Influence of antigen on the development of MALT lymphoma

Role of non-Helicobacter pylori gastric Helicobacters in helicobacter pylori-negative gastric mucosa-associated lymphoid tissue lymphoma

Marginal zone lymphomas rank as the third most prevalent form of non-Hodgkin B-cell lymphoma, trailing behind diffuse large B-cell lymphoma and follicular lymphoma. Gastric mucosa-associated lymphoid tissue lymphoma (GML) is a low-grade B-cell neoplasia frequently correlated with Helicobacter pylori (H. pylori)-induced chronic gastritis. On the other hand, a specific subset of individuals diagnosed with GML does not exhibit H. pylori infection. In contrast to its H. pylori-positive counterpart, it was previously believed that H. pylori-negative GML was less likely to respond to antimicrobial therapy. Despite this, surprisingly, in-creasing evidence supports that a considerable proportion of patients with H. pylori-negative GML show complete histopathological remission after bacterial eradication therapy. Nonetheless, the precise mechanisms underlying this treatment responsiveness are not yet fully comprehended. In recent years, there has been growing interest in investigating the role of non-H. pylori gastric helicobacters (NHPHs) in the pathogenesis of H. pylori-negative GML. However, additional research is required to establish the causal relationship between NHPHs and GML. In this minireview, we examined the current understanding and proposed prospects on the involvement of NHPHs in H. pylori-negative GML, as well as their potential response to bacterial eradication therapy.

Recent advances in understanding the biology of marginal zone lymphoma

There are three different marginal zone lymphomas (MZLs): the extranodal MZL of mucosa-associated lymphoid tissue (MALT) type (MALT lymphoma), the splenic MZL, and the nodal MZL. The three MZLs share common lesions and deregulated pathways but also present specific alterations that can be used for their differential diagnosis. Although trisomies of chromosomes 3 and 18, deletions at 6q23, deregulation of nuclear factor kappa B, and chromatin remodeling genes are frequent events in all of them, the three MZLs differ in the presence of recurrent translocations, mutations affecting the NOTCH pathway, and the transcription factor Kruppel like factor 2 ( KLF2) or the receptor-type protein tyrosine phosphatase delta ( PTPRD). Since a better understanding of the molecular events underlying each subtype may have practical relevance, this review summarizes the most recent and main advances in our understanding of the genetics and biology of MZLs.

The spectrum of MALT lymphoma at different sites: biological and therapeutic relevance

Extranodal marginal zone (MZ) B-cell lymphomas of the mucosa-associated lymphoid tissue (MALT) arise from lymphoid populations that are induced by chronic inflammation in extranodal sites. The best evidence of an etiopathogenetic link is provided by the association between Helicobacter pylori–positive gastritis and gastric MALT lymphoma. Indeed, successful eradication of this microorganism with antibiotics can be followed by gastric MALT lymphoma regression in most cases. Other microbial agents have been implicated in the pathogenesis of MZ lymphoma arising at different sites. Apart from gastric MALT lymphoma, antibiotic therapies have been adequately tested only in ocular adnexal MALT lymphomas where upfront doxycycline may be a reasonable and effective initial treatment of patients with Chlamydophila psittaci–positive lymphoma before considering more aggressive strategies. In all other instances, antibiotic treatment of nongastric lymphomas remains investigational. Indeed, there is no clear consensus for the treatment of patients with gastric MALT lymphoma requiring further treatment beyond H pylori eradication or with extensive disease. Both radiotherapy and systemic treatments with chemotherapy and anti-CD20 antibodies are efficacious and thus the experience of individual centers and each patient’s preferences in terms of adverse effects are important parameters in the decision process.

Beyond the stomach: An updated view of Helicobacter pylori pathogenesis, diagnosis, and treatment

Helicobacter pylori (H. pylori) is an extremely common, yet underappreciated, pathogen that is able to alter host physiology and subvert the host immune response, allowing it to persist for the life of the host. H. pylori is the primary cause of peptic ulcers and gastric cancer. In the United States, the annual cost associated with peptic ulcer disease is estimated to be $6 billion and gastric cancer kills over 700000 people per year globally. The prevalence of H. pylori infection remains high (> 50%) in much of the world, although the infection rates are dropping in some developed nations. The drop in H. pylori prevalence could be a double-edged sword, reducing the incidence of gastric diseases while increasing the risk of allergies and esophageal diseases. The list of diseases potentially caused by H. pylori continues to grow; however, mechanistic explanations of how H. pylori could contribute to extragastric diseases lag far behind clinical studies. A number of host factors and H. pylori virulence factors act in concert to determine which individuals are at the highest risk of disease. These include bacterial cytotoxins and polymorphisms in host genes responsible for directing the immune response. This review discusses the latest advances in H. pylori pathogenesis, diagnosis, and treatment. Up-to-date information on correlations between H. pylori and extragastric diseases is also provided.

