked to the IgCH allotype locus. The 2E9 cross-reactive idiotype was also found in all of the F1 mice (BALB/c X C57BL/6) tested, and the level of expression of this idiotype in the F1 mice was quantitatively equivalent to the allotype/idiotype homozygous mice. The expression of the 2E9 idiotype in the phthalate repertoire has been followed in 12 different wild mouse populations. As expected, the 2E9 idiotype was observed in a large proportion of the wild mouse strains. Surprisingly, several examples of nonconcordance in the expression of idiotype and allotype were observed in these mice. One likely explanation for the linkage breakdown is a crossing over of the heavy chain constant and variable region gene complexes. In the SM/J inbred strain of mice, where such a crossover has occurred, nonconcordance between allotype and 2E9 idiotype expression was demonstrated. By using the recombinant inbred BXD strains of mice, the VH gene encoding the 2E9 idiotype has been mapped with respect to other known VH gene families. Relative to other VH genes the VH-Xmp is situated very close to the IgCH gene region.     

Genetics of the anti-dextran B512 and the autoanti-idiotypic response: codominant expression in F1 hybrids and dichotomy of response and allotype-linked idiotype

The IgM plaque-forming response to the alpha 1-6 epitope of dextran B512 is linked to the Ig-1 heavy chain allotypes j and b characteristic of CBA and C57BL strains, respectively, and the response typically induces the formation of autoanti-idiotypic antibodies that can distinguish between anti-dextran antibodies of CBA and C57BL origin. Nevertheless, some substrains of Balb/c mice (allotype a) and some Bailey recombinant stains give a PFC response although they do not possess allotypes j or b. The anti-dextran antibodies in these strains lack the idiotypes characteristic of either CBA and C57BL antibodies to dextran, but they possess their own particular idiotype. F1 hybrids between two responder strains possessing different idiotypes on their antibodies against dextran, produce both idiotypes and two different autoanti-idiotypic antibodies. CBA(Ig-1b) mice were high responders to dextran and possessed the idiotype of C57BL, whereas C57BL/6(Ig-1a) mice were low responders. The V(H) recombinant strains BAB.14 and CB-8KN that possess the Ig-1b allotype of C57BL, but have some of the V(H) genes from Balb/c and the rest from C57BL/6 were high responders to dextran, but did not possess the C57BL idiotype, suggesting that the genes determining the response against dextran and the idiotype may have different locations in the heavy chain locus.     

Allotypically related sequences in the Fd fragment of rabbit immunoglobulin heavy chains

The sequence has been completed of the N-terminal 94 residues of the variable section of the Fd fragment of heavy chains from rabbit immunoglobulin G (IgG) of allotype As1. Most of the sequence of the same section from IgG of allotype Aa3 is also reported. These results, in conjunction with a substantial sequence of the variable region of allotype Aa2 reported elsewhere (Fleischman, 1971), show the presence of 16 positions (including six consecutive positions) in which the residue present correlates with the allotype. No allotype-related sequence variation has been found in the constant section of the Fd fragment. This evidence supports the view that two genes code for the heavy chain and it can be used as evidence in favour of somatic mutation as the origin of the variability in the sequence of the N-terminal section. The evolutionary origin of the ;a' locus allotypes of rabbit immunoglobulins remains obscure.     

Inheritance of idiotype expression unlinked to the H chain allotype locus. Novel features of genetic control in the Ia.7 system

