Unique expansion of IL-21+ Tfh and Tph cells under control of ICOS identifies Sjögren's syndrome with ectopic germinal centres and MALT lymphoma.

OBJECTIVES: To explore the relevance of T-follicular-helper (Tfh) and pathogenic peripheral-helper T-cells (Tph) in promoting ectopic lymphoid structures (ELS) and B-cell mucosa-associated lymphoid tissue (MALT) lymphomas (MALT-L) in Sjögren's syndrome (SS) patients. METHODS: Salivary gland (SG) biopsies with matched peripheral blood were collected from four centres across the European Union. Transcriptomic (microarray and quantitative PCR) analysis, FACS T-cell immunophenotyping with intracellular cytokine detection, multicolor immune-fluorescence microscopy and in situ hybridisation were performed to characterise lesional and circulating Tfh and Tph-cells. SG-organ cultures were used to investigate functionally the blockade of T-cell costimulatory pathways on key proinflammatory cytokine production. RESULTS: Transcriptomic analysis in SG identified Tfh-signature, interleukin-21 (IL-21) and the inducible T-cell co-stimulator (ICOS) costimulatory pathway as the most upregulated genes in ELS+SS patients, with parotid MALT-L displaying a 400-folds increase in IL-21 mRNA. Peripheral CD4+CXC-motif chemokine receptor 5 (CXCR5)+programmed cell death protein 1 (PD1)+ICOS+ Tfh-like cells were significantly expanded in ELS+SS patients, were the main producers of IL-21, and closely correlated with circulating IgG and reduced complement C4. In the SG, lesional CD4+CD45RO+ICOS+PD1+ cells selectively infiltrated ELS+ tissues and were aberrantly expanded in parotid MALT-L. In ELS+SG and MALT-L parotids, conventional CXCR5+CD4+PD1+ICOS+Foxp3- Tfh-cells and a uniquely expanded population of CXCR5-CD4+PD1hiICOS+Foxp3- Tph-cells displayed frequent IL-21/interferon-γ double-production but poor IL-17 expression. Finally, ICOS blockade in ex vivo SG-organ cultures significantly reduced the production of IL-21 and inflammatory cytokines IL-6, IL-8 and tumour necrosis factor-α (TNF-α). CONCLUSIONS: Overall, these findings highlight Tfh and Tph-cells, IL-21 and the ICOS costimulatory pathway as key pathogenic players in SS immunopathology and exploitable therapeutic targets in SS.

Higher frequency of circulating, but not tissue regulatory T cells in patients with endometriosis.

BACKGROUND: Endometriosis is one of the most common chronic gynecological disorders affecting women at reproductive age. Dysregulation of immune cells, including regulatory T (Treg) cells has contributed to the growth of ectopic lesion in patients with endometriosis. OBJECTIVE: The present study investigated the frequency of Tregs in peripheral blood and the expression of Foxp3 in eutopic and ectopic endometriotic tissues in women with and without endometriosis. MATERIALS AND METHODS: Peripheral blood mononuclear cells (PBMCs) and eutopic and ectopic endometriotic tissues were obtained from 23 endometriotic and 20 non-endometriotic control women. The frequency of Treg cells in PBMCs was measured using flowcytometry and the expression of Foxp3 in eutopic and ectopic endometriotic tissues was determined by real-time PCR, western blotting and immunohistochemistry. RESULT: The frequency of circulating Tregs was significantly higher in endometriotic patients compared with non-endometriotic controls (P < 0.01). The mRNA and protein expression of Foxp3 in eutopic and ectopic endometriotic tissues had no significant differences between the two study groups. CONCLUSION: Higher frequency of circulating Tregs in patients with endometriosis compared with controls may be considered as a compensatory mechanism to regulate the inflammatory condition in this disease.

Ectopic hamartomatous thymoma in an immunocompromised male.

