101
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Abstract
The immunoglobulin (Ig) variable region (V) genes expressed by IgM chronic lymphocytic leukemia (CLL) B cells display little or no somatic mutations. However, preliminary findings have shown that Ig V genes of IgA and IgG CLLs may be somatically mutated, suggesting that isotype-switched CLLs may represent a “subtype” of the disease. To investigate the degree and nature of somatic mutations and the role of antigen (Ag) in the clonal selection and expansion of isotype-switched CLLs, and to determine whether specific oncogene or tumor suppressor gene mutations are associated with isotype-switched CLLs, we analyzed the expressed Ig VH gene, bcl-1 and bcl-2 proto-oncogene, and p53 tumor suppressor gene configurations of 3 IgA-, 1 IgG-, and 1 IgA/IgG-expressing CLLs. These isotype-switched CLL B cells expressed surface HLA-DR, CD19, CD23, and CD5, and displayed no alterations of the bcl-1 and bcl-2 oncogenes and the p53 tumor-suppressor gene. The cDNA VH -D-JH gene sequence was joined with that of the Cα gene in the B cells of the three IgA CLLs, and with that of the Cγ gene in the IgG CLL B cells. In the IgA/IgG-coexpressing CLL B cells, identical VH -D-JH cDNA sequences were spliced to either Cα or Cγ genes. In all five CLLs, the pattern of Cμ DNA probe hybridization to the digested genomic DNAs was consistent with deletion of the Cμ exon from the rearranged Ig gene locus, suggesting that these CLL B cells had undergone DNA switch recombination. In one IgA CLL, the expressed VH gene was unmutated. In all other class-switched CLLs, the Ig VH segment gene was mutated, but the point mutations were not associated with intraclonal diversification. In one IgA and in the IgA/IgG-coexpressing CLL, the nature and distribution of the mutations were consistent with Ag selection. These findings suggest that IgA- and/or IgG-expressing CLLs represent, in their VH gene structure, transformants of B cells at different stages of ontogeny. They also suggest that Ag may play a role in the clonal selection of some of these isotype-switched leukemic cells, but bcl-1 and bcl-2 oncogene rearrangements and p53 tumor suppressor gene mutation are not associated with the pathogenesis of isotype-switched CLLs.
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102
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Abstract
Abstract
The immunoglobulin (Ig) variable region (V) genes expressed by IgM chronic lymphocytic leukemia (CLL) B cells display little or no somatic mutations. However, preliminary findings have shown that Ig V genes of IgA and IgG CLLs may be somatically mutated, suggesting that isotype-switched CLLs may represent a “subtype” of the disease. To investigate the degree and nature of somatic mutations and the role of antigen (Ag) in the clonal selection and expansion of isotype-switched CLLs, and to determine whether specific oncogene or tumor suppressor gene mutations are associated with isotype-switched CLLs, we analyzed the expressed Ig VH gene, bcl-1 and bcl-2 proto-oncogene, and p53 tumor suppressor gene configurations of 3 IgA-, 1 IgG-, and 1 IgA/IgG-expressing CLLs. These isotype-switched CLL B cells expressed surface HLA-DR, CD19, CD23, and CD5, and displayed no alterations of the bcl-1 and bcl-2 oncogenes and the p53 tumor-suppressor gene. The cDNA VH -D-JH gene sequence was joined with that of the Cα gene in the B cells of the three IgA CLLs, and with that of the Cγ gene in the IgG CLL B cells. In the IgA/IgG-coexpressing CLL B cells, identical VH -D-JH cDNA sequences were spliced to either Cα or Cγ genes. In all five CLLs, the pattern of Cμ DNA probe hybridization to the digested genomic DNAs was consistent with deletion of the Cμ exon from the rearranged Ig gene locus, suggesting that these CLL B cells had undergone DNA switch recombination. In one IgA CLL, the expressed VH gene was unmutated. In all other class-switched CLLs, the Ig VH segment gene was mutated, but the point mutations were not associated with intraclonal diversification. In one IgA and in the IgA/IgG-coexpressing CLL, the nature and distribution of the mutations were consistent with Ag selection. These findings suggest that IgA- and/or IgG-expressing CLLs represent, in their VH gene structure, transformants of B cells at different stages of ontogeny. They also suggest that Ag may play a role in the clonal selection of some of these isotype-switched leukemic cells, but bcl-1 and bcl-2 oncogene rearrangements and p53 tumor suppressor gene mutation are not associated with the pathogenesis of isotype-switched CLLs.
