Double light-chain production by leukemic cells of common clonal origin: a case report with review of pertinent literature

Presence of somatic hypermutation and activation-induced cytidine deaminase in acute lymphoblastic leukemia L2 with t(14;18)(q32;q21)

AIM

Acute lymphoblastic leukemia (ALL) with L2 (FAB) morphology has rarely been reported to show t(14;18)(q32;q21). We aimed to delineate the stage at which this type of ALL is derived in B-lineage differentiation.

METHODS

The somatic hypermutation (SHM) of the variable region of immunoglobulin heavy chain (IgV(H)) gene and the expression of terminal deoxynucleotidyl transferase (TdT), recombination-activating gene 1 and 2 (RAG-1 and -2), and activation-induced cytidine deaminase (AID) were investigated in three cell lines and two fresh samples, including a pair of matched fresh and cell line cells.

RESULTS

TdT, RAG-1, and RAG-2 were variably expressed. AID was expressed in four of five samples. SHM of the IgV(H) gene was found in all samples with high average frequency (11.84%) comparable with that in follicular lymphoma. Ongoing mutation was seen in two fresh samples.

CONCLUSION

As AID and SHM are generally regarded as properties exhibited by mature B cells, the presence of AID and SHM in this study seems to be incompatible with the general understanding of the early stage derivation of ALL in B-lineage differentiation. The results here give some insight into the relationship between disease type (ALL or lymphoma) and derivation stage, the overlapping of the early stage phenotype and the mature genomic characteristics, and the probable relationship between the mechanism of the occurrence of t(14;18)(q32;q21) and the machinery causing SHM.

A novel L3-acute lymphoblastic leukemia cell line (BALM-27) carrying cytoplasmic immunoglobulin 8 chain but lacking expression of cell surface immunoglobulin chains

A human acute lymphoblastic leukemia (ALL) cell line, BALM-27, was established from the peripheral blood specimen of a patient with B-cell ALL L3 type (ALL-L3) at diagnosis. As with the original leukemia cells, the established line was negative for all cell surface immunoglobulin (Ig) chains, but carrying only cytoplasmic Ig delta heavy chain. Southern blot analysis of the various Ig chain genes demonstrated homozygous deletion of the Jkappa gene, germ line configuration of the Jlambda and rearrangement of IgJH genes. Cytogenetic analysis of both primary leukemic bone marrow and BALM-27 cells showed the der(8;15)(q10;q10) chromosomal alteration, in addition to the t(8;22)(q24;q11) abnormality which is highly associated with ALL-L3 and Burkitt's lymphoma. The established cell line BALM-27 represents a rich resource of abundant, accessible, and manipulable cell material for analyzing the unique expression of Ig chain and for investigating the pathogenesis of B-cell malignancy. The scientific significance of BALM-27 lies in (1) the rarity of this type of leukemia cell lines, and (2) its unique chromosomal aberrations.

Establishment of novel B-cell precursor leukemia sister cell lines NALM-36 and NALM-37: shift of immunoglobulin phenotype to double light chain positive B-cell

Two novel B-cell precursor (BCP) acute lymphoblastic leukemia (ALL) sister cell lines, designated NALM-36 and NALM-37, were established from the peripheral blood (at diagnosis) and bone marrow (at relapse) of a 37-year-old woman with ALL. Immunophenotyping showed BCP type III pre-B cell characteristics including TdT, CD10, CD19, CD22, CD79a and HLA class II. T cell and myeloid-associated antigens tested were negative except CD5 which was 100% positive for both cell lines. The surrogate light chains lambda5 and VpreB were positive for both cell lines. Cytogenetic analysis of NALM-36 revealed an abnormal karyotype with 46, XX, add(1)(q?42), -14, +mar. Southern blot analysis of the immunoglobulin (Ig) genes status of NALM-36 at 10 months after establishment showed germ line configuration of the kappa light chain gene, and rearrangement of the lambda light and mu heavy chain genes. At 16 months we detected a phenotypic shift of Ig chain protein expression from a BCP-III pre-B cell phenotype to a BCP-IV mature B cell phenotype, with kappa and lambda double Ig light chain and mu heavy chain expression, both on the cell surface and in the cytoplasm. We designated this subline as NALM-36KL. Authenticity of the NALM-36KL, NALM-36 and NALM-37 cell lines was demonstrated by DNA fingerprinting. The extensive characterization of the sister cell lines suggests that these three novel cell lines, derived from a single patient, may represent unique and relevant in vitro model systems for BCP-type leukemia cells. They may provide useful models and unprecedented opportunities for analyzing the multitude of biological aspects of normal and neoplastic B-lymphocytes and their precursors.