Ectopic hamartomatous thymoma (EHT) is a rare benign neoplasm classically occurring in the lower neck of adult males. Here we present a case of EHT occurring in a 43-year-old immunocompromised male and a brief review of existing literature. The patient presented with a palpable mass overlying the left clavicle which, on imaging, showed a solitary nodule possibly eroding the cortical bone. A biopsy predominantly showed spindle cells that were immunopositive for keratin AE1/AE3 as well as weakly positive for CD99, SMA, and CD34. A diagnosis of synovial sarcoma was favored; at which point surgical resection was performed. The resected mass was well-demarcated with a tan-yellow cut surface. Microscopically, the lesion was composed of a mixture of spindle cells, glands, and mature adipose tissue. The spindle cells were plump with bland nuclei, and the epithelial component showed morphology similar to glands of salivary or breast tissue with a bilayered appearance (luminal and basal). No pleomorphism, mitotic figures, or necrosis was present. Immunohistochemical stains were performed and showed the spindle cells to express a myoepithelial phenotype (cytokeratin AE1/AE3, p63, calponin positive). The glands showed SMA and p63 positivity in the basal cells (similar to salivary gland and breast). Overall, given the clinical context, histomorphologic, and immunohistochemical profile, a diagnosis of EHT was made. At 12 months of follow-up there was no evidence of recurrence.

Serum and Ectopic Endometrium from Women with Endometriosis Modulate Macrophage M1/M2 Polarization via the Smad2/Smad3 Pathway.

OBJECTIVE: This study investigated the alterations in macrophage polarization in patients with endometriosis as well as the underlying molecular mechanisms. METHODS: Peritoneal washings, serum samples, and endometrial tissues were collected from endometriosis patients and control subjects. Endometrial stromal cells (ESCs) were isolated from endometrial tissue, and conditioned medium was prepared by treating ESCs with or without various concentrations of interleukin- (IL-) 6, estrogen, or progestin. The frequencies of CD86+ and CD163+ cells and expression levels of these markers as well as the cytokines IL-12 and IL-10 were measured in THP-1- (human monocytic leukemia cell) derived macrophages. RESULTS: There was a decrease in the percentage of CD86+ macrophages in the peritoneal wash solution of patients with endometriosis. Ectopic endometrial homogenates could promote M1 to M2 macrophage polarization in response to lipopolysaccharide (LPS), as evidenced by the increased percentage of CD163+ macrophages and increased IL-10 expression as well as a decreased percentage of CD86+ cells and lower IL-12 expression. In contrast, addition of serum from women with endometriosis to THP-1 cells resulted in the polarization of macrophages towards both M1 and M2 phenotypes. Upregulation of Smad2/Smad3 in macrophages upon exposure to eutopic and ectopic endometrial homogenates as well as serum of women with endometriosis was observed, and blockage of Smad2/Smad3 with their inhibitor SB431542 could reverse the macrophage polarization from M1 to M2. Conditioned medium induced by IL-6, but neither estrogen nor progestin, could facilitate M2 polarization. Neutralization of IL-6 diminished macrophage M2 polarization in endometriosis. CONCLUSION: This study provides detailed evidence supporting alterations in M1 to M2 macrophage polarization that may contribute to the initiation as well as progression of endometriosis.

Role of TFH Cells in Promoting T Helper 17-Induced Neuroinflammation.

Both T cells and B cells are implicated in the pathology of multiple sclerosis (MS), but how these cells cooperate to drive disease remains unclear. Recent studies using experimental autoimmune encephalomyelitis (EAE) demonstrated that the TH17 pathway is correlated with increased numbers of ectopic B-cell follicles in the central nervous system (CNS). As follicular T helper (TFH) cells are regulators of B cell responses, we sought to examine the role of TFH cells in EAE induced by the transfer of myelin-specific TH17 cells (TH17-EAE). In this study, we first confirmed previous reports that B-cells are a major cell type infiltrating the CNS during TH17-EAE. In addition, we found that B cells contribute to the severity of TH17-EAE. Class-switched B-cells in the CNS were positively correlated with disease and, strikingly, the severity TH17-EAE was diminished in B cell deficient mice. We next focused on the role TFH cells play in TH17-EAE. We found substantial numbers of CXCR5+PD1+CD4+ TFH cells in the CNS tissue of TH17-EAE mice and that at the peak of disease, the number of infiltrating TFHs was correlated with the number of infiltrating B-cells. Using congenic CD45.1+ donor mice and CD45.2+ recipient mice, we determined that the TFH cells were recipient-derived, whereas IL-17+ cells were donor-derived. We assessed whether myelin-specific TFH cells are capable of inducing EAE in recipient mice and found that transferring TFH cells failed to induce EAE. Finally, we tested the effects of blocking TFH trafficking in TH17-EAE using an antagonistic antibody against CXCL13, the chemokine ligand for CXCR5 on TFH cells. We found anti-CXCL13 treatment significantly reduced TH17-EAE disease. This treatment blocked CD4+ T cells from entering the CNS, but had no effect on infiltration of B cells. Strikingly, this antibody treatment had no measurable effect on TH17 disease in B cell-deficient mice. These data demonstrate that infiltrating TFH cells are a key cell type that contributes to an inflammatory B cell response in TH17-EAE and provide evidence for targeting TFH cells as a treatment for neuro-autoimmune diseases like MS.

