V4-34 Gene Research Articles

NOTCH1 Mutations Are Associated With The 14q Deletion In Chronic Lymphocytic Leukemia (CLL) and Small Lymphocytic Lymphoma (SLL)

Deletions of the long arm of chromosome 14 are rare (<5%) but recurrently observed in mature B-cell neoplasms, particularly in CLL. The size of the deletions is variable, and the molecular consequences are unknown. The aim of our study is to characterize this abnormality in a large cohort of patients.The Groupe Francophone de Cytogenetique Hematologique (GFCH) collected data from 89 patients with CLL or Small Lymphocytic Lymphoma (SLL), harboring a del14q. Morphological review was performed for 65 of them and immunological review for 48. All karyotypes were reviewed by members of the GFCH. Fluorescence in situ hybridization (FISH) analysis was performed with CEP12, 13q14, TP53, ATM, 6q21, and IGH probes, and BACs RP11-35D12 and RP11-226F19 covering the ZFP36L1 gene on 14q24.1. SNP-array analysis (illumina omni1, omin2.5) was performed for 37 patients. The IGHV status was analyzed locally, or in our laboratory. The mutation hotspots of NOTCH1 (exon 34), SF3B1 (exons 14-16), XPO1 (exons 14-15), MYD88 (exon 5) and TP53 (exons 4-10) were analyzed by direct sequencing.Patients were classified as 49 CLL Matutes score 4-5, 5 atypical CLL score 3 (all CD5+, CD23+), and 27 SLL. Eight patients were excluded with a Matutes score<3 or not evaluable. The sex ratio M/F was 1.02, the median age at diagnosis was 64.5 years [29-87]. Regarding all CLL, there were 35 (66%) stages A, 10 (19%) stages B and 8 (15%) stages C. The median time between diagnosis and the first treatment (TTT) was 17 months [0-144], the overall survival (OS) at 5 years was 93.7%. For the 27 SLL patients, the median TTT was 1 month [0-85], and the OS at 5 years was 88.1%.The karyotype showed chromosomal translocation in 26/79 (33%) (10 balanced, 16 unbalanced) and was complex (> 3 abnormalities) in 26/79 (33%) cases. Using karyotype and FISH, we observed 28/79 (35%) trisomy 12, 12/79 (15%) 13q14 deletions, 11/80 (14%) TP53 deletions, 5/79 (6%) ATM deletions, 3/76 (4%) 6q21 deletions. The whole CLL cohort showed 15/53 (28%) tri 12, 11/53 (21%) del13q, 8/54 (15%) delTP53, 4/53 (7%) delATM, 2/50 (4%) del6q.IGHV status was not mutated in 41/53 (77%) patients, and the gene IGHV1-69 was rearranged in 21/52 (40%) cases. NOTCH1 gene was mutated in 14/45 (31%) patients, SF3B1 in 2/45 (4%), XPO1 in 2/45 (4%), MYD88 in 0/43, TP53 in 6/43 (14%) cases. A significant association was observed between TP53 disrupted and NOTCH1 mutations (p=.04). NOTCH1 mutation was not correlated with tri12.Regarding all the cytogenetic and molecular data, there was no significant difference between CLL score 4-5 and CLL score 3, and between CLL and SLL.Compared with common CLL in the literature, CLL with del14q dysplayed more tri12 (p<.03) and NOTCH1 mutations (p<.003), less del13q (p<.0006), more unmutated IGHV (p<.00001) and V1-69 repertoire (p<.00001). Compared with common SLL in the literature, SLL with del14q also exhibited more tri12, unmutated IGHV (p<.01) and V1-69 (p<.04).The 14q deletions appeared distributed along chromosome 14 from bands q11 to q32. The centromeric and telomeric breakpoints of the 14q deletion were investigated by FISH or SNP-array when material was available, and allowed us to identify a main group (Group 1) among 4 groups: Group 1: 37/77 (48%) patients, with IGH and ZFP36L1 loci rearranged; Group 2: 17/77 (22%), with ZFP36L1 deleted and IGH not deleted; Group 3: 7/77 (9%), with ZFP36L1 and IGH not deleted; Group 4, 16/77 (21%), all the other combinations. Group 1 showed a deletion del14q24.1-14q32.3 of about 38 megabases, which broke in or near ZFP36L1, and in the IGH gene. It included 26 (70%) CLL score 4-5 and 11 (30%) SLL. When compared to the other groups, Group 1 showed significantly more tri12 (p=.004), and NOTCH1 mutations (p=.02). IGHV status was unmutated in 22/24 (92%) patients in Group 1, 12/24 (50%) harboring the gene V1-69.In conclusion, the size of the 14q deletion is variable, with in about half of the cases a recurrent interstitial deletion 14q24.1-14q32.3. Both CLL and SLL with del14q, particularly with the 14q24.1-14q32.3 deletion, are associated with poor prognosis parameters, like short time to treatment, trisomy 12, NOTCH1 mutated, and unmutated IGHV status, with an overrepresentation of the V1-69 gene. Disclosures:No relevant conflicts of interest to declare.

