Kappa Light Chain Rearrangements Research Articles

Next-Generation Sequencing-Based Clonality Detection of Immunoglobulin Gene Rearrangements in B-Cell Lymphoma.

Immunoglobulin (IG) clonality assessment is a widely used supplementary test for the diagnosis of suspected lymphoid malignancies. The specific rearrangements of the immunoglobulin (IG) heavy and light chain genes act as a unique hallmark of a B-cell lymphoma, a feature that is used in clonality assessment. The widely used BIOMED-2/EuroClonality IG clonality assay, visualized by GeneScanning or heteroduplex analysis, has an unprecedented high detection rate because of the complementarity of this approach. However, the BIOMED-2/EuroClonality clonality assays have been developed for the assessment of specimens with optimal DNA quality. Further improvements for the assessment of samples with suboptimal DNA quality, such as from formalin-fixed paraffin-embedded (FFPE) specimens or specimens with a limited tumor burden, are required. The EuroClonality-NGS Working Group recently developed a next-generation sequencing (NGS)-based clonality assay for the detection of the IG heavy and kappa light chain rearrangements, using the same complementary approach as in the conventional assay. By employing next-generation sequencing, both the sensitivity and specificity of the clonality assay have increased, which not only is very useful for diagnostic clonality testing but also allows robust comparison of clonality patterns in a patient with multiple lymphoma's that have suboptimal DNA quality. Here, we describe the protocols for IG-NGS clonality assessment that are compatible for Ion Torrent and Illumina sequencing platforms including pre-analytical DNA isolation, the analytical phase, and the post-analytical data analysis.

Incidental splenic findings in pancreatosplenectomy specimens resected for primary pancreatic lesions.

Little has been written on the frequency and nature of incidental splenic lesions diagnosed on histopathological examination of pancreatosplenectomy specimens. For 191 such specimens, incidental histological findings after haematopathologist re-review were tabulated. Cases suspicious for lymphoid malignancy underwent molecular analysis for immunoglobulin heavy and kappa light chain rearrangement. Follow-up was obtained on selected cases. In five cases (3%), the spleen was sampled but not mentioned in the original microscopic report; all were normal on re-review. Otherwise, most (171 of 186, 92%) were initially diagnosed as normal, with 160 (94%) remaining so on re-review. Findings on re-review not initially described (n=11, 6%) included four cases with splenic morphology suspicious for possible leukaemia/lymphoma involvement. Additional findings included abscess formation, foamy macrophages, necrotising granulomas and simple cysts. Fifteen spleens were initially diagnosed as abnormal; the histopathological process was confirmed in all, including non-necrotising granulomas, cysts, Gamna-Gandy bodies, foamy macrophages, involvement by pancreatic neoplasm and involvement by known chronic lymphocytic leukaemia (CLL). Molecular analysis was performed on the five cases of known/suspected lymphoma and two were positive for monoclonal gene rearrangement, including the known CLL and a previously undiagnosed case with similar immunophenotype. Incidental splenic findings are not uncommon in pancreatosplenectomy specimens. While most are of limited clinical significance, low-grade lymphoproliferative disorders may go undetected if the spleen is overlooked. We recommend careful observation of splenic findings in these specimens, with a low threshold for haematopathological consultation when in doubt.

The Use of Immunoglobulin Gene Rearrangement Polymerase Chain Reaction Assays for Detection of B-Cell Clonality for Plasma Cell Neoplasms Using Novel PCR Primers