Treg and NK cells related cytokines are associated with deep rectosigmoid endometriosis and clinical symptoms related to the disease.

The aim of this study was to evaluate Treg and NK cells related cytokines in deep infiltrating endometriosis lesions and its relationship with clinical symptoms of the disease. mRNA expression of Transforming Growth Factor Beta (TGFB), Interleukin (IL)10, Interferon Gamma (IFNG), IL7, and IL15 was analyzed by Real-Time PCR in eutopic endometrium and rectosigmoid lesions from 11 women with deep infiltrating endometriosis and in eutopic endometrium from 11 healthy women. IL10, IFNG, and IL7 expression was significantly higher in endometriotic bowel lesions than in eutopic endometrium from women with endometriosis. IL10 and TGFB expression was significantly higher in endometriotic bowel lesions than in eutopic endometrium from healthy women. In addition, TGFB and IL15 levels correlated positively with deep dyspareunia and cyclic dyschezia, respectively, while IL7 levels correlated negatively with dysmenorrhea. Deep infiltrating rectosigmoid endometriosis displays alterations in Treg and NK cells related cytokine, and TGFB, IL7 and IL15 expression is related with dyspareunia, dysmenorrhea and cyclic dyschezia, respectively, in patients with the disease.

"What do we know about regulatory T cells and endometriosis? A systematic review".

Endometriosis is a benign, chronic inflammatory disease that presents alterations in immune response that can be detected in eutopic endometrium, peritoneal fluid and peripheral blood of affected women. Regulatory T (TReg) cells are a subpopulation of T lymphocytes specialized in immune regulation that seem to participate in the development of endometriosis, by suppressing the immune response and favoring the establishment of lesions. Our aim was to review the scientific literature that evaluates TReg cell phenotypes in the context of endometriosis. PRISMA statement for systematic reviews was applied, using "regulatory T cells" and "endometriosis" as keywords in the following databases: PubMed, Cochrane, EMBASE and Lilacs. The initial search and abstract review yielded 41 papers relating to the subject. At the end, 12 studies, published between 2009 and 2016, were included. Most studies that analyzed TReg cells did not characterize these cells with current Bona Fide markers. In peritoneal fluid and endometriotic lesions, there was a higher concentration of TReg cell phenotype and/or TReg cell expression markers in patients with endometriosis when compared with controls. However, there is still not a consensus about TReg cells concentration in eutopic endometrium and peripheral blood between the revised studies. Taken together, this data collection suggests that endometriosis is related to TReg cells alterations, although further studies are necessary to reach more precise conclusions, especially regarding the percentage of these cells in eutopic endometrium and peripheral blood. This systematic review attempted to provide instructive and up-to-date collection of data that may help better design future studies.

Characteristics of germinal center-like structures in patients with Sjögren's syndrome.

