Origin of follicular dendritic cell in the chicken spleen

The ellipsoid-associated cell (EAC) is a blood-borne phagocytic cell, residing in the antigen trapping zone of the chicken spleen. Binding and endocytosis of βGalactosidase (βGal) are independent from the Fc and complement receptors, because sulfated polysaccharides, in a concentration manner, inhibit the bacterial antigen uptake. The βGal-positive cells migrate to the periarterial lymphatic sheath (PALS), the preexisting germinal centers (GC), and form clusters with B- and T-cells. βGal, E5G12 double positive cells on the surface of the ellipsoid and in the PALS, GC and clusters prove that the EACs carry the enzyme. The EAC and the follicular dendritic cell (FDC) express, 68.2 and E5G12 and, 74.3 and E5G12, antigens, respectively. During migration the cessation of 68.2 and expression of 74.3 indicate the differentiation of EAC to FDC. By day 14 the clusters had disappeared, and in several GC the presence of double positive cells (74.3 and βGal; E5G12 and βGal) showed that the clusters had developed to GC. The presence of βGal⁺ cells in the PALS, where interdigitating dendritic cells (IDC) cooperate with the T-cells, suggests that in the spleen alternate routes exist for the EAC differentiation to FDC: EAC to FDC: βGal-loaded cells in the preexisting GC; and EAC through IDC to FDC: βGal⁺ EAC in the PALS and clusters. The EAC-FDC axis works exclusively inside the spleen; therefore; this system may be operated in pneumococcus infection.This work was supported by OTKA Grant number: T-042558.     

Ontogenetic aspects of immune-complex trapping in the spleen and popliteal lymph nodes of the rat

Summary An ontogenetic approach was used to obtain information about the relation between structure and function of lymphoid tissues. In particular the development of the capacity to trap immune complexes was studied in relation to the development of the lymphoid compartments. For this purpose isologous horseradish (HRP)-anti-HRP complexes were injected into neonatal rats, and their fate was studied in the spleen and popliteal lymph nodes. Immune-complex trapping occurred as soon as primary follicles could be recognized; without follicles no trapping was observed. Several explanations for this simultaneous development of trapping capacity and follicular structure are discussed.Abbreviations i.v. intravenous(ly) - s.c. subcutaneous(ly) - HRP horseradish peroxidase - MZ marginal zone - PALS periarteriolar lymphocyte sheath     

Ultrastructural study of highly enriched follicular dendritic cells reveals their morphology and the periodicity of immune complex binding

Follicular dendritic cells (FDCs) are immune accessory cells found in the follicles of secondary lymphoid organs where they promote B cell maturation in germinal centers (GCs) that develop following antigen exposure. Recently, we published a method for isolating functional murine FDCs in high purity. We reasoned that disruption of FDC reticula in vivo would alter FDC morphology. The present study was undertaken to determine the morphological features of isolated FDCs. FDC-M1 and immune complex (IC) labeling were used to identify FDCs in isolated preparations. Results at the light-microscopic level revealed that isolated FDCs trapped ICs, expressed FDC-M1 and cadherins, but generally appeared non-dendritic. However, at the ultrastructural level, the majority of FDCs exhibited dendrites and typical euchromatic nuclei that appeared as single, bilobed, or double nuclei. Based on morphology, four varieties of FDCs were distinguishable, possibly indicative of differences in maturity. Remarkably, ICs trapped by FDCs showed a distinctive periodic arrangement consistent with that known to induce immune responses by thymus independent-2 (TI-2) antigens that engage and cross-link multiple B cell receptors. The ability of FDCs to trap ICs and then display these T-cell-dependent antigens with repeating periodicity suggests that multiple B cell receptors are cross-linked by antigen on FDCs, thus promoting B cell stimulation and proliferation. Rapid proliferation is characteristic of the GC reaction, and the arrangement of T-dependent antigens in this periodic fashion may help to explain the profuse B cell proliferation in the GC microenvironment. This work was supported by National Institutes of Health Grant AI-17142. Electron microscopy and confocal microscopy were performed at the VCU Department of Neurobiology and Anatomy Microscopy Facility supported, in part, by funding from an NIH-NINDS Center core grant (5P30NS047463).     