Autoantibodies binding to ubiquitin-fold modifier-conjugating enzyme 1 (Ufc1) and pleckstrin homology domain containing, family G (with RhoGef domain) member 2 (Plekhg2) are associated with mycobacterial infections

OBJECTIVES

The diagnosis of extrapulmonary tuberculous infections and nontuberculous mycobacterial (NTM) infections is difficult because the symptoms are nonspecific and suitable specimens for bacterial culture are often not available. Recent publications reported the existence of autoantibodies in tuberculous infections. We screened for specific autoantibodies in mycobacterial infections.

METHODS

We screened four in 29 patients with active mycobacterial infections and different controls using protein array technology. We could identify autoantibodies against ubiquitin-fold modifier-conjugating enzyme 1 (Ufc1) and pleckstrin homology domain containing, family G (with RhoGef domain) member 2 (Plekhg2) in all four patients. Subsequently, we designed enzyme-linked immunosorbent assays (ELISAs) for the detection of autoantibodies binding to Ufc1 and Plekhg2.

RESULTS

Autoantibodies binding to Ufc1 and Plekhg2 were found in 19 of 29 patients (66%) with active mycobacterial infections. In comparison, we found these autoantibodies in one of 31 patients (3%) with successfully treated mycobacterial infections, in three of 40 (8%) HIV-infected patients not receiving combination antiretorviral therapy (cART) and in six of 134 (5%) blood donors. Interestingly, six of eight (75%) patients with HIV-associated B-cell non-Hodgkin lymphoma (B-NHL) at the onset of disease had autoantibodies against Ufc1 and Plekhg2, but none of nine (0%) patients after treatment of HIV-associated B-NHL, none of seven patients with non-HIV-associated B-NHL and 11 of 115 (10%) patients with other malignant diseases had autoantibodies against both proteins.

CONCLUSIONS

In view of the high frequency of these autoantibodies, we postulate that they might be of potential use for additional diagnostics for mycobacterial infections, and further studies may shed light on the pathomechanisms of these two autoantibodies.

Immunoglobulin gene repertoire diversification and selection in the stomach - from gastritis to gastric lymphomas

Chronic gastritis is characterized by gastric mucosal inflammation due to autoimmune responses or infection, frequently with Helicobacter pylori. Gastritis with H. pylori background can cause gastric mucosa-associated lymphoid tissue lymphoma (MALT-L), which sometimes further transforms into diffuse large B-cell lymphoma (DLBCL). However, gastric DLBCL can also be initiated de novo. The mechanisms underlying transformation into DLBCL are not completely understood. We analyzed immunoglobulin repertoires and clonal trees to investigate whether and how immunoglobulin gene repertoires, clonal diversification, and selection in gastritis, gastric MALT-L, and DLBCL differ from each other and from normal responses. The two gastritis types (positive or negative for H. pylori) had similarly diverse repertoires. MALT-L dominant clones (defined as the largest clones in each sample) presented higher diversification and longer mutational histories compared with all other conditions. DLBCL dominant clones displayed lower clonal diversification, suggesting the transforming events are triggered by similar responses in different patients. These results are surprising, as we expected to find similarities between the dominant clones of gastritis and MALT-L and between those of MALT-L and DLBCL.

Molecular and cytogenetic characterization of expanded B-cell clones from multiclonal versus monoclonal B-cell chronic lymphoproliferative disorders