We have designed a standardized protocol with multiplex-primer sets capable of detecting majority IG kappa (IGK) and IG lambda (IGL) light chain rearrangements in plasma cell neoplasms (PCN). Thirty primers were combined in three multiplexed PCR reactions to target IGK, KDE and IGL rearrangements. Variable region (V) primers were designed to prevent “primer dimers”, provide matching melting temperatures (Tm), minimize amplicon size, and optimize sequencing time. Amplicons were subjected to capillary gel electrophoresis for analysis. In a discovery series, we tested 37 plasma cells neoplasms PCN (28 PCNs at diagnosis and 9 PCNs post-treatment). The assay investigated an additional 52 prospective PCN cases in the validation series. Results were compared to bone marrow morphology, immunohistochemical (IHC), flow cytometry data, and standard IGH FRIII gene rearrangement assay. In the discovery series, the following sensitivities/specificities were obtained for mature B-cell neoplasms: IGH FRIII: 29.7%/100%, IGK: 80.4%/100%, KDE: 25.0%/100%, and IGL: 35.1%/96.8%. The combination of IGH FRIII, IGK, and KDE detected 83.8% (31/37) vs 67.3% (35/52) in the discovery vs validation series, respectively, for the PCN population. Interestingly, 21.2% (11/52) of the validation samples positive by IG clonality, were negative by IHC and flow cytometry. In IHC/flow cytometry positive cases with a PCN representing a tumor burden of >50%, 10% to 50%, 1% to 10%, 0% to 1% of cells, the combined sensitivity of the IG clonality assay was 100% (20/20), 72% (23/32), 53% (10/19) and 20% (1/5) respectively. This IGK/IGL clonality assay has good sensitivity at diagnosis.

Minimal Residual Disease Detection By Next Generation Sequencing in Adult B-Cell Acute Lymphoblastic Leukemia (ALL) Patients Treated on SWOG Trial S0333

▪We used next generation sequencing (NGS) of the immunoglobulin genes to evaluate minimal residual disease (MRD) in 153 specimens from 32 patients with newly diagnosed adult B cell ALL enrolled in the phase II SWOG S0333 multi-center study.We used the clonoSEQTM assay developed by Adaptive Biotechnologies that detects 1 leukemic cell in a background of 1 million nucleated cells and focuses in the B cell receptor (Ig). Initially, a set of pre-study specimens was sequenced in order to identify the precise sequence of the VDJ or DJ fragments. Clones representing more than 5% of the total repertoire of IgH molecules profiled were considered potentially leukemic. The follow-up specimen IgH repertoire sequences were compared to the diagnostic clonal ones and the leukemic marker sequence(s) previously identified were searched for explicitly.At least one Ig clonotype was detected in 29/32 (91%) cases analyzed. The 3 remaining cases were reviewed, and in 2 cases the specimens available for NGS had been reported as having no blasts by morphology.The leukemic clonal sequence was a complete VDJ rearrangement in 17/32 patients (53%), an incomplete DJ rearrangement in 8/32 patients (25%), and in 3/32 cases both VDJ and DJ rearrangements coexisted. One patient had a kappa light chain rearrangement. 17/32 (53%) cases contained more than one IgH rearrangement at diagnosis (median=2, range: 1 - 4). One of our patients is a potential case of therapy driven clonal selection. He presented at diagnosis with two related clones, one representing 75% of VDJ sequences and the second one 18%. At relapse, the second clone was responsible for most of the VDJ sequences (95%).The NGS results were compared to the MRD results detected by multiparameter flow cytometry (MFC) in 66 specimens analyzed by both methods. The concordance between the methods in the qualitative determination of the presence or absence of leukemia was 82% (54/66). In 12 specimens (18%) MRD was detected by sequencing but not by MFC. One specimen had MRD detected at very low levels by MFC and was negative by NGS.Our study includes 54 paired bone marrow (BM) and peripheral blood (PB) specimens. The median values of leukemia detected by NGS were 6-fold higher in BM than PB (range: 0.38 - 821-fold). Twenty-five pairs show no detectable MRD in either specimen. MRD was still detectable in 20 of the remaining 29 PB cases (for one of the pairs the BM specimen was negative). In 6/9 (67%) pairs of samples with disease detectable in BM but not in PB by NGS, no MRD was detected by MFC in the BM specimen.Lastly, outcome analysis was conducted in 21/32 patients with specimen available for MRD studies at the time of registration to second induction. Patients without MRD by NGS had a 5-year relapse free survival (RFS) of approximately 80%, while patients with MRD positive by both NGS and flow have the poorest outcome (p = 0.003) (see Figure). Patients with MRD detectable only by NGS have and intermediate RFS (p = 0.078, and p = 0.04 when compared to patients with MRD negative by both techniques, and patients with leukemia detected both by NGS and flow respectively). These results suggest that MRD detection by immunoglobulin gene sequencing is a very sensitive technique, and may identify patients with an excellent survival. Moreover, the increased sensitivity of the method may allow peripheral blood testing to supplement routine marrow sampling for MRD determination. [Display omitted] DisclosuresWilliamson:Adaptive Biotechnologies: Employment, Equity Ownership. Kirsch:Adaptive Biotechnologies: Employment, Equity Ownership. Robins:Adaptive Biotechnologies: Consultancy, Equity Ownership.

