Role Of Follicular Dendritic Cells Research Articles

Identifying the role of complement receptor 2 (CR2) on follicular dendritic cells (FDCs) in the persistence of foot and mouth disease virus (FMDV)

More than 50 % of cattle (regardless of foot and mouth disease (FMD) vaccination) become persistently infected for long periods of time (years) after exposure to FMD virus (FMDV). The mechanisms associated with establishment of persistent infections are still poorly understood. I am testing the hypothesis that complement receptor 2 (CR2) on follicular dendritic cells (FDCs) located in the germinal centers of the lymphoid tissue, are involved in the trapping and long-term persistence of FMDV and that this persistence is essential for the maintenance of long-term antibody responses to FMDV. The aim of this study was to assess FMDV antigen retention and the generation of the specific immune response in vivo, in a mouse model. Groups of mice were treated with an anti-CR2 monoclonal antibody, named 4B2, which has been described previously to block CR2 long-term in vivo, blocking for 6 weeks after a single injection of 2 mg (Kulik et al., 2015). After treatment with 4B2, animals were infected with FMDV and lymphoid tissues and serum samples evaluated for the presence of antigen and the humoral immune response, respectively. The ability of 4B2 to block the binding of FMDV and PAP immune complexes (ICs) to FDCs in vitro as well as results about the role of FDC in trapping FMDV via CR2 in vivo is currently being investigated and will be discussed.

Integrin specific hydrogels as lymphoid tumors organoids for B cell receptor signaling and drug resistance

Event Abstract Back to Event Integrin specific hydrogels as lymphoid tumors organoids for B cell receptor signaling and drug resistance Ye F. Tian1, Haelee Ahn2, Rebecca Schneider3, Shao Ning Yang2, Lidia Roman-Gonzalez2, Leandro Cerchietti2, Ari M. Melnick2 and Ankur Singh1 1 Cornell University, Mechanical and Aerospace Engineering, United States 2 Weill Cornell Medical College, Division of Hematology and Oncology, Department of Medicine, United States 3 Cornell University, School of Chemical and Biomolecular Engineering, United States Introduction: Non-Hodgkin lymphomas (NHL) are a heterogeneous group of lymphoproliferative disorders of B and T cell origin. Pre-clinical research in NHL has relied on testing compounds with suspension cultures of human lymphoma cell lines, without taking into account the lymphoid niche in which these tumors arise and reside. This traditional approach for drug testing risks losing potential useful compounds by considering them as ineffective due to the conditions of the assays. This is the case for compounds with a mechanism of action that relies on suppressing survival signals from microenvironmental cues, such as integrin inhibitors. Our recent findings have demonstrated that knockdown or pharmacologic inhibition of the integrin αvβ3 abrogated the proliferation of malignant T cells in vitro and in patient-derived xenograft mice models, an effect partially mediated by defective angiogenesis[1]. Given the increasing importance of the ECM and the stromal cells to NHL biology and drug response, there is a need to develop 3D tissues that mimic the diseased lymphoid microenvironment and are adaptable to disease-specific needs. Method: Human B- and T-NHL cell lines were encapsulated in organoids of 4-arm Maleimide functionalized polyethylene glycol (PEG-MAL) and thiolated, enzymatically degradable crosslinker peptides along with human tonsil tissue derived follicular dendritic cells (FDC). Prior to organoid formation, PEGMAL was functionalized with thiolated peptides targeting αvβ3 and α4β1 on B and T-NHLs. The survival, proliferation, and drug studies were performed with confocal microscopy and biochemical assays. For drug-response analysis, organoids were cultured for 4 days before the 24 hr of exposure to Doxorubicin or Panobinostat, a histone deacetylate inhibitor and apoptosis studies were performed. Results: Our gene expression analysis shows that while αvβ3 integrin is consistently overexpressed in T-NHLs, these cells also express varying levels of α4β1[2]. B-NHLs on the other hand, do not have a predictable pattern of integrin expression. When NHLs were presented with integrin ligands in the organoids, both B and T-NHLs formed large clusters as a function of integrin ligands (αvβ3 ligand RGD > α4β1 ligand REDV). Importantly, REDV peptide significantly increased B-NHL proliferation while T-NHL proliferation was dependent on RGD signaling. Both B and T-NHLs, when cultured in organoids, demonstrated drug-resistance to Doxorubicin and the Panobinostat (Fig 1). We observed the 3D microenvironment to upregulate IgM B cell receptors BCR expression level (Fig. 2), which indicate enhanced survival and possibly explains the enhanced proliferation observed with B cell lymphomas. We predicted that activation of BCR is likely supporting the survival of B NHLs in 3D niches over 2D cultures by means of both up-regulating BCR and cross-talk with integrins. This hypothesis was supported by our findings with Syk inhibition that caused significantly higher apoptosis in the 3D group as compared to the 2D groups. Conclusions: Taken together, these results emphasize the role of biomaterials-based 3D tissues and the importance of integrin mediated signaling in malignant B and T cell tumors, as well as the role of FDCs in lymphoma proliferation. In the past, these factors have been largely ignored in drug evaluation or mechanistic studies of B and T cell lymphomas, ex vivo. Giorgio Inghirami