Chronic antigen-stimulation has been recurrently involved in the earlier stages of monoclonal B-cell lymphocytosis, chronic lymphocytic leukemia and other B-cell chronic lymphoproliferative disorders. The expansion of two or more B-cell clones has frequently been reported in individuals with these conditions; potentially, such coexisting clones have a greater probability of interaction with common immunological determinants. Here, we analyzed the B-cell receptor repertoire and molecular profile, as well as the phenotypic, cytogenetic and hematologic features, of 228 chronic lymphocytic leukemia-like and non-chronic lymphocytic leukemia-like clones comparing multiclonal (n=85 clones from 41 cases) versus monoclonal (n=143 clones) monoclonal B-cell lymphocytosis, chronic lymphocytic leukemia and other B-cell chronic lymphoproliferative disorders. The B-cell receptor of B-cell clones from multiclonal cases showed a slightly higher degree of HCDR3 homology than B-cell clones from mono clonal cases, in association with unique hematologic (e.g. lower B-lymphocyte counts) and cytogenetic (e.g. lower frequency of cytogenetically altered clones) features usually related to earlier stages of the disease. Moreover, a subgroup of coexisting B-cell clones from individual multiclonal cases which were found to be phylogenetically related showed unique molecular and cytogenetic features: they more frequently shared IGHV3 gene usage, shorter HCDR3 sequences with a greater proportion of IGHV mutations and del(13q14.3), than other unrelated B-cell clones. These results would support the antigen-driven nature of such multiclonal B-cell expansions, with potential involvement of multiple antigens/epitopes.

Combined patterns of IGHV repertoire and cytogenetic/molecular alterations in monoclonal B lymphocytosis versus chronic lymphocytic leukemia

Background

Chronic lymphocytic leukemia (CLL)-like monoclonal B lymphocytosis (MBL) with (MBL^hi) or without (MBL^lo) absolute B-lymphocytosis precedes most CLL cases,the specific determinants for malignant progression remaining unknown.

Methodology/Principal Findings

For this purpose, simultaneous iFISH and molecular analysis of well-established cytogenetic alterations of chromosomes 11, 12, 13, 14 and 17 together with the pattern of rearrangement of the IGHV genes were performed in CLL-like cells from MBL and CLL cases. Our results based on 78 CLL-like MBL and 117 CLL clones from 166 subjects living in the same geographical area, show the existence of three major groups of clones with distinct but partially overlapping patterns of IGHV gene usage, IGHV mutational status and cytogenetic alterations. These included a group enriched in MBL^lo clones expressing specific IGHV subgroups (e.g. VH3-23) with no or isolated good-prognosis cytogenetic alterations, a second group which mainly consisted of clinical MBL^hi and advanced stage CLL with a skewed but different CLL-associated IGHV gene repertoire (e.g. VH1-69), frequently associated with complex karyotypes and poor-prognosis cytogenetic alterations, and a third group of clones with intermediate features, with prevalence of mutated IGHV genes, and higher numbers of del(13q)⁺ clonal B-cells.

Conclusions/Significance

These findings suggest that the specific IGHV repertoire and IGHV mutational status of CLL-like B-cell clones may modulate the type of cytogenetic alterations acquired, their rate of acquisition and/or potentially also their clinical consequences. Further long-term follow-up studies investigating the IGHV gene repertoire of MBL^lo clones in distinct geographic areas and microenvironments are required to confirm our findings and shed light on the potential role of some antigen-binding BCR specificities contributing to clonal evolution.

Lymphoid proliferations of indeterminate malignant potential arising in adults with common variable immunodeficiency disorders: unusual case studies and immunohistological review in the light of possible causative events

Patients with common variable immunodeficiency disorders (CVIDs) who developed B cell lymphoproliferation of indeterminate malignant potential are described in order to raise a discussion of the relationship between infection and lymphoproliferation in infection prone patients. Those with CVID are at risk of developing either polyclonal or monoclonal lymphoproliferation in part due to the dysregulation of their adaptive immune systems. The aetiologies of the lymphoproliferations are unknown but intriguing; the relevance of infection being particularly problematic. The patients described here demonstrate variability in preceding infection, age at presentation, response to antibiotics and other types of therapy as well as outcome. The question of treatment is also controversial; issues include whether antibiotics or chemotherapy are the first line of therapy in all patients and whether transformation to aggressive B cell malignancy is inevitable or depends on other factors and if so, the length of time for such progression.