滤泡树突细胞肉瘤二例报道并文献复习

目的探讨滤泡树突细胞肉瘤（FDCS）的临床表现、病理形态、免疫组化、生物学行为和预后,提高对该病的认识。方法对2例滤泡树突细胞肉瘤进行报道,并结合临床资料、肿瘤大体及镜下特征、免疫组化标记结果及预后和国内外文献进行分析。结果2例FDCS,1例发生于颈部淋巴结,另1例发生于肠系膜,镜检肿瘤由梭形及卵圆形细胞组成,呈束状、漩涡状、编织状排列;免疫组化显示肿瘤细胞CD21、CD23和CD35阳性;患者预后不良。结论滤泡树突细胞肉瘤是一种罕见且容易误诊的低度恶性肿瘤,组织化学和免疫组化染色有助于该肿瘤的诊断及鉴别诊断,减少误诊。     

Precise localization of antigens on follicular dendritic cells

Summary Horse-spleen ferritin or bovine serum albumin conjugated to colloidal gold (BSA-gold) were injected subcutaneously in preimmunized mice. In draining lymph nodes both antigens were located in macrophages or between the cytoplasmic processes of follicular dendritic cells (FDC). Some of the antigens remained trapped on FDC until day 31 after injection. Simultaneous injection of both antigens showed that they were located between the infoldings of the same FDC. These cells are thus able to retain at least two different antigens on their surface. The peculiar arrangement of ferritin between the cytoplasmic infoldings suggests that this antigen is fixed on both cell membranes by specific antibodies. The trapped immune complexes could thus stabilize the FDC membrane system.The antigen retention requires the presence of specific antibodies since BSA-gold or ferritin injected without preimmunization were not found between FDC processes. Nonantigenic materials, such as colloidal gold or carbon particles, are not trapped by FDC, except when injected in large amounts.The antigens were trapped on the surface of FDC, however unfrequently in close contact with lymphocytes. FDC might protect lymphocytes against an excess of immune complexes and act as regulators of contacts between lymphocytes and immune complexes.Abbreviations BSA bovine serum albumin - BSA-gold BSA conjugated to colloidal gold particles - FDC follicular dendritic cells     

Development of follicular dendritic cells in lymph nodes of B-cell-depleted mice

Summary We have studied follicular dendritic cells (FDC) in lymph nodes of normal and thymus dysgeneic nude mice depleted of B-cells by chronic treatment with anti-IgM antibodies. We found that B cell depletion was accompanied by the absence of mature FDC as defined morphologically at the ultrastructural level. Only precursor FDC (p-FDC) could be demonstrated. Upon release of B-cell suppression, the repopulation of lymph nodes with B-cells was associated with the reappearance of fully differentiated FDC in primary follicles of nude mice and in secondary follicles of T-cell competent mice. We conclude that mature B-cells and/or B-cell products are required for the development of mature follicular dendritic cells in the mouse lymph node.     

Progesterone is involved in the maturation of murine spleen CD11c-positive dendritic cells

Progesterone (Prog), a female sex steroid hormone, not only plays an important role in the female mammary pregnancy but also influences the immune response. In the present study, murine spleen CD11c-positive dendritic cells (SDCs) were treated with various concentrations of Prog for 24 h, and their viability, phenotype, nuclear factor kappa B P65 (NF-kappaB P65), endocytosis, stimulatory capacity, and cytokine expression were analyzed. The results showed that Prog increased the expressions of MHC-II and CD40, stimulatory capacity and intracellular levels of IL-6 and IL-10, while decreased the expressions of CD54 and IL-12, endocytosis and nuclear level of NF-kappaB P65 of SDCs. These data suggested that Prog may promote the maturation of SDCs and enhance their ability to interact with T cells so as to change the course of autoimmune diseases.     