Regulation of lupus-antigen specific B cells by follicular dendritic cells (BA12P.113)

Abstract Humoral responses are central to many autoimmune diseases such as systemic lupus erythematosus (SLE). Yet little is known about the cells and factors that are vital for maturation and sustenance of autoreactive B cells. In this study, we used a B cell receptor (specific for RNP complexes) knock-in strain 564Igi to demonstrate an important role of follicular dendritic cells (FDCs) in loss of tolerance of autoreactive B cells. Breeding the lupus-prone strain to a C4-deficient background resulted in escape of tolerance of auto-reactive idiotype+ (Id+) B cells. Total ablation or in vivo de-differentiation of FDCs in the C4-/- 564Igi mice resulted in a dramatic decrease in auto-reactive B cells and germinal centers suggesting their role in promoting loss of tolerance. Gene expression analysis of FDCs isolated from C4 -/- 564Igi mice show an increased expression of IFN-alpha (IFN-a) and downstream response genes. Treatment of the mice with anti-IFN-a receptor (IFNAR) resulted in restoration of tolerance. Blockade of myeloid cell IFNAR was identified as the critical pathway as mixed marrow chimeras of C4-/- 564Igi and IFNAR- deficient bone marrow into C4-/- recipients have a significantly lower frequency of auto-reactive B cells, which underlines the importance of IFN-a signaling in myeloid cells. Hence, we propose a model in which IFN-a secreted by activated FDCs act on dendritic cells, which in turn supports auto-reactive B cells by producing factors like IFN-a and BAFF.

B-cell extrinsic CR1/CR2 promotes natural antibody production and tolerance induction of anti-αGAL–producing B-1 cells

AbstractB-1b cells produce IgM natural antibodies against α1-3Galβ1-4GlcNAc (αGal). These can be tolerized by nonmyeloablative induction of mixed chimerism using αGal-positive (αGal+) donor marrow. We assessed the role of CR1/2 in this model for induction of tolerance of B-1b cells. Mixed hematopoietic chimerism was induced in α1-3galactosyltransferase (GalT−/−) and GalT−/−Cr2−/− mice with αGal+ BALB/c marrow donors. Anti-αGal Ab and anti-αGal Ab–producing B cells became undetectable in GalT−/− chimeras, whereas they persisted in chimeric GalT−/−Cr2−/− mice. To determine whether CR1/2 expression on stromal cells and/or hematopoietic cells was critical for B-1–cell tolerance, we generated GalT−/− radiation chimeras in which CR1/CR2 was expressed on either stromal cells, hematopoietic cells, neither, or both. After induction of mixed chimerism from αGal+ allogeneic bone marrow (BM) donors, anti-αGal–producing B cells were rendered tolerant in reconstituted recipients expressing only stromal CR1/CR2. Our results suggest a possible role for follicular dendritic cells that pick up immune complexes via CR1/CR2 receptors in the tolerization of B-1b cells.

Role of gut macrophages in mice orally contaminated with scrapie or BSE

While there is a growing consensus on the understanding of the propagation pathways after oral infection of transmissible spongiform encephalopathy (TSE) agents and even if the central role of follicular dendritic cells is identified, little is known about the key players in the first steps of the infection and about the site of the disease development. We investigated the role of gut macrophages, which are capable of capturing aggregates of the prion protein. PLGA particles containing clodronate were designed in order to be orally administered and to target Peyer's patches for inducing gut-associated macrophages suicide in mice. Mice were subsequently infected with scrapie or BSE by the oral route. It was found that the efficacy of macrophage suppression in the Peyer's patches correlated well with an earlier appearance of PrPres in these formations and with a higher amount of PrPres at a later stage of the infection. Thus, the capture of infectious particles that have crossed the epithelial gut barrier and their elimination by macrophages seems to be a key event to restrict the amount of agent initiating the infection.

Role of follicular dendritic cells in the early HIV-1 infection: in vitro model without specific antibody.

