Biased use of the IGHV4 family and evidence for antigen selection in Chlamydophila psittaci-negative ocular adnexal extranodal marginal zone lymphomas

Distinct groups of autoantigens as drivers of ocular adnexal MALT lymphoma pathogenesis

Chronic B-cell receptor signals incited by cognate antigens are believed to play a crucial role in the pathogenesis of mucosa-associated lymphoid tissue lymphomas. We have explored the immunoglobulin variable regions (IGHV) expressed by 124 ocular adnexal MALT lymphomas (OAML) and tested the in vitro reactivity of recombinant IgM derived from 23 OAMLs. Six of 124 OAMLs (5%) were found to express a high-affinity stereotyped rheumatoid factor. OAMLs have a biased IGHV4-34 usage, which confers intrinsic super auto-antigen reactivity with poly-N-acetyllactosamine (NAL) epitopes, present on cell surface glycoproteins of erythrocytes and B cells. Twenty-one OAMLs (17%) expressed IGHV4-34-encoded B-cell receptors. Five of the 23 recombinant OAML IgMs expressed IGHV4-34, four of which bound to the linear NAL i epitope expressed on B cells but not to the branched NAL I epitope on erythrocytes. One non-IGHV4-34-encoded OAML IgM was also reactive with B cells. Interestingly, three of the 23 OAML IgMs (13%) specifically reacted with proteins of U1-/U-snRNP complexes, which have been implicated as cognate-antigens in various autoimmune diseases such as systemic lupus erythematosus and mixed connective tissue disease. The findings indicate that local autoimmune reactions are instrumental in the pathogenesis of a substantial fraction of OAMLs.

Sequencing the B Cell Receptor Repertoires of Antibody-Deficient Individuals With and Without Infection Susceptibility

PURPOSE

Most individuals with antibody deficiency (hypogammaglobulinemia) need immunoglobulin replacement therapy (IgG-RT) from healthy plasma donors to stay clear of infections. However, a small subset of hypogammaglobulinemic patients do not require this substitution therapy. We set out to investigate this clinical conundrum by asking whether the peripheral B cell receptor repertoires differ between antibody-deficient patients who do and do not need IgG-RT.

METHODS

We sequenced and analyzed IgG and IgM heavy chain B cell receptor repertoires from peripheral blood mononuclear cells (PBMCs) isolated from patients with low serum IgG concentrations who did or did not require IgG-RT.

RESULTS

Compared to the patients who did not need IgG-RT, those who needed IgG-RT had higher numbers of IgG antibody clones, higher IgM diversity, and less oligoclonal IgG and IgM repertoires. The patient cohorts had different heavy chain variable gene usage, and the patients who needed IgG-RT had elevated frequencies of IgG clones with higher germline identity (i.e., fewer somatic hypermutations).

CONCLUSION

Antibody-deficient patients with infection susceptibility who needed IgG-RT had more diverse peripheral antibody repertoires that were less diverged from germline and thus may not be as optimal for targeting pathogens, possibly contributing to infection susceptibility.

Clinical relevance of molecular aspects in extranodal marginal zone lymphoma: a critical appraisal

Extranodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma) is among the more common types of lymphoma accounting for up to 8% of newly diagnosed lymphoma cases. As opposed to other B-cell lymphomas, however, no predominant genetic hallmark has been defined in MALT lymphoma, but different localizations appear to be affected by different, sometimes distinct changes. Nonetheless, a high proportion of these genetic changes reported in MALT lymphomas dysregulate the pathways leading to NF-kB activation. t(11;18)(q21;q21)/BIRC3::MALT1 appears to be MALT lymphoma specific and is found in 24% of gastric and 40% of pulmonary MALT lymphomas. The translocation is associated with more disseminated disease in gastric MALT lymphoma and is found in a large percentage of patients whose lymphoma is unresponsive to antibiotic eradication of Helicobacter pylori. In addition to t(11;18)(q21;q21), nuclear expression of BCL10 or NF-kB appears to be highly associated with lymphoma cell survival independence of H. pylori-mediated stimulations. Antibiotic eradication, however, is the recommended therapy of choice irrespective of genetic findings, and molecular analysis is not required before initiation of therapy. The influence of genetic translocations including t(11;18)(q21;q21) on systemic therapies, however, is less clearly defined. While small series have shown no influence on the outcome for treatment with the anti-CD20 antibody rituximab (R) or treatment with cladribine (2-CdA), conflicting data have been reported for alkylating agents, especially chlorambucil and the combination of R + chlorambucil. None of other genetic changes seen in MALT lymphoma to date has discernible value in routine clinical applications, but recent data suggest that changes in TNFAIP3(A20), KMTD2 and CARD11 might be associated with response to Bruton kinase inhibitors.

