Search

Introduction: Cytogenetic aberrations as well as presence of IGVH mutations are the underlying reason for clinical heterogeneity in Chronic Lymphocytic Leukemia (CLL). The presence of IGVH mutations as well as the predominant gene usage shows geographical variations. However, there is no study from India addressing immunogenetics of CLL. In a first Indian study we document the immunogenetics of CLL in a large tertiary hospital. Methods: We analyzed IGVH mutation status, VH gene usage, cytogenetic abnormalities using FISH, immunophenotyping data and correlated them with standard clinical variables in 84 patients of CLL. Results: Advanced Rai stage (Stage 3/4) was seen in 45% of our patients, where as 13q deletion was the commonest clonal cytogenetic abnormality detected in 48.4% of the cases. IGVH unmutated cases (55.2%) showed higher proportion expressing CD38 and CD49d, a preferential usage for VH1 and VH3 families (55.2%), presentation at an advanced Rai stage (52.8%) as well as more frequent presence of p53 deletions. As compared to the IGVH mutated cases greater proportion of IGVH unmutated patients (70%) required treatment. However, there was no significant difference in the time to treatment between mutated and unmutated cases which can be attributed to relatively short median follow up of 10 months. Conclusion: To summarize, we have seen a higher proportion of IGVH unmutated patients in our cohort (55.2%). The commonly used VH genes in the Indian population are IGVH 2-5, IGVH 1-2 and IGVH 1-69. Longer clinical follow up and a larger cohort is necessary to confirm the prognostic value of IGVH mutation analysis in Indian Patients with CLL.

A total of 29 cases of diffuse large B-cell lymphoma initially manifesting in the bone marrow (BM-DLBCL) were analyzed for VH gene sequence, and expression microarray of chemokines and chemokine receptors and immunohistochemical analysis were done. Seminested polymerase chain reaction (PCR) and sequencing analyses of 18 cases revealed that the VH gene usage in 6 cases was restricted to VH3-7, in 3 cases to VH4-34, and in 2 cases to VH4-39, which were all previously reported to be autoreactive. In total, 14 of 18 VH genes were those associated with autoimmune diseases, including VH3-21, VH3-23, and VH3-48. Furthermore, cDNA microarray analysis specific for chemokine and chemokine receptors revealed that chemokine receptor XCR1 expression was significantly elevated in the BM-DLBCL cases (P < .05), which was confirmed by quantitative reverse transcriptase--PCR and immunohistochemical analysis. Expression of the chemokine receptor XCR1 and frequent usage of autoreactive VH genes seem to be distinct characteristics of BM-DLBCL. [ABSTRACT FROM AUTHOR]

Background Accurate assessment of the somatic mutational status of clonal immunoglobulin variable region (IgV) genes is relevant in elucidating tumour cell origin in B-cell lymphoma; virgin B cells bear unmutated IgV genes, while germinal centre and postfollicular B cells carry mutated IgV genes. Furthermore, biases in the IgV repertoire and distribution pattern of somatic mutations indicate a possible antigen role in the pathogenesis of B-cell malignancies. Objectives This work investigates the cellular origin and antigenic selection in primary cutaneous B-cell lymphoma (PCBCL). Methods We analysed the nucleotide sequence of clonal IgV heavy-chain gene (IgVH) rearrangements in 51 cases of PCBCL (25 follicle centre, 19 marginal zone and seven diffuse large B-cell lymphoma, leg-type) and compared IgVH sequences with their closest germline segment in the GenBank database. Molecular data were then correlated with histopathological features. Results We showed that all but one of the 51 IgVH sequences analysed exhibited extensive somatic hypermutations. The detected mutation rate ranged from 1·6% to 21%, with a median rate of 9·8% and was independent of PCBCL histotype. Calculation of antigen-selection pressure showed that 39% of the mutated IgVH genes displayed a number of replacement mutations and silent mutations in a pattern consistent with antigenic selection. Furthermore, two segments, VH1-69 (12%) and VH4-59 (14%), were preferentially used in our case series. Conclusions Data indicate that neoplastic B cells of PBCBL have experienced germinal centre reaction and also suggest that the involvement of IgVH genes is not entirely random in PCBCL and that common antigen epitopes could be pathologically relevant in cutaneous lymphomagenesis. [ABSTRACT FROM AUTHOR]

Abstract: This study determined IgVH gene usage in 228 chronic lymphocytic leukaemia patients to investigate associations between gene usage and other biological or clinical characteristics. VH3–48 [N =8] and VH3–53 [N =4] gene rearrangements showed biased λ light chain restriction and were predominantly found in female patients with short lymphocyte doubling time but without adverse prognosis cytogenetics. Overuse of VL3–21(Vλ2–14) gene and highly homologous LCDR3 sequences were found in VH3–48 patients. VH3–21 gene usage [N =18, 7.9%] was associated with poor prognosis, overuse of VL3–21(Vλ2–14) gene and highly homologous heavy- and light-chain CDR3 sequences, but was not associated with poor prognosis chromosomal aberrations. [Copyright &y& Elsevier]