Under Scope of the Current Redefinition Process of Optimal Response in Multiple Myeloma: Assesment of Molecular Response by Fluorescent PCR of Ig Genes Has Similar Applicability and Prognosis Impact to Immunophenotypic Response. (A GEM/PETHEMA study),

Abstract 3951▪▪This icon denotes a clinically relevant abstract Aim:The aims of this study were on one hand, to evaluate the significance of achieving molecular response (MR) by fluorescent-PCR (F-PCR) of Ig genes in a prospective way, particularly in patients with singular cytogenetics’ features. On the other hand, to compared MR with immunophenotypic response (IR) and complete remission by immunofixation (CR). Patients: 130 new MM patients who had achieved CR or VGPR were analyzed by PCR, multiparametric flow cytometry (MFC) and immunofixation at diagnosis, and after induction therapy or transplantation: 48 patients received conventional chemotherapy as induction therapy followed with ASCT and were included in the GEM2000 trial and the other 82 patients were enrolled in the GEM2005 clinical trials in which the induction and maintenance therapy were based on Bortezomib and/or Thalidomide. Methods: The molecular analysis of Immunoglobulin (Ig) gene rearrangements at diagnosis was carried out by fluorescent PCR in DNA from bone marrow samples according to the Biomed-2 protocols. Briefly three different multiplex PCRs: DHJ; Ig Kappa light chain (IGK) rearrangements K-VJ and Kappa deleting element (KDE). DHJ and light chain rearrangements detected at the diagnosis were used in the follow-up. The sensitivity of PCR was between 1/103 and 1/104 as Martínez P. et al previously published in BJH, 2008. Regarding MFC the following monoclonal antibody combinations (FITC/PE/PerCP-Cy5.5/APC) were used at the diagnosis to identify different aberrant plasma cells phenotypes which were used as patient-specific probes for Minimal Residual Disease. Results: 64 patients had negative F-PCR and 66 patients had positive F-PCR after induction therapy. The OS was 77.32% and 59.18%, respectively and the medians OS were 116 and 67 months for each group (P= 0.03). Regarding the PFS, 28 of the 64 F-PCR negative patients relapsed while there were 44 relapses in the group of positive F-PCR. The 5y PFS was 56.44% and 27.43% respectively; the medians PFS were 60 and 36 months respectively (P= 0.0005). The multivariate analysis showed that achieving molecular response by F-PCR had a independent prognostic value in PFS (P=0.003, HR 2.3). Interestingly amongst patients who achieved CR, F-PCR identified a population of patient with a better PFS, figure A (P= 0.04, HR 2.179).The applicability of the F-PCR was almost equivalent to that observed by MFC (91.5 vs. 92%). Nevertheless we found discordant results between these two response criteria. Approximately the 20% of patients who had achieved a MR no obtained IR. The opposite pattern also was observed (IR/noMR) in 10% of the patients. In order to see if the PCR showed differences in terms of survival in patients with high or low risk cytogenetics features at the diagnosis, we made two independent analysis: in one hand we analyzed 14 patients with high-risk cytogenetics [t(4;14), t(14;16) and/or del(17p)] and on the other hand 72 patients with standard-risk cytogenetics. In the former analysis, 4 of the 8 who had negative F-PCR relapsed after the induction therapy while the totality of the other six with positive F-PCR did. The medians PFS were 32 and 17 months respectively (P= 0.0002). In connection with the 72 patients with standard-risk cytogenetics, 13 of the 34 who had negative F-PCR relapsed while 24 of the 38 with positive F-PCR did. The medians PFS times were 75 and 38 months respectively, figure B (P= 0.01). Conclusion: F-PCR of IgH rearrangements is a simple, cheap and feasible method for evaluating response in MM patients after induction therapy or transplantation. Additionally achieving MR provides a similar prognostic value to IR in patients differentially treated, and particularly in patients with singular cytogenetics’ features as well as in patients with CR by immunofixation. Disclosures:Paiva:Jansen-Cillag: Honoraria; Celgene: Honoraria. Rosiñol:Janssen: Honoraria; Celgene: Honoraria. Alegre:Janssen: Honoraria; Celgene: Honoraria. Blade:Centocor Ortho Biotech Research & Development: Research Funding. San Miguel:Janssen-Cilag: Honoraria; Celgene: Honoraria. Lahuerta:Celgene: Honoraria; Janssen: Honoraria.