About 90% of HIV-1 RNA in the lymph nodes is reported to localize in follicular dendritic cellsnetwork (FDC-NW) as early as several days after infection and as much as that in the late stage. But the mechanism remains to be fully understood. To elucidate the role of follicular dendritic cells (FDC) in the early stage of HIV-1 infection, FDC-like cell strains (FDCLC) were established and they were characterized in the co-culture system with T cells for their effect on HIV-1 trapping and replication in p24 immunoassay, immunohistochemistry as well as confocal and electronmicroscopy. Established FDCLC were positive for CNA-42, S-100alpha and intercellular desmosome-like junctions. L-SIGN and DC-SIGN were also detected in FDCLC. Alu-HIV-1 PCR analysis showed no HIV-1 integration in FDCLC. FDCLC trapped HIV-1 and transferred them to uninfected MOLT-4 T cells (MOLT-4) efficiently in the absence of specific antibody. FDCLC also accelerated HIV-1 replication in HIV-1-pre-exposed MOLT-4. These unique FDCLC effects were explained, at least partly, by the fact that FDCLC up-regulated CD4 expression in MOLT-4 and helped T cells escape from apoptosis in the co-culture. These data suggest that FDC/FDCLC engage not only in trapping but also in active expansion of HIV-1 in the absence of specific antibody.

Human follicular dendritic cells and fibroblasts share the 3C8 antigen

Although the pivotal role of follicular dendritic cells (FDCs) in humoral immune responses has been demonstrated, little is known of the molecular basis of biological functions and the cellular origin of FDC. We have recently generated a monoclonal antibody (mAb) against FDC by immunizing mice with FDC-like tonsillar stromal cells. The mAb 3C8 does not cross-react with bone marrow-derived blood cells. Partial amino acid sequencing revealed that 3C8 Ag is a novel human protein. In this study, we carried out a detailed analysis of 3C8 immunoreactivity with tonsil sections to examine cellular distribution of 3C8 Ag. 3C8 Ab recognized connective tissue fibroblasts in addition to FDC. Western blot analysis indicated that 3C8 antigen is expressed in various fibroblasts and is specific to human species. Furthermore, there was a correlation between 3C8 expression in several stromal cell lines and their co-stimulatory activity of germinal center B cell proliferation. These findings strongly support the view that FDCs originate from local fibroblasts.

3C8 antigen is a novel protein expressed by human follicular dendritic cells

Although the pivotal role of follicular dendritic cells (FDCs) in humoral immune responses has been demonstrated, little is known at the molecular level of how FDCs contribute to the organogenesis, B cell differentiation, and regulation of T cell functions in the germinal center. By immunizing with FDC-like cells, we have developed a monoclonal antibody (MAb), which stains the germinal centers in tonsil section. In the current study, the target cell of MAb 3C8 was identified as FDC by confocal scanning fluorescence microscopy. Unlike other MAbs against FDC, MAb 3C8 does not cross-react with bone marrow-derived blood cells. Amino acid sequencing of NH 2-terminal region of immunoprecipitated 3C8 Ag reveals that 3C8 is a novel FDC protein. Further studies of 3C8 molecule will shed light on the cellular origin of FDC and reveal unknown functions of FDC.

Distribution and accumulation of PrP in gut-associated and peripheral lymphoid tissue of scrapie-affected Suffolk sheep.

The distribution of disease-associated prion protein (PrP) was investigated in eight animals (20-24 months of age) from a flock of Suffolk sheep that had experienced frequent cases of natural scrapie over a period of several years. Tissue from the central nervous system (CNS), alimentary tract, peripheral nervous system and lymphoreticular system was examined by histopathology and immunohistochemistry. The lymphoid tissues were subjected further to histoblot and immunofluorescence examination. The four clinically affected PrP(ARQ/ARQ) sheep had widespread accumulations of disease-associated PrP in the CNS, lymphoreticular system and peripheral ganglia. In the two PrP(ARQ/ARQ) sheep that did not show clinical signs of scrapie, only limited vacuolation and PrP accumulation were detected in the brain, but the results from the lymphoreticular system and peripheral nervous system were comparable with the clinically affected animals. The remaining PrP(ARR/ARR) and PrP(ARR/ARQ) sheep did not show proteinase K-resistant PrP accumulations in the lymphoid tissues examined and immunohistochemistry did not reveal the presence of disease-associated PrP. In lymphoid tissues of the PrP(ARQ/ARQ) sheep, the dominant localization of disease-associated PrP was in lymphoid nodules and double immunofluorescence labelling for PrP and CD21 provided further support for the role of follicular dendritic cells in scrapie in sheep. A striking finding in the present study was the large accumulations of disease-associated PrP in the lymphoid nodules of the alimentary tract at the late sub-clinical and clinical stage of the infection. The study also identified disease-associated PrP in extra-nodular sites of lymphoid tissues, such as the marginal zone of the spleen, and these observations were used to argue that cells of the mononuclear phagocyte system of sheep may be involved in the uptake, transport, elimination and shedding of the scrapie agent.

