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E C Hoefsmit

Publications and source records attributed to E C Hoefsmit.

At least 73 records · Page 4Linked to original sources
PubMed1983

Characterization of non-lymphoid cells in Peyer's patches of the rat.

The aim of the present study was to correlate in vitro and in situ observations on nonlymphoid cells in Peyer's patches (PP) of the rat. By carrying out enzyme cytochemical reactions (acid phosphatase, APh, and non-specific esterase, NSE) and immunocytochemistry (Ia antigen staining) on cell suspensions and cryostat sections of PP, two classes of nonlymphoid cells could be distinguished. These were (1) strongly APh- and NSE-positive cells without or with a slight Ia membrane staining and (2) strongly Ia-positive cells with a weak APh and NSE activity. The first cell class comprised the classical macrophages which, except for tingible body macrophages, were glass-adherent. The second cell class was non-adherent and comprised dendritic (interdigitating) cells. The role of this Ia-positive non-adherent cell population was discussed, and a hypothesis was presented on the relation between mononuclear blood cells, veiled cells, and interdigitating cells in PP.

Acid Phosphatase↗
PubMed1982

Lymph node macrophages and reticulum cells in the immune response. The secondary response to paratyphoid vaccine.

The morphology and kinetics of macrophages and reticulum cells of rat lymph nodes have been studied in relation to the immune response to a second exposure to antigen. During the first 24 h after stimulation monocyte-like exudate macrophages, including some scattered interdigitating cells (IDC), contain granules similar to those present in epidermal Langerhans cells and lymph-borne veiled cells. In this induction phase these macrophages migrate from the marginal sinus into the paracortex and during the migration they gradually transform into IDC. In the proliferation phase the paracortex is mainly populated by transitional macrophages and there are almost no typical IDC present between the lymphoblasts. In the memory phase the relative number of IDC again rapidly increases. During this period in the paracortex there are often typical IDC which contain partially digested necrotic lymphocytes, thus resembling tingible body macrophages (TBM) of the germinal centre in this respect. It is suggested that the newly arrived macrophages induce the lymphoblast reaction, while mature IDC may have an inhibitory function in the memory phase of the immune response. In this phase the phagocytic potential of IDC is clearly shown.

Animals↗
PubMed1982

Interdigitating cells and macrophages in the acute involuting rat thymus. An electron-microscopic study on phagocytic activity and population development.

Phagocytic activity and population development of medullary interdigitating cells (IDC) and cortical macrophages have been studied in the rat thymus after irradiation-induced thymocyte necrosis. IDC clearly demonstrate phagocytic activity particularly in the 16 h stage after irradiation. At this stage the number of necrotic thymocytes is maximal and the total number of phagocytic cells is insufficient to phagocytize all necrotic material. IDC increase in number slightly and are predominantly phagocytizing in the corticomedullary region (CMR), where they appear to develop from macrophage-like cells. The results indicate that medullary IDC can be phagocytic but have a different developmental pathway than cortical macrophages. Cortical macrophages greatly increase in number and acquire the appearance of tingible body macrophages by phagocytizing many necrotic thymocytes. they seem to develop from monocytes that normally enter the thymus at the CMR. During the acute involution macrophages probably also enter the cortex via the connective tissue capsule. It is suggested that thymus medullary IDC probably belong to the mononuclear phagocytes, as do the cortical macrophages. In the specific medullary environment IDC gradually develop their characteristic ultrastructure for an apparently other than phagocytic function. The similarities between IDC and epidermal Langerhans cells are discussed.

Animals↗
PubMed1982

Relation between langerhans cells, veiled cells, and interdigitating cells.

Tissue macrophages are bone marrow derived mononuclear cells which play an important role in the immune response, especially as antigen presenting cells. They comprise a heterogeneous population of cells with phagocytic activity. On morphological functional and cytochemical criteria it is likely that the Langerhans cell (LC) in the epidermis, the veiled cell (VC) in the afferent lymph and the interdigitating cell (IDC) in the thymus dependent area of peripheral lymphoid organs and the thymus medulla belong to a subpopulation of the macrophages. They are low phagocytic, Ia positive and are highly immunogenic. VC and IDC may contain Birbeck granules, the characteristic organelles of the LC, suggesting a relationship between these cell types. An epithelial micro-environment as present in the skin epidermis and the thymus is necessary for the induction of these granules, which appear to have no immunological significance. In a scheme the development from monocyte into LC or into VC and subsequently IDC is postulated. Probably VC transport antigen from the skin area via the afferent lymphatics into the draining lymph node. In the thymus dependent area of this organ they present this antigen to T cells and mature into IDC. IDC in the medullary area of the thymus may also be involved in antigen presentation to immunocompetent T cells. However, in this central lymphoid organ a function in instruction of helper T cells may not be excluded.

Animals↗
PubMed1982

Culture of human bone marrow in the teflon culture bag: identification of the human monoblast.

The proliferation of human bone marrow cells was studied in a liquid culture system without colony-stimulating factor. Bone marrow cells suspended in medium containing horse serum and fetal calf serum were incubated in the Teflon culture bag. During the first week there was an increase in the number of blast cells and early cells of the granulocytic series, both of which showed a high 3H-thymidine labeling index. The total number of mononuclear phagocytes increased during the first two weeks of culture. A number of characteristics of the cultured cells (alpha-naphthyl butyrate esterase, N-acetyl-DL-alanyl alpha-naphthyl esterase, Fc receptors, and phagocytosis) were determined. It was not feasible to recognize promonocytes and monoblasts with light microscopy, but with electron microscopy and the use of peroxidatic activity as marker, monoblasts and promonocytes were identified. The monoblast is a round cell with a few surface microextensions, a large nucleus, and few cytoplasmic granules. The nuclear envelope, the rough endoplasmic reticulum, and the granules show peroxidatic activity.