Assessment of BIOMED-2 assays for detection of clonal Ig gene rearrangements in mature B-cell lymphomas

To evaluate the efficiency of the BIOMED-2 PCR assay and its implication in the diagnosis of mature B-cell non-Hodgkin's lymphomas. Clinical, morphological and immunohistochemical features of 72 cases of non-Hodgkin's lymphomas were studied, including 25 reactive lymphoid hyperplasia, 37 diffuse large B cell lymphomas (DLBCL) and 35 extranodal marginal zone lymphomas of mucosa associated lymphoid tissues (MALT lymphoma and in addition, 25 cases of reactive lymphoid hyperplasia were used as the controls). DNA was exacted from the paraffin embedded formalin fixed tissue blocks and the quality of DNA was assessed using the BIOMED-2 specimen control reaction. Adequate samples were then analyzed by BIOMED-2 for immunoglobulin heavy and kappa light chain rearrangements. Adequate DNA was obtained in 83 of 97 samples, including 60 mature B cell lymphomas and 23 reactive lymphoid hyperplasia. Clonal B-cell gene rearrangements were detected in 57 of 60 (95%) lymphomas. In contrast, clonal Ig gene rearrangements were not detected in any of the 23 cases of reactive lymphoid hyperplasia. BIOMED-2 assay is highly sensitive and specific for the detection of clonal B cell gene rearrangement using routine paraffin embedded formalin fixed specimens.

IGH and IGK gene rearrangements as PCR targets for pediatric Burkitt's lymphoma and mature B-ALL MRD analysis

We recently reported that minimal residual disease (MRD) and minimal disseminated disease (MDD), assessed by long-distance PCR (LD-PCR) for t(8;14), are negative prognostic factors in mature B-cell acute lymphoblastic leukemia (B-ALL) and in Burkitt's lymphoma (BL). However, t(8;14) is detectable in only about 70% of patients, thus preventing MRD studies by this approach in the remaining patients. At present, no molecular assays have been reported for MRD and MDD analysis in t(8;14)-negative patients. The aim of our study was to evaluate the characteristics of patient-specific immunoglobulin (Ig) gene rearrangements as RQ-PCR targets for MRD analysis, in order to extend MRD studies to those patients who are not eligible for the LD-PCR assay. The study was performed according to the guidelines of the European Study Group on MRD detection in ALL (ESG-MRD-ALL). Overall, 36 B-ALL and 19 BL cases were analyzed. Multiple PCR reactions were performed for each sample to identify heavy and kappa light-chain rearrangements. A total of 97 RQ-PCR targets (62 for B-ALL, 35 for BL) were analyzed for sensitivity. The rearrangement pattern identified was similar to that reported for normal peripheral blood lymphocytes. In 88% of the targets, a sensitivity of at least 10−4 was achieved. In 87% of patients (84% of B-ALLs, 95% of BLs) at least one sensitive target was available. All PCR targets identified at diagnosis were preserved at relapse. Our results suggest that MDD and MRD can be successfully studied using a single sensitive Ig target in the great majority of B-ALL and BL cases. The combination of LD-PCR and Ig-based assays will allow MRD analysis in virtually all of the patients.