Follicular dendritic cell of the knock-in mouse provides a new bioassay for human prions

Infectious prion diseases initiate infection within lymphoid organs where prion infectivity accumulates during the early stages of peripheral infection. In a mouse-adapted prion infection, an abnormal isoform (PrP(Sc)) of prion protein (PrP) accumulates in follicular dendritic cells within lymphoid organs. Human prions, however, did not cause an accumulation of PrP(Sc) in the wild type mice. Here, we report that knock-in mouse expressing humanized chimeric PrP demonstrated PrP(Sc) accumulations in follicular dendritic cells following human prion infections, including variant Creutzfeldt-Jakob disease. The accumulated PrP(Sc) consisted of recombinant PrP, but not of the inoculated human PrP. These accumulations were detectable in the spleens of all mice examined 30 days post-inoculation. Infectivity of the spleen was also evident. Conversion of humanized PrP in the spleen provides a rapid and sensitive bioassay method to uncover the infectivity of human prions. This model should facilitate the prevention of infectious prion diseases.     

Isolation of multicellular complexes of follicular dendritic cells and lymphocytes: Immunophenotypical characterization,electron microscopy and culture studies

Summary The morphological and phenotypical features of multicellular complexes formed by follicular dendritic cells and lymphocytes (FDC-LC) isolated from human hyperplastic tonsils and adenoids are described. FDC-LC obtained with this procedure were morphologically and immuno-phenotypically heterogeneous. In one type of FDCLC, probably obtained from germinal centers, the lymphocytes exhibited ultrastructural features of centroblasts and centrocytes. In a second type, likely derived from follicular mantles, the enclosed lymphocytes were small in size and characterized by a condensed chromatin pattern. Similar heterogeneity was observed by immuno-phenotypical analysis, which revealed a prevalence of IgD+, CD3-, MT2+ small lymphocytes in a high proportion of FDC-LC. Both types of FDC-LC contained desmoplakin immunoreactivity in a typical punctate pattern corresponding to intercellular junctions when tested with a specific antibody. These findings confirm the importance of FDC in maintaining the follicular structure and also suggest that the different zones forming lymphoid follicles (mantle zone and germinal center) are formed by lymphocytes gathered in single domains by cytoplasmic processes of FDC. These domains have strong resistance to mechanical stress, such as that used in isolation procedures. FDC-LC have also been maintained as organized multicellular clusters for short periods (more than 48 h) in agarose gel cultures.Supported in part by: Ministero Pubblica Istruzione, Italy, and A.I.R.C., Milano, Italy     

Development and cell phenotypes in primary follicles of foetal sheep lymph nodes

Lymph nodes from sheep foetuses and postnatal lambs were examined to determine the participation of different leucocyte populations in primary follicle formation, with special emphasis on the emergence and subsequent development of follicular dendritic cells during late gestation and early postnatal life. A series of immune and enzyme histochemical markers was used. The first 5-nucleotidase-positive primary follicles were found at 80 days gestational age (gestation in sheep is 150 days) in superficial cervical lymph nodes. In the last month of gestation the primary follicles possessed follicular dendritic cells, macrophages, dendritic cells, and CD5-positive lymphocytes, in addition to IgM-positive cells. Follicular dendritic cells in primary follicles were found to be ultrastructurally immature. These follicular dendritic cells were characterised by a few, coarse surface projections and many ribosomes attached to the endoplasmic reticulum. A final differentiation to mature follicular dendritic cells was coincident with the postnatal germinal centre reaction. Computer-assisted morphometric analysis demonstrated that the size of 5-nucleotidase-positive primary follicles in the distal jejunal lymph node, but not in the superficial cervical lymph node, increased significantly during late gestation. It was concluded that stromal cells in primary follicles of foetal sheep lymph nodes were a continuously developing population but that ultrastructural maturity was only achieved in the germinal centres of postnatal lambs.     