AIM: To analyze the relationship between ectopic germinal centers (GCs) in the salivary glands and the clinical/laboratory characteristics of patients with Sjögren's syndrome (SS). METHODS: Retrospectively, 126 patients with primary SS (pSS) and 16 patients with secondary SS (sSS) were analyzed. Minor salivary gland biopsies were evaluated for the presence of GC-like morphology by hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining for CD21. Clinical and serological data were obtained from medical records. RESULTS: GC-like structures were observed in 36/126 (28.6%) pSS patients and 4/16 (25.0%) sSS patients. The mean inflammatory focus score of the gland was significantly higher in GC-positive samples than in GC-negative ones in both pSS and sSS patients (P = 0.007 and 0.024, respectively). In pSS, significantly elevated titers of rheumatoid factor (RF)-IgM (P = 0.023) and antinuclear antibodies (ANA) (P = 0.036), increased levels of IgA (P = 0.012) and IgG (P = 0.017) were encountered in GC-positive patients. The GC-positive group also presented higher prevalence of anti-SSA antibodies, lower levels of white blood cells, higher levels of erythrocyte sedimentation rate and γ-globulin, although not statistically significant. In sSS patients with ectopic GC formation, ANA titers were remarkably elevated. The anticyclic citrullinated peptide (anti-CCP)-IgG titers and the prevalence of antikeratin antibody (AKA)-IgG, antiperinuclear factor (APF)-IgG were also increased, yet not significantly. GCs were found to be associated with antibody and immunoglobulin production. CONCLUSION: This study indicates that SS patients with ectopic GCs have distinct features. Ectopic GC structures were particularly noted in patients with higher focus scores, and might play an essential role in sustaining antibody production as well as B cell activation.

Ectopic lymphoid follicles: inducible centres for generating antigen-specific immune responses within tissues.

Lymphoid neogenesis is traditionally viewed as a pre-programmed process that promotes the formation of lymphoid organs during development. Here, the spatial organization of T and B cells in lymph nodes and spleen into discrete structures regulates antigen-specific responses and adaptive immunity following immune challenge. However, lymphoid neogenesis is also triggered by chronic or persistent inflammation. Here, ectopic (or tertiary) lymphoid organs frequently develop in inflamed tissues as a response to infection, auto-immunity, transplantation, cancer or environmental irritants. Although these structures affect local immune responses, the contribution of these lymphoid aggregates to the underlining pathology are highly context dependent and can elicit either protective or deleterious outcomes. Here we review the cellular and molecular mechanisms responsible for ectopic lymphoid neogenesis and consider the relevance of these structures in human disease.

Antibodies against carbamylated proteins are present in primary Sjögren's syndrome and are associated with disease severity.

OBJECTIVES: Herein, we investigate the presence and prognostic value of autoantibodies against carbamylated proteins (anti-CarP) in the serum of patients with primary Sjögren's syndrome (pSS). PATIENTS AND METHODS: Serum levels of anti-CarP antibodies were measured in Norwegian patients with pSS (n=78) and corresponding controls (n=74) using ELISA and analysed in relation with exocrine gland function, degree of salivary gland inflammation, signs of ectopic germinal centre (GC) formation and immunological markers. For univariate comparisons, the Mann-Whitney U test and χ(2) or Fisher's exact tests were used. Correlations were assessed with Spearman's rank testing. Multivariate regression analyses were used to assess the effect of anti-CarP positivity on clinical manifestations. RESULTS: Of the patients with pSS, 27% were positive for anti-CarP IgG antibodies. Levels of anti-CarP correlated positively with total IgG, IgM, rheumatoid factor and ß2-microglobulin. Importantly, after adjusting for confounding factors, patients positive for anti-CarP had significantly higher focus score. Furthermore, positive anti-CarP status coincided with 9.2-fold higher odds of having developed GC-like structures in the minor salivary glands. As a patient group considered having worse disease outcome, individuals with ectopic GC-like structures also presented with significantly higher levels of anti-CarP antibodies. CONCLUSIONS: Presence of anti-CarP in patients with pSS is strongly associated with increased focal lymphocytic infiltration, formation of ectopic GC-like structures in minor salivary glands, and diminished salivary gland function. Even taking into consideration our relatively small cohort we believe that anti-CarP antibodies offer new possibilities for identifying patients with more active disease and at risk of developing additional comorbidity.

Artery Tertiary Lymphoid Organs Control Aorta Immunity and Protect against Atherosclerosis via Vascular Smooth Muscle Cell Lymphotoxin ß Receptors.

