Dendritic Accessory Cells Research Articles

Lymphocyte subpopulations in hypertrophied adenoid in children

Adenoid hypertophy is a common feature of childhood. It is currently accepted that it is caused by the antigen-stimulated increased activity of lymphocyte B (D. Bani, O. Gallo, O. Fini-Storchi, Intraepithelial lymphocyte subpopulations and dendritic accessory cells in normal and hypertrophic adenoids, Laryngoscope 10 (1994) 869–873). The adenoid decreases its size with age but the accompanying function alterations are not fully understood (L. Zawadzka-Glos, M. Chmielik, M. Wasik, Cell mediated response in hypertrophied tonsils in children, Nowa Pediatr. 4 (1997) 12–13). The understanding of the adenoid structure that undergoes some changes during the growth period is essential for evaluation of indications for adnoidectomy and assessment of its potential results. The aim of this study was to evaluate lymphocyte subpopulations in adenoid according to age. The analysed material was adenoids removed on the grounds of hypertrophy, which caused obstructive symptoms and/or otitis media with effusion onset. In the present study, we did not find any statistically significant differences among lymphocytes B, Th, and Ts subpopulations, respectively, in the adenoids of any of the age groups. We have found a statistically significant CD3 + HLA-DR + cell percentage decrease in the group of children from 5 to 10 and above 10 years of age, respectively. We have also found a statistically significant increase in the percentage of NK (CD3 − CD16 + 56 +) lymphocytes in relation to age. On the grounds of the current study, it may be stated that some changes in lymphocyte subpopulations in the adenoid take place with age.

Murine follicular dendritic cells: accessory activities in vitro.

Follicular dendritic cells (FDC) are accessory cells found in association with B lymphocytes in the follicles of stimulated secondary lymphoid tissues. Accessory cells are known to collaborate with lymphocytes and enable them to carry out their essential functions. FDC present antigen (Ag) to B cells and facilitate B cell functions; they may be thought of as B cell-associated accessory cells. In contrast, other dendritic cells, including Langerhans cells, interdigitating cells, and veiled cells, interact primarily with T lymphocytes. These dendritic accessory cells, collectively referred to as dendritic cells (DC) in vitro, present antigen to T cells and may be thought of as T cell-associated accessory cells (TEW et al. 1992a). Data supporting the accessory activities of most accessory cells, such as DC and macrophages, have been collected using in vitro experimentation. In contrast, most of the data available on FDC has been collected using in vivo models. We have reviewed these in vivo data on murine FDC in a number of recent articles.

Interferon-Gamma and Tumor Necrosis Factor-Alpha Promote the Binding of Dendritic Cells to Fibronectin

Connective tissue dendritic accessory cells (DC) accumulate at sites of extracellular matrix (ECM) deposition. The adherence of DC to purified ECM proteins was examined. Splenic and pulmonary DC were purified from Lewis rats and incubated on slides coated with fibronectin (FN), laminin (LN), or collagen (COLL) types I, III and IV. In other experiments, DC were pre-incubated with selected proinflammatory cytokines (IL-1, IL-2, IFN-gamma, TNF-alpha) in order to determine their abilities to modulate cell adherence to ECM. Both splenic and pulmonary DC showed dose-dependent binding to FN that was inhibited by the synthetic peptide arg-gly-asp-ser. There was minimal DC binding to LN or COLL. Pretreating DC with IFN-gamma or TNF-alpha enhanced DC binding to FN but did not increase binding to LN or COLL. IL-1 and IL-2 had no demonstrable effect on DC binding to ECM. Our results suggest that FN is a critical ligand for DC in their binding to the ECM. IFN-gamma and TNF-alpha increase adherence of DC to FN and may promote their accumulation in the lung during inflammation.

Does the epithelium play a central role in the immune function of rhinopharyngeal tonsils? An immunocytochemical and ultrastructural study

Enlarged adenoids from 10 children with chronic rhinitis and otitis media with effusion have been studied immunocytochemically and ultrastructurally, to better define the possible role of the epithelium and the dendritic accessory cells in the immune activation of lymphoid cells, and provide further insight into the pathogenesis of the disease. The presence within the columnar epithelium of lymphocytes positive for CD8 antigen, and which electron microscopically have been found frequently apposed to degenerating epithelial cells suggests that the latter cells are targets for cytotoxic activity of intraepithelial lymphocytes, rather than being engaged in antigen presentation. Furthermore, the finding of typical dendritic accessory cells, recognized by their typical immunophenotypic and ultrastructural features, in the lamina propria, indicates that antigen presentation is more likely exerted by dendritic accessory cells. This is further supported by the fact that these cells express major histocompatibility (MHC) class II molecules, which are needed for antigen presentation, whereas epithelial cells do not. A possible relationship between epithelial damage and the pathogenesis of adenoidal enlargement is discussed.

