Follicular Dendritic Cell Networks Research Articles

Fate mapping reveals origin and dynamics of lymph node follicular dendritic cells.

Follicular dendritic cells (FDCs) regulate B cell function and development of high affinity antibody responses but little is known about their biology. FDCs associate in intricate cellular networks within secondary lymphoid organs. In vitro and ex vivo methods, therefore, allow only limited understanding of the genuine immunobiology of FDCs in their native habitat. Herein, we used various multicolor fate mapping systems to investigate the ontogeny and dynamics of lymph node (LN) FDCs in situ. We show that LN FDC networks arise from the clonal expansion and differentiation of marginal reticular cells (MRCs), a population of lymphoid stromal cells lining the LN subcapsular sinus. We further demonstrate that during an immune response, FDCs accumulate in germinal centers and that neither the recruitment of circulating progenitors nor the division of local mature FDCs significantly contributes to this accumulation. Rather, we provide evidence that newly generated FDCs also arise from the proliferation and differentiation of MRCs, thus unraveling a critical function of this poorly defined stromal cell population.

Close interactions between sympathetic neural fibres and follicular dendritic cells network are not altered in Peyer’s patches and spleen of C57BL/6 mice during the preclinical stage of 139A scrapie infection

During preclinical stage of prion diseases, secondary lymphoid organs seem to play an important role in prion amplification prior the invasion of the associated peripheral nervous system. In mice, it was shown that the relative positioning of follicular dendritic cells (FDC) and sympathetic nervous system (SNS) affects the velocity of neuroinvasion following scrapie inoculation. In this study, we checked if scrapie infection, by oral or intraperitoneal route, could influence this neuroimmune interface between FDC and tyrosine hydroxylase (TH) positive neural fibres within Peyer’s patches (PP) and spleen of the C57BL/6 mouse strain. We concluded that, in vivo, scrapie 139A and ME7 strains do not modify FDC–SNS neuroimmune interface. However, age seems to alter this neuroimmune interface and thus could influence the neuroinvasion in prion pathogenesis.

B cells in classical Hodgkin lymphoma are important actors rather than bystanders in the local immune reaction

Recent studies, largely focusing on cellular immunity, have demonstrated that the composition of the abundant inflammatory background of Hodgkin lymphoma may affect outcome. This investigation aimed to characterize the potential role of infiltrating B cells and follicular dendritic cell networks in classical Hodgkin lymphoma (cHL) to better assess the role of components of humoral immunity. One hundred two cHL biopsies were investigated by immunohistochemistry with antibodies specific for CD20, CD138, activation-induced cytidine deaminase, and CD21 to characterize B cell distribution and follicular structures. To further subclassify B cells, analyses of tissue microarrays were performed investigating the expression of Mum1, Bcl6, IgD, IgG, IgG4, IgM, T-bet, CD38, CD5, and CD10. For evaluation a computer assisted quantification method was compared with a scoring system. Survival analysis and correlation analysis were performed. The B cell infiltrate was dominated by CD20+ B cells, followed by plasma cells, whereas only few AID+ cells were observed. High numbers of CD21+ follicular dendritic cell networks, CD20+ B cells, IgM+ cells, CD20+ aggregates, and Bcl6+ cells were associated with a better outcome of cHL patients, whereas Pax5+/CD38+ cells had an adverse prognostic impact. Other parameters showed no influence on survival. Our findings suggest that a complex network of B cells is present in the microenvironment of cHL and that B cells might actively contribute to a local anti- as well as pro-tumoral immune response. This indicates that the network of B cells in tumors is probably just as diverse as the T cellular infiltrate and probably functionally as heterogenous.

OP0080 Lesional IL-21 Expression Correlates with Functional Germinal Center Formation and T Follicular Helper Cell Infiltration in the Salivary Glands of Sjögren’s Syndrome

BackgroundIL-21 is a pro-inflammatory cytokine that plays a key role in the activation and differentiation of B cells1. B cells infiltrate the salivary glands (SG) of Sjögren’s syndrome (SS), an...

AB0249 Investigating the effect of etanercept on the peripheral B cell compartment in children with juvenile idiopathic arthritis

BackgroundBoth B cells and TNF have been shown to play an important role in the pathogenesis of rheumatoid arthritis and juvenile idiopathic arthritis (JIA). However, it remains unclear whether these...