We have observed a pattern of inherited idiotype expression in three mouse strains that is unexpected from the genetics of the strains: a dominant idiotype that was expressed at high levels in two parental strains was expressed only at low levels in a heavy chain allotype congenic strain derived from them. In the C3H.SW strain, the antibody response to the class II MHC Ag I-E is of limited diversity, with dominant expression of an idiotype and the V kappa 21 L chain. The C57BL/10 strain expresses the same idiotype at high levels, whereas the CWB/12 strain, which was derived by replacing the Ig H chain Igh-Cj allele of C3H.SW with the Igh-Cb allele derived from C57B1/10, has been found to express little of this dominant idiotype. CWB/12 responds, with titers equal to those of the parental strains, to the I-E epitope responsible for dominant idiotype expression, and it expresses normal V kappa 21 levels; thus deficiencies in epitope-specific responsiveness or in V kappa 21 expression cannot explain the low Id expression in CWB/12. Furthermore, Southern blot analysis of three VH families gave no evidence of recombination within the the VH locus of CWB/12, which was Igh-Vb throughout. Black-cross analysis demonstrated that expression of the dominant idiotype segregated independently of Ig allotype, and was therefore due to genes unlinked to the H chain gene locus. To our knowledge, this pattern of Id expression is unprecedented, and indicates the need for caution in the interpretation of studies using allotype congenic strains. It also demonstrates a role for genes outside the Igh locus in the control of Id expression.     

Polymorphism of kappa variable region (V kappa-1) genes in inbred mice: relationship to the Ig kappa-Ef2 serum light chain marker

We describe here the cloning and complete sequence analysis of the rearranged kappa variable region gene from the V kappa-1A-producing myeloma (C.AL20-TEPC-105). A 5'-flanking region probe from the V kappa-1A gene has been used to study the V kappa-1 germ-line gene family in strains of mice differing at the Ig kappa-Ef2 locus. All Ef2a strains examined possess an identical pair of BamHI restriction fragments strongly hybridizing to the 5' probe. Surprisingly, only two of the six strains of mice previously designated Ef2b (NZB and C58) possessed clearly altered restriction fragment sizes for V kappa-1 genes. The remaining four Ef2b strains, namely BDP/J, CE/J, I/LnJ, and P/J, appear to carry V kappa-1 genes similar to those of Ef2a strains. It is suggested that these strains may carry a third form of the V kappa-1A gene, differing in the protein coding region but indistinguishable at the DNA level with the use of BamHI or EcoRI. Alternatively, these strains may fail to express V kappa-1A light chains due to a regulatory defect involving this subgroup of kappa genes.     

Genetic control of antibody specificity in the mouse

Genetic markers related to the antigen binding specificity of mouse immunoglobulins (idiotypes and fine specificity characteristics) are used to investigate the polymorphism of genes encoding heavy chain variable regions (V _H genes). The distribution of eight such specificity related markers in inbred strains and their segregation together with allotype indicate linkage to genes that specify the heavy chain constant regions (C _H genes). A number of recombinant mice allowed the construction of a chromosomal map consisting of threeV _H subloci, oneC _h sublocus, and a region which contains nonimmunoglobulin coding genes. All data are consistent with a linear arrangement of genes in this linkage group so thatV _H andC _H genes are discontinuous. Each of theV _H subloci is correlated to a particular set of antigen binding specificities which include protein antigens, polysaccharides, and haptens. This suggests that specific complementarity determining sequence portions are conserved in the germ line of the mouse.     

Influence of IgH V-region genes on the growth kinetics of a murine B cell leukemia (BCL1)