Use of similar immunoglobulin VH gene segments by MALT lymphomas of the ocular adnexa

Extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue type (MALT lymphomas) develop from acquired reactive infiltrates directed against external or autoantigens. Although some European cases of ocular adnexal MALT lymphoma have been associated with Chlamydia psittaci infections, C. psittaci has not been detected in large studies of US-based cases. To evaluate whether the growth of US-based ocular adnexal MALT lymphomas may be promoted by a similar antigen, we identified and analyzed the expressed immunoglobulin VH genes in 10 cases. Interestingly, the VH genes in two cases used the same VH1 family V1-2 gene segment, and three cases used the same VH4 family V4-34 gene segment. The other five cases all used different gene segments V4-31, V5-51, V3-23, V3-30, and V3-7. All of the VH genes were mutated from germ line, with percent homologies ranging between 96.9 and 89.0%. The distribution of replacement and silent mutations within the VH genes was nonrandom consistent with the maintenance of immunoglobulin function and also strongly suggestive of antigen selection in the six VH genes with highest mutation loads. The CDR3 sequences in two of three VH-34 cases were the same size (15 amino acids) and had similar sizes in the two VH1-2 cases (18 and 16 amino acids). In conclusion, US-based MALT lymphomas of the ocular adnexa preferentially express a limited set of VH gene segments not frequently used by other MALT lymphomas and consistent with some recognizing similar antigens. Analysis of somatic mutations present within the VH genes is also consistent with antigen binding stimulating the growth of these lymphomas.

Chronic lymphocytic leukemia patients with a V1-69 gene rearrangement do not have inferior survival with respect to patients that express other unmutated V H genes

Recent studies indicate that V H gene usage in B-CLL may have prognostic impact independently of V H gene mutation status. The V1-69 gene is the most frequently rearranged V H gene in B-CLL and is almost always unmutated. We therefore investigated whether patients with a V1-69 gene rearrangement differ in clinical course and outcome with respect to patients expressing other unmutated V H genes. We show that V1-69 B-CLLs constitute a uniform group of patients that more often present at advanced clinical stages and require early treatment, but their survival does not differ significantly from patients with other unmutated V H genes.

IgVH genes mutation and usage, ZAP-70 and CD38 expression provide new insights on B-cell prolymphocytic leukemia (B-PLL)

B-prolymphocytic leukemia (B-PLL) is a rare disease with poor prognosis. To further characterize the biological features of this disease, we analyzed immunoglobulin heavy chain (IgVH) mutations, ZAP-70 and CD38 in 19 cases with de novo B-PLL. Immunoglobulin heavy chain genes analysis showed an unmutated pattern (>98% homology to germ line) in 9/17 cases (53%), with 100% homology in eight. In the remaining, it ranged from 90 to 97.4%, with three cases slightly mutated (98-95%) and five heavily mutated (<95%). All B-PLL utilized members of VH3 (11/17) and VH4 (6/17) families, with V3-23, V4-59 and V4-34 gene accounting for more than half of them, regardless of mutational status. ZAP-70, assessed by flow cytometry, ranged from 1 to 91% cells, being > or =20% in 57% of cases. CD38 ranged from 1 to 99% (median 21%). There was no correlation between IgVH status and ZAP-70 or CD38 expression, but male gender and del(17p) were more common in the unmutated group. Neither IgVH mutations, CD38 expression nor del(17p) influenced patients' outcome. Unexpectedly, ZAP-70+ B-PLL patients survived longer (40 months) than ZAP-70- B-PLL (8 months). B-PLL appears biologically heterogeneous regarding IgVH mutations, ZAP-70 and CD38 expression, showing a pattern distinct from that of other lymphoproliferative disorders.