OP0082 Expression of Fractalkine in Sjögren’s Syndrome Patients: Cellular and Molecular Characterization of CX3CL1 and CX3CR1 in Sera and Salivary Glands

BackgroundPrimary Sjögren’s syndrome (SS) is an autoimmune disease characterized by chronic lymphocytic inflammation and destruction of acinar tissue within the salivary glands (1). Fractalkine (CX3CL1, FKN) is the sole member...

Identifying the cellular interactions required for diversification of the primary antibody repertoire in rabbit GALT (P6101)

Abstract Rabbits generate an initial antibody repertoire of limited diversity due to preferential use of the 3’-most VH gene segment during V-D-J gene rearrangement. Around one week of age, rabbit B cells begin diversifying this antibody repertoire in gut-associated lymphoid tissue (GALT), by mutating their V-D-J genes in response to antigen-independent signals acquired from intestinal commensals. To identify the cell-cell and cell-microbe interactions required for V-D-J gene diversification, we examined B cell expression levels of four chemokine receptors that mediate homing to important sites within GALT. We stained the chemokine receptors CXCR4, CCR6, CXCR5 and CCR7 on appendix B cells from two- to eight-day-old rabbits with fluorescence-labeled antibodies or chemokine-Ig fusion proteins and analyzed them by flow cytometry. The changes in chemokine receptor expression we observed during the first week of life suggest that, after entering appendix follicles, B cells first home to the follicle-associated epithelium, where they likely encounter commensal bacteria sampled from the intestinal microbiota. B cells then home sequentially to the follicular dendritic cell network, the T cell area and finally to the basal region of the follicle, where they proliferate and diversify their V-D-J genes to generate the primary antibody repertoire.

Obesity-Associated Autoantibody Production Requires AIM to Retain the Immunoglobulin M Immune Complex on Follicular Dendritic Cells

Natural immunoglobulin M (IgM) is reactive to autoantigens and is believed to be important for autoimmunity. Blood pentameric IgM loaded with antigens forms a large immune complex (IC) that contains various elements, including apoptosis inhibitor of macrophage (AIM). Here we demonstrate that this IgM-AIM association contributes to autoantibody production under obese conditions. In mice fed a high-fat diet, natural IgM increased through B cell TLR4 stimulation. AIM associated with IgM and protected AIM from renal excretion, increasing blood AIM levels along with the obesity-induced IgM augmentation. Meanwhile, the AIM association inhibited IgM binding to the Fcα/μ receptor on splenic follicular dendritic cells, thereby protecting the IgM IC from Fcα/μ receptor-mediated internalization. This supported IgM-dependent autoantigen presentation to B cells, stimulating IgG autoantibody production. Accordingly, in obese AIM-deficient (AIM(-/-)) mice, the increase of multiple IgG autoantibodies observed in obese wild-type mice was abrogated. Thus, the AIM-IgM association plays a critical role in the obesity-associated autoimmune process.

OMIP‐017: Human CD4+ helper T‐cell subsets including follicular helper cells

This panel was optimized to measure the relative frequencies of CD4+ T-helper cell subsets and follicular helper T-cells in peripheral blood mononuclear cells (PBMC) from healthy individuals (Table 1). It works well with cryopreserved PBMC and we have observed similar result with fresh specimens. Other tissue types have not been tested. Activated CD4+ T-cells differentiate into lineages, commonly referred to as T-helper (Th) subtypes such as Th2, with unique phenotypes, cytokine signatures, and functions. The present panel (Table 2) was designed to identify major Th subsets described to date according to disparate chemokine receptor expression patterns. Immunity to intracellular infections and viruses requires CCR4− CCR6− CCR10− CXCR3+ Th1 cells that produce interferon-γ (IFN-γ) (1, 2), while CCR4+ CCR6− CXCR3− Th2 cells produce interleukin-4 (IL-4), IL-5, and IL-13 and mediate the host defense against helminthes (3). Th9 cells are CCR4− CCR6+ IL-9-producing cells that could be involved in wound healing of pleural mesothelial cells during Mycobacterium tuberculosis infection (4). CCR4+ CCR6+ CCR10− CXCR3− Th17 cells are crucial for the host defense against extracellular pathogens, and mainly produce IL-17A, IL-22, and granulocyte-macrophage colony-stimulating factor (GM-CSF) (2, 5). Finally, CCR4+ CCR6+ CCR10+ Th22 cells produce IL-22, IL-26, and IL-13 and are thought to be involved in skin immunity (2, 6). However, there is plasticity in the system and some of these phenotypes and functional characteristics, previously thought mutually exclusive, can be expressed by the same cell. One such example is Th17Th1 cells that are CCR4− CCR6+ CXCR3+ and capable of producing both IFN-γ and IL-17 (5). The affinity maturation of plasma cells in the germinal centers of B-cell follicles requires the help from another specialized CD4+ T-cell lineage called follicular helper cells, or TFH (7). These cells express CXCR5, which confers homing to follicular dendritic cell networks within the germinal centers. The gating scheme for evaluating all these subsets with the present panel is illustrated in Figure 1. First, live CD4+ T-cells are identified (Fig. 1A), before gating on TFH (Fig. 1B) or other Th lineage cells (Fig. 1C). Additional non-lineage defining markers, namely CCR7, CD45RA, CD161, and PD-1, were included in order to further characterize the phenotype of individual subsets. Example staining and gating. A: Identification of CD4+ T-cell. After selecting live CD3+ single cells, eventual dye aggregates are excluded (gray box), followed by identification of lymphocytes and CD4+CD8− cells for further analysis as shown in (B, C, D). B: Identification of CXCR5+ TFH within CD4+ T-cells. The phenotype of TFH is investigated by overlaying these cells (blue) onto total CD4+ T-cells (gray). C,D: Enumeration of CD4+ helper T-cell subsets according to differential expression of the chemokine receptors CCR4, CCR6, CCR10, and CXCR3; gates indicate putative subtypes as defined in the literature (see discussion). None to date. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Inducible tertiary lymphoid structures, autoimmunity, and exocrine dysfunction in a novel model of salivary gland inflammation in C57BL/6 mice.