Mature B-cell malignancies stem from B cells transformed at various developmental stages, accounting for the wide range of heterogeneous features observed in the different disease entities. Analysis of the immunoglobulin (Ig) genes can facilitate the identification of the normal B-cell counterpart of lymphomas and leukemias, as Ig genes acquire somatic hypermutation in germinal centers during the immune response to antigen. Therefore, lymphomas that derive from a naïve, pregerminal center B cell lack somatic hypermutation in the clonal Ig gene, whereas germinal center-derived lymphomas, such as diffuse large B-cell lymphoma and follicular lymphoma, display somatic hypermutation of their Ig genes. Furthermore, biases in the Ig variable heavy chain gene repertoire in B-cell malignancies can indicate a possible antigenic influence in pathogenesis. Much work has been accomplished in the past decade to characterize the Ig genes in different lymphoma entities, and the separation of chronic lymphocytic leukemia into two prognostic subgroups in the late 1990s based on the presence or absence of somatic hypermutation led to investigations of Ig genes in larger cohorts of previously uncharacterized entities, such as mantle cell lymphoma. This review will briefly discuss relevant aspects of normal B-cell development, and then focus on what can be ascertained from Ig studies of newly characterized entities, mantle cell lymphoma, hairy cell leukemia, lymphoplasmacytic lymphoma/Waldenström’s macroglobulinemia, and splenic marginal zone lymphoma, from the point of view of cellular origin and variable heavy chain gene restrictions as a sign of antigen involvement. Correlations with gene expression profiling data and the clinical implications of Ig gene studies, when relevant, will be mentioned. The recent evidence that an alternative pathway of gaining somatic hypermutation might exist is also considered, and the implications this has for understanding the cellular origin of B-cell malignancies. [ABSTRACT FROM AUTHOR]

Galα1–3Gal (anti-Gal), a polyclonal so-called natural antibody (Ab), is present in large amounts in human serum not only as IgG-, but also as IgM- and IgA-isotypes. It has gained a particular interest in the context of xenotransplantation, because the endothelial pig cells express the terminal Galα1–3Gal determinant on several adhesion molecules. Little is known of it's function and direct examination of the structure of the Ig genes responsible for coding anti-Gal is lacking. We used the technique of isoelectric focussing (IEF)/affinity immunoblotting for direct analysis of the clonal distribution and spectrotype analysis of IgM- and IgG anti-Gal. By single cell analysis of magnetic bead and fluorescent-activated cell sorter (FACS) isolated mature anti-Gal bearing human B cells from whole blood we analyzed the VH gene families involved in anti-Gal production. Oligoclonal and individually distinct IgG banding patterns were found with isoelectric points between 4 and 9. IgM spectrotypes revealed to be more uniform with a polyclonal banding pattern of more than 12 bands at a pH between 4.7 and 7. IgG- and IgM-banding patterns over a period of 6 months remained unchanged. Single cell polymerase chain reaction (PCR), with all family specific primers, revealed the use of the VH 2f gene family for the IgG2 isoptype. The differences found in the spectrotype banding patterns of IgG and IgM could be explained by the suggestion that anti-Gal IgM were produced by the use of unmutated germline genes and the possibility of the absence of somatic mutations. The greater clonal heterogeneity in the IgG population could be explained by somatic hypermutations during the switch from IgM to IgG. The use of this VH 2f gene family, which is also involved in the generation of Abs against bacterial pathogens, could mean that this is a predominant region used for the generation of such natural occurring antibodies. [ABSTRACT FROM AUTHOR]

Abstract: Mantle cell lymphoma (MCL) is considered to derive from naïve, pregerminal center (GC) CD5+ B-cells. However, the cell of origin has been questioned in recent studies that showed somatic hypermutations in the immunoglobulin (Ig) variable heavy chain (V H ) genes in subsets of MCL. To clarify this issue, we analyzed the IgV H genes for the presence of somatic hypermutations in 51 MCL cases. Twenty percent of the MCL cases displayed somatically mutated V H genes (defined as >2% mutated), whereas 80% showed unmutated V H genes. This finding suggests that MCL is a genetically heterogeneous disease, with the majority of cases originating from unmutated pre-GC B-cells and a subset deriving from more mature B-cells which have been exposed to the GC environment and have undergone somatic hypermutation. A biased V H gene usage has been demonstrated in several B-cell malignancies; however, this has not yet been investigated in MCL, although V H 4-34 overusage has been indicated by small studies. Interestingly, we found a restricted usage of three individual V H genes in our MCL material; V H 4-34 (22%), V H 3-21 (16%) and V H 5-51 (12%). This novel finding of preferential V H gene usage in half of the MCL cases may suggest an antigen driven process occurring in B-cells expressing specific V H genes, thus implicating that Ig specificity could be involved in mantle cell lymphoma development. [ABSTRACT FROM AUTHOR]