Gastric Cancer Pre-Stage Detection and Early Diagnosis of Gastritis Using Serum Protein Signatures

Background: A gastric cancer (GC) diagnosis relies on histopathology. Endoscopy rates are increasing. Helicobacter pylori infection is a major GC risk factor. In an effort to elucidate abundant blood biomarkers, and potentially reduce the number of diagnostic surgical interventions, we investigated sera and biopsies from a cohort of 219 H. pylori positive and negative patients diagnosed with GC, gastritis, and ulcers. This allowed the comparative investigation of the different gastroduodenal diseases, and the exclusion of protein changes resulting from bacterial infection or inflammation of the gastric mucosa when searching for GC-dependent proteins. Methods: High-definition mass spectrometry-based expression analysis of tryptically digested proteins was performed, followed by multivariate statistical and network analyses for the different disease groups, with respect to H. pylori infection status. Significantly regulated proteins differing more than two-fold between groups were shortlisted, and their role in gastritis and GC discussed. Results: We present data of comparative protein analyses of biopsies and sera from patients suffering from mild to advanced gastritis, ulcers, and early to advanced GC, in conjunction with a wealth of metadata, clinical information, histopathological evaluation, and H. pylori infection status. We used samples from pre-malignant stages to extract prospective serum markers for early-stage GC, and present a 29-protein marker panel containing, amongst others, integrin β-6 and glutathione peroxidase. Furthermore, ten serum markers specific for advanced GC, independent of H. pylori infection, are provided. They include CRP, protein S100A9, and kallistatin. The majority of these proteins were previously discussed in the context of cancer or GC. In addition, we detected hypoalbuminemia and increased fibrinogen serum levels in gastritis. Conclusion: Two protein panels were suggested for the development of multiplex tests for GC serum diagnostics. For most of the elements contained in these panels, individual commercial tests are available. Thus, we envision the design of multi-protein assays, incorporating several to all of the panel members, in order to gain a level of specificity that cannot be achieved by testing a single protein alone. As their development and validation will take time, gastritis diagnosis based on the fibrinogen to albumin serum ratio may be a quick way forward. Its determination at the primary/secondary care level for early diagnosis could significantly reduce the number of referrals to endoscopy. Preventive measures are in high demand. The protein marker panels presented in this work will contribute to improved GC diagnostics, once they have been transferred from a research result to a practical tool.

The Biology of Ocular Adnexal Marginal Zone Lymphomas

This review focuses on the biology of ocular adnexal marginal zone B-cell lymphomas of the mucosa-associated lymphatic tissue (MALT) (OAMZL) subtype. The ocular adnexa includes all structures and tissues within the orbit except for the eye bulb. In the region of the ocular adnexa, MALT lymphomas represent the most common subtype of lymphoma, accounting for around 8% of all non-Hodgkin lymphomas. These lymphomas are often preceded by inflammatory precursor lesions. Either autoantigens or infectious antigens may lead to disease development by functioning as continuous antigenic triggers. This triggering leads to a constitutive activation of the NF-κB signaling pathway. The role of antigenic stimulation in the pathogenesis of OAMZL is supported by the detection of somatic mutations (partially with further intraclonal diversity) in their rearranged immunoglobulin V genes; hence, their derivation from germinal-center-experienced B cells, by a restricted IGHV gene usage, and the validation of autoreactivity of the antibodies in selected cases. In the established lymphomas, NF-κB activity is further enforced by mutations in various genes regulating NF-κB activity (e.g., TNFAIP3, MYD88), as well as recurrent chromosomal translocations affecting NF-κB pathway components in a subset of cases. Further pathogenetic mechanisms include mutations in genes of the NOTCH pathway, and of epigenetic regulators. While gene expression and sequencing studies are available, the role of differential methylation of lymphoma cells, the role of micro-RNAs, and the contribution of the microenvironment remain largely unexplored.