The growth kinetics of an IgM-bearing B cell leukemia of BALB/c (Ig-1a) origin, designated BCL1, has been investigated in 2 allotype immunoglobulin (Ig) heavy (H) chain congenic strains, C.B-20 (Ig-1b) and C.AL-20 (Ig-1d), and an (H) chain recombinant strain, BAB-14 (Ig-1a/1b), that carries Ig-1a genes in the variable (V)-region and Ig-1b genes in the constant (C)-region. When large numbers (10(6) to 10(7)) of BCL1 cells were injected into these mice, leukemia, as measured by the appearance of leukemic cells in peripheral blood with subsequent mortality, did not occur in C.B-20, was delayed in C.AL-20, and progressed at the same rate in BAB-14 relative to BALB/c control mice. These results indicate that an immune response directed against an antigen encoded for by an H chain V region gene (idiotype or variable-region allotype) or linked gene (minor histocompatibility antigen) prevents the growth of the BCL1 leukemia in the C.B-20 mice. Tumor resistance appears to be due to T cell activity since adoptive transfer of such cells from C.B-20 tumor rejectors protected sublethally irradiation recipients from subsequent tumor challenge. Although H-2 restricted, anti-BCL1 cytotoxic cells were detected in C.B-20 mice challenged in vivo and restimulated in vitro with BCL1 cells, evidence is discussed that suggests that the resistance observed is not due to these effector cells. The resistance of allotype congenic mice to BCL1 was not absolute; a small inoculum (10(2)) was as lethal in C.B-20 and C.AL-20 as BALB/c mice. Thus, Ig-encoded cell surface antigens, although immunogenic, in no way ensure ultimate host survival.     

Influence of the immunoglobulin heavy chain locus on expression of the VK1GAC light chain

The VK1GAC light chain represents the dominant V kappa structure employed in the antibody response of A/J mice to streptococcal group A carbohydrate ( GAC ). Two anti-idiotypic antisera, anti- Id5 and anti- Id20 , with specificity for the VK1GAC light chain were used to examine anti- GAC antibody responses in a series of inbred mouse strains that differ at the heavy chain constant region ( IgCH ) allotype locus. Both idiotypes were expressed in normal and immune sera from mice of most IgCH allotypes, except IgCHb (C57BL/6J) and IgCHf (CE/J). C57BL/6J mice expressed Id5 , but not Id20 , whereas CE/J mice did not express either idiotype. Testing of recombinant inbred strains between BALB/c and C57BL/6 indicated that the pattern of idiotype expression did not correlate with IgCH allotype. The C X B recombinants expressed all three idiotype patterns that were observed in the panel of inbred strains. Testing of allotype congenic mice between BALB/c and C57BL/6 showed that CB.20 and BC.8 mice were Id20 -, whereas BAB-14 mice were Id20 +, indicating that both VH and background (V kappa or regulatory) loci must be derived from BALB/c to obtain Id20 expression. The difference in the frequency of idiotype expression observed between BALB/c and BAB-14 mice indicates that the IgCH locus may exert a quantitative influence on the expression of this light chain. To examine the Id20 -, Id5 + antibodies of C57BL/6 mice, anti- GAC hybridomas were prepared. Of 16 C57BL/6-derived anti- GAC monoclonal antibodies, six were reactive with anti- Id5 and not with anti- Id20 . Isoelectric focusing of the purified kappa light chains from three of these antibodies revealed two distinct spectrotypes that co-migrated with the two known VK1GAC spectrotypes observed with A/J anti- GAC light chains. Idiotypic analysis of in vitro recombinants between the heavy and light chains of A/J and C57BL/6 monoclonal antibodies demonstrated that the C57BL/6 light chains were idiotypically similar to A/J light chains when they were free in solution or paired with A/J heavy chains. These results demonstrate that C57BL/6 mice can express a light chain that is very similar, if not identical, to the VK1GAC light chain, although the light chain is expressed in lower frequency and is paired with a distinct VH structure, which can mask expression of one of the VK1GAC idiotypes. These effects on V kappa expression map to at least three genetic loci: VH, CH, and an unlinked locus.     

Duplications and deletions of Vh genes in inbred strains of mice

evolution of variable region (Vh) gene family copy number and polymorphism was investigated by the analysis of the immunoglobulin heavy chain variable region (Igh-V) locus in 74 inbred strains and substrains of mice. Several strains were found to have slight differences from Igh-V haplotypes previously identified, usually of a single Vh gene family. These results indicate that the evolution of copy number in the mouse Igh-V locus proceeds largely by the accumulation of incremental changes, reflecting the clustered organization of the mouse Igh-V locus. We have found no evidence of very large or frequent duplication or deletion events indicative of rapid expansion or contraction processes. The existence of one or more particularly large Vh gene families most likely reflects random copy number variation, rather than selection for the amplification of their members. The identification of strains with recombinant Vh gene arrays demonstrates that recombination, both within and between haplotypes, appears to be the predominant mechanism generating the high restriction fragment length polymorphism in the Igh-V locus.Abbreviations used in this paper Igh-V immunoglobulin heavy chain variable region locus - Vh heavy chain variable region gene - Dh heavy chain diversity region gene - V immunoglobulin kappa light chain variable region gene - V T-cell receptor beta chain variable region gene     

Allelic polymorphism of murine IgE controlled by the seventh immunoglobulin heavy chain allotype locus

Two alloantisera against hybridoma-derived IgE detected allotypic determinants expressed on the murine s chain. An antiserum raised in BALB/c mice against monoclonal IgE of C57BL/6 origin reacted exclusively with IgE of strains having Igh-1^b (IgG_2a) allotype. The second antiserum, C57BL/6 anti-BALB/c monoclonal IgE, reacted with IgE of strains having Igh-1^a, Igh-1^d, Igh-1^e and Igh-1^j allotypes. The genetic studies of (BALB/c x C57BL/6)F₁ and backcross F₂ animals indicated that the locus controlling the IgE allotype is linked to the Igh-1 locus. This was further confirmed by the possession of respective IgE allotypes by Igh-C congenic mice, BALB/c and BAB-14, C3H.SW/Hz and CWB/Hz. Thus, the allotype detected on the chain is controlled by the seventh murine immunoglobulin allotype locus, and should be designated as the Igh-7 allotype.Abbreviations used in this paper PCA passive cutaneous anaphylaxis - RID radioimmunodiffusion - i.p. intraperitoneally - EA egg albumin - Igh-C immunoglobulin heavy chain constant region locus - DNP 2,4-dinitrophenyl - PBS phosphate-buffered saline - NMS normal mouse serum - KLH keyhole limpet hemocyanin Visiting investigator supported by the Scientific and Humanistic Development Council from the Central University of Venezuela, currently at the following address: Consejo de Desarrollo Cientifico y Universidad Central de Venezuela, Av. Principal Urb. La Floresta Ota., Silenia Caracas, Venezuela.     

Allelic forms of the immunoglobulin heavy chain variable region

The complete variable region sequence of the heavy chain from a phosphorylcholine-binding myeloma protein of C57/BL allotype has been determined. When this sequence was compared with the germ line-coded heavy chain variable region sequence of BALB/c phosphorylcholine-binding proteins, five differences were observed. Four of the substitutions were located in the framework portion of the variable region and the fifth in the "J" or joining segment. Two of the framework substitutions were found at positions 14 and 16. Previous studies have shown that heavy chains from all anti-phosphorylcholine antibodies induced in C57/BL mice have the same amino acids at positions 14 and 16 as the C57/BL myeloma protein described in this communication. It has therefore been concluded that these residues are encoded in the C57/BL germ line in contrast to two alternatives in the BALB/c genome. This finding, in addition to the 96% homology found between the C57/BL and BALB/c sequences, suggests that these structures represent allelic forms of an entire variable region.     

Influence of the Ig H chain locus on autoantibody production in autoimmune mice.