The significance of the subcompartments of the marginal zone for directing lymphocyte traffic within the splenic pulp of the rat

Summary These studies were designed to gain more detailed information on the sites of lymphocyte migration into the marginal zone, on lymphocyte segregation within this area and on subsequent migration of the cells in individual compartments of the rat spleen. A lymphocyte population enriched in T-lymphocytes was obtained from rat lymph nodes and was labeled with 5-(³H)uridine in vitro. Observations on localization of labeled lymphocytes at short time intervals following their intravenous transfusion into syngeneic recipients, indicate that the sites of emigration from the blood are the internal and external layers of the marginal zone. From here, the cells migrate towards the periarteriolar lymphoid sheath and the red pulp.Fellow of the Alexander-von-Humboldt-Stiftung. On leave from the Department of Histology and Embryology, Institute of Biostructure, Academy of Medicine, ul. Swiecickiego 6, PL-60-781 Pozna, Poland     

Expression of the intercellular adhesion molecule-1 on high endothelial venules and on non-lymphoid antigen handling cells: interdigitating cells,antigen transporting cells and follicular dendritic cells

Intercellular adhesion molecule-1 (ICAM-1)¹ has been implicated in the development of germinal center reactions in vitro, and the present study was undertaken to determine the distribution of ICAM-1 in active germinal centers in vivo and in murine secondary lymphoid tissues in general. Anti-ICAM-1-specific monoclonal antibodies were used in conjunction with immunohistochemistry at both the light and ultrastructural levels of resolution. Examination of cryostat sections of lymph nodes, spleens, and Peyer's patches revealed that anti-ICAM-1 distinctly labeled cells in the light zones of germinal centers, a few cells in the T cell zones (e.g. paracortex of lymph nodes), cells in the sinus floor of the subcapsular sinuses of lymph nodes, and high endothelial venules (HEV). Ultrastructural studies revealed that the cells labeling with anti-ICAM-1 in germinal centers were follicular dendritic cells (FDC) which appeared to have more ICAM-1 than any other cell type. The surfaces of well-developed, intricate, convoluted FDC processes were intensely labeled even under conditions where B cells appeared negative. Interdigitating cells (IDC) were also labeled as were certain endothelial cells in the HEV. The cells in the subcapsular sinus floor labeling with anti-ICAM-1 were the antigen transporting cells (ATC) that carry antigen-antibody complexes into lymph node follicles. We suspect ATC are FDC precursors which mature into FDC in the follicles. Interestingly, FDC, IDC, and ATC are 3 important accessory cells known to handle antigens in specific compartments of lymphoid tissues. The marked localization of this adhesion molecule on these critical antigen handling cells supports the concept that ICAM-1 is important in providing the intercellular adhesion necessary for optimal initiation of immune responses in vivo.Abbreviations ICAM-1 Intercellular adhesion molecule-1 - LFA-1 leukocyte functional antigen-1 - IDC interdigitating cells - ATC antigen transporting cells - FDC follicular dendritic cells - HEV high endothelial venules - DC dendritic cells - PBS phosphate-buffered saline - PLP periodate-lysine-4% paraformaldehyde - GPLP periodate-lysine-0.1% glutaraldehyde-2% paraformaldehyde - EM electron microscopy - HRP horseradish peroxidase - DAB diaminobenzidine tetrahydrochloride - HSA human serum albumin     