Salivary glands in patients with Sjögren's syndrome (SS) develop ectopic lymphoid structures (ELS) characterized by B/T cell compartmentalization, the formation of high endothelial venules, follicular dendritic cell networks, functional B cell activation with expression of activation-induced cytidine deaminase, as well as local differentiation of autoreactive plasma cells. The mechanisms that trigger ELS formation, autoimmunity, and exocrine dysfunction in SS are largely unknown. In this article, we present a novel model of inducible ectopic lymphoid tissue formation, breach of humoral self-tolerance, and salivary hypofunction after delivery of a replication-deficient adenovirus-5 in submandibular glands of C57BL/6 mice through retrograde excretory duct cannulation. In this model, inflammation rapidly and consistently evolves from diffuse infiltration toward the development of SS-like periductal lymphoid aggregates within 2 wk from AdV delivery. These infiltrates progressively acquire ELS features and support functional GL7(+)/activation-induced cytidine deaminase(+) germinal centers. Formation of ELS is preceded by ectopic expression of lymphoid chemokines CXCL13, CCL19, and lymphotoxin-β, and is associated with development of anti-nuclear Abs in up to 75% of mice. Finally, reduction in salivary flow was observed over 3 wk post-AdV infection, consistent with exocrine gland dysfunction as a consequence of the inflammatory response. This novel model has the potential to unravel the cellular and molecular mechanisms that regulate ELS formation and their role in exocrine dysfunction and autoimmunity in SS.

Guidelines for the investigation and management of mantle cell lymphoma.

The guideline group was selected to be representative of UK-based medical experts and patients representatives. Ovid MEDLINE, EMBASE and NCBI Pubmed were searched systematically for publications in English from 1980 to 2011 using the MeSH subheading 'lymphoma, mantle cell' and 'lymphoma, mantle cell' as a keyword, as well as all subheadings. In addition, all references to mantle cell lymphoma in the World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissue (Swerdlow et al, 2008) and the British Committee for Standards in Haematology (BCSH) Guideline: Best Practice in Lymphoma Diagnosis and Reporting (Parker et al, 2010) have been included. The writing group produced the draft guideline, which was subsequently revised by consensus by members of the Haemato-oncology Task Force of the BCSH. The guideline was then reviewed by a sounding board of approximately 50 UK haematologists, the BCSH and the British Society for Haematology Committee and comments incorporated where appropriate. The 'GRADE' system was used to quote levels and grades of evidence, details of which can be found in Appendix I. The objective of this guideline is to provide healthcare professionals with clear guidance on the investigation and management of patients with mantle cell lymphoma. The guidance may not be appropriate to patients with other lymphoma sub-types and in all cases individual patient circumstances may dictate an alternative approach.