Structural and Functional Features of the B-Cell Receptor in IgG-Positive Chronic Lymphocytic Leukemia

To determine the origin and relationship of the rare IgG+ variant of chronic lymphocytic leukemia (CLL) to the two common IgM+IgD+ subsets that are distinguished by expression of unmutated or mutated V(H) genes, with the former having a worse prognosis. IgG+ CLL cells were characterized using phenotypic, functional, and immunogenetic analyses. IgG+ CLL was phenotypically similar to mutated IgM+IgD+ CLL (M-CLL) and variably expressed CD38 (4 of 14). ZAP-70, a tyrosine kinase preferentially expressed in unmutated CLL, was found in only 2 of 14 cases. The ability to signal via surface IgM (sIgM) varies between the main subsets of CLL and is associated with expression of ZAP-70. In IgG(+) CLL, 9 of 14 responded to engagement of sIgG with no apparent requirement for expression of CD38 or ZAP-70. However, signal capacity correlated with intensity of sIgG expression. Most switched immunoglobulin variable region genes were somatically mutated without intraclonal variation, and no case expressed activation-induced cytidine deaminase. Derivation from a postgerminal center B cell is, therefore, likely, and a relationship with M-CLL is suggested. This is supported by a shared biased usage of the V4-34 gene. Similar bias in normal B cells developed with age, providing an expanded population for transforming events. However, conserved sequences detected in the CDR3 of V4-34-encoded gamma chains were not found M-CLL, indicating no direct path of isotype switch from M-CLL. IgG+ CLL is likely to arise from an age-related expanded pool of B cells, on a path parallel to M-CLL, and perhaps with a similar clinical course.

Distinct gene expression patterns in chronic lymphocytic leukemia defined by usage of specific VH genes

The mutation status and usage of specific VH genes such as V3-21 and V1-69 are potentially independent pathogenic and prognostic factors in chronic lymphocytic leukemia (CLL). To investigate the role of antigenic stimulation, we analyzed the expression of genes involved in B-cell receptor (BCR) signaling/activation, cell cycle, and apoptosis control in CLL using these specific VH genes compared to VH mutated (VH-MUT) and VH unmutated (VH-UM) CLL not using these VH genes. V3-21 cases showed characteristic expression differences compared to VH-MUT (up: ZAP70 [or ZAP-70]; down: CCND2, P27) and VH-UM (down: PI3K, CCND2, P27, CDK4, BAX) involving several BCR-related genes. Similarly, there was a marked difference between VH unmutated cases using the V1-69 gene and VH-UM (up: FOS; down: BLNK, SYK, CDK4, TP53). Therefore, usage of specific VH genes appears to have a strong influence on the gene expression pattern pointing to antigen recognition and ongoing BCR stimulation as a pathogenic factor in these CLL subgroups.

Chronic Lymphocytic Leukemia Patients with a V1-69 Gene Rearrangement Do Not Have Inferior Survival with Respect to Patients That Express Other Unmutated VH Genes.