Simultaneous expression of kappa and lambda light chains in a murine IgG3 anti-Cryptococcus neoformans hybridoma cell line

Allelic exclusion normally results in the expression of only one light and one heavy chain gene. However, some hybridomas have been reported to express two different heavy chain genes. Here we report that the IgG3 hybridoma 4H3.C8B expresses both kappa and lambda light chains. 4H3.C8B was originally recovered by screening for antibody binding to Cryptococcus neoformans polysaccharide antigen and characterized as gamma 3 lambda. The gamma 3 lambda but not the gamma 3 kappa binds to polysaccharide antigen. Some of the antibody molecules were heterodimers composed of both lambda and kappa. IgG1 and IgG2b isotype switch variants were identified and isolated by the technique of sib selection, using the ELISA spot assay. Like the parent IgG3 line, the switch variants continued to express both kappa and lambda light chains but only the lambda-containing antibodies bound to the antigen. Our experience suggests that hybridomas recovered by assays that are antigen dependent should also be tested for the expression of other isotypes and light chains in a non-antigen-binding immunoassay.

Unusual patterns of immunoglobulin gene rearrangement and expression during human B cell ontogeny: human B cells can simultaneously express cell surface kappa and lambda light chains

Immunoglobulin gene rearrangement during mammalian B cell development generally follows an ordered progression, beginning with heavy (H) chain genes and proceeding through kappa and lambda light (L) chain genes. To determine whether the predicted kappa-->lambda hierarchy was occurring in vitro, we generated Epstein-Barr virus-transformed cell lines from cultures undergoing human pre-B cell differentiation. A total of 143 cell lines were established. 24 expressed cell surface mu/lambda by flow cytometry and were clonal by Southern blotting. Surprisingly, two of the mu/lambda-expressing cell lines contained both kappa alleles in germline configuration, and synthesis/expression of conventional lambda L chains was directly proven by immunoprecipitation/sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in one of them. Thus, human fetal bone marrow B lineage cells harbor the capacity to make functional lambda L chain gene rearrangements without rearranging or deleting either kappa allele. A third unusual cell line, designated 30.30, was observed to coexpress cell surface kappa and lambda L chains associated with mu H chains. The 30.30 cell line had a diploid karyotype, a single H chain rearrangement, both kappa alleles rearranged, and a single lambda rearrangement. Immunoprecipitation/SDS-PAGE confirmed that 30.30 cells synthesized and expressed kappa and lambda L chains. Multiparameter flow cytometry was used to demonstrate the existence of kappa+/lambda+ cells in fetal bone marrow and fetal spleen at frequencies of 2-3% of the total surface Ig+ B cell population. The flow cytometry data was confirmed by two-color immunofluorescence microscopy. The existence of normal human B cells expressing cell surface kappa and lambda refutes the widely accepted concept that expression of a single L chain isotype is immutable. The kappa+/lambda+ cells may represent transients undergoing L chain isotype switching.

IGM kappa/lambda EBV human B cell clone: an early step of differentiation of fetal B cells or a distinct B lineage?

In agreement with the clonal theory, one B lymphocyte synthesizes one antibody due to allelic and isotypic exclusion. We analyzed an EBV B-cell clone, E29.1, derived from an 11 week-old embryo, and secreting both IgM kappa and IgM lambda. Structural analysis of produced IgM, indicated that lambda-containing pentamers could be considered hybrid molecules, expressing both the kappa and lambda. chains, with a kappa/lambda ratio between 5 and 10. It was also found that 60% of the lambda chains were secreted in free form, presumably as a result of a better affinity of mu chains for kappa chains. The sequence of the three transcripts had an entirely ORF (Open Reading Frame), and were very close to germline sequences, with, however, an additional codon between V kappa and J kappa gene which has never been described in adult myeloma protein or cDNA human sequence. This observation is suggestive of N diversity taking place in kappa chains. The possible role of Kde (kappa deleting element) recombination onto kappa/lambda locus activation was analyzed on a collection of 23 lambda clones. The status of rearrangement of kappa genes indicated that 35% of these clones had retained, at least, one kappa allele without the Kde recombination, four lambda clones had one kappa allele in germline configuration. Different hypotheses of maturation from pre-B cell to B cell with activation of light chain genes are discussed.

