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

Biomarkers of lymphoma in Sjögren's syndrome: what's the latest?

INTRODUCTION

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease standing in the crossroads of autoimmunity and lymphomagenesis, characterized by chronic B-cell hyperactivity and ectopic lymphoid tissue neoformation, potentially driving lymphoid malignant transformation. Lymphoma development is considered the most serious complication of pSS.

AREAS COVERED: “

Old-classical" biomarkers (clinical, serological, hematological, and histological) validated in the past are analyzed under the perspective of recently published research. Biomarkers that have emerged during the last decade are subdivided to "old-new" and "newly proposed-novel" ones, including biomarkers pathophysiologically related to B-cell differentiation, lymphoid organization, and immune responses, identified in serum and tissue, both at genetic and protein level. Upcoming new imaging biomarkers, promising for further patient stratification, are also analyzed.

EXPERT OPINION

Salivary gland enlargement and cryoglobulinemia still remain the best validated "classical-old" biomarkers for lymphoma development. Though new biomarkers still need to be validated, some can be used for the identification of high-risk patients long before lymphoma diagnosis, some might be more relevant in distinct age subgroups, while others have an added value in the assessment of lymphoma remission or relapse. Future development of composite indices integrating old and recently proposed biomarkers could contribute to a more precise lymphoma prediction model.

Repertoire Analysis of B-Cells Located in Striated Ducts of Salivary Glands of Patients With Sjögren's Syndrome

A major complication of primary Sjögren's syndrome (pSS) is development of mucosa associated lymphoid tissue (MALT) B-cell lymphoma, particularly in salivary glands. These lymphomas express FcRL4 and are characteristically associated with lymphoepithelial lesions. Neoplastic B-cells may be derived from non-neoplastic glandular intraductal B-cells, also virtually all expressing FcRL4. A characteristic feature of MALT lymphomas is the production of rheumatoid factors (RFs), which are largely encoded by stereotypic immunoglobulin variable heavy chain (IGHV) sequences. The aim of this study was to examine whether there is a relationship between the intraductal and periductal B-cells and whether the intraductal B-cells are selected for RF. RNA was extracted from laser-microdissected infiltrated ductal areas and periductal infiltrates from frozen parotid gland tissue sections of 5 pSS patients. PCR amplified IGHV transcripts were cloned into pCR™4-TOPO vector and subsequently sequenced. Microdissected ducts yielded 96 unique IGHV sequences derived from intraductal B-cells, while 119 unique IGHV sequences were obtained from periductal infiltrates. No major difference in VH-gene usage was observed between intraductal and periductal B-cells. Nearly all (>90%) IGHV sequences derived from both intraductal and periductal B-cells were mutated. Clonal expansions as defined by shared VDJ rearrangements were also present among both intraductal and periductal B-cells: in total 32 clones were found, from which 12 were located within ducts, 15 in periductal areas, and five clones shared members in both areas. We observed 12 IGHV rearrangements encoding for RF sequences from which two were derived from intraductal B-cells and 10 from periductal B-cells. Nine RF sequences were part of a clone. Together these findings indicate that intraductal and periductal B-cells are closely related to each other. Intraductal B-cells are most likely derived from periductal B-cells. We did not obtain evidence that RF-specific B-cells are enriched within the striated ducts. We speculate that in principle any activated B-cell can enter the striated ducts from the periductal infiltrate, irrespective of its antigenic specificity. Within the ducts, these B-cells may receive additional activation and proliferation signals, to further expand at these sites and by acquisition of driver-mutations develop toward lymphoma.

Immunoglobulin Vlambda light chain gene usage in patients with Sjögren's syndrome

OBJECTIVE

To determine whether patients with Sjögren's syndrome (SS) have abnormalities in Ig Vlambda and Jlambda gene usage, differences in somatic hypermutation, defects in selection, or indications for perturbations of B cell maturation.

METHODS

Individual peripheral B cells from SS patients were analyzed for their Vlambda gene usage by single-cell polymerase chain reaction amplification of genomic DNA and compared with those from normal controls.

RESULTS

Molecular differences from controls in Vlambda-Jlambda recombination were identified that were reflected by findings in the nonproductive Vlambda repertoire of the patients, including enhanced rearrangement of Vlambda10A and Jlambda2/3 gene segments. In addition, a number of abnormalities in the productive repertoire were identified, indicating disordered selection. A greater usage of 4 Vlambda genes (2A2, 2B2, 2C, and 7A), representing 56% of all productive Vlambda rearrangements, was observed, suggesting positive selection of these genes. Overutilization of Jlambda2/3 and underutilization of Jlambda7 in both nonproductive and productive Vlambda rearrangements of SS patients compared with controls suggested decreased receptor editing in SS. The mutational frequency did not differ from that in controls, and positive selection of mutations into the productive V gene repertoire was found, similar to that in controls, although mutational targeting toward RGYW/WRCY motifs, typically found in controls, was not found in SS patients.

CONCLUSION

Disturbed regulation of B cell maturation with abnormal selection, defects in editing Ig receptors, and abnormal mutational targeting may contribute to the emergence of autoimmunity in SS.

Preliminary classification of nonmalignant B cell proliferation in Sjögren's syndrome: perspectives on pathobiology and treatment based on an integrated clinico-pathologic and molecular study approach

A classification of nonmalignant lymphoproliferation in Sjögren's syndrome is presented, based on the results of international meetings regarding Sjögren's syndrome-associated lymphomagenesis and on our results of a clinico-pathologic and molecular study and long-term follow-up in well-characterized patients. Sjögren's syndrome pathobiology has similarities to hepatitis C virus-related B-cell lymphoproliferation. Antigen stimulation with the preferential expansion of rheumatoid factor-positive clones and specific immunoglobulin gene expression and recombination represent key biologic events in lymphoproliferation. This classification is based on the coupling of molecular and histological studies and may result in more selective treatment approaches.

Cells of the marginal zone--origins, function and neoplasia

Splenic marginal zone B cells of humans and mice are anatomically positioned with specialized macrophages, dendritic and endothelial cells. Together, they function as the first line of defense against blood borne pathogens with a low triggering threshold for B cells providing a rapid proliferative and antibody response to infections. In humans, B cells with similar cytology and physical relations to follicles are found in lymph nodes and Peyer's patches. However, they also develop in mucosa-associated lymphoid tissue (MALT) and other sites, such as the thyroid and salivary gland, that normally lack organized lymphoid tissue. Chronic antigenic stimulation at these sites or in response to infection with Hepatitis C provides the milieu for mutations at FAS, API2/ML, TP53 and INK4a/p19ARF and the development of marginal zone lymphomas (MZL) in node, spleen and MALT. Only splenic MZL are seen in mice. A reduced threshold for triggering to proliferation may predispose the marginal zone B cell to neoplasia with mutations in genes regulating apoptosis playing a leading role.