The mutational status of the immunoglobulin variable heavy chain genes (VH) is a major prognostic indicator in patients with CLL. More recently, additional prognostic categories have been identified by recognizing disease subsets which utilize unique VH genes. Examples include the V3-21 and V3-72 genes which are invariably associated with progressive and stable disease, respectively. The V1–69 gene is the most frequently rearranged VH gene in CLL and is almost always unmutated. We therefore investigated whether CLL patients that express this VH gene differ in clinical course and outcome with respect to CLL patients expressing other unmutated VH genes. The study group consisted of 106 consecutive CLLs that had been diagnosed at our institution prior to 2000. The 25 V1–69 cases (23.6%) were identified by allele-specific VH gene fingerprinting and all were found to be unmutated by nucleotide sequencing. Forty of the remaining cases were randomly selected for VH gene nucleotide sequence analysis; 19 cases expressed another unmutated VH gene, 14 cases expressed a mutated VH gene and the VH gene sequence could not be determined in 7 cases. The V1–69 cases did not differ significantly from cases with other unmutated VH genes with respect to age (median age 60 years for both subgroups), gender (male: female=21:4 for V1–69 cases and 13:6 for other VH unmutated cases, P=n.s.) and median follow-up (V1–69 cases: median 56 months, range 6 to 109; other VH unmutated cases: median 59 months, range 20 to 97, P=n.s.). The percentage of cases presenting at an advanced stage was higher in the V1–69 subgroup (36% of cases in Rai high risk category) than in the subgroup with other unmutated VH genes (5% of cases in Rai high risk category, P=0.027), whereas no significant difference was observed with respect to Ly counts and total tumor burden at diagnosis. Interestingly, 80% of the V1–69 cases compared to 42% of cases with other unmutated VH genes had received treatment immediately following diagnosis, but median time to treatment was not significantly different between the two subgroups (1 month vs. 9 months, respectively, P=0.085). To date 24 V1–69 cases (96%) and 15 cases with other unmutated VH genes (79%) have died, with median survival times of 56 and 60 months, respectively (P=0.9). For comparison, median survival of the 14 VH mutated cases from this series was 125 months (P<0.0001 with respect to both subgroups with unmutated VH genes). We therefore conclude that chronic lymphocytic leukemia patients with a V1–69 gene rearrangement constitute a uniform group with unfavorable prognosis, but their survival does not differ significantly from patients with other unmutated VH genes. [Display omitted]

Common Patterns of B Cell Perturbation and Expanded V4-34 Immunoglobulin Gene Usage in Autoimmunity and Infection

Features of the lymphocyte population in systemic lupus erythematosus (SLE) include a disordered B cell profile and production of autoantibodies. An additional distinctive perturbation is the over-expression of V4-34-encoded serum immunoglobulins (Ig). A similar rise in V4-34-encoded Ig occurs in normal subjects following infection with c ertain herpesviruses, and is found in Epstein–Barr virus (EBV)-associated infectious mononucleosis (IM). To assess common and distinctive features of B cells in patients with SLE and IM, we compared the B cell profile and V4-34 gene involvement in patients with SLE and IM. B cell profiles from patients with IM paralleled those of patients with SLE, showing a differential loss of naïve and memory B cells and the maintenance of plasmablast/early plasma cells. Class-switched V4-34-encoded IgG from plasmablast/early plasma cells was evident both in patients with SLE and IM and revealed common features of oligoclonal expansions with most having undergone somatic hypermutation. It has been proposed that, in healthy individuals, expression of the V4-34 gene is specifically censored prior to isotype switch as a control on autoreactivity. If so, censoring is bypassed following EBV infection, after which equilibrium is restored. Continuing high serum levels in SLE may arise either by disordered regulation, or by subclinical reactivation of endogenous virus.

The role of antigen in the selection of the human V3-23 immunoglobulin heavy chain variable region gene.

The immune system mounts antibody responses using few of the available immunoglobulin variable region (IgV) genes with some, such as the V3-23 heavy chain gene, regularly over-represented in responses to many antigens. The reasons for the over-representation of some V genes have not been established; the process could be either stochastic or selective. We demonstrated previously that the V3-23 gene, which is over-represented in the primary B lymphocyte repertoire in humans, encodes antibodies with differing antigen-binding reactivities in transgenic mice that express the human V3-23 gene. The aim of the current study was to assess if V3-23 gene over-representation is stochastic or could be influenced by antigen exposure. Transgenic mice were immunized with human IgG-Fc (hIgG-Fc), bovine collagen type II (bCII) or tetanus toxoid (TT), and hybridomas secreting human mu chain-containing antibodies generated. These were tested for binding to the immunogens and a panel of self- and exogenous antigens. In hybridomas derived from hIgG-Fc-immunized mice, 53% secreted antibodies specific for hIgG-Fc. A similar proportion (54%) of hybridomas from bCII-immunized mice secreted antibody that bound to collagen. By contrast, only 21% of hybridomas from mice immunized with TT bound to tetanus toxoid. Intriguingly, chimaeric antibodies generated from mice immunized with bCII or TT were mainly polyreactive, similar to antibodies generated from naive transgenic mice. However, hybridomas generated from mice immunized with hIgG-Fc were mainly specific, reacting exclusively with hIgG-Fc. These results suggest that selection and eventual expansion of B lymphocytes expressing the V3-23 gene are likely to be determined by exposure to self- and/or environmental antigens.