Accessory Cells of the Lung. II. Ia+ Pulmonary Dendritic Cells Display Cell Surface Antigen Heterogeneity

In earlier studies, we had determined that class II (Ia) major histocompatibility complex (MHC) antigen expression in the normal rat lung was limited to dendritic cells and type II alveolar cells. In order to characterize the Ia+ pulmonary dendritic cells of the lung parenchyma, Lewis rat lungs were dissected free of their major airways, enzymatically digested, and serially subjected to density centrifugation on bovine serum albumin, overnight adherence, and immunopanning with a murine anti-rat monoclonal antibody (anti-OX-6) that reacts specifically with class II (Ia) MHC antigens. The purified Ia+ pulmonary cells displayed the morphologic and functional features of dendritic accessory cells, including extended cell processes, absence of nonspecific esterase staining, minimal phagocytosis of latex beads, rapid clustering with T lymphocytes, and co-stimulation of T-cell mitogen responses. Detailed immunophenotyping by cytofluorimetry and immunohistology showed that the purified dendritic cells were Ia (OX-6)+, CD45R (OX-1)+, CD45Rb (OX-22)-, ICAM-1+, and OX-43-. As many as 50% of the cells bound heat-aggregated IgG, while a smaller percentage expressed the CD43 sialophorin antigens (W3/13) expressed by a variety of blood-derived cells, and/or the OX-41 and RMA macrophage antigens. We conclude that Ia+ dendritic cells of lung are heterogeneous with respect to their expression of surface membrane differentiation antigens and may prove to be functionally distinct with respect to their accessory activities.

Accessory Cells of the Lung. I. Interferon-gamma Increases Ia+ Dendritic Cells in the Lung Without Augmenting their Accessory Activities

Dendritic cells are specifically adapted to provide accessory signals for the growth of T lymphocytes. Ia+ dendritic cells are present within the normal lung; however, little is known concerning their regulation in vivo. Interferon-gamma (IFN-gamma) is a proinflammatory lymphokine that augments the expression of Ia antigens and promotes the accessory activities of a variety of cells. In order to determine whether IFN-gamma regulates pulmonary dendritic cells in vivo, Lewis rats were injected intraperitoneally with recombinant murine IFN-gamma (2 x 10(5) U/rat/day) or with buffered saline for 5 consecutive days. Following sacrifice, the lungs were excised, and the distribution and number of Ia (OX-6)+ cells was determined in situ. Dendritic cells were localized in the mucosal lining of the tracheobronchial tree, in pulmonary capillaries, as well as in the alveolar septal interstitium and subjacent to the pleural surfaces. IFN-gamma yielded a specific increase in Ia+ dendritic cells in alveolar septa and in pulmonary airways. Purified Ia+ dendritic cells from enzymatic digests of lung were excellent accessory cells for the proliferative responses of both antigen-primed and naive T lymphocytes. IFN-gamma did not, however, further augment the expression of Ia antigens or the accessory activities of pulmonary dendritic cells. These results suggest that IFN-gamma may promote pulmonary T cell-mediated inflammatory responses in vivo by increasing the number of Ia+ dendritic accessory cells in the lung.

Multimarker immunohistochemical staining of calgranulins, chloroacetate esterase, and S100 for simultaneous demonstration of inflammatory cells on paraffin sections.