Chronic graft-versus-host reaction is associated with a decrease in Ig light chain receptor editing in bone marrow self-reactive B cells.

The encounter of developing B cells in the bone marrow with soluble hen egg lysozyme (sHEL) self antigen induces anergy and endogenous kappa light chain rearrangements ('receptor editing'). We have previously shown that induction of chronic graft-versus-host reaction (GVH) in tolerant Ig/sHEL mice results in prevention of B cell anergy in the bone marrow and the spleen. We now report that in chronic GVH, immature self-reactive B cells also show reduced levels of receptor editing in the bone marrow. This is evidenced by the following observations: (a) a small population of'receptor-edited' B cells, which is found in tolerant mice, is markedly reduced in mice that have lost tolerance in chronic GVH; (b) self-reactive B cells in GVH mice have reduced levels of endogenous kappa chain rearrangements; and (c) recombinase-activating gene (RAG)-2 expression is markedly decreased in immature self-reactive B cells in the bone marrow of chronic GVH mice. These results suggest that in chronic GVH newly emerging B cells escape tolerance, in part because of decreased receptor editing in the bone marrow. Thus, the autoimmunity induced by chronic GVH may ultimately result from the failure of B cell tolerance at multiple checkpoints.

Expression of recombination-activating genes and terminal deoxynucleotidyl transferase and secondary rearrangement of immunoglobulin kappa light chains in rheumatoid arthritis synovial tissue.

Lymphocytic infiltrates in rheumatoid arthritis (RA) synovium often resemble lymphoid follicles and contain clonally related Ig transcripts, suggesting in situ antigen-dependent B cell selection. Recent reports have shown expression of recombination-activating genes (RAGs) and concurrent secondary rearrangement of Ig genes in normal peripheral lymphoid organs (receptor revision). We sought to determine if RAG-mediated receptor revision of Ig kappa light chains occurs in B cells within the RA synovium. Because we previously reported enhanced N-region addition at V(L)-J(L) joins in clonally expanded light-chain transcripts from RA synovium, we also sought expression of terminal deoxynucleotidyl transferase (TdT), which is normally expressed only in B cell precursors or immature B cells. Reverse transcription-polymerase chain reaction (PCR) was used to detect RAG and TdT transcripts from unselected and B cell-enriched synovial and peripheral blood mononuclear cells obtained from 12 RA patients. Activity of RAG protein was sought using ligation-mediated PCR to detect recombination intermediates, and immunohistochemistry was performed to identify RAG+ cells within synovia. We found evidence of RAG-mediated secondary Ig kappa light chain rearrangements in about one-third of RA synovia. TdT expression was found in several samples, but did not correlate with RAG expression. RAG-mediated secondary Ig rearrangements of kappa light chains may contribute to the local production of antibodies to autoantigens (e.g., rheumatoid factor) or exogenous antigens, or it may represent a failed attempt at immune tolerance. TdT expression suggests the presence of immature B cells in RA synovia. These findings have important implications for the local generation of antibodies in RA and other chronic inflammatory diseases.

Immunoglobulin kappa light-chain V, J, and C gene sequences of the owl monkey Aotus nancymaae.

Sequences of Aotus nancymaae immunoglobulin kappa light-chain rearrangements were analyzed after reverse transcription polymerase chain reaction. Among 22 in-frame rearrangements analyzed, 12 IGKV genes belonging to the families 1, 2, or 3 were identified. Aotus counterparts for all five human IGKJ genes were found. The identity of the deduced human and Aotus amino acid sequences was between 83% and 92% for junctional regions and 74% for the constant region. Sequence comparisons between rearrangements indicated that somatic mutations, the addition of nongermline-encoded nucleotides, and exonuclease trimming contribute to the generation of diversity of Aotus immunoglobulin kappa chains. The high identity of Aotus and human IGK genes is comparable to that of T-cell receptor genes and further supports the proposal to use the Aotus Plasmodium falciparum infection model for the evaluation of malaria vaccine candidates.