Evidence for involvement of a hydrophobic patch in framework region 1 of human V4-34-encoded Igs in recognition of the red blood cell I antigen.

The monoclonal IgM cold agglutinins that bind to the I/i carbohydrate Ags on the surface of RBCs all have Ig H chains encoded by the V4-34 gene segment. This mandatory use indicates that distinctive amino acid sequences may be involved in recognition. Critical amino acids exist in framework region 1 (FR1) of V4-34-encoded Ig, and these generate a specific Id determinant which apparently lies close to the I binding site. However, I binding by Id-expressing Ig can be modulated by sequences in complementarity-determining region (CDR)(H)3. Examination of the crystal structure of an anti-I cold agglutinin has revealed a hydrophobic patch in FR1 involving residue W7 on beta-strand A and the AVY motif (residues 23-25) on beta-strand B. In this study we used mutagenesis to show that each of the strand components of the hydrophobic patch is required for binding the I carbohydrate Ag. In addition, the crystal structure reveals that amino acids in the carboxyl-terminal region of CDR(H)3 form a surface region adjacent to the hydrophobic patch. We propose that the I carbohydrate Ag interacts simultaneously with the entire hydrophobic patch in FR1 and with the outside surface of CDR(H)3. This interaction could leave most of the conventional binding site available for binding other Ags.

Splenic Marginal Zone Lymphomas Appear to Originate from Different B Cell Types

Splenic marginal zone lymphomas (SMZLs) have been proposed to originate from postgerminal center memory B cells that usually have mutated immunoglobulin heavy-chain variable (VH) genes. However, the majority of SMZLs are thought to express both IgD and IgM, which is more typical of naïve B cells that have unmutated VH genes. To better define the SMZL cell of origin and pathogenesis, we studied the histological and immunophenotypic features of eight cases and also sequenced their rearranged VH genes. Half of the cases had unmutated VH genes consistent with a naïve B-cell origin and half had mutated VH genes consistent with a memory B-cell origin. Most of the unmutated cases (three of four) were positive for IgD, which further supports a naïve B-cell origin, whereas the others were negative. In addition, VH gene segment use seems to be nonrandom because seven of eight cases used genes from the VH1 or VH4 families and repetitive use of the V1-2, V1-69, and V4-34 gene segments was observed. Our results suggest there are two types of SMZLs, one that originates from naïve marginal zone B cells in addition to one that originates from memory marginal zone B cells, and that antigen selection may be occurring during lymphomagenesis.

Polymorphism in the immunoglobulin VH gene V1-69 affects susceptibility to rheumatoid arthritis in subjects lacking the HLA-DRB1 shared epitope.

To investigate the contribution of polymorphism in the immunoglobulin heavy chain variable region V1-69 gene set to genetic susceptibility to rheumatoid arthritis (RA) in Czech and British patients. We used V1-69 gene sequence-specific polymerase chain reaction (PCR) and restriction enzyme digestion to study polymorphism in the V1-69 gene set in germline DNA of 109 Czech and 159 British RA patients and 164 ethnically matched controls. Polymorphism was further studied by nucleotide sequencing of the V1-69 gene locus in germline DNA. We found that all patients and controls had at least one V1-69 gene copy. In the Czech RA cohort, the dimorphic nucleotide in codon 73 of V1-69 (GAA or AAA) was present in the homozygous form 73(A/A) in 31 of 109 (28.4%) RA patients vs 12 of 79 (15.2%) controls [odds ratio (OR)=2.22, P<0.001]. When the RA patients and controls were classified according to HLA shared epitope (SE) status, 73(A/A) was found in 18 of 76 (23.7%) SE(+) patients compared with 13 of 38 (34.2%) SE(-) patients, four of 12 (18.2) SE(+) controls and eight of 57 (14%) SE(-) controls. This suggests that homozygosity for the dimorphic sequence 73(A) contributed to susceptibility to RA in SE(-) Czech individuals (OR=3.2, P<0.001). The most striking observation was that none of the 38 SE(-) Czech patients, compared with 11 of 76 (14.5%) SE(+) RA patients, three of 22 (13.6%) SE(+) and 11 of 57 (19.3%) SE(-) ethnically matched controls, were homozygous for the alternative dimorphic sequence 73(G/G) (OR=9.1, P<0.05). These data, however, were not replicated in a Caucasoid British RA population. The dimorphic sequence at codon 73 (73(A/A)) of the V1-69 gene contributes to genetic susceptibility in SE(-) Czech RA patients.