Primary vitreoretinal lymphomas display a remarkably restricted immunoglobulin gene repertoire

Primary vitreoretinal lymphoma (PVRL) is a high-grade lymphoma affecting the vitreous and/or the retina. The vast majority of cases are histopathologically classified as diffuse large B-cell lymphoma (DLBCL) and considered a subtype of primary central nervous system lymphoma (PCNSL). To obtain more insight into the ontogenetic relationship between PVRL and PCNSL, we adopted an immunogenetic perspective and explored the respective immunoglobulin gene repertoire profiles from 55 PVRL cases and 48 PCNSL cases. In addition, considering that both entities are predominantly related to activated B-cell (ABC) DLBCL, we compared their repertoire with that of publicly available 262 immunoglobulin heavy variable domain gene rearrangement sequences from systemic ABC-type DLBCLs. PVRL displayed a strikingly biased repertoire, with the IGHV4-34 gene being used in 63.6% of cases, which was significantly higher than in PCNSL (34.7%) or in DLBCL (30.2%). Further repertoire bias was evident by (1) restricted associations of IGHV4-34 expressing heavy chains, with κ light chains utilizing the IGKV3-20/IGKJ1 gene pair, including 5 cases with quasi-identical sequences, and (2) the presence of a subset of stereotyped IGHV3-7 rearrangements. All PVRL IGHV sequences were highly mutated, with evidence of antigen selection and ongoing mutations. Finally, half of PVRL and PCNSL cases carried the MYD88 L265P mutation, which was present in all 4 PVRL cases with stereotyped IGHV3-7 rearrangements. In conclusion, the massive bias in the immunoglobulin gene repertoire of PVRL delineates it from PCNSL and points to antigen selection as a major driving force in their development.

Mechanisms of B Cell Receptor Activation and Responses to B Cell Receptor Inhibitors in B Cell Malignancies

The B cell receptor (BCR) pathway has been identified as a potential therapeutic target in a number of common B cell malignancies, including chronic lymphocytic leukemia, diffuse large B cell lymphoma, Burkitt lymphoma, follicular lymphoma, mantle cell lymphoma, marginal zone B cell lymphoma, and Waldenstrom's macroglobulinemia. This finding has resulted in the development of numerous drugs that target this pathway, including various inhibitors of the kinases BTK, PI3K, and SYK. Several of these drugs have been approved in recent years for clinical use, resulting in a profound change in the way these diseases are currently being treated. However, the response rates and durability of responses vary largely across the different disease entities, suggesting a different proportion of patients with an activated BCR pathway and different mechanisms of BCR pathway activation. Indeed, several antigen-dependent and antigen-independent mechanisms have recently been described and shown to result in the activation of distinct downstream signaling pathways. The purpose of this review is to provide an overview of the mechanisms responsible for the activation of the BCR pathway in different B cell malignancies and to correlate these mechanisms with clinical responses to treatment with BCR inhibitors.

Prevalence of Chlamydia psittaci, Chlamydia pneumoniae, and Chlamydia trachomatis Determined by Molecular Testing in Ocular Adnexa Lymphoma Specimens

OBJECTIVES

To assess the prevalence of Chlamydia psittaci, Chlamydia pneumoniae, and Chlamydia trachomatis in ocular adnexa lymphoma (OAL) determined by molecular testing in different countries and the potential association of Chlamydia infection with mucosa-associated lymphoid tissue (MALT) histotype by performing a systematic review and meta-analysis.

METHODS

Electronic databases were searched for studies assessing the presence of Chlamydia in OAL. Pooled prevalence of the three Chlamydia species was calculated in each country. An odds ratio was calculated for the association between Chlamydia and MALT histotype, with a significant P < .05.

RESULTS

Thirty-seven studies with 1,188 OALs were included. Pooled prevalence of C psittaci, C pneumoniae, and C trachomatis by country was done. Chlamydia infection was significantly associated with MALT histotype (odds ratio, 2.183; P = .027).

CONCLUSIONS

The involvement of C psittaci in OAL is highly variable, with the highest prevalence in Italy and Korea. Chlamydia is associated with MALT histotype.