一种拮抗HIV-1并靶向DC的融合基因的设计及表达鉴定

艾滋病病毒 (Human immunodeficiency virus,HIV) 通过与靶细胞膜的融合感染宿主细胞,研究表明阻断HIV与受体靶分子的结合可以阻止HIV进入宿主细胞,抑制HIV病毒的感染。设计合成了一个包含CD4和CCR5与HIV-1结合的主要功能结构区,及Flt3-L和Mip-3α分子的融合基因,构建了2个融合基因的真核表达载体pABK-CKR5-CD4/Flt3L-Mip3α (pABK-HIV-MF) 和pABK-CKR5-CD4 (pABK-HIV-MT),在人胚肾293细胞中进行了表达。RT-PCR、细胞免疫荧光技术、ELISA和Western blotting检测结果表明融合基因在真核细胞中获得了正确的表达,这为进一步研究其对于HIV-1的拮抗并靶向树突状细胞 (DC) 清除研究奠定了基础。     

Identification of dendritic cell subsets responding to genital infection by Chlamydia muridarum

Dendritic cells (DCs) are central for the induction of T-cell responses needed for chlamydial eradication. Here, we report the activation of two DC subsets: a classical CD11b+ (cDC) and plasmacytoid (pDC) during genital infection with Chlamydia muridarum . Genital infection induced an influx of cDC and pDC into the genital tract and its draining lymph node (iliac lymph nodes, ILN) as well as colocalization with T cells in the ILN. Genital infection with C. muridarum also stimulated high levels of costimulatory molecules on cDC central for the activation of naïve T cells in vivo . In contrast, pDC expressed low levels of most costimulatory molecules in vivo and did not secrete cytokines associated with the production of T helper (Th)1 cells in vitro . However, pDC upregulated inducible costimulatory ligand expression and produced IL-6 and IL-10 in response to chlamydial exposure in vitro . Our findings show that these two DC subsets likely have different functions in vivo . cDCs are prepared for induction of antichlamydial T-cell responses, whereas pDCs have characteristics associated with the differentiation of non-Th1 cell subsets.     

Impact of histamine on dendritic cell functions

A rapidly growing body of evidence highlighted that histamine, a small biogenic amine, is implicated in the regulation of DC (dendritic cell) functions. It is well established that DCs represent the most potent antigen-presenting cells of the body, linking innate and acquired immunity and regulating the outcome of immune responses. Signals, associated with ongoing inflammation and uptake of foreign antigens, promote maturation of DCs and activation of T-cell responses in secondary lymphatic organs. These bone marrow-derived cells patrol continuously all over the body. During their persistent migration, several mediators may influence the behaviour and functions of DCs. Histamine, produced by mast cells, basophils or DCs themselves, may have an important role in the life cycle of DCs. From the differentiation, through their never-ending circulation, until the induction of T-cell response, histamine is present and influences the life cycle of DCs. Here, we summarize recent progress in histamine research with respect to DC functions. We also point out some controversial aspects of histamine action on DCs.     

双峰驼卵泡发育过程中卵泡液差异蛋白质组学

为了比较双峰驼卵泡发育过程中卵泡液中差异表达的蛋白质,将卵泡按照直径分为6 类,运用双向电泳技术构建双峰驼卵泡液蛋白质二维凝胶电泳图谱,凝胶经考马斯亮蓝染色后用PDQuest 8. 0 检测差异蛋白,结果表明在6 类大小不同的卵泡中共检测到13 个差异蛋白点,这些蛋白点经LC -MS/ MS 鉴定出7 种不同的蛋白质,它们分别是:血红蛋白、toll-like 受体9、抗凝血酶、聚泛素、γ 纤维蛋白原、重组活化蛋白1 和跨膜与卷曲螺旋域3。基于这些蛋白的功能和表达模式,结合实验结果讨论了这些蛋白质在生殖中的功能,发现toll-like 受体9、聚泛素、γ 纤维蛋白原和重组活化蛋白1 可能与卵泡发育或卵母细胞的成熟有关。这些蛋白质的发现为了解双峰驼卵泡发育和卵母细胞成熟的生理机制奠定基础。     

Dark and light zones of germinal centres of the human tonsil: an ultrastructural study with emphasis on heterogeneity of follicular dendritic cells