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103
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Maloum K, Pritsch O, Magnac C, Davi F, Binet JL, Merle-Beral H, Dighiero G. VH gene expression in CD5 positive and CD5 negative B cell chronic lymphoid malignancies. Leuk Lymphoma 1997; 24:437-48. [PMID: 9086435 DOI: 10.3109/10428199709055582] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this review, we report analyses of VH genes in mature B cell malignancies generally or occasionally bearing CD5 antigen such as B CLL, MCL, SLVL and PLL. In the majority of cases, B CLL and MCL use VH genes in germline configuration. However in some cases a higher rate of random mutations is observed. These differences are not related to CD5 expression but are accounted by Ig phenotype, since less mutations are observed in CLL cases expressing membrane mu delta, when compared to forms exclusively expressing membrane mu. PLL and SLVL cases display mutated V genes independently of CD5 expression. Although there is some evidence that CD5+ B cells constitute a separate lineage, the possibility that CD5 constitutes an activation marker cannot be ruled out. Indeed, CD5- B cells can be induced to differentiate into CD5+ B cells and VH gene analyses showed no significative differences between CD5+ and CD5- B cell lymphoproliferative disorders. In this review we have tried to examine B cell chronic malignancies on the basis of phenotype and VH gene usage. Thus we propose a tentative classification where these disorders are allocated according to these characteristics.
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Affiliation(s)
- K Maloum
- Département d'Hématologie, CHU Pitié-Salpêtrière, Paris, France
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104
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Lankester AC, Schijndel GM, Pakker NG, Van Oers RH, van Lier RA. Antigen receptor function in chronic lymphocytic leukemia B cells. Leuk Lymphoma 1996; 24:27-33. [PMID: 9049959 DOI: 10.3109/10428199609045711] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Functional studies revealed that two groups of B chronic lymphocytic leukemia (B-CLL) can be distinguished based on their capacity to mount a proliferative response following B-cell antigen receptor (BCR) cross-linking. The molecular basis for the functional distinction between these B-CLL groups most probably resides within or proximal to the BCR since non-responsive B-CLL, in marked contrast to responsive B-CLL, do not respond to BCR ligation with tyrosine phosphorylation of cellular substrates and increases in the free intracellular [Ca++]. Detailed biochemical analysis showed overall structural identity between responsive and non-responsive B-CLL with respect to both transmembrane and intracellular associates of the BCR complex. However expression levels of the protein tyrosine kinase syk, which is a key enzyme for the early signalling through the BCR, were found to be markedly lower in non-proliferating B-CLL. Here we will review current functional and biochemical data on responding and non-responding B-CLL and discuss the relevance of these findings for disease progression and our insight into the immunobiology of B-CLL.
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Affiliation(s)
- A C Lankester
- Central Laboratory of The Netherlands Red Cross Blood Transfusion Service, University of Amsterdam, The Netherlands
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105
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Fais F, Sellars B, Ghiotto F, Yan XJ, Dono M, Allen SL, Budman D, Dittmar K, Kolitz J, Lichtman SM, Schulman P, Schuster M, Vinciguerra VP, Rai K, Stevenson FK, Gregersen PK, Ferrarini M, Chiorazzi N. Examples of in vivo isotype class switching in IgM+ chronic lymphocytic leukemia B cells. J Clin Invest 1996; 98:1659-66. [PMID: 8833916 PMCID: PMC507600 DOI: 10.1172/jci118961] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Chronic lymphocytic leukemia (CLL) usually involves the expansion of a clone of CD5+ B cells synthesizing IgM antibodies. These B cells appear to be blocked at the antigen receptor-expressing stage of B cell differentiation and are thought not to undergo an isotype class switch to IgG or IgA production. In vivo and in vitro studies suggest, however, that in some instances terminal differentiation and isotype switching can occur. To test the hypothesis that in vivo isotype class switching occurs in IgM+ B-type CLL cells, we analyzed the PBMC of 19 CLL patients for the presence of transcripts encoding the rearranged CLL V(H)DJ(H) associated with either gamma or alpha H chains. The molecular data indicate that approximately 50% of B-CLL patients have amplifications of IgM+ B cells that undergo an isotype class switch. Switching to IgA appears to occur more often than to IgG; also, switching can involve different IgG subclasses in individual patients. In many instances, these CLL-related gamma and alpha transcripts are much more plentiful than those of normal B cells that produce the same isotype. These switched transcripts do not reveal evidence for the accumulation of significant numbers of new V(H) gene mutations. The cellular data indicate that B cells with lesser amounts of surface membrane IgD and higher IgM/IgD ratios are more likely to undergo this switching process. Furthermore, B cells expressing IgG and IgA of the same idiotype or V(H) family and the same CDR3 length as those of the CLL IgM+ clone can be identified in the blood of patients studied using multiparameter immunofluorescence analyses. Collectively, these data suggest that not all members of a B-CLL clone are frozen at the surface membrane Ig-expressing stage of B cell maturation, and that some members can switch to the production of non-IgM isotypes. The occurrence of switching without the accumulation of V gene mutations indicates that the processes of differentiation and diversification are not linked.