Role of follicular dendritic cells in the apoptosis of germinal center B cells

Follicular dendritic cells (FDCs) provide the most obvious source of antigens, which are essential for the differentiation of GC B cells. It has been reported that most proliferating B cells in germinal centers undergo apoptosis. Quantitative histology shows macrophages with apoptotic debris throughout the germinal center, the highest frequency of these cells being found in the dense FDC network. Based on these findings, we hypothesized that FDC may be involved in an apoptotic pathway of the germinal center B cells. To prove this hypothesis, we performed double immunohistochemical analysis using anti-FDC mAb and peanut agglutinin (PNA), with their respective TUNEL kits. Collated data showed that a great proportion of the apoptotic cells, most of which were positive for PNA, were in close contact with FDC, which indicated an interaction between FDC and B cells in the apoptotic pathway. Further studies using double immunohistochemical staining and FACS analyses demonstrated the expression of Fas–ligand (FasL) in a subset of the FDC. These results suggest that FDC may play a role in the apoptosis of germinal center B cells via Fas–FasL interaction.

Distinct role of follicular dendritic cells and T cells in the proliferation, differentiation, and apoptosis of a centroblast cell line, L3055.

Germinal center (GC) B cells undergo complex interactions with follicular dendritic cells (FDC) and T cells in the course of differentiation into memory B and plasma cells. To delineate the individual roles of FDC and T cells at each stage of GC B cell differentiation at the clonal level and to analyze the signals involved, we adopted a unique experimental model using an FDC line, HK, and a lymphoma cell line, L3055, that resembles centroblasts. A detailed phenotypic analysis revealed L3055 cells to be a clonal population originating from the GC. Like freshly isolated centroblasts, L3055 cells underwent spontaneous apoptosis when cultured in the absence of fresh FDC or HK cells. L3055 cells proliferated continuously in the presence of HK cells, while they differentiated into a population with the phenotype of centrocytes after stimulation with CD40 ligand (CD40L) and IL-4. The CD40L-stimulated L3055 cells underwent CD95-mediated apoptosis, which was reminiscent of the feature of CD40L-stimulated tonsillar GC B cells. In contrast to HK cells that did not protect L3055 cells from anti-Ig killing, CD40L plus IL-2, IL-4, and IL-10 prevented anti-Ig-induced apoptosis. These experimental results demonstrate a distinct function of FDC and activated T cells, in that FDC provide signals for rapid proliferation of centroblasts, whereas T cells confer signals for differentiation of centroblasts into centrocytes and resistance to B cell receptor-mediated apoptosis. T cells collaborate with FDC in the protection and expansion of the Ag-specific GC B cells.

Role of follicular dendritic cells in the regulation of B cell proliferation.

Within secondary lymphoid organs, B and T lymphocytes are not randomly distributed but they specifically inhabit highly organized regions that contain areas where B and T cells are largely segregated and other areas where different populations of cells can interact and differentiate (Thorbecke et al. 1962). Specifically, in lymph nodes and tonsils, the majority of B cells localize to follicles, whereas most T cells are found in the paracortex (Nieuwenhuis and Ford 1976). Following initial entrance into the interfollicular areas of secondary lymphoid tissues, it is not known what drives B cells to localize to follicles; however, the formation of follicles is an antigen (Ag)-driven process that requires the presence and participation of T lymphocytes.KeywordsHairy Cell LeukemiaFollicular Dendritic CellInterfollicular AreaStimulate Tyrosine PhosphorylationStaphylococcus Aureus CowanThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Quantitative analysis of molecules which distinguish functional compartments within germinal centers.

