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Neuroanatomical Basis
Published in Fuad Lechin, Bertha van der Dijs, Neurochemistry and Clinical Disorders: Circuitry of Some Psychiatric and Psychosomatic Syndromes, 2020
Fuad Lechin, Bertha van der Dijs, Jose Amat, Marcel Lechin
BSRF cells have extensive ascending and descending projections. Golgi studies in rodents indicate that a considerable number of reticular neurons give off an axon which dichotomizes and has a long ascending branch and a long descending branch. The number of reticular cells with ascending projections diminishes towards the caudal area. The relative sparsity of reticular projetions ascending from medulla oblongata to midbrain or beyond in rats is in keeping with data on mammals (see Figures 11, 14, and 15)
Lymphocyte trafficking from inductive sites to effector sites
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Valerie Verhasselt, William Agace, Oliver Pabst, Andrew Stagg
On entry into the lymph node, lymphocytes are guided by chemokines into distinct anatomical localizations, most prominently the paracortical T-cell zone and the B-cell follicles (Figure 16.6). The backbone of the lymph node is made up of nonhematopoietic stromal cells, fibers, and extracellular matrix. Stromal cells constitute a heterogeneous array of nonhematopoietic cells that can be subdivided into endothelial cells (including cells forming the HEVs), follicular dendritic cells (FDCs) in the B-cell follicles, and fibroblastic reticular cells in the T-cell regions. Fibroblastic reticular cells are distributed throughout the T-cell zone, forming a three-dimensional network of cells that surround highly organized extracellular channels termed conduits. The conduits are composed of a fibrous collagen core that is surrounded by a basement membrane, through which molecules of low molecular weight, including antigens, cytokines, and chemokines, can disperse. Of particular relevance to lymphocyte migration is the fact that conduits can channel chemokines to HEVs. Thus, HEVs can display chemokines produced at distant sites that are channeled to HEVs through the conduit system.
Cells and Organs of the Immune System
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
The white pulp contains lymphoid cells aggregating in structures called lymphoid follicles or nodules (see below), and in periarteriolar lymphoid sheaths (PALS). The pulp surrounding the periarteriolar sheaths is called the marginal zone, an area where arterioles end and dump their contents into the loose matrix of splenic tissue. The PALS contains mainly T cells, while the surrounding follicles and marginal zone are composed mostly of B cells. Reticular cells and their extracellular matrix, vascular endothelial cells, and specialized phagocytic cells (interdigitating cells and several distinct types of macrophages) also play important roles in splenic immune activity.
Adenosine A2a receptor promotes lymphangiogenesis and lymph node metastasis
Published in OncoImmunology, 2019
Bertrand Allard, Isabelle Cousineau, David Allard, Laurence Buisseret, Sandra Pommey, Pavel Chrobak, John Stagg
Using flow cytometry, we compared the immune and vascular composition of both sentinel and contralateral lymph nodes of WT and A2a-deficient mice bearing B16F10-CD73 foot pad tumors. Two weeks after tumor inoculation, we observed that the cellular composition of WT sentinel lymph nodes was drastically modified compared to their contralateral counterparts. We observed an enrichment in T and B cells (Figure S6A and S6B) and an accumulation of vascular cells including LEC (Figure 4(c,d)), reflecting increased lymphangiogenesis in tumor-draining versus non-draining lymph nodes in WT mice. In sharp contrast, tumor-draining lymph nodes from A2a-deficient mice displayed limited vascular and immune remodeling when compared to WT sentinel lymph nodes. The accumulation of LEC, BEC and B cells in sentinel lymph nodes (relative to contralateral lymph nodes) was significantly lower (i.e. reduced by 50%) in A2a-deficient mice compared to WT mice (Figure 4(c,d), S6A and S6B). In contrast, the accumulation of myeloid cells and follicular reticular cells (FRC) was not different (Figure 4(e), S6C and S6D). Together, these observations indicate that A2a-deficiency is associated with a general decreased responsiveness to tumor-derived signals that normally promote sentinel lymph node lymphangiogenesis and immune remodeling.
Engineering polymeric nanocapsules for an efficient drainage and biodistribution in the lymphatic system
Published in Journal of Drug Targeting, 2019
Ana Sara Cordeiro, José Crecente-Campo, Belén L. Bouzo, Santiago F. González, María de la Fuente, María José Alonso
Upon arrival at the lymph nodes, it is essential that the antigen nanocarriers mediate an interaction with the main APCs, macrophages and dendritic cells. The subcapsular sinus is the region of the lymph node where pathogens, antigens and particulate materials first arrive, encountering mostly macrophages. These cells sample the flowing lymph to internalise foreign materials and make them available to B cells in the follicular region of the lymph node. Smaller sized antigens and particles may also enter the structures known as fibroblastic reticular cell conduits (FRC), which extend from the subcapsular sinus into the follicles and are surrounded by B cells and follicular dendritic cells (FDCs) [78,79]. The antigens can then be directly internalised by the B cells, or transported by FDCs for T cell presentation. Both pathways are schematically represented in Figure 5. On the other hand, the medullary region is also rich in macrophages and dendritic cells, increasing the chances of antigens and particulate carriers to be sampled from the lymph as it flows through the subcapsular sinus to this region [48,80].
One cell one niche: hematopoietic microenvironments constructed by bone marrow stromal cells with fibroblastic and histiocytic features
Published in Ultrastructural Pathology, 2019
Yong-Xin Ru, Shu-Xu Dong, Shi-Xuan Zhao, Yuan Li, Hao-Yue Liang, M.M. Fengkui Zhang, Xiaofan Zhu, Yizhou Zheng
Interestingly, BMSCs were characterized by not only fibroblastic features of aplenty elongated rER and long processes but also histiocytic features of large electron-dense lysosomal granules, giant mitochondria and phagosomes in BMG-hs and mice bone marrows in situ, as well as in isolated state from BMAs of patients. On scanning electron microscopy and TEM, Weiss and other researchers demonstrated the fibroblastic “reticular cells” which processes enveloