Analysis of tumor-specific immunoglobulin gene rearrangement in peripheral blood B-cells of multiple myeloma patients

The search for bone marrow clone neoplastic precursors in the peripheral blood of multiple myeloma (MM) patients has been the subject of a number of studies which, using different methodological approaches, have led to conflicting results. With the aim of contributing toward resolving this controversy, immunoglobulin (Ig) gene rearrangement in the bone marrow mononuclear cells (BMMC) and B-lymphocyte enriched peripheral cells (BePBC) of 11 appropriately selected advanced MM patients was studied by means of Southern blotting. Peripheral mononuclear cells (PBMC) and BePBC were studied immunophenotypically by evaluating the presence of cytoplasmic Ig positive cells (CyIg+) and CD19/PCA-1 reactivity. A pattern of Ig gene rearrangement identical to that observed in the respective BMMC was found in only two patients who, moreover, had a significant number of CyIg+ cells. Ig gene rearrangement was not found in any of the remaining patients who showed no evidence of the presence of CyIg+ cells, although there were CD19/PCA-1 positive cells. Consequently, the significance of the presence of malignant pre-plasma cell peripheral B-lymphocytes needs to be reconsidered and, in any case, these cells should be looked for in cell populations greatly enriched in B-lymphocytes and, above all, completely lacking in plasma cells or CyIg+ cells.

Southern blot analysis in a case of Richter's syndrome. Evidence for a postrearrangement heavy chain gene deletion associated with the altered phenotype

Richter's syndrome (RS) can be defined as the emergence of an aggressive lymphoma in patients suffering from chronic lymphocytic leukemia (CLL). The authors performed immunophenotypic and Southern blot analysis of the peripheral blood and tissue specimen of a patient with RS. Using immunoperoxidase and immunogold-silver staining techniques and a panel of monoclonal antibodies, the authors found that the large cells characteristic of RS showed an altered immunophenotype as compared with the CLL cells and did not express mu heavy chain. Southern blot analysis revealed identical kappa light chain rearrangements in both tumoral cell populations consistent with a common clonal origin. Using the JH probe and several restriction enzymes, the authors also found evidence for a postrearrangement deletion of the heavy chain mu gene. These findings suggest that in this case of RS, a deletion of the heavy chain mu gene resulted in loss of mu expression by the larger cells that were characteristic of RS and was associated with their altered phenotype.

Endogenous immunoglobulin expression in mu transgenic mice

Transgenic mice (M54) containing a functional mu heavy chain were examined to determine the effects of the transgene on rearrangement and expression of endogenous immunoglobulin genes. Two major novel findings are presented. (i) In transgenic mice, the expressed endogenous VH repertoire in LPS-generated B cell blasts and hybridomas is skewed toward expression of JH-proximal VH families (VH7183 and Q52). (ii) There is an increase in the frequency of B cells expressing lambda light chain genes in transgenic mice. Furthermore, in Abelson-MuLV transformed pre-B cells, VH to DJH is inhibited more than the D to JH rearrangement. The results presented indicate that the transgene skews the expressed VH repertoire by inhibiting the VH to DJH rearrangement while permitting an expansion of B cells expressing limited VH and lambda light chain genes.

Establishment and characterization of a new human B-cell line (ONHL-1) from non-Hodgkin's lymphoma: constant expression of bcl-2 gene during mitogen-induced growth inhibition

A new B-cell line (ONHL-1) was established from non-Hodgkin's lymphoma. ONHL-1 was free from Epstein-Barr virus nuclear antigen and expressed CD20, CD24, and slg (mu, delta, gamma and kappa), thus being equivalent to the mature B-cell stage. Chromosome analysis revealed a markedly abnormal pattern including 14q+ and 6q-. In accordance with the positive expression of surface kappa light chains, one of the kappa genes was found to be rearranged. However, rearrangement of the lambda locus was also detected, contrary to the supposed hierarchy for the rearrangement of the light-chain genes. Further, the rearranged fragments of the JH, C lambda, and bcl-2 genes were of the same size in the EcoRI and HindIII digests on the same filter. This may suggest that the bcl-2 gene is juxtaposed with the JH and C lambda locus. The proliferation of ONHL-I was inhibited by adding Staphylococcus aureus Cowan 1 or 12-O-tetradecanoyl-phorbol-13-acetate. During this growth inhibition, the expression of c-myc decreased, while that of bcl-2 mRNA remained steady. This result suggests that not the bcl-2 gene but other oncogenes, such as c-myc, play a key role in the proliferation of ONHL-1. This agrees with the hypothesis that the bcl-2 gene is not concerned with aggressive proliferation but with cell survival. This new cell line will therefore be of value in studying the differentiation and tumorigenesis of B cells.

Detection of minimal residual disease in acute lymphoblastic leukemia using immunoglobulin hypervariable region specific oligonucleotide probes

To develop a sensitive and specific assay for minimal residual disease in acute lymphoblastic leukemia (ALL), we exploited the enormous diversity of genomic sequences created by immune receptor gene rearrangements. To isolate clone-specific sequences, we first synthesized oligonucleotides that match conserved variable (VH) and joining (JH) sequences flanking the third hypervariable region (HVR3) in the rearranged immunoglobulin heavy chain (IgH) locus. In polymerase chain reactions (PCR), these primers were then used to amplify the intervening HVR3 segments from leukemic DNA samples. Of 12 B-lineage ALLs studied, ten generated one or more fragments of the size expected for HVR3 gene segments. Thus, this single pair of amplimers was sufficient to isolate HVR3 sequences from a majority of acute lymphoblastic leukemias. To verify that the amplified fragments originated from HVR3 alleles and to assess their diversity, we sequenced 7 PCR products derived from 6 leukemias. In addition to elements of recognized D segments, each of the 7 fragments contained novel VH-D and D-JH junctional sequences, including N nucleotides, not known to be present in the germline. Each sequence was unique, and allele-specific oligonucleotide probes hybridized only to HVR3 segments from which the probes were derived. Therefore, as anticipated, these HVR3 segments appeared to possess the diversity required to serve as clonal markers for leukemic populations. To demonstrate that these amplified HVR3 alleles could serve as the basis for a sensitive and specific assay to detect rare leukemic cells, we analyzed in detail one pre-B leukemia that had rearranged 2 IgH alleles. The HVR3 sequences were shown to be linked to rearranged JH-containing restriction fragments in digests of genomic DNA, establishing their origin in the leukemic cells. We synthesized oligonucleotides corresponding to the unique junctional sequences in the HVR3 segments. Using these novel amplimers in an allele-specific amplification and hybridization procedure, we showed that this assay can detect 10 leukemic cells in a background of 10(6) normal blood mononuclear cells. In contrast, the leukemic HVR3 sequences were not detected in extracts of normal or unrelated remission leukemic leukocytes. We conclude that the assay for specific IgH HVR3 sequences is a realistic strategy for detection of minimal residual disease in B-lineage ALL.

Immunophenotypic and genotypic characterization of primary non-Hodgkin's lymphoma of the gastrointestinal tract

Antigen receptor gene rearrangement studies have been applied to gastrointestinal (GI) lymphoid proliferations in only a limited number of cases, and their use and contribution to the diagnosis and characterization of GI lymphomas is unknown. We retrospectively studied 17 cases of primary GI lymphoma using fresh/frozen tissue with a combination of immunophenotypic and genotypic techniques. The vast majority of the neoplasms were B-cell lymphomas (88%) with rare T-cell tumors. The most common B-cell immunophenotype was IgM-kappa (40%), while five of the B-cell lymphomas (33%) lacked surface light chain immunoglobulin. Immunophenotypic evidence of histiocytic differentiation was not identified. Clonality was confirmed in 59% (10/17) of the neoplasms by immunophenotyping and 88% (15/17) by antigen receptor gene rearrangement studies. All of the 15 B-cell lymphomas (100%) demonstrated clonally rearranged immunoglobulin gene rearrangement. The two lymphomas with T-cell immunophenotypes did not demonstrate T-cell receptor beta-chain gene rearrangement. Antigen receptor gene rearrangement data can be useful and may even be necessary in certain cases for the proper classification and/or diagnosis of GI lymphoid proliferations.

Identification of a recombinational signal sequence-specific DNA-binding protein(s) of Mr 115,000 in the nuclear extracts from immature lymphoid cell lines

Rearrangements of immunoglobulin genes are mediated by highly conserved heptamer and nonamer recombinational signal sequence. Using a protein-blotting procedure, a heptamer and nonamer recombinational signal sequence-specific DNA-binding protein(s) was examined in the nuclear extracts from lymphoid and nonlymphoid cell lines. Nuclear extracts were subjected to SDS-polyacrylamide gel electrophoresis, and transferred by electroblotting to nitrocellulose filters. Then the filters were hybridized to 32P-labelled synthetic double-stranded heptamer-23bp-nonamer or nonamer-12bp-heptamer recombinational signal sequence probes. A relatively large amount of a DNA-binding protein(s) of Mr 115,000 for both probes was detected in the nuclear extracts from immature B and immature T cell lines. No DNA-binding proteins were detected in a myeloma cell line. Interestingly, this DNA-binding protein(s) might be able to recognize both heptamer and nonamer. Recombinational signal sequence-specific DNA-binding activity of the protein(s) and the presence of the protein(s) in a stage-specific manner strongly suggest that the protein(s) of Mr 115,000 detected here may play an important role in the recombination of Ig and TCR genes.

A human anti-cardiolipin autoantibody is encoded by developementally restricted heavy and light chain variable region genes

Based on recent structural analyses of monoclonal autoantibodies, it appears that a number of these antibodies express germ-line immunoglobulin variable region (V) genes with little or no somatic mutation. In addition, our group and others have noted the identity or near identity of some autoantibody-associated V genes to V genes apparently expressed preferentially in the fetal pre-B cell repertoire. To extend these data, we now report that the heavy and light chain V genes of an anti-cardiolipin antibody derived from a healthy individual display 99% nucleotide sequence homology with V genes expressed in early B cell ontogeny. Sequence comparisons indicate the likely use of fetal-restricted V genes by this autoantibody. Taken together with other data on autoantibody V gene usage, these findings provide further evidence for overlap between the autoantibody-associated and early ontogeny expressed V gene repertoires and suggest that natural autoreactivity may be instrumental in the development and maintenance of the normal immune repertoire.