Origin and diversification of the clonogenic cell in multiple myeloma: lessons from the immunoglobulin repertoire.

The study of immunoglobulin genes in multiple myeloma over the last decade has provided important information regarding biology, ontogenetic assignment, disease evolution, pathogenic consequences and tumor-specific therapeutic intervention. Detailed analysis of VH genes has revealed the clonal relationship between switch variants expressed by the bone marrow plasma cell and myeloma progenitors in the marrow and peripheral blood. Regarding VH usage, a bias was found against the V4-34 gene encoding antibodies with cold agglutinin specificity (anti-I/i), thus explaining in part the absence of autoimmune phenomena in myeloma compared to other B cell lymphoproliferative disorders. However, in some studies a substantial number of cases analyzed were carrying the rearranged Humkappav325 Vkapppa gene, known to be over utilized by B cell chronic lymphocytic leukemia clones and possessing autoantibody binding activity. VH genes accumulate somatic hypermutations following a distribution compatible with antigen selection, but with no intraclonal heterogeneity. The analysis of Vkappa genes indicates a bias in usage of Vkappa family members; somatic hypermutation, in line with antigen selection, of the expressed Vkappa genes is higher than any other B cell lymphoid disorder. Similar conclusions were reached for Vlambda genes; in this case, the analysis raises the controversial issue of N nucleotide insertion at Vlambda-Jlambda junctions, apparently as a result of TdT activity. A complementary imprint of antigen selection as evidenced by somatic hypermutation of either the VH or VL clonogenic genes has been observed. The absence of ongoing somatic mutations in either VH or VL genes gives rise to the notion that the cell of origin in myeloma is a post-germinal center memory B cell.

Salivary gland mucosa-associated lymphoid tissue lymphoma immunoglobulin VH genes show frequent use of V1-69 with distinctive CDR3 features

AbstractSalivary gland mucosa associated lymphoid tissue (MALT) type lymphomas are B-cell neoplasms that develop out of a reactive infiltrate, often associated with Sjoügren’s syndrome. Previous reports from our laboratory involving 10 patients suggested these lymphomas expressed a restricted immunoglobulin (Ig)VH gene repertoire with over use ofV1-69 gene segments. To better determine the frequency ofV1-69 use and whether there may also be selection for CDR3 structures, we sequenced the VH genes from 15 additional cases. Over half of the potentially functionalVH genes (8 of 14) used aVH1 family V1-69 gene segment, whereas the other cases used different gene segments from theVH1 (V1-46),VH3 (V3-7, V3-11, V3-30.3, V3-30.5), and VH4(V4-39) families. The 8 V1-69 VHgenes used 5 different D segments in various reading frames, but all used a J4 joining segment. The V1-69 CDR3s showed remarkable similarities in lengths (12-14 amino acids) and stretches of 2 to 3 amino acids between the V-D and D-J junctions. They did not resemble CDR3s typical of V1-69 chronic lymphocytic leukemias. This study extends our earlier work in establishing that salivary gland MALT lymphomas represent a highly selected B-cell population. Frequent use of V1-69 appears to differ from MALT lymphomas that develop at other sites. The high degree of CDR3 similarity among the V1-69cases suggests that different salivary gland lymphomas may bind similar, if not identical epitopes. Although the antigen specificities are presently unknown, similar characteristic CDR3 sequences are often seen with V1-69 encoded antibodies that have anti-IgG or rheumatoid factor activity.