Mac387 monoclonal antibody (MAb) recognizes two calcium binding, myeloid-associated proteins, now termed calgranulins, expressed at high levels by neutrophils and monocytes. Calgranulins are related to migration inhibitory factor (MIF) and are lost in a few days from monocytes differentiated in vitro. This marker is therefore potentially useful to analyze macrophage heterogeneity and turnover in tissue sections. In this study, we developed an immunohistochemical multimarker technique, including calgranulin demonstration, suitable for analyzing different inflammatory cells on paraffin-embedded material. The technique was carried out in subsequent steps demonstrating (a) naphthol AS-D chloroacetate esterase (CAE); (b) S100 immunoreactivity using a rabbit antibody in peroxidase-antiperoxidase (PAP) staining; and (c) Mac387 immunoreactivity using the alkaline phosphatase-anti-alkaline phosphatase (APAAP) technique. CAE staining was introduced in this method to distinguish Mac387+/CAE- macrophages from Mac387+/CAE+ neutrophils, and Mac387-/CAE+ mast cells. S100 protein is strongly expressed within lymphoid tissues by dendritic accessory cells and was then applied to distinguish these cells from S100-macrophages. We have also verified the possibility of reducing the staining time for this time-consuming procedure by use of microwave irradiation. The technique was applied to a representative variety of normal and pathological samples to assess its usefulness for study of cell heterogeneity. Our results showed the multimarker technique to be highly informative in the study of inflammatory lesions (e.g., rheumatoid arthritis, sarcoid and cat-scratch granulomas, dermathopathic lymphadenopathy), and is of wide potential value as an aid to histopathological diagnosis of several diseases.

Lymphoid Dendritic Accessory Cells of the Rat

The expression of MHC class II antigens on potential APC is a crucial step in T-lymphocyte activation and the initiation of an immune response. The studies which are presented here were initiated to characterize the critical APC present in physiologically normal, untreated rats. Such a cell should constitutively express these antigens at high density and therefore provide the apparatus necessary to provoke both primary and secondary immune responses at any time. DAC were found to fulfill these criteria. In the absence of specific surface markers of rat DAC, the results are based on the strict combination of morphological appearance and functional activity. However, the high expression of MHC class II antigens may be regarded as semispecific markers for DAC which are distributed at strategic positions in many lymphoid and nonlymphoid tissues (Hart & Fabre 1981, Steiniger et al. 1984). The relatively low number of these cells observed in tissue sections and in in vitro isolates (0.1% of all cells) may explain their high activity as APC. This would facilitate the presentation of antigen in vivo to a sufficient number of competent T lymphocytes. DAC differentiate from a bone marrow progenitor cell pool preferentially under the influence of spleen cell-derived activities. Although the exact lineage has not yet been determined it may be fair to speculate that DAC form a new cell lineage probably related to interdigitating cells but not to macrophages which differentiate from bone marrow-derived precursors under the influence of colony-stimulating activities. However, the cooperation between DAC plus macrophages may provide the stage for T-lymphocyte activation and T-T collaboration (Mitchison 1990). There are still many open questions concerning the general role of DAC in vivo and in vitro. To further characterize rat DAC, their tissue distribution, role in the immune response and possible influence on intrathymic lymphopoiesis, with respect to T-lymphocyte subpopulations and the selection of the T-lymphocyte antigen-receptor repertoire, a panel of DAC-specific monoclonal antibodies must be generated in the future. Such antibodies will also be useful to study the mechanism by which DAC activate T lymphocytes.

Induced type-B reticulum cell neoplasia in mice III. The importance of T-cell proliferation and cellular relocation in accessory cell transformation.

After the transfer of spleen cells from old CBA/T6T6 mice (greater than 75 weeks) into young syngeneic CBA/Ca recipients there usually follows a selective expansion of the donor T-cell population and the emergence of type B reticulum cell neoplasms (RCN-B), also of donor origin though probably derived not from the T-cells but from lymphoid dendritic accessory cells. As few as one million injected cells led to significant donor T-cell hyperplasia and tumour induction. Injection of cells from young donors did not have such consequences. Similar tumours were induced by transferring syngeneic cells in both C57BL and DBA/2 mice, although in the latter strain there was no requirement for the injected cells to derive from old donors. It appeared that T-cell proliferation was independent of donor accessory cells or RCN-B induction, since injection of enriched T-cells led to few tumours, although the T-cell chimaerism was indistinguishable from that in recipients of unseparated spleen cells. Development of tumours, however, seemed to be dependent upon stimulated T-cells. Recipients of spleen cells from old T-cell-deprived mice did not develop tumours; conversely, tumours, mostly of donor origin, were induced in recipients of young syngeneic cells when an extrinsic stimulus to T-cell proliferation was provided by continued allostimulation. The apparent selectivity of tumorigenesis for donor cells has led to the proposal that cellular relocation, as a result of transfer, may be an important predisposing factor in malignant transformation in circumstances of T-cell stimulation provided by antigenic challenge or by transfer of T-cells from old donors.

Immunoregulation in the Peyer's patch microenvironment. Cellular basis for the enhanced responses by the B cells of X-linked immunodeficient CBA/N mice.