Autoimmune disease is influenced by multiple genes. In this study, we investigated the role of one genetic locus, Ig H chain. IgG2a antichromatin, anti-ssDNA, and antihistone autoantibodies (autoAb) from (MRL/Mp-lpr/lpr x C57BL/6-lpr/lpr), (Ighj/b); (C57BL/6-lpr/lpr x C57BL/6-lpr/lpr-Igha), (Ighb/a); and (MRL/Mp-lpr/lpr x MRL/Mp-lpr/lpr-Ighb), (Ighj/b) mice were determined using allotype-specific ELISA. Strikingly, antichromatin and antihistone antibodies (Ab) were comprised of significantly more b allotype than either a or j allotype in all cohorts of F1 mice examined. In mice that produced anti-Sm Ab, the b allotype was used preferentially for these autoAb as well. However, no allotype skewing was observed in IgG2a Ab directed against TNP or DNA, or for total IgG2a. An Igh recombinant locus was utilized to examine the genetic control of b allotype skewing in lpr mice and in chronic graft vs host disease. In both models, the VH region did not appear to be responsible for the preferential use of b allotype. These results indicate a contribution to autoimmunity by the Igh locus and raise the possibility that Ig allotype may influence autoimmune disease by its effect on the production of certain autoAb.     

Amino acid sequence of the N-terminal sixty-nine residues of heavy chain derived from a homogeneous rabbit antibody

The sequence of the N-terminal 69 residues of heavy chain from a homogeneous rabbit antibody to type III pneumococcal polysaccharide was determined. The sequence is similar to that found in heavy chains of normal pooled rabbit immunoglobulins of the same allotype Aa1. Two regions of the homogeneous heavy chain (residues 35-46 and 62-69) are very similar to corresponding regions of heavy chains from rabbit Aa2 immunoglobulin, as well as from mouse, guinea-pig and human immunoglobulins. In contrast, residues 47-62 appear to be variable. Comparison in this section with another homogeneous anti-pneumococcal antibody (Strosberg et al., 1972) of related specificity and of the same allotype indicates sequence variation in at least three positions. An antibody to group C streptococcal carbohydrate of allotype Aa2 (Fleischman, 1971) differs by five amino acids in the same region of the heavy chain. Sequence variability between these three antibodies does not occur in homologous positions within this variable section. Allotype-related sequences could not be identified in section 34-65.     

The heavy chain genes of a lupus anti-DNA autoantibody are encoded in the germ line of a nonautoimmune strain of mouse and conserved in strains of mice polymorphic for this gene locus

The variable region of the heavy chain of a prototypic anti-DNA autoantibody from the lupus-prone mouse, MRL-lpr/lpr, was cloned and sequenced. The VH and JH genes expressed by this antoantibody were found to be identical to germ line genes from the nonautoimmune mouse strain, BALB/c. The D gene of this autoantibody differed by one nucleotide from several members of the germ line SP2 family, but has been found in expressed D genes from several strains of mice. These results show that a normal mouse strain contains all of the structural information necessary for the expression of the heavy chain variable region of a lupus autoantibody. A fragment that is present in both BALB/c and MRL mice is highly homologous in both coding and flanking sequences to the autoantibody VH gene (VH130) and is the same size as the BALB/c germ line gene. This suggests that these two strains may share the same allele of this VH gene, despite the fact that they are polymorphic for this VH gene family. Other mouse strains that are polymorphic for this locus contained one to three VH genes that were highly related to VH130 in both coding and flanking regions. Thus, VH genes that may be allelic to the antibody VH gene or that may have arisen by gene conversion, unequal crossing over or gene duplication, are conserved in many mouse strains.     

Lupus prone (SWR x NZB)F1 mice produce potentially nephritogenic autoantibodies inherited from the normal SWR parent

The incidence of nephritis in autoimmune NZB mice is low, but when they are crossed with normal SWR mice, almost 100% of the female F1 hybrids (SNF1) develop lethal glomerulonephritis. To define the contribution of the normal SWR strain to the development of nephritis, we analyzed 65 monoclonal anti-DNA autoantibodies derived from SNF1 mice and compared them with those obtained from the NZB parent. The majority of the SNF1-derived anti-DNA antibodies were IgG and cationic in charge. By contrast, 77% of the NZB-derived antibodies were IgM. Moreover, all three NZB-derived IgG anti-DNA antibodies were anionic. The cationic property of the SNF1-derived IgG autoantibodies was not restricted to any particular antigenic specificity pattern or IgG subclass, nor was there a preference for the allotype of either parent. However, we identified a set of highly cationic (pI at 8.2 to 8.8 pH) IgG2b anti-DNA antibodies from SNF1 hybrids that had the SWR allotype. Isoelectric focusing of intact antibodies and isolated heavy and light chains showed that the highly cationic charge of these antibodies was determined by the variable regions of their heavy chains. Because IgG anti-DNA antibodies with cationic charge are especially pathogenic, those antibodies bearing the allotype of the normal SWR parent may account for the high incidence of severe nephritis in the F1 hybrids. The results indicate that pathogenic autoantibodies, which are encoded by genes of the nonautoimmune SWR parent, are expressed in the SNF1 mice due to some cellular and genetic regulatory influence of the NZB parent.     