The Adjuvant LT-K63 Can Restore Delayed Maturation of Follicular Dendritic Cells and Poor Persistence of Both Protein- and Polysaccharide-Specific Antibody-Secreting Cells in Neonatal Mice

Ab responses in early life are low and short-lived; therefore, induction of protective immunity requires repeated vaccinations. One of the major limitations in early-life immunity is delayed maturation of follicular dendritic cells (FDCs), which play a central role in mediating the germinal center (GC) reaction leading to production of Ab-secreting cells (AbSCs). We assessed whether a nontoxic mutant of Escherichia coli heat-labile enterotoxin (LT-K63) and CpG1826 as model adjuvants could accelerate FDC maturation and immune response in neonatal mice, using a pneumococcal polysaccharide of serotype 1 conjugated to tetanus toxoid (Pnc1-TT) as a model vaccine. In neonatal NMRI mice, a single dose of Pnc1-TT coadministered with LT-K63 enhanced Pnc1-TT-induced GC reaction. In contrast, CpG1826 had no effect. Accordingly, LT-K63, but not CpG1826, accelerated the maturation of FDC networks, detected by FDC-M2(+) staining, characteristic for adult-like FDCs. This coincided with migration of MOMA-1(+) macrophages into the GCs that can enhance GC reaction and B cell activation. The FDC-M2(+) FDC networks colocalized with enhanced expression of TNF-α, which is critical for the maintenance of mature FDCs and is poorly expressed in neonates. The accelerated maturation of FDC networks correlated with increased frequency and prolonged persistence of polysaccharide- and protein-specific IgG(+) AbSCs in spleen and bone marrow. Our data show for the first time, to our knowledge, that an adjuvant (LT-K63) can overcome delayed maturation of FDCs in neonates, enhance the GC reaction, and prolong the persistence of vaccine-specific AbSCs in the BM. These properties are attractive for parenteral vaccination in early life.

Ectopic Lymphoid Neogenesis and Lymphoid Chemokines in Sjogren’s Syndrome: At the Interplay between Chronic Inflammation, Autoimmunity and Lymphomagenesis

It has long been demonstrated that a subset of patients with Sjogren's syndrome (SS) develop ectopic lymphoid structures (ELS) in the salivary glands (SG). These structures are characterised by periductal clusters of T and B lymphocytes, development of high endothelial venules and differentiation of follicular dendritic cells (FDC) networks. Evidence in patients with and animal models of SS demonstrated that the formation and maintenance of ELS in the SG is critically dependent on the ectopic expression of lymphotoxins (LT) and lymphoid chemokines CXCL13, CCL19, CCL21 and CXCL12. 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 some of these factors during chronic inflammation in SS. In this review we focus on the cellular and molecular mechanisms regulating the formation of ELS in SS SG, with particular emphasis on the role of lymphoid chemokines. In addition, we summarise accumulating data in support of the notion that ELS in SS represent functional niches whereby autoreactive B cells undergo affinity maturation, clonal selection and differentiation into autoantibody producing cells, thus contributing to autoimmunity over and above secondary lymphoid organs. Furthermore, we review the emerging role of ELS and lymphoid chemokines in driving extranodal B cell lymphomagenesis in SS and we focus on recent evidence suggesting that ELS identify subsets of SS patients at increased risk of developing systemic manifestations and lymphoma.

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.

Chemokine-mediated B cell trafficking in rabbit GALT during diversification of the primary antibody repertoire (160.15)

Abstract Rabbits preferentially rearrange the 3’-most VH gene segment during VDJ gene rearrangement. Early in life, rabbit B cells generate a diversified primary antibody repertoire by mutating their VDJ genes in gut-associated lymphoid tissue (GALT) in response to signals acquired from intestinal commensals. To gain insight into the cell-cell and cell-microbe interactions required for VDJ gene diversification, we examined B cell surface expression levels of four chemokine receptors that mediate trafficking to important sites within GALT during repertoire diversification. We stained the chemokine receptors CXCR4, CCR6, CXCR5 and CCR7 on appendix B cells from two- through seven-day-old rabbits with fluorescence-labeled antibodies or Ig-fusion proteins of their ligands and analyzed them by flow cytometry. The changes in relative chemokine receptor expression levels we observed during the first week of life suggest that B cells, upon entering appendix follicles, first traffic to the follicle-associated epithelium, where they likely encounter commensal bacteria sampled from the intestinal microbiota. B cells subsequently migrate to, and likely receive additional signals from, the follicular dendritic cell network. Upon becoming activated, B cells then traffic to the basal region of the follicle, where they proliferate and diversify their VDJ genes to generate the primary antibody repertoire.