Rearrangement of the immunoglobulin heavy chain gene in juvenile chronic myeloid leukaemia.

Five patients with clinical and laboratory features typical for juvenile chronic myeloid leukaemia (JCML) are presented. Rearrangement of the j joining region of the immunoglobulin heavy chain (Jh) was demonstrated in three children out of five analysed. As no Vh to DhJh nor kappa light chain rearrangements were demonstrated, it is reasonable to speculate that the transforming event of the stem cell happened at the stage when Dh to Jh rearrangement took place. As the monocytic lineage is prominent in JCML, it is suggested that the transforming event happens in a unique stem cell with intermediate differentiation towards the myelomonocytic as well as the B-lymphatic lineage. This stem cell, which is present at a certain stage of embryogenesis, disappears later. Such an early 'hybrid' cell is sometimes involved in leukaemias of early infancy, and may be the transformed cell in some cases of infantile leukaemia.

Simultaneous immunoglobulin/T‐cell receptor gene rearrangements and multiclonality in childhood acute lymphoblastic leukemia

Twenty-five children less than 16 years of age with acute lymphoblastic leukemia (ALL) were investigated with immunologic, cytogenetic and molecular genetic techniques at diagnosis. All pre-B-cell ALL showed clonal rearrangements in the immunoglobulin heavy chain gene (JH and/or C mu). A very high proportion of the pre-B-cell leukemias (17 of 23 cases) also showed clonal rearrangements in T-cell receptor genes (T gamma and/or T beta). The two T-cell leukemias exhibited clonal T-cell receptor gene rearrangements and in one JH and kappa light chain rearrangements also. The T-cell receptor gene rearrangements found in pre-B-cell leukemias appeared to occur randomly with respect to the T beta and T gamma genes. A significant proportion of the leukemias (at least 24%) seemed to harbor more than one malignant (sub)clone at diagnosis. Cytogenetic studies revealed a clonal abnormality in 10 cases. Only 2 showed hyperdiploidy (> 50 chromosomes). The only correlation between cytogenetic findings and rearrangement patterns was extra bands corresponding to a possible trisomy of chromosome 14. Our data indicate, in line with previous studies, that childhood ALL has complex rearrangement patterns not useful for lineage sub-classification. For this purpose immunophenotyping appears to be superior. However, molecular analysis can reveal the presence of more than one clone not detected by immunophenotyping or karyotyping, and distribution of clones in different compartments. In this study no correlation with clinical outcome was observed.

Heterogeneous immunoglobulin gene rearrangement in a B-chronic lymphocytic leukemia progressing into non-Hodgkin lymphoma (richter syndrome)

The relationship between chronic lymphocytic leukemia (CLL) and supervening non-Hodgkin lymphoma is debated, as is whether a particular genomic pattern is related to the emergence of the terminal lymphoma. To investigate these features, the molecular organization of the immunoglobulin (Ig) gene region in a case during both the B-CLL and Richter transformation phase was studied. B-CLL and non-Hodgkin lymphoma cells were processed for Southern blot analysis of Ig heavy- and light-chain gene configuration. Molecular studies of B-CLL cells revealed the presence of a single Ig heavy-chain rearrangement with both kappa and lambda light-chain rearranged genes, which was consistent with the occurrence of multiple mutational events during the development of the B-CLL clone. Molecular analysis of the lymphoma DNA showed new Ig heavy- and kappa light-chain rearrangements in addition to the original ones related to the CLL phase, indicating that the lymphoma tissue consisted of two genotypically distinct populations of cells. On the basis of the overall molecular configuration, this heterogeneous pattern of Ig gene rearrangement was interpreted as an inherent genetic instability of the CLL clone, in which multiple mutational events allowed a selective pressure toward more aggressive subclones, resulting in the emergence of the terminal lymphoma.

Southern Blot Analysis in a Case of Richter's Syndrome: Evidence for a Postrearrangement Heavy Chain Gene Deletion Associated with 571 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.

Induced rearrangement of kappa genes in the BLIN-1 human pre-B cell line correlates with germline J-C kappa and V kappa transcription.