Allelic polymorphism of mouse Igh-J locus,which encodes immunoglobulin heavy chain joining (JH) segments

The mouse genome contains four functional J _H genes, which encode immunoglobulin heavy chain joining segments. The J _H gene cluster is located a few kilobases 5 from the constant region genes (C genes) on chromosome 12. The polymerase chain reaction (PCR)-technique was used to amplify DNA stretches from mouse genome of approximately 1 340 nucleotides in length containing all four J _H genes (Igh-J locus). PCR products were directly used as templates in Sanger's dideoxy-sequencing, and sequences were determined. Twelve inbred mouse strains belonging to ten different Igh-C haplotypes were studied. The strains were: BALB/c, C58/J, RIII, DBA/2, CE, RF, CBA, NZB/J, AKR, C57BL/10, SJL, and A/J. Five allelic forms of the Igh-J locus were found among these strains. The A/J mouse has an allele (e) which differs from the BALB/c allele (a) by 15 nucleotides. C57BL and SJL have the allele (b) with eight differences from BALB/c. The CBA allele (j) has two differences, and the CE allele (f) has a single nucleotide difference compared with the BALB/c sequence. Based on the J _H , variable (V) and constant (C) region sequences we conclude that independent reshuffling of V _H ,J _H , and C _H gene clusters occurred during the evolution of Mus musculus.The nucleotide sequence data reported in this paper have been submitted to the EMBL nucleotide sequence database and have been assigned the accession numbers X63146-X63175.     

Characterization of allelic V kappa-1 region genes in inbred strains of mice

Germ line genes encoding mouse Ig kappa-chains belonging to the V kappa-1 group have been isolated from BALB/c, NZB, and CE, three inbred strains of differing kappa haplotype. The V kappa-1A and V kappa-1C germ line genes isolated from BALB/c (Ig kappa c) were identical to those previously described. These are the two major V kappa-1 germ line genes in BALB/c and together account for 40 of the 53 expressed V kappa-1 sequences that have been reported to date. Allelic differences in a single germ line variable region gene (V kappa-1A) in different strains of mice explain the differences in L chain IEF patterns previously associated with the Ig kappa-Ef2 locus. The rearranged kappa-gene expressed in the BALB/c myeloma MOPC-460 has been isolated and found to represent a V kappa-1A somatic variant differing by three nucleotides from the germ line V kappa-1A gene. Germ line genes isolated from NZB (Ig kappa b) and CE (Ig kappa f) show greater than 95% identity with the BALB/c genes over the 1700 nucleotides compared. Comparison by region indicated the greatest conservation of sequence occurs in and around the leader exon followed by the V-region exon. The NZB gene encodes the amino acid sequence found in the myeloma PC-2205, previously designated V kappa-1B. The V kappa-1 gene isolated from CE is likely an allele of the BALB/c V kappa-1C gene as the two share greater than 96% identity over 1700 nucleotides. The CE gene has been designated V kappa-1Cf. Ancient remnants of LINE-1 repetitive elements were detected approximately 400 bp downstream of all of the V kappa-1 genes. These possess greater homology with repetitive elements found near other kappa genes than they do with the native L1Md sequence.