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Affiliation(s)
- F Fais
- Department of Medicine, North Shore University Hospital and Cornell University Medical College, Manhasset, New York 11030, USA
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106
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Dighiero G, Kipps T, Schroeder HW, Chiorazzi N, Stevenson F, Silberstein LE, Caligaris-Cappio F, Ferrarini M. What is the CLL B-lymphocyte? Leuk Lymphoma 1996; 22 Suppl 2:13-39. [PMID: 9021706 DOI: 10.3109/10428199609102700] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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107
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Efremov DG, Ivanovski M, Batista FD, Pozzato G, Burrone OR. IgM-producing chronic lymphocytic leukemia cells undergo immunoglobulin isotype-switching without acquiring somatic mutations. J Clin Invest 1996; 98:290-8. [PMID: 8755637 PMCID: PMC507430 DOI: 10.1172/jci118792] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The malignant B cells in chronic lymphocytic leukemia (CLL) typically express low-density membrane IgM or IgM/IgD. In vitro experiments have shown that the CLL cells can be induced to differentiate into cells that secrete immunoglobulin (Ig) and can occasionally undergo heavy (H) chain class switching. We now show that the CLL cells also undergo isotype-switching in vivo, since gamma and/or alpha H chain transcripts with identical FW3/CDR3/FW4 regions as the mu CLL transcripts were detected in all of the 13 investigated patients with IgM+ CLL. In most cases switching had occurred to alpha1 and gamma3, but CLL transcripts corresponding to the other gamma chain isotypes were also detected. In one case both the productively and nonproductively rearranged allele were found to undergo H chain class switching. CLL gamma transcripts were also present in surface IgG+ sorted B cells, demonstrating that a small subset of the CLL cells express membrane IgG. In addition, transcripts encoding secretary gamma2 and gamma3 H chains were detected in two cases, which suggests that some serum IgG could be produced by the leukemic clone. Analysis of sorted PBL showed that isotype-switching occurs in CLL cells that express the CD5 antigen. Finally, nucleotide sequence analysis showed that the mu, alpha, and gamma CLL transcripts are identical, demonstrating that the CLL cells do not accumulate somatic mutations in their variable region genes after the H chain class switching. These data provide in vivo evidence that isotype-switching is a frequent phenomenon in CLL, and indicate that a subset of the CLL lymphocytes progress to later stages of B cell differentiation.
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Affiliation(s)
- D G Efremov
- International Centre for Genetic Engineering and Biotechnology, Area Science Park, Trieste, Italy
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108
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Abstract
A recent meeting discussed advances in our understanding of germinal centers, B-cell malignancies and B-cell signal transduction. Such developments have yielded a more refined view of the role of B-cells in health and disease.
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Affiliation(s)
- F Caligaris-Cappio
- Dipartimento di Scienze Biomediche e Oncologia Umana, Università di Torino, Italy
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109
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Hashimoto S, Dono M, Vinciguerra V, Silver J, Chiorazzi N. Clonal heterogeneity in membrane expression of CD5 in a patient with chronic lymphocytic leukemia. Ann N Y Acad Sci 1995; 764:482-4. [PMID: 7486571 DOI: 10.1111/j.1749-6632.1995.tb55869.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
MESH Headings
- Antigens, Neoplasm/biosynthesis
- Antigens, Neoplasm/genetics
- Antigens, Neoplasm/metabolism
- Antigens, Surface/biosynthesis
- Antigens, Surface/genetics
- Antigens, Surface/metabolism
- B-Lymphocyte Subsets/drug effects
- B-Lymphocyte Subsets/metabolism
- Base Sequence
- CD5 Antigens/biosynthesis
- CD5 Antigens/genetics
- CD5 Antigens/metabolism
- Clone Cells/metabolism
- Cohort Studies
- Gene Expression Regulation, Leukemic
- Gene Rearrangement, B-Lymphocyte, Heavy Chain
- Genes, Immunoglobulin
- Humans
- Immunoglobulin G/biosynthesis
- Immunoglobulin G/genetics
- Immunoglobulin Heavy Chains/genetics
- Immunoglobulin Variable Region/genetics
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Leukemia, Lymphocytic, Chronic, B-Cell/immunology
- Leukemia, Lymphocytic, Chronic, B-Cell/pathology
- Molecular Sequence Data
- Polymerase Chain Reaction
- RNA, Messenger/biosynthesis
- RNA, Neoplasm/biosynthesis
- Sequence Alignment
- Sequence Homology, Nucleic Acid
- Tetradecanoylphorbol Acetate/pharmacology
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Affiliation(s)
- S Hashimoto
- Department of Neurology, Tokyo Women's Medical College, Japan
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110
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Dono M, Hashimoto S, Ferrarini M, Chiorazzi N. In vivo isotype class switching in CD5+ chronic lymphocytic leukemia B cells. Ann N Y Acad Sci 1995; 764:478-81. [PMID: 7486570 DOI: 10.1111/j.1749-6632.1995.tb55868.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- M Dono
- Department of Medicine, North Shore University Hospital, Manhasset, New York, USA
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