B-cell receptor signaling and CD40 ligand-independent T cell help cooperate in Helicobacter-induced MALT lymphomagenesis

Gastric B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) develops in the context of chronic inflammation caused by Helicobacter pylori infection. Most pathophysiological features of the early stages of MALT lymphomagenesis can be reproduced by experimental infection of BALB/c mice with Helicobacter species. We have previously shown that MALT lymphomas are infiltrated by T-helper cell type 2-polarized T cells and that human and murine tumor B cells carry polyreactive surface immunoglobulins. Using the murine model of the disease, in this study we show that explanted tumor B cells proliferate upon stimulation with the same panel of self and foreign antigens that are recognized by their surface antibodies. Tumor cell proliferation is strongly enhanced by the presence of intratumoral CD4(+) T cells in a CD40/CD40L-independent manner. A large proportion of tumor-infiltrating CD4(+) T cells are CD25(+)FoxP3(+) regulatory T cells (Tregs) with highly suppressive activity, which are recruited by the tumor cells through secretion of the Treg-attracting chemokines CCL17 and CCL22. The depletion of CD25(+) cells was as efficient as CD4(+) T cell depletion in blocking tumor growth in vitro and in vivo. In conclusion, our data suggest that B-cell receptor-derived signals cooperate with T-helper cell signals in driving the progression of MALT lymphoma, providing an explanation for the unique antigen dependence of this B-cell malignancy.

Gastric MALT lymphoma B cells express polyreactive, somatically mutated immunoglobulins

Gastric B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) arises against a background of chronic inflammation caused by persistent Helicobacter pylori infection. The clinical and histopathologic features of the human tumor can be reproduced by Helicobacter infection of BALB/c mice. In this study, we have analyzed the antibody sequences and antigen specificity of a panel of murine and human MALT lymphoma-derived antibodies. We find that a majority of tumors in patients as well as experimentally infected mice are monoclonal. The tumor immunoglobulin heavy chain genes have undergone somatic hypermutation, and approximately half of all tumors show evidence of intraclonal variation and positive and/or negative selective pressure. Recombinantly expressed MALT lymphoma antibodies bind with intermediate affinity to various unrelated self- and foreign antigens, including Helicobacter sonicate, immunoglobulin G (IgG), DNA, and stomach extract; antigen binding is blocked in a dose-dependent manner in competitive enzyme-linked immunosorbent assays. A strong bias toward the use of V(H) gene segments previously linked to autoantibodies and/or polyreactive antibodies in B-cell malignancies or autoimmune pathologies supports the experimental finding of polyreactivity. Our results suggest that MALT lymphoma development may be facilitated by an array of local self- and foreign antigens, providing direct antigenic stimulation of the tumor cells via their B-cell receptor.

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.

The majority of cutaneous marginal zone B-cell lymphomas expresses class-switched immunoglobulins and develops in a T-helper type 2 inflammatory environment

Extranodal marginal zone B-cell lymphomas (MZBCLs) arise on a background of chronic inflammation resulting from organ-specific autoimmunity, infection, or by unknown causes. Well-known examples are salivary gland MZBCL in Sjögren's sialadenitis and gastric MZBCL in Helicobacter pylori gastritis. MZBCLs express CXCR3, a receptor for interferon-γ–induced chemokines highly expressed in the chronic inflammatory environment. The immunoglobulin (Ig) variable heavy/light chain (IgVH/IgVL) gene repertoire of salivary gland and gastric MZBCL appears restricted and frequently encodes B-cell receptors with rheumatoid factor reactivity. Primary cutaneous marginal zone B-cell lymphomas (PCMZLs) are regarded as the skin-involving counterparts of extranodal MZBCLs. Although PCMZLs have been associated with Borrelia burgdorferi dermatitis, PCMZLs generally arise because of unknown causes. We studied an extensive panel of PCMZLs and show that PCMZLs do not conform to the general profile of extranodal MZBCL. Whereas most noncutaneous MZBCLs express IgM, PCMZLs in majority express IgG, IgA, and IgE and do not show an obvious immunoglobulin repertoire bias. Furthermore, the isotype-switched PCMZLs lack CXCR3 and seem to arise in a different inflammatory environment, compared with other extranodal MZBCLs.

Lymphoma in common variable immunodeficiency: interplay between immune dysregulation, infection and genetics

PURPOSE OF REVIEW

Common variable immunodeficiency represents the largest group of primary immunodeficiency patients. The variable clinical manifestations include an increased susceptibility to chronic infections, granulomatous disease and the lymphoproliferative predisposition to develop lymphoma. This review discusses the latest insights into common variable immunodeficiency and uses common variable immunodeficiency as a model to examine the links between immunodeficiency and chronic infections in causing lymphoma.

RECENT FINDINGS

Newly identified disease genes within the common variable immunodeficiency population, have advanced the understanding of human immunodeficiency and the molecular basis of B-cell biology. Refined laboratory techniques have better defined this heterogeneous condition by classifying the underlying B-cell and T-cell abnormalities. New sensitive methods have also identified the presence of persistent infections that may play a role in the development of lymphoma.