Summary The cellular composition of the dark and light zones of germinal centres in human tonsils was quantitatively determined by electron microscopy. In addition to the well known germinal-centre B-cells, we defined the cleaved blast as a new distinct cell type in the germinal centre. The dark and the light zones clearly differed in their content of lymphoid and non-lymphoid germinal-centre cells. The dark zone was characterized by higher frequencies of cleaved blasts and small centroblasts, a higher blast-centrocyte ratio and a higher incidence of mitotic figures. In contrast, the light zone had higher frequencies of centrocytes, centroplasmacytoid cells, lymphocytes and follicular dendritic cells (FDC) and an inverted blast-centrocyte ratio. Seven distinct appearances of FDC (FDC.1-FDC.7) could be recognized on the basis of their ultrastructure. The distribution pattern of these subtypes differed between the dark and light zone. The undifferentiated subtypes FDC.2 and FDC.3 predominated in the dark zone. In contrast, the highly differentiated subtypes FDC.4 and FDC.5 were present at a much higher density in the light zone. These findings suggest that the dark and light zones are different compartments with regard to proliferation and differentiation of germinal-centre B-cells and that both compartments have a specific microenvironment influenced by FDC.     

OP9-DL1 cell co-culture enhances anti-tumour immunity of mouse bone marrow-derived dendritic cells

DCs (dendritic cells) are the strongest professional APCs (antigen-presenting cells) to initiate immune responses against pathogens, but they are usually incompetent in initiating efficient immune responses in the progress of solid tumours. We have shown that Notch signalling plays a pivotal role in DC-dependent anti-tumour immunity. Compared with the control DCs, OP9-DL1 (Delta-like1) cell co-cultured DCs gained increased tumour suppression activity when inoculated together with tumour cells. This was probably due to the activation of Notch signalling in DCs enhancing their ability to evoke anti-tumour immune responses in solid tumours. Indeed, the OP9-DL1 cell co-cultured DCs expressed higher levels of MHC I, MHC II, CXCR4 (CXC chemokine receptor 4), CCR7 (CC chemokine receptor 7), IL-6 (interleukin 6), IL-12 and TNFα (tumour necrosis factor α), and a lower level of IL-10 than control DCs, resulting in more efficient DC migration and T-cell activation in vivo and in vitro. T-cells stimulated by OP9-DL1 cells co-cultured DCs more efficiently; and were cytotoxic against tumour cells, in contrast with control DCs. These results indicated that up-regulation of Notch signalling in DCs by co-culturing with OP9-DL1 cells enhances DC-dependent anti-tumour immune reactions, making the Notch signalling pathway a target for the establishment of the DC-based anti-tumour immunotherapies.     

The immunostimulatory effects of retinoblastoma cell supernatant on dendritic cells

Dendritic cells (DCs) are crucial for the induction and maintenance of tumor-specific immune responses. Studies have shown that tumor-associated DCs are immunosuppressed in some human tumors. However, phenotype and function of DCs in retinoblastoma (RB) remain unclear. RB cell supernatant (RBcs) was used to treat DCs in vitro to explore the effect of RB cells on DCs. DCs were generated from peripheral blood mononuclear cells of healthy donors. On day 5 of culture, DCs were treated with RBcs for 24 h, and then purified using magnetic beads. The maturation of DCs was induced by TNF-α or LPS. After treatment with RBcs, expression of co-stimulatory molecules CD80 and CD86 was elevated in DCs, accompanied by increased production of IL-12p70, TNF-α, IL-6, IL-1β, and IL-8 but decreased production of IL-10. RBcs neither inhibited DC maturation nor promoted DC apoptosis. Moreover, RBcs-exposed DCs stimulated allogenetic T cell proliferation and T cell-derived cytokine production. These results indicate that RBcs can improve DCs’ antigen presenting function and capability to activate T cells, suggesting that RB cells may have an immunostimulatory effect on DCs, and Dcbased immunotherapy may be adopted in the treatment of RB.