Tertiary lymphoid organs (TLOs) emerge during nonresolving peripheral inflammation, but their impact on disease progression remains unknown. We have found in aged Apoe(-/-) mice that artery TLOs (ATLOs) controlled highly territorialized aorta T cell responses. ATLOs promoted T cell recruitment, primed CD4(+) T cells, generated CD4(+), CD8(+), T regulatory (Treg) effector and central memory cells, converted naive CD4(+) T cells into induced Treg cells, and presented antigen by an unusual set of dendritic cells and B cells. Meanwhile, vascular smooth muscle cell lymphotoxin ß receptors (VSMC-LTßRs) protected against atherosclerosis by maintaining structure, cellularity, and size of ATLOs though VSMC-LTßRs did not affect secondary lymphoid organs: Atherosclerosis was markedly exacerbated in Apoe(-/-)Ltbr(-/-) and to a similar extent in aged Apoe(-/-)Ltbr(fl/fl)Tagln-cre mice. These data support the conclusion that the immune system employs ATLOs to organize aorta T cell homeostasis during aging and that VSMC-LTßRs participate in atherosclerosis protection via ATLOs.

Langerhans cells proliferation in ectopic micronodular thymoma with lymphoid stroma: a case report.

Ectopic micronodular thymoma (MNT) is a rare tumor. We described a 76-year-old woman, who was referred to our institutional for a mass in the left cervical region. The Magnetic Resonance Imaging (MRI) scan showed a 3.7 cm × 1.7 cm × 2.0 cm mass. The neoplasm was composed of epithelial tumor cells arranged in a micronodular growth pattern set in a stroma showing lymphoid hyperplasia with germinal centers. Immunohistochemical studies showed that the neoplastic epithelial cells were reactive for AE1/AE3, CK5/6, P63, and the lymphoid component to be of mixed B- and immature T-cell lineage. Langerhans cells were confirmed within epithelial nodules for the first time with langerin, S-100, CD1a expression. We report a case of cervical ectopic MNT to emphasize the langerhans cells proliferation and the histopathologic features and differential diagnosis of the rare lesion to promote a better and broader understanding of this less understood subject.

Additional B-cell deficiency does not affect growth and angiogenesis of ectopic human endometrium in T-cell-deficient endometriosis mouse models during long-term culture.

Heterologous endometriosis mouse models characterized by transplantation of human endometrial tissue into immunodeficient mice are widely used to develop novel treatment strategies for this gynecological disease. The majority of these experiments have been performed for up to one month in athymic T-cell-deficient nude mice, which, however, still exhibit intact B-lymphocytes possibly affecting growth and persistence of the xenografts. We describe here the heterologous mouse models used so far and comparatively analyze the characteristics of human endometrial tissue after subcutaneous and intraperitoneal transplantation in nude and in Rag-1-deficient mice exhibiting T- and B-cell deficiency. Moreover, we extended the time of culturing to three months in both mouse strains. Size, histomorphology, and vascularization of xenografts of intraperitoneal and subcutaneous localization did not differ significantly nor did those of the two immunodeficient mouse strains for up to three months of culturing. Whereas the rate of lesions was similar at both localizations in nude mice, in Rag-1 knockout mice significantly more intraperitoneal than subcutaneous lesions could be recovered. Interestingly, in both mouse strains a considerable number of xenografts completely invaded the peritoneal lining after intraperitoneal transplantation and could only be recovered histomorphologically. This has to be taken into account in studies depending on the quantitative analysis of ectopic peritoneal lesions. In conclusion, T-cell deficiency seems to be sufficient for the long-term culture of human endometrial tissue in subcutaneous and intraperitoneal localizations. Additional B-cell deficiency does not provide advantages with regard to the maintenance, morphology, and blood vessel supply of the ectopic endometrial lesions.

Ectopic lymphoid-like structures in infection, cancer and autoimmunity.

Ectopic lymphoid-like structures often develop at sites of inflammation where they influence the course of infection, autoimmune disease, cancer and transplant rejection. These lymphoid aggregates range from tight clusters of B cells and T cells to highly organized structures that comprise functional germinal centres. Although the mechanisms governing ectopic lymphoid neogenesis in human pathology remain poorly defined, the presence of ectopic lymphoid-like structures within inflamed tissues has been linked to both protective and deleterious outcomes in patients. In this Review, we discuss investigations in both experimental model systems and patient cohorts to provide a perspective on the formation and functions of ectopic lymphoid-like structures in human pathology, with particular reference to the clinical implications and the potential for therapeutic targeting.