Presence of Immunoglobulin Heavy Chain Rearrangement in So-Called IgG4-Related Plasma Cell Granuloma of the Eyelid

So-called inflammatory pseudotumor (IPT) affects almost all major organs. The histological appearance of IPT varies from fibrohistiocytic proliferation to plasma cell-dominated lesions. The latter are composed of numerous plasma cells, lymphocytes, and histiocytes as well as mesenchymal cells, that is, plasma cell granuloma (PCG). Recently, Zen et al. demonstrated that some of the pulmonary PCGs represent an immunoglobulin G4 (IgG4)-related sclerosing disease. We report here a unique case of IgG4-related PCG of the eyelid. An 85-year-old man had a history of bronchial asthma for several years. He presented with a right upper eyelid mass, and under a diagnosis of squamous cell papilloma underwent tumor resection in May 2008. The surgical tissue was diagnosed as an inflammatory granulation tissue. Preoperative patient laboratory examination results were within normal limits. Serum IgG4 level was not examined. Two years later, he also presented with a left upper eyelid mass, and mass resection was performed under the diagnosis of chalazion. There was no other evidence of disease and the patient remained free of disease on examination 12 months later. Histologically, initial and recurrent lesions presented similar findings. In a lowpower field, both lesions were characterized by chronic inflammatory processes, and irregular fibrosis and/or sclerosis were not prominent (Fig. 1a). In a highpower field, these lesions demonstrated severe infiltration of mature plasma cells, plasmacytoid cells, and small lymphocytes with scattered eosinophils (Fig. 1b). Scattered Russell bodies (intracytoplasmic inclusions) were present in both lesions (Fig. 1b), but there were no centrocyte-like (CCL) cells, Dutcher bodies (intranuclear inclusions), or amyloid deposition. A few isolated small lymphocytes and mature plasma cells invaded into the Meibomian gland epithelium. However, there was no lymphoepithelial lesion (LEL) (Fig. 1b). Elastica-van Gieson staining demonstrated that there was no obliterative phlebitis or arteritis. Immunohistochemical studies were performed using the antigen retrieval method on the Histofine Histostainer (Nichirei Bioscience Inc., Tokyo, Japan) according to the manufacturer’s instructions. Staining for CD20, CD3, and CD5 showed the mixed nature of the small lymphocytes. There were no CD43 B-cells in either lesion. In situ hybridization (ISH) and immunohistochemical studies of k-chain and l-chain demonstrated polyclonality of the plasma cells and plasmacytoid cells in both lesions (Figs. 1c & 1d). There were numerous IgG-positive plasma cells with scattered IgAor IgM-positive plasma cells. However, IgG4 cells comprised more than 40% of the IgG plasma cells (Figs. 1e & 1f). There were no LELs detected even by immunostaining for cytokeratin in any of the two lesions (Fig. 1g). CD23 immunostain demonstrated no residual follicular dendritic cell network in both lesions. On ISH study, there were no Epstein-Barr virus (EBV)-encoded small RNA (EBER) cells in either lesion. By polymerase chain reaction (PCR) for immunoglobulin heavy chain (IgH) gene, a discrete band of amplified IgH gene was found for the recurrent lesion, while for the initial lesion, only germline bands were detected (Fig. 1h). IgG4 is the least common of the 4 subclasses of IgG4,

Nodular lymphocyte predominant Hodgkin lymphoma and diffuse large B-cell lymphoma: a study of six cases concurrently involving the same site

Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) is a slowly progressing neoplasm with a favourable prognosis. However, in a minority of cases (3-12%) it progresses to a clonally related diffuse large B-cell lymphoma (DLBCL), diagnosed between 6 months and 24 years after NLPHL. This study investigated six cases of NLPHL and DLBCL at the same location. The patients were five men and one woman. In four cases, the site was an axillary lymph node, and in two it was inguinal. In all cases, NLPHL areas had typical morphological and immunophenotypic features. DLBCL involvement was multifocal, diffuse, and characterized by large centroblastic and anaplastic cells. Immunohistochemical studies showed DLBCL cells to be positive for CD20, CD45, and BCL6. In one case, DLBCL cells were positive for BCL2, and in two cases they were positive for MUM-1. There were no networks of follicular dendritic cells (FDC) associated with DLBCL. Rosettes of PD-1-positive and CD57-positive cells surrounding malignant cells in NLPHL were absent in DLBCL. All the cases were negative for Epstein-Barr virus. No translocations involving MYC were identified in DLBCL. Treatment and outcome were known in four cases. All of these patients were treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), and this was followed by clinical remission (CR). In adequately sampled tumors, DLBCL can be associated with NLPHL at diagnosis. Diffuse architecture, loss of FDC networks, sometimes immunophenotype shift are characteristics of DLBCL associated with NLPHL. Treatment with R-CHOP usually leads to CR.

