John Brevé

Migration of Alveolar Macrophages from Alveolar Space to Paracortical T Cell Area of the Draining Lymph Node

In this report we studied the translocation of fluorescent particulate antigens to the draining lymph node, and the migration of fluorescent labeled alveolar macrophages (AM) and peritoneal macrophages (PM) in mice. The results show that intratracheally (IT) instilled particulate antigens translocate to the paracortical T cell area of the draining lymph node. When labeled AM were injected IT, they were found to migrate from the alveolar space into the paracortical T cell area of the draining lymph node. An identical localisation was found after IT injection of labeled PM. When either labeled AM, or PM were injected into the peritoneal cavity, a different migration pattern was observed. Via this route the labeled macrophages migrated to the subcapsular sinus and medulla of the draining lymph nodes. It is shown that the migrated cells are not dendritic cells (DC) present in the cell preparations. A possible role for the micro-environment of the injection site, and the significance of the specific migration pattern of AM is discussed.

The functional activity of high endothelial venules : a role for the subcapsular sinus macrophages in the lymph node

Adherence of lymphocytes to high endothelial venules (HEV3) is the first step in normal lymphocyte emigration and recirculation. At sites of chronic inflammation, venules often become high-walled and may also be a site for leukocytes to leave the bloodstream. The immunologic and inflammatory mediators, responsible for these effects on endothelial cells, may be important for the maintenance and function of HEV in physiological conditions. It is reported here that the morphological and functional aspects of HEV can be studied by organ cultures of lymph nodes (LN). At 24 h of culture, the appearance of the node was still quite normal, whereas the HEV became flat-walled, with a 45-50% reduction in the capacity to bind lymphocytes. This decrease in function of HEV could be reduced when LN were cultured in the presence of lipopolysaccharides (LPS). The effect of LPS on the function of HEV was presumably mediated by macrophages in the subcapsular sinus, because HEV in LN, which were depleted of subcapsular sinus and medullary macrophages previous to culture, could not be stimulated by addition of LPS to the cultures.

The role of sialic acid in the localization of lymphocytes in the spleen

The role of carbohydrate structures in the interaction of lymphocytes and endothelial cells is well established. Here the influence of sialic acid in the entrance and localization of lymphocytes in the lymphoid white pulp area of the spleen was studied by injecting sialidase in vivo. A role for sialic acid molecules on stromal elements of the spleen was determined. Although the identity of the cells that bear sialidase sensitive receptors could not be established, a role for marginal zone macrophages could be ruled out by macrophage depletion studies.

In Vivo Antigen Presentation Capacity of Dendritic Cells from Oral Mucosa and Skin Draining Lymph Nodes

Epidermal Langerhans cells (LC) have been implicated as pivotal antigen processing cells in the induction and expression of contact sensitivity. Following epicutaneous exposure with a variety of sensitizing antigens, LC are induced to migrate from the epidermis, via the efferent lymphatics, to regional lymph nodes. Using fluoresceinated antigen, it has been possible to identify the cells within the population of interdigitating dendritic cells (DC) which are extremely potent antigen presenting cells [1,2]. No B-cells, T-cells or macrophages were bearing detectable levels of antigen [3].

The Influence of Dendritic Cells on T-Cell Cytokine Production

Pretreatment of mice with picryl chloride via the oral mucosa leads to a T-cell mediated tolerance after sensitization, while mice that do not receive this treatment react with a contact sensitivity (CS) response after topical skin application of picryl chloride(1). It is assumed that both in the oral epithelium and in the skin dendritic Langerhans cells are involved in the uptake of the antigen and subsequent transportation into the draining lymph nodes. Here the Langerhans cells will present antigen to T-cells in the para-cortical areas as interdigitating, dendritic cells.