SUMMARY

There are several reasons for an increased risk of lymphoma in common variable immunodeficiency patients. These include genetics, immune dysregulation, radiosensitivity and chronic infections such as Helicobacter pylori, human herpes virus type 8 and cytomegalovirus. Chronic infections may enhance the development of lymphoma in an antigen specific manner. The interaction between chronic infections and the development of lymphoma is still unclear but studies to clarify this may lead to prevention measures and lymphoma reduction strategies.

Improved methods for detecting selection by mutation analysis of Ig V region sequences

Statistical methods based on the relative frequency of replacement mutations in B lymphocyte Ig V region sequences have been widely used to detect the forces of selection that shape the B cell repertoire. However, current methods produce an unexpectedly high frequency of false positives and are sensitive to intrinsic biases of somatic hypermutation that can give the appearance of selection. The new statistical test proposed here provides a better trade-off between sensitivity and specificity compared with previous approaches. The low specificity of existing methods was shown in silico to result from an interaction between the effects of positive and negative selection. False detection of positive selection was confirmed in vivo through a re-analysis of published sequence data from diffuse large B cell lymphomas, highlighting the need for re-analysis of some existing studies. The sensitivity of the proposed method to detect selection was validated using new Ig transgenic mouse models in which positive selection was expected to be a significant force, as well as with a simulation-based approach. Previous concerns that intrinsic biases of somatic hypermutation could give the appearance of selection were addressed by extending the current mutation models to more fully account for the impact of microsequence on relative mutability and to include transition bias. High specificity was confirmed using a large set of non-productively rearranged Ig sequences. These results show that selection can be detected in vivo with high specificity using the new method proposed here, allowing greater insight into the existence and direction of antigen-driven selection.

Musculoskeletal syndromes associated with malignancy (excluding hypertrophic osteoarthropathy)

PURPOSE OF REVIEW

To examine recent data about the association between rheumatic disorders and cancer. This article focuses on paraneoplastic rheumatic disorders, which usually precede by a short period of time the diagnosis of malignancy, and on malignant transformation, which occurs late in the course of rheumatic disorders. Evidence of causality between malignancies and rheumatic disorders was reviewed based on statistical indicators (standardized incidence ratios and odds ratios) and by applying Bradford Hill's criteria of causality.

RECENT FINDINGS

Firm epidemiological evidence was found attesting that dermatomyositis and polymyostis may present as paraneoplastic syndromes. Several other musculoskeletal disorders may be present akin to paraneoplastic syndrome, based on clinicians' impressions, but with scarce epidemiological evidence supporting a causal determinism. In contrast, robust evidence has accumulated on the role of longstanding rheumatoid arthritis, Sjögren's syndrome and systemic sclerosis as premalignant conditions. Evidence that systemic lupus erythematosus may evolve into lymphoma is equivocal.

SUMMARY

The link between malignancies and rheumatic disorders may impact on clinical practice. First, paraneoplastic rheumatic syndromes can provide the clinician with hints for earlier diagnosis of occult cancer. Second, the risk of malignant transformation during the course of rheumatic disorders may motivate the search for strategies aimed at prevention.

The emerging concept of antigen-driven lymphomas: epidemiology and treatment implications

PURPOSE OF REVIEW

Dramatic increases in the incidence of lymphomas worldwide have stimulated considerable efforts to identify factors that contribute to the etiology of this heterogeneous group of malignancies. The treatment and, ultimately, the prevention of lymphoma depend on our understanding of the complex interaction of exogenous agents with the molecular milieu which initiates and sustains a lymphoid malignancy. This review discusses the current evidence for the role of foreign or self antigens in the initiation of lymphomagenesis.

RECENT FINDINGS

Recent data have demonstrated an increased risk of lymphoma among individuals with chronic inflammatory conditions, persistent infections or immunodeficient states. Common to these clinical conditions is antigenic stimulation leading to an inflammatory cascade of cellular and cytokine reactions that may tax the host immune response, provoke tissue injury and eventually result in lymphoid neoplasia.

SUMMARY

Efforts to detect and suppress chronic, antigen-driven inflammation have suggested that neoplastic progression may often be interrupted and controlled. Elucidation of the etiologic mechanisms critical to the survival of these malignancies would provide promising alternatives for the prevention and treatment of some lymphomas.