Orbital lymphoma

Orbital lymphomas constitute 50-60% of ocular adnexal lymphomas. A total of 2211 cases of orbital lymphoma with a known subtype have been reported in the last 24 years (1994-2017). The vast majority of orbital lymphomas are of B-cell origin (97%), of which extranodal marginal zone B-cell lymphoma (EMZL) (59%) is the most common subtype, followed by diffuse large B-cell lymphoma (23%), follicular lymphoma (9%), and mantle cell lymphoma (5%). Orbital lymphoma is primarily a disease of the elderly. Gender distribution varies according to lymphoma subtype. However, extranodal marginal zone B-cell lymphoma (53%) and follicular lymphoma (75%) show a female predominance, whereas diffuse large B-cell lymphoma shows an even gender distribution. Mantle cell lymphoma has a striking male predominance of 80%. The histopathological subtype and the clinical stage of the disease are the best indicators of prognosis and patient outcome. Low-grade lymphomas such as extranodal marginal zone B-cell lymphoma and FL have a good prognosis, whereas high-grade lymphomas (diffuse large B-cell lymphoma and mantle cell lymphoma) are associated with a poor prognosis. When managing solitary low-grade lymphomas, radiotherapy is the treatment of choice. Chemotherapy, with or without radiotherapy, should be chosen for disseminated and high-grade lymphomas.

A gene is known by the company it keeps: enrichment of TNFAIP3 gene aberrations in MALT lymphomas expressing IGHV4-34 antigen receptors

Associations between immunoglobulin (IG) receptors with distinctive immunogenetic features and particular gene mutations are a recurring theme in mature B-cell lymphomas. Relevant observations have been made in chronic lymphocytic leukemia (CLL), where gene mutations are distributed asymmetrically in cases bearing or not somatic hypermutations within the clonotypic immunoglobulin heavy chain variable region (IGHV) genes (e.g. TP53 mutations predominate in IG-unmutated CLL, whereas the opposite is seen for MYD88 mutations, enriched in IG-mutated CLL) and in subsets of cases with stereotyped IG (enrichment for SF3B1 mutations in CLL subset #2). Moreover, similar findings have been reported in splenic marginal-zone lymphoma, where KLF2 mutations are biased to cases expressing IGHV1-2*04 IG receptors, and in hairy cell leukemia, where IGHV4-34-expressing cases display a low frequency of BRAF mutations but a high frequency of MAP2K1 mutations. The list is now growing with the report of increased frequency of inactivating mutations in the TNFAIP3 gene in MALT lymphomas expressing IG receptors encoded by the IGHV4-34 gene, particularly of the ocular adnexa. Considering that TNFAIP3 encodes a negative regulator of NF-κB, this finding further highlights the importance of NF-κB pathway activation in the natural history of MALT lymphomas. Altogether, these findings allude to selection of genomic aberrations in lymphoma cases with distinctive immune signaling profiles linked to the expression of particular IG receptors. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

MALT lymphoma: A paradigm of NF-κB dysregulation

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) invariably arises from a background of chronic microbial infection and/or autoimmune disorder at diverse mucosal sites. The prolonged chronic infection and/or autoimmunity generate active immune and inflammatory responses that provide a setting for evolution and development of autoreactive B-cells, their expansion and eventual malignant transformation following acquisition of genetic changes. The immune responses also play a critical role in sustaining the growth and survival of the transformed cells as shown by complete regression of a high proportion of MALT lymphoma of the stomach, ocular adnexa and skin following anti-microbial treatment. B-cell receptor engagement by auto-antigen as well as T-cell help including both cognate interaction and bystander help via soluble ligands such as CD40L and BAFF are thought to underpin the immunological drive in the lymphoma development through activation of the canonical and non-canonical NF-κB pathway respectively. Similarly, the three MALT lymphoma associated chromosome translocations, namely t(1;14)(p22;q32)/BCL10-IGH, t(14;18)(q32;q21)/IGH-MALT1,and t(11;18)(q21;q21)/BIRC3 (API2)-MALT1, are also capable of activating both canonical and non-canonical NF-κB pathways. Furthermore, TNFAIP3 (A20) inactivation by deletion and/or mutation abolishes the auto-negative feedback to several signalling including BCR and TLR, which connect to the canonical NF-κB activation pathway. Thus, there is a considerable overlap in the molecular pathways dysregulated by immunological drive and somatic genetic changes, strongly arguing for their oncogenic cooperation in the development of MALT lymphoma.