Nodal follicular lymphoma without complete follicular dendritic cell networks is related to localized clinical stage

Follicular lymphoma is the most common low-grade lymphoma and it frequently presents with a systemic disease, often showing advanced clinical stage (III/IV). The lymphoma cells are usually growing associated with follicular dendritic cell (FDC) networks. Abnormal FDC networks have been reported in duodenal follicular lymphoma, in which cases exhibit lower clinical stages than the nodal cases. In the present study, we analyzed the FDC network distribution pattern of 242 nodal follicular lymphomas by immunohistochemistry. Out of the 242 cases, 27 cases (11%) demonstrated an atypical pattern of FDC networks, in which the CD21 staining totally or partially disappeared in the neoplastic follicles. Furthermore, we compared the clinical data of these 27 cases and 58 typical FDC network cases of follicular lymphoma. We found that in the typical cases, 52 out of 58 patients (90%) showed advanced clinical stage (III or IV), whereas 10 of 27 (37%) atypical FDC network cases showed localized clinical stage (I or II) (P < 0.01). In conclusion, nodal follicular lymphoma with total loss or partially disrupted FDC networks therefore show a lower clinical stage.

A Disintegrin and Metalloproteinase 10 Regulates Antibody Production and Maintenance of Lymphoid Architecture

A disintegrin and metalloproteinase 10 (ADAM10) is a zinc-dependent proteinase related to matrix metalloproteinases. ADAM10 has emerged as a key regulator of cellular processes by cleaving and shedding extracellular domains of multiple transmembrane receptors and ligands. We have developed B cell-specific ADAM10-deficient mice (ADAM10(B-/-)). In this study, we show that ADAM10 levels are significantly enhanced on germinal center B cells. Moreover, ADAM10(B-/-) mice had severely diminished primary and secondary responses after T-dependent immunization. ADAM10(B-/-) displayed impaired germinal center formation, had fewer follicular Th cells, decreased follicular dendritic cell networks, and altered chemokine expression in draining lymph nodes (LNs). Interestingly, when spleen and LN structures from immunized mice were analyzed for B and T cell localization, tissues structure was aberrant in ADAM10(B-/-) mice. Importantly, when ADAM10-deficient B cells were stimulated in vitro, they produced comparable Ab as wild type B cells. This result demonstrates that the defects in humoral responses in vivo result from inadequate B cell activation, likely because of the decrease in follicular Th cells and the changes in structure. Thus, ADAM10 is essential for the maintenance of lymphoid structure after Ag challenge.

Complement Activation and Complement Receptors on Follicular Dendritic Cells Are Critical for the Function of a Targeted Adjuvant

A detailed understanding of how activation of innate immunity can be exploited to generate more effective vaccines is critically required. However, little is known about how to target adjuvants to generate safer and better vaccines. In this study, we describe an adjuvant that, through complement activation and binding to follicular dendritic cells (FDC), dramatically enhances germinal center (GC) formation, which results in greatly augmented Ab responses. The nontoxic CTA1-DD adjuvant hosts the ADP-ribosylating CTA1 subunit from cholera toxin and a dimer of the D fragment from Staphylococcus aureus protein A. We found that T cell-dependent, but not -independent, responses were augmented by CTA1-DD. GC reactions and serum Ab titers were both enhanced in a dose-dependent manner. This effect required complement activation, a property of the DD moiety. Deposition of CTA1-DD to the FDC network appeared to occur via the conduit system and was dependent on complement receptors on the FDC. Hence, Cr2(-/-) mice failed to augment GC reactions and exhibited dramatically reduced Ab responses, whereas Ribi adjuvant demonstrated unperturbed adjuvant function in these mice. Noteworthy, the adjuvant effect on priming of specific CD4 T cells was found to be intact in Cr2(-/-) mice, demonstrating that the CTA1-DD host both complement-dependent and -independent adjuvant properties. This is the first demonstration, to our knowledge, of an adjuvant that directly activates complement, enabling binding of the adjuvant to the FDC, which subsequently strongly promoted the GC reaction, leading to augmented serum Ab titers and long-term memory development.