Salivary gland mucosa-associated lymphoid tissue lymphoma immunoglobulin VH genes show frequent use of V1-69 with distinctive CDR3 features

Salivary gland mucosa associated lymphoid tissue (MALT) type lymphomas are B-cell neoplasms that develop out of a reactive infiltrate, often associated with Sjögren's syndrome. Previous reports from our laboratory involving 10 patients suggested these lymphomas expressed a restricted immunoglobulin (Ig)VH gene repertoire with over use ofV1-69 gene segments. To better determine the frequency ofV1-69 use and whether there may also be selection for CDR3 structures, we sequenced the VH genes from 15 additional cases. Over half of the potentially functionalVH genes (8 of 14) used aVH1 family V1-69 gene segment, whereas the other cases used different gene segments from theVH1 (V1-46),VH3 (V3-7, V3-11, V3-30.3, V3-30.5), and VH4(V4-39) families. The 8 V1-69 VHgenes used 5 different D segments in various reading frames, but all used a J4 joining segment. The V1-69 CDR3s showed remarkable similarities in lengths (12-14 amino acids) and stretches of 2 to 3 amino acids between the V-D and D-J junctions. They did not resemble CDR3s typical of V1-69 chronic lymphocytic leukemias. This study extends our earlier work in establishing that salivary gland MALT lymphomas represent a highly selected B-cell population. Frequent use of V1-69 appears to differ from MALT lymphomas that develop at other sites. The high degree of CDR3 similarity among the V1-69cases suggests that different salivary gland lymphomas may bind similar, if not identical epitopes. Although the antigen specificities are presently unknown, similar characteristic CDR3 sequences are often seen with V1-69 encoded antibodies that have anti-IgG or rheumatoid factor activity.

Recognition of auto- and exoantigens by V4-34 gene encoded antibodies.

The antigenic specificities of 24 V4-34-encoded monoclonal antibodies were compared with the amino acid sequence. The specificities were divided into three categories, red blood cells, B lymphocytes and auto/exoantigens. Six anti-I monoclonal antibodies, with multiple substitutions in their VH region, did not bind B lymphocytes or auto/exoantigens. Reactivity to these two antigens segregated with the 16 anti-i monoclonal antibodies, which were derived from the near germline V4-34 gene. All anti-i monoclonal antibodies bound B lymphocytes, albeit with varying intensities. B-cell binding correlated with basic amino acids in the VH-CDR3. Reactivity to auto/exoantigens was demonstrated only by a subset anti-i monoclonal antibodies and did not correlate with B-lymphocyte or i-antigen binding. These anti-ssDNA reactive monoclonal antibodies had basic amino acids in the VH-CDR3, strongly supporting the suggested role of arginine in DNA binding. However, an arginine-rich CDR3 was not enough to ensure DNA reactivity, since six other anti-i monoclonal antibodies that fulfilled this criteria did not bind ssDNA. Thus it is possible that the anti-DNA reactivity of V4-34-encoded monoclonal antibodies is mediated by the classic antigen-binding groove generated by the CDRs of the heavy/light chains. In contrast, anti-B-cell/i-antigen reactivity is mediated, unconventionally, by the V4-34 protein with a dominant influence of the VH-CDR3.

Molecular characterization of cold agglutinins

An unusual bias involving the exclusive usage of the V4-34 gene segment by pathogenic antibodies with I/i antigen specificity has been documented in the literature. In addition, all unmutated and several mutated V4-34 encoded antibodies have been shown to be reactive with the anti-idiotypic monoclonal antibody 9G4. The 9G4 Id, therefore, is a marker for V4-34 gene segment expression. Based on these two correlations, it became vital to localize and characterize the nature of the 9G4 Id and to determine the relationship between the Id and I binding. Mutational analysis indicated that the 9G4 Id is located in framework region 1 (FR1) of V4-34 encoded antibodies. Two distinct sections of FR1, encompassing amino acid residues 6-12 and 23-25, form the 9G4 Id. Mutational analysis demonstrated that both FR1 and CDR H3 were required for I binding. When either one was disrupted, the mutant antibody could not bind I. This indicates that I binds through a framework region, and not exclusively through CDR H3. This renders the I interaction with the V4-34 encoded portion of immunoglobulins unconventional, with characteristics similar to superantigen binding to immunoglobulin through FR. When the FR1 DNA sequence of V4-34 was exchanged for FR1 sequences from other V H families I binding was lost, providing a structural explanation for this restricted V H usage. An understanding of the localization and structure of the 9G4 Id and the requirements of V4-34 encoded antibodies for I binding provide insights into the structure of pathogenic antibodies and their requirements for binding antigen. This information should be useful in analyzing new interactions such as the lytic activity of some V4-34 encoded antibodies for B cells.