The human pre-B acute lymphoblastic leukemia cell line, BLIN-1, has been previously shown to undergo kappa light chain rearrangement in vitro, making it a valuable resource for analyzing pre-B to B cell differentiation. We have examined the recombination potential of BLIN-1 by characterizing several independently derived kappa-expressing subclones for DNA rearrangement and V kappa gene usage. Analysis of five kappa-expressing subclones (all having the same heavy chain rearrangement) demonstrated independent kappa light chain rearrangement events by DNA hybridization analysis. Northern blot analysis using probes recognizing the four different V kappa families revealed that two subclones used the most proximal V kappa (V kappa IV), one subclone used a V kappa I, and one subclone used a V kappa II. By polymerase chain reaction analyses, we detected transcripts from rearranged V-J-C kappa genes as well as transcripts from germline J-C kappa and V kappa in BLIN-1 cells induced to rearrange the kappa locus. kappa germline transcripts were also detected in normal developing B cell populations in fetal liver and bone marrow. Our collective results indicate that: (a) BLIN-1 can be induced to rearrange the kappa locus, and this correlates with the expression of germline kappa locus transcripts that may play a role in activating or targeting gene rearrangement; and (b) active rearrangement and usage of V genes representing different kappa families suggest that, like in the mouse, repertoire diversification in humans occurs in the presence of a fixed heavy chain rearrangement.

Cellular and molecular studies on infant null acute lymphoblastic leukemia

We have studied the cellular and molecular basis of eight cases of infant null acute lymphoblastic leukemia (ALL). All eight patients were under 9 months of age and presented with leukocyte counts in excess of 60 X 10(9)/L, organomegaly, and in two cases CNS infiltration. Although seven cases were morphologically classified as ALL, one patient had both lymphoid and myeloid features. Phenotypic analysis of leukemic blasts from all patients showed a typical null ALL pattern, ie, CD10 (common ALL antigen)-negative, strongly HLA-DR-positive, and CD19 (B4)- positive. The presence of terminal deoxynucleotidyl transferase (TdT) at presentation was positive in six patients' cells and negative in two. Two patients also expressed the myeloid-associated markers CD33 (MY9) and CD15 (TG1), and coexpression of CD19 and CD33 was confirmed in these two by using dual marker flow cytometry (fluorescence- activated cell sorting). Electron microscopic examination of the same two patients' cells showed the presence of monocytoid blasts that labeled with the pan-B cell antibody B4 (CD19). Short-term culture of one of these patients cells in the presence of phorbol ester resulted in the majority of the cells exhibiting myeloid markers, strong nonspecific esterase positivity, and phagocytic properties. Cytogenetic analysis showed the common feature in 7 of 8 cases to be a break in band 11q23. Molecular analysis of DNA from the blast cells of all eight patients showed rearrangement of the immunoglobulin heavy-chain genes in all cases without, however, any evidence of kappa light-chain rearrangement. T cell receptor genes were present in the germline configuration in all cases. Rearrangements of the c-ets 1 oncogene, which maps to band 11q23, were not detected, thus providing no evidence for involvement of this oncogene in the common disease process. Our data indicate that although infant null ALL may present as a heterogeneous disease the similarity of many features between cases suggests a common derivation from a precursor cell sharing phenotypic and genotypic features of both B and myeloid progenitor cells.

Immunoglobulin gene rearrangement in immature B cells.

Two types of immature B cells, namely fetal liver hybridomas and the leukemic cell line 70Z/3, both of which have cytoplasmic mu chains but no light chains, were examined for DNA rearrangements of their light chain and heavy chain immunoglobulin genes. In the fetal liver hybridomas, which were constructed from fetal liver cells and a tumor cell, no light chain gene rearrangement was observed, whereas in the 70Z/3 cell line a kappa light chain rearrangement probably occurred. The results suggest that, although the lack of light chain synthesis can be due to a lack of gene rearrangement, there may also be transcriptional regulation, which may also be important for the expression of light chain immunoglobulins in immature B cells.