Five zones in the secondary follicles of human tonsils are described, which are distinguished by the phenotype of their constituent cells. Moving from the apex to the base of the follicle the zones are termed: follicular mantle, outer zone, apical light zone, basal light zone and dark zone. The dark zone contains proliferating, CD77high, centroblasts and thin, widely spaced processes of follicular dendritic cells (FDC). The apical and basal light zones on the other hand contain a dense network of FDC which express CD21 and CD54 strongly. The FDC of the apical light zone differ from those of the basal light zone by their high expression of CD23. Centroblasts of the dark zone give rise to non-proliferating centrocytes which move apically through the light zone (Eur. J. Immunol. 1991. 21:2951). The centrocytes of the basal light zone are more pyroninophilic, more closely-packed and larger than those in the apical light zone. Consequently, by conventional histology the basal light zone appears to be part of the dark zone. The nomenclature adopted, however, adheres to the convention that the dark zone is filled with proliferating centroblasts. Cells undergoing apoptosis were identified both in the dark and light zones, but more than half of these cells were located in the basal light zone. This is consistent with the concept that the progeny of cells which undergo somatic mutation in their immunoglobulin variable region genes in the dark zone migrate to the light zone where they are selected on the basis of their capacity to bind to antigen held on FDC. Cells receiving an antigen-dependent signal survive while those that do not kill themselves by apoptosis. The outer zone does not contain CD23high cells and in this way is distinguished from the adjacent follicular mantle and apical light zone. It contains small lymphoid cells, blasts and plasmacytoid cells. Many cells of the outer zone express CDw75 strongly. The outer zone also extends as a narrow band around the dark zone. Possible roles of FDC and T cells of the light zone and outer zone in inducing centrocytes to differentiate to memory cells or plasmablasts are discussed.

The Central Role of Follicular Dendritic Cells in Lymphoid Tissues

Publisher Summary This chapter discusses the role of follicular dendritic cells in lymphoid tissues. Characteristic features of primary and secondary lymphoid follicles are follicular dendritic cells (FDCs) that are not found in any other human organ. FDCs were first described as a nonlymphoid population of embryonic nonphagocytic reticulum cells. Other names for FDCs have been used in the past, for example, dendritic reticulum cells (DRCs), follicular dendritic reticulum cells, antigen-retaining reticular cells, follicular antigen-binding dendritic cells, and dendritic macrophages. FDCs are considered as having a passive role in the function of the germinal center. It is characterized as nonphagocytic cells that capture and retain complexes of antigen, antibodies, and C3 on their cell surface. By expressing antigen–antibody complexes and a large number of cell–cell and cellmatrix molecules, FDCs were shown to regulate normal B cell function. There is growing evidence that FDCs could be important constituents of the malignant counterpart of the germinal center. In addition, FDCs were demonstrated to be the target cells in human immunodeficiency virus (HIV)-related lymphadenopathy. These data can be integrated into a concept of FDCs as the key component of the germinal center microenvironment. FDCs demonstrate a unique antigen pattern by co-expressing myeloid and B cell markers.

Follicular dendritic cells and their role in HIV infection

Recently, much attention has focussed on the role of follicular dendritic cells as a reservoir of infectious particles in retroviral, particularly HIV, infection. In this report from a recent meeting ∗ ∗ The European Workshop of Follicular Dendritic Cells was held at the Manor House at the Forschungsinstitut Borstel on 21–22 October 1991, as a satellite meeting of the 22nd Annual Conference of the Gesellschaft für Immunologie and was organized by H-D. Fland and J. Gerdes in cooperation with the Deutsche Gesellschaft für Zellbiologie. , Johannes Gerdes and Hans-Dieter Flad describe these studies in the context of a growing awareness of the morphological, phenotypic and functional heterogeneity of the cells.

Follicular Dendritic Cells in the Regulation and Maintenance of Immune Responses

The objectives of this report are to explore known and potential regulatory roles of follicular dendritic cells (FDCs) in immune responses. FDCs are found in B-cell areas of lymphatic tissue and are especially rich around germinal centers where B-cell proliferation is occurring. Recent advances in isolating FDCs in our laboratories made it possible to begin investigating interactions of FDCs with other cells in vitro. In a series of experiments, we sought to determine whether a low concentration of FDC-enriched cells (2-10%) could enhance B-cell and/or T-cell mitogenesis. The results showed that an enriched population of FDCs markedly enhanced lipopolysaccharide-induced stimulation of nude mouse spleen cells, while an equivalent number of resident peritoneal cells or thymocytes had no effect. Depletion of Thy 1.2 positive cells or an exposure to 2400 rads of gamma radiation did not abrogate the enhancing capacity of FDC-enriched cells. FDC-enriched cells also increased phytohemagglutinininduced proliferation. Scanning electron microscopy of FDC preparations showed that antigen-bearing dendritic processes of Type 2 FDCs have a «beaded» appearance. It was proposed that these immune complex coated microspheres may represent an important mechanism for exposing persisting antigen to the immune system. The gradual shedding of these microspheres may play an important role in regulating and maintaining immune responses within lymphoid tissues.