Monoclonal origin of B cells producing k, lambda and k lambda immunoglobulin light chains in a patient with chronic lymphocytic leukemia

Immunoglobulin gene rearrangements can be used as genetic markers of clonality in the study of B-cell populations [4]. We have therefore analysed the structure and expression of heavy and light chain immunoglobulin genes in lymphocytes of a patient with chronic lymphocytic leukemia, where we found both k and lambda producing B cells, but in most of the cells both k and lambda chains were co-expressed on the same surface membrane. Single rearrangements were observed in mu, JH, k and lambda DNA sequences, thus providing strong evidence for the monoclonal origin of the cells bearing different light chains. Moreover, the analysis of Ig sequence RNA showed, in addition to normal mu, k and lambda mRNA molecules, high levels of a small lambda related RNA sequence. These findings are discussed in relation to a model of B-lymphocyte differentiation which could be either an additional or an alternative hypothesis to the current one of isotypic exclusion.

Biclonal and hypodiploid multiple myeloma

Plasma cell DNA and RNA content was measured by flow cytometry of acridine orange-stained bone marrow cells from 72 untreated patients with multiple myeloma. Biclonal or hypodiploid DNA stemlines were identified in 10 patients, nine of whom had a low RNA content and did not have response to chemotherapy. Biclonal tumors often showed atypical myeloma protein changes with chemotherapy, suggesting that one clone was reduced whereas the other remained unchanged. These findings suggest a genetic basis for the resistance of low RNA tumors to chemotherapy.

Cytoplasmic immunoglobulin content in multiple myeloma

Bone marrow cells of 82 patients with multiple myeloma were subjected to flow cytometric analysis of DNA and cytoplasmic immunoglobulin (CIg) content using propidium iodide and direct immunofluorescence assays. Except for two patients with nonsecretory myeloma, there was conformity in the immunoglobulin type derived from immunoelectrophoresis and plasma cell CIg staining. One patient with nonsecretory myeloma exhibited monotypic CIg staining, while the second showed no reaction. In eight patients with IgG lambda myeloma, the same tumor cells contained both lambda and kappa light chains, suggesting the productive rearrangement of both light chain genes. 14 patients with previously unrecognized plasma cells of low RNA content, all of whom were resistant to chemotherapy, were identified by CIg staining. By revealing previously unrecognized plasma cells with low RNA content, CIg analysis identified more patients with treatment-refractory myeloma.

Biclonal B-cell lymphoma

The cells of most tumors are considered to be genetically homogeneous because they are assumed to represent a single clone descended from one abnormal cell. We have discovered three cases of B-cell lymphoma for which this generalization is not true. In each case, the tumor was composed of two subpopulations of cells, each expressing a different immunoglobulin molecule. Antibodies directed against these immunoglobulins were used to separate the two cell subpopulations of each tumor on a fluorescence-activated cell sorter. DNA extracted from the original tumor and the two fractionated subpopulations was analyzed to determine the configuration of immunoglobulin genes. Differences were found in the arrangement of DNA in at least one immunoglobulin gene for each of the two subpopulations. Thus, biclonality of these tumors was revealed by examination of both protein markers (cell-surface immunoglobulin) and DNA markers (immunoglobulin-gene rearrangements). Our results indicate that the incidence of biclonal B-cell lymphoma may be higher than previously recognized, possibly as high as 10 per cent of all B-cell lymphomas. Furthermore, our findings may have important implications for the diagnosis and therapy of lymphoid cancers.

Biclonal IgM gammopathy in a lymphoproliferative disorder

An unusual case of an IgM producing lymphoproliferative disorder is presented. Using immunofluorescent techniques, this study shows that the heavy chain is associated with kappa light chain in some cells, and with lambda light chain in other cells. This indicates the presence of two distinct malignant cell populations in this patient.

Malignant lymphoma with a high content of epithelioid histiocytes (so-called Lennert's lymphoma). Immunocytochemical and ultrastructural observations

The clinicopathological findings of four cases of an uncommon form of non-Hodgkin's lymphoma called malignant lymphoma with a high content of epithelioid histiocytes (MLHH) are described. In each case the peroxidase antiperoxidase technique was used for detecting cytoplasmic immunoglobulins (CIg) in the diagnostic lymphoid tissue. In one case (patient 1), IgG and IgM heavy chains and kappa light chain were detected in 30 to 40 percent of the atypical lymphoid cells. This result suggests that the proliferating B lymphocytes in this patient with MLHH are neoplastic rather than reactive in nature. We were unable to identify CIg in the proliferating lymphoid cells of the other three patients. Our case when coupled with others reported in the literature suggest that the morphologic features of MLHH (so-called Lennert's lymphoma) can be associated with a neoplastic proliferation of either T or B lymphocytes. The ultrastructural findings of one case are presented.