Bone Marrow Cells↗
PubMed1981

Antigen-presenting cells, including Langerhans cells, veiled cells and interdigitating cells.

The accessory functions attributed to macrophages, such as antigen presentation, are probably carried out by specialized, marrow-derived cells which always have Ia antigen on their surfaces. These cells are not actively phagocytic, but are mainly engaged in engulfing large volumes on fluid. They are found in the epidermis as sessile cells, the Langerhans cells, but some re-enter the dermis and appear in afferent lymph as actively moving, veiled cells. Here they are joined by other veiled cells which have differentiated in the dermis: both populations then enter the draining lymph node. A similar process of differentiation probably occurs in other specialized tissues leading to the formation of cells that enter the afferent lymph and become veiled cells. In the lymph node, veiled cells localize in the paracortex or T-dependent area and later differentiate into another sessile cell type, the interdigitating cell. The life-style of this family of cells appears to be well-adapted for the transport of antigen into the paracortex, an area from which free antigen is largely excluded, and it seems likely that T-cell activation is triggered by the arrival of veiled cells bearing a new antigen on their surfaces.

Animals↗
PubMed1981

Ultrastructure of the rat thymus: the micro-environment of T-lymphocyte maturation.

The ultrastructure of the micro-environment of the fully functional rat thymus was studied. The thymus consists of two discrete compartments, viz., an epithelial and a mesenchymal compartment. Thymus fibroblasts/fibrocytes, mast cells and granulocytes, are restricted to the mesenchymal compartment. The thymocyte maturation process seems to occur in the epithelial compartment in a network of reticular epithelial cells. The cortex is finely meshed and filled with proliferating thymocytes and some scattered macrophages. Moreover, in the medulla vacuolated epithelial cells from part of a loosely meshed reticulum which is filled with thymocytes and interdigitating cells (IDCs). IDCs frequently contain Birbeck granules and appear to be phagocytic. Together with macrophages, they probably enter the thymus, predominantly in the cortico-medullary region, and cross the separating wall between the two compartments. Some functional aspects of the non-lymphoid cells and in particular the IDCs, which form the micro-environment of the thymus, are discussed with respect to T-cell development.

Animals↗
PubMed1980

Depletion of macrophages and disappearance of postcapillary high endothelial venules in lymph nodes deprived of afferent lymphatic vessels.

The afferent lymphatic vessels of rat popliteal lymph nodes were interrupted, and the histological alterations in the lymph nodes occurring 1 to 14 weeks after operation were studied. One week after operation the number of macrophages was considerably reduced and continued to decrease during the subsequent time periods studied. At 6 weeks most macrophages had disappeared. Simultaneously the immunological activity diminished and had completely disappeared 8 weeks after operation. Three weeks after operation the endothelial cells of the postcapillary high endothelial venules had flattened, and the number of immigrating lymphocytes was greatly reduced. Subsequently the lymph nodes became depleted of both macrophages and lymphocytes, leaving only the reticuloendothelial framework.

Animals↗
PubMed1978

Lymph node macrophages and reticulum cells in the immune response. I. The primary response to paratyphoid vaccine.

The reactivity of rat lymph node macrophages and reticulum cells has been studied in relation to the course of the immune response. Special attention was paid to the interdigitating cells (IDC) in the paracortex and the dendritic reticulum cells (DRC) in the germinal centre. Different types of macrophage predominate in the three different phases of the immune response. In the induction phase exudate macrophages predominate. They transform their morphology depending on the micro-environment in which they settle. These cells may contain Birbeck granules. Our experiments suggest, that these granules are immunologically specific organelles, associated with the induction of a primary humoral response. In the proliferation phase transitional cells between newly arrived macrophages and IDC predominate in the paracortex and the number of IDC decreases. In the memory phase IDC repopulate this thymus dependent area, indicating that the characteristic morphology of these cells results from the immune response in the T cell environment. The DRC are specifically related to the germinal centre, the morphological transformation of this peculiar reticulum cell occurs under the influence of the germinal centre reaction. The germinal centre reaction originates by tingible body macrophages (TBM).

Animals↗
PubMed1978

Augmentation of mitogen responsiveness in human lymphocytes by a humoral factor obtained from thymic epithelial cultures.

Supernatants derived from thymic epithelial cultures were studied for their effect in augmenting mitogen responsiveness in human thymocytes and lymphocytes. Incubation of these cells for 20 hr in diluted supernatants obtained from 14 to 25 day old cultures of thymic epithelium resulted in a significant increase in the response to Con A. The epithelial nature of the cells was confirmed by electron microscopy. Supernatants from fibroblast cultures or thymic epithelial cultures overgrown by fibroblasts were not effective, nor were supernatants from secondary epithelial outgrowths. The molecular weight of the active fraction appeared to be between 17,000 and 45,000 daltons. The data indicated that human thymus epithelium produced one or more humoral factors which were identical to, or shared properties with, thymic hormones.

Cell Extracts↗