Clinical aspects of malt lymphomas

Extranodal marginal zone lymphoma of the mucosa-associated lymphoid tissue (MALT) is an indolent lymphoma arising in extranodal sites. Several infectious agents and autoimmune disorders have been implicated in its pathogenesis. The stomach represents the most common and best-studied organ involved by MALT lymphoma and its development is strongly associated with Helicobacter pylori (Hp) infection. MALT lymphomas are characterized by an indolent clinical course and excellent survival in most cases, independently of the treatment delivered. Recent progress in the knowledge of the etiology and the cellular and molecular pathological events related to MALT lymphomas allowed us to improve our clinical understanding of this disease entity and to better define treatment strategies.

Primary extranodal marginal zone lymphoma of the endometrium: report of four cases and review of literature

Primary extranodal marginal zone lymphoma of the endometrium (PEMZL-EM) is exceedingly rare and has not been well characterized. Herein, we study the clinicopathological, cytogenetic and molecular features of four cases, the largest case series reported to date. The median age of the four patients was 59 years. Clinical presentations included abnormal vaginal bleeding (three cases) and incidental finding (one case). There were no constitutional symptoms in any of the cases. None of the patients had evidence of lymphoma in any other anatomic sites including bone marrow. Histologically, the lymphoma was characterized by a nodular proliferation of small lymphocytes admixed with occasional immunoblasts and variable number of plasma cells, which was restricted to the endometrium in most cases. Lymphoepithelial lesions were not identified in any of the cases. All cases displayed the immunophenotype of marginal zone B-cell lymphoma. Cytogenetics and FISH studies revealed absence of characteristic chromosomal translocations. Molecular analysis demonstrated immunoglobulin heavy chain gene rearrangement in all cases, two of which were found to use IgVH3-30 gene by DNA sequencing. Three of the four patients were still alive after a median follow-up of three years. PEMZL-EM predominantly affects postmenopausal women and is characterized by distinct histological patterns, lack of specific genomic alterations, and indolent clinical course.

The analysis of VH and VL genes repertoires of Fab library built from peripheral B cells of human rabies virus vaccinated donors

A human combinatorial Fab antibody library was generated from immune repertoire based on peripheral B cells of ten rabies virus vaccinated donors. The analysis of random Fab fragments from the unselected library presented some bias of V gene usage towards IGHV-genes and IGLV-gen families. The screening of the Fab library on rabies virus allowed specific human Fab antibody fragments characterized for their gene encoding sequences, binding and specificities to RV. Genetic analysis of selected Fabs indicated that the IGHV and IGLV differ from the germ-line sequence. At the level of nucleotide sequences, the IGHV and IGLV domains were found to share 74-92% and 90-96% homology with sequences encoded by the corresponding human germ-line genes respectively. IGHV domains are characterized most frequently by IGHV3 genes, and large proportions of the anti-RV heavy chain IGHV domains are obtained following a VDJ recombination process that uses IGHD3, IGHD2, IGHD1 and IGHD6 genes. IGHJ3 and IGHJ4 genes are predominantly used in RV-Fab. The IGLV domains are dominated by IGKV1, IGLV1 and IGLV3 genes. Numerous somatic hypermutations in the RV-specific IGHV are detected, but only limited amino acid replacement in most of the RV-specific IGLV particularly in those encoded by J proximal IGLV or IGKV genes are found. Furthermore, IGHV3-IGKV1, IGHV3-IGVL1, and IGHV3-IGLV3 germ-line family pairings are preferentially enriched after the screening on rabies virus.

Molecular and genomic aberrations in Chlamydophila psittaci negative ocular adnexal marginal zone lymphomas

The etiology and pathogenesis of ocular adnexal extranodal marginal zone lymphoma (OAEMZL) are still unknown and the association with Chlamydophila psittaci (C. psittaci) has been shown in only some geographic regions. Herein, we comprehensively examined the frequency of chromosomal translocations as well as CARD11, MYD88 (L265P), and A20 mutations/deletions in 45 C. psittaci negative OAEMZLs. t(14;18)(q32;q21) IGH-MALT1 and t(11;18)(q21;q21) API2-MALT1 were not detected in any of the analyzed tumors while three tumors harbored IGH translocations to an unidentified partner. CARD11 mutations were not found in all analyzed tumors, while the MYD88 L265P mutation was detected in three (6.7%) tumors. A20 mutations and deletions were each detected in seven (15.6%) and six (13.3%) tumors, respectively. Therefore, the observed genetic aberrations could account for the activation of the nuclear factor (NF)-kB signaling pathway in only a minority of the cases. Further studies are needed to identify the molecular mechanisms underlying the pathogenesis of OAEMZL.