The Peyer's patches (PP) of X-linked immunodeficient (xid) CBA/N and hemizygous (CBA/N X DBA/2)F1 (CDF1) male mice contain a B cell subpopulation that expresses the Lyb-5 maturational marker and is responsive to type 2 and T cell-dependent antigens in vitro, a B cell phenotype which is absent from the spleens of xid mice. Experiments reported here show that xid spleen B cells co-cultured with B cell-depleted PP cells from xid mice differentiated into specific plaque-forming cells in response to trinitrophenyl-Ficoll (type 2) and sheep erythrocytes (T cell-dependent). Two cell types were involved in this normalization of xid B cell responses. An accessory cell activity present in the PP, but not the spleens, of both CDF1 male (xid) and CDF1 female (normal) mice was required for the response to either the type 2 or T cell-dependent antigens. In the presence of this PP accessory cell, T cells from the PP of either xid or normal mice supported responses to both classes of antigens. In contrast, T cells from the spleens of xid mice did not support the response to trinitrophenyl-Ficoll, although the splenic T cells from normal mice did synergize with PP accessory cells in allowing plaque-forming cell development by xid B cells to this type 2 antigen. The xid PP T cell activity required for the type 2 response by xid B cells was present in the Ly-1+, Lyt-2- subpopulation, and the xid PP accessory cell activity was provided by an enriched population of dendritic accessory cells. These results demonstrate the the lymphoreticular cells comprising the PP microenvironment provide effective support for the differentiation of xid B cells in response to type 2 and T cell-dependent antigens.

Regulatory T cell networks in the secretory immune system.

The mucosal surfaces of man and other mammals are in direct continuity with the external environment. As such, they are continually exposed to antigens from the environment and represent the major bodily site of antigenic exposure and recognition. In the case of ingested antigens, there is selective uptake into the Peyer’s patches (PP), which are distinct aggregates of lymphoreticular nodules along the anti-mesenteric aspect of the gastrointestinal (GI) tract and a major component of the gut-associated lymphoreticular tissues (GALT). The PP contain a large subpopulation of B lymphocytes that are committed to IgA synthesis (1), macrophages (2), dendritic accessory cells (3) and regulatory T lymphocytes of the T-helper (Th), T suppressor (Ts) and T contrasuppressor (Tes) subsets (4–7). Overlying the PP is a lymphoepithelium which contains microfold cells (M cells; also termed follicular-associated epithelial cells) with highly developed pinocytotic channels which allow sampling of antigens from the gut lumenal contents, and transport of these antigens to the underlying lymphoreticular cells (8,9). The oral administration of antigen leads to the stimulation of both the B lymphocyte (follicular) and T lymphocyte (parafollicular) zones within the PP, but B lymphocyte maturation to the plasma cell stage does not occur in this tissue.

Rat Bone Marrow Precursors Develop into Dendritic Accessory Cells under the Influence of a Conditioned Medium

Primary in vitro immune responses require the interaction between T lymphocytes and Ia-positive antigen-presenting cells. Recently, techniques were established including discontinuous bovine serum albumin gradients, adherence, irradiation, and Fc-rosetting which led to a positive selection of rat dendritic cells and their identification as the major if not the only accessory cell for rat T lymphocytes treated with the mitogen, sodium periodate, or stimulator cells in mixed lymphocyte reactions. Rat dendritic cells which were found to be present in both lymphoid and non-lymphoid tissues have a low density, are non-adherent, radioresistant, nonspecific esterase-negative, Fc-receptor negative and Ia-positive. Dendritic accessory cells were detected in cultures of low-density bone marrow cells and developed from radiosensitive precursors especially in a medium containing 10-20% of a supernatant elaborated by mitogen-preactivated syngeneic spleen cells. When compared to purified lymph node dendritic cells they were found to be identical in potency and phenotype. Adherent cells from bone marrow possessed neither accessory activity nor influenced the development of dendritic accessory cells. The mature dendritic accessory cells which could be enriched 1000-fold were no longer radiosensitive. The production of dendritic accessory cells from bone marrow precursors was influenced by the culture medium. Serum components were found to suppress their development. However, semipurified factor(s) released by mitogen-preactivated spleen cells enhanced the number of dendritic cells considerably. Activity resided in substances with a molecular weight in the range of 40,000 Daltons. This material could be separated on a Sephadex G75 column from rat Interleukin 2 which had no effect on the formation of dendritic cells but did support proliferation of accessory cell-depleted, mitogen-treated lymph node cells.