Primary Central Nervous System Lymphomas Are Derived from Germinal-Center B Cells and Show a Preferential Usage of the V4–34 Gene Segment

Primary central nervous system lymphomas (PCNSLs) have recently received considerable clinical attention due to their increasing incidence. To clarify the histogenetic origin of these intriguing neoplasms, PCNSLs from 10 HIV-negative patients were analyzed for immunoglobulin (Ig) gene rearrangements. All tumors exhibited clonal IgH gene rearrangements. Of the 10 cases, 5 used the V4-34 gene segment, and all of these lymphomas shared an amino acid exchange from glycine to aspartate due to a mutation in the first codon of the complementarity-determining region 1. No preferential usage of D(H), J(H), V(kappa), J(kappa), V(lambda), or J(lambda) gene segments was observed. All potentially functional rearrangements exhibited somatic mutations. The pattern of somatic mutations indicated selection of the tumor cells (or their precursors) for expression of a functional antibody. Mean mutation frequencies of 13. 2% and 8.3% were detected for the heavy and light chains, respectively, thereby exceeding other lymphoma entities. Cloning experiments of three tumors showed ongoing mutation in at least one case. These data suggest that PCNSLs are derived from highly mutated germinal-center B cells. The frequent usage of the V4-34 gene and the presence of a shared replacement mutation may indicate that the tumor precursors recognized a shared (super) antigen.

VH Gene Sequences From Primary Central Nervous System Lymphomas Indicate Derivation From Highly Mutated Germinal Center B Cells With Ongoing Mutational Activity

Primary central nervous system lymphoma (PCNSL) represents 1% to 3% intracranial tumors. Most PCNSL are located in the brain, and 75% are large B-cell lymphomas. The largest subgroup of these tumors contains cells that resemble centroblasts and has been labelled diffuse centroblastic (polymorphous) lymphoma. To investigate the cell of origin and the clonal history of these tumors, we have analyzed VH gene of 5 cases of PCNSL, all confirmed by histological studies to be Epstein-Barr virus (EBV)-negative, high-grade diffuse B-cell lymphomas. The V4-34 gene of the VH4 family was used in 4 of 5 cases. All VHgenes were found to have accumulated very high levels of somatic mutation (14% to 25%). In 3 of 5 cases, intraclonal nucleotide heterogeneity, including codon deletion in some clones in 1 case, was observed, indicating that the VH genes were still under the influence of the somatic hypermutation mechanism. Analysis of the distribution of silent and replacement mutations showed evidence for preservation of immunoglobulin structure in all cases. These results suggest that, although there is no evidence for germinal center formation in the brain tissue, PCNSL is derived from a B cell with features associated with location in a germinal center environment.

VH Gene Sequences From Primary Central Nervous System Lymphomas Indicate Derivation From Highly Mutated Germinal Center B Cells With Ongoing Mutational Activity

AbstractPrimary central nervous system lymphoma (PCNSL) represents 1% to 3% intracranial tumors. Most PCNSL are located in the brain, and 75% are large B-cell lymphomas. The largest subgroup of these tumors contains cells that resemble centroblasts and has been labelled diffuse centroblastic (polymorphous) lymphoma. To investigate the cell of origin and the clonal history of these tumors, we have analyzed VH gene of 5 cases of PCNSL, all confirmed by histological studies to be Epstein-Barr virus (EBV)-negative, high-grade diffuse B-cell lymphomas. The V4-34 gene of the VH4 family was used in 4 of 5 cases. All VHgenes were found to have accumulated very high levels of somatic mutation (14% to 25%). In 3 of 5 cases, intraclonal nucleotide heterogeneity, including codon deletion in some clones in 1 case, was observed, indicating that the VH genes were still under the influence of the somatic hypermutation mechanism. Analysis of the distribution of silent and replacement mutations showed evidence for preservation of immunoglobulin structure in all cases. These results suggest that, although there is no evidence for germinal center formation in the brain tissue, PCNSL is derived from a B cell with features associated with location in a germinal center environment.