Biased immunoglobulin light chain use in the Chlamydophila psittaci negative ocular adnexal marginal zone lymphomas

Ocular adnexal mucosa associated lymphoid tissue lymphomas (OAMALTL) are the most common lymphomas of the eye. The potential roles for specific antigens in these lymphomas are still controversial. Previously we examined IGHV usage and mutations in Chlamydophila (C) psittaci-negative OAMALTL, demonstrating biased use of the IGHV4 family and IGHV4-34 gene and evidence for antigen selection. Herein, we examined the IGKV/IGLV gene usage and mutations in 34 C. psittaci-negative OAMALTL originating from the orbit (15), conjunctivae (14), and lacrimal gland (5). Clonal potentially functional IGKV/IGLV gene sequences were identified in 30 tumors (18 kappa and 12 lambda). An overrepresentation of the IGKV4 family (P < 0.01) was observed. The IGKV3-20*01 allele was used at a greater frequency than in normal peripheral blood B-lymphocytes (P = 0.02) and commonly paired with the IGHV4-34 allele. Twenty-seven of the 30 unique light chain sequences displayed mutations from germline and evidence for antigen selection. Overall our findings demonstrate that in C. psittaci-negative OAMALTL there is a biased usage of IGKV families and genes, which harbor somatic mutations. These findings and the specific paring between the IGKV3-20*01 and IGHV4-34 alleles suggest that specific antigens could play an important role in the pathogenesis of these lymphomas.

Natural and man-made V-gene repertoires for antibody discovery

Antibodies are the fastest-growing segment of the biologics market. The success of antibody-based drugs resides in their exquisite specificity, high potency, stability, solubility, safety, and relatively inexpensive manufacturing process in comparison with other biologics. We outline here the structural studies and fundamental principles that define how antibodies interact with diverse targets. We also describe the antibody repertoires and affinity maturation mechanisms of humans, mice, and chickens, plus the use of novel single-domain antibodies in camelids and sharks. These species all utilize diverse evolutionary solutions to generate specific and high affinity antibodies and illustrate the plasticity of natural antibody repertoires. In addition, we discuss the multiple variations of man-made antibody repertoires designed and validated in the last two decades, which have served as tools to explore how the size, diversity, and composition of a repertoire impact the antibody discovery process.

Molecular characterization of immunoglobulin gene rearrangements in diffuse large B-cell lymphoma: antigen-driven origin and IGHV4-34 as a particular subgroup of the non-GCB subtype

The pathogenesis of diffuse large B-cell lymphoma (DLBCL) remains partially unknown. The analysis of the B-cell receptor of the malignant cells could contribute to a better understanding of the DLBCL biology. We studied the molecular features of the immunoglobulin heavy chain (IGH) rearrangements in 165 patients diagnosed with DLBCL not otherwise specified. Clonal IGH rearrangements were amplified according to the BIOMED-2 protocol and PCR products were sequenced directly. We also analyzed the criteria for stereotyped patterns in all complete IGHV-IGHD-IGHJ (V-D-J) sequences. Complete V-D-J rearrangements were identified in 130 of 165 patients. Most cases (89%) were highly mutated, but 12 sequences were truly unmutated or minimally mutated. Three genes, IGHV4-34, IGHV3-23, and IGHV4-39, accounted for one third of the whole cohort, including an overrepresentation of IGHV4-34 (15.5% overall). Interestingly, all IGHV4-34 rearrangements and all unmutated sequences belonged to the nongerminal center B-cell-like (non-GCB) subtype. Overall, we found three cases following the current criteria for stereotyped heavy chain VH CDR3 sequences, two of them belonging to subsets previously described in CLL. IGHV gene repertoire is remarkably biased, implying an antigen-driven origin in DLBCL. The particular features in the sequence of the immunoglobulins suggest the existence of particular subgroups within the non-GCB subtype.