CX3CL1 and CX3CR1 expression in tertiary lymphoid structures in salivary gland infiltrates: fractalkine contribution to lymphoid neogenesis in Sjogren's syndrome.

OBJECTIVES: Primary SS is an autoimmune disease characterized by chronic lymphocytic inflammation and ectopic germinal centre (GC) formation within salivary glands. Fractalkine (CX3CL1), associated with the pathogenesis of RA, is the sole member of the CX3C chemokine (CK) family and acts as an adhesion and chemotactic molecule. The objectives of this work are to determine to what extent CX3CL1 and its receptor CX3CR1 expression might be altered in salivary glands obtained from patients and to establish whether these CKs might be involved in SS ectopic lymphoneogenesis. METHODS: We assessed the presence of CX3CL1 protein in sera by ELISA in 21 patients with primary SS, 11 patients with Sicca syndrome (Sicca), 20 RA patients and 10 blood donors. Histological evaluation was performed on sequential sections of salivary gland tissue. Using TaqMan RT-PCR we studied CX3CL1 and CX3CR1 mRNA expression in salivary gland tissues from a molecular point of view. RESULTS: Increased serum levels of CX3CL1 protein were observed in SS patients compared with controls (P < 0.0001) and in RA patients compared with controls (P < 0.0001), but no difference was found between Sicca patients and controls (P = 0.22). We identified histologically the cells expressing CX3CL1 and CX3CR1 in salivary glands of SS patients and we localized the molecule within tertiary lymphoid structures. Finally, the mRNA levels of the CK and its receptor were up-regulated in SS salivary glands. CONCLUSION: We believe that our findings point to the need for future studies on CX3CL1 and CX3CR1 proteins as contributors to the formation of ectopic GCs and possibly as a new tool in the evaluation and diagnosis of SS.

Maintenance of anti-Sm/RNP autoantibody production by plasma cells residing in ectopic lymphoid tissue and bone marrow memory B cells.

Although ectopic lymphoid tissue formation is associated with many autoimmune diseases, it is unclear whether it serves a functional role in autoimmune responses. 2,6,10,14-Tetramethylpentadecane causes chronic peritoneal inflammation and lupus-like disease with autoantibody production and ectopic lymphoid tissue (lipogranuloma) formation. A novel transplantation model was used to show that transplanted lipogranulomas retain their lymphoid structure over a prolonged period in the absence of chronic peritoneal inflammation. Recipients of transplanted lipogranulomas produced anti-U1A autoantibodies derived exclusively from the donor, despite nearly complete repopulation of the transplanted lipogranulomas by host lymphocytes. The presence of ectopic lymphoid tissue alone was insufficient, as an anti-U1A response was not generated by the host in the absence of ongoing peritoneal inflammation. Donor-derived anti-U1A autoantibodies were produced for up to 2 mo by plasma cells/plasmablasts recruited to the ectopic lymphoid tissue by CXCR4. Although CD4(+) T cells were not required for autoantibody production from the transplanted lipogranulomas, de novo generation of anti-U1A plasma cells/plasmablasts was reduced following T cell depletion. Significantly, a population of memory B cells was identified in the bone marrow and spleen that did not produce anti-U1A autoantibodies unless stimulated by LPS to undergo terminal differentiation. We conclude that 2,6,10,14-tetramethylpentadecane promotes the T cell-dependent development of class-switched, autoreactive memory B cells and plasma cells/plasmablasts. The latter home to ectopic lymphoid tissue and continue to produce autoantibodies after transplantation and in the absence of peritoneal inflammation. However, peritoneal inflammation appears necessary to generate autoreactive B cells de novo.

The role of ectopic germinal centers in the immunopathology of primary Sjögren's syndrome: a systematic review.

OBJECTIVES: To determine whether the presence of germinal centers (GCs) in salivary glands of patients with primary Sjögren's syndrome (pSS) is related to the severity of disease course and distinct immunopathology features. METHODS: A systematic search was performed in September 2011 for terms and synonyms of Sjögren's syndrome and germinal centers. A total of 80 articles were retrieved, of which 16 were included for (meta-) analysis. RESULTS: GC morphology was present in a mean ± SD 25.1 ± 5.0% of pSS patients. Mean lymphocyte focus scores were 1.25 points higher in patients with GCs as compared to those without GCs. Saliva production was reduced in patients with GCs, although this did not reach statistical significance. Percentages of patients positive for rheumatoid factor, anti-Sjögren's syndrome A (SSA), and anti-Sjögren's syndrome B (SSB) antibodies were significantly higher in patients with GCs (mean increase, 15%, 18%, and 18%, respectively). Additionally, patients with GCs were characterized by enhanced levels of local and systemic proinflammatory mediators. Importantly, these patients have a higher risk of lymphoma development (14% versus 1%). CONCLUSIONS: Patients with GCs are characterized by more severe disease, although the small number of studies and their design hamper generalizability of results. The precise mechanisms that contribute to the development and persistence of germinal centers in pSS are largely unknown. This and the strongly increased risk of lymphoma development warrant intensive studies for the role of germinal centers in the immunopathology of pSS.

Ectopic lymphoid tissue alters the chemokine gradient, increases lymphocyte retention and exacerbates murine ileitis.

BACKGROUND: The earliest endoscopically-evident lesion in Crohn's disease is the aphthous ulcer, which develops over ectopic lymphoid tissues (ie, inducible lymphoid follicles (ILF), tertiary lymphoid tissue (TLT)) in the chronically inflamed intestine. ILF/TLT are induced within effector sites by homeostatic lymphoid chemokines, but their role in the development of intestinal ILF/TLT and in the pathogenesis of Crohn's disease is poorly understood. DESIGN: Using a mouse model of Crohn's-like ileitis (TNFARE) which develops florid induction of ILF/TLT within its terminal ileum, the contribution of the CCR7/CCL19/CCL21 chemokine axis during the development of TLT and its role in disease pathogenesis were assessed. RESULTS: Both CCL19 and CCL21 were increased within the inflamed ileum of TNFARE mice, which resulted in CCR7 internalisation and impaired T cell chemotaxis. ILF/TLT were a major source of CCL19 and CCL21 and increased local synthesis, augmented recruitment/retention of effector, naïve and central memory T cell subsets within the inflamed ileum. Immunoblockade of CCR7 resulted in further effector T cell retention and exacerbation of ileitis. CONCLUSIONS: Induction of ILF/TLT in the chronically inflamed intestine alters the homeostatic CCL19-CCL21 lymphoid-chemokine gradient and increases recruitment/retention of effector CCR7+ T cell subsets within the terminal ileum, contributing to the perpetuation of chronic inflammation. Thus, blockade of CCR7 or its ligands might result in deleterious consequences for subjects with chronic inflammatory diseases.

Role of lymphoid chemokines in the development of functional ectopic lymphoid structures in rheumatic autoimmune diseases.

A sizeable subset of patients with the two most common organ-specific rheumatic autoimmune diseases, rheumatoid arthritis (RA) and Sjögren's syndrome (SS) develop ectopic lymphoid structures (ELS) in the synovial tissue and salivary glands, respectively. These structures are characterized by perivascular (RA) and periductal (SS) clusters of T and B lymphocytes, differentiation of high endothelial venules and networks of stromal follicular dendritic cells (FDC). Accumulated evidence from other and our group demonstrated that the formation and maintenance of ELS in these chronic inflammatory conditions is critically dependent on the ectopic expression of lymphotoxins (LT) and lymphoid chemokines CXCL13, CCL19, CCL21 and CXCL12. In this review we discuss recent advances highlighting the cellular and molecular mechanisms, which regulate the formation of ELS in RA and SS, with particular emphasis on the role of lymphoid chemokines. In particular, we shall focus on the evidence that in the inflammatory microenvironment of the RA synovium and SS salivary glands, several cell types, including resident epithelial, stromal and endothelial cells as well as different subsets of infiltrating immune cells, have been shown to be capable of producing lymphoid chemokines. Finally, we summarize accumulating data supporting the conclusion that ELS in RA and SS represent functional niches for B cells to undergo affinity maturation, clonal selection and differentiation into plasma cells autoreactive against disease-specific antigens, thus contributing to humoral autoimmunity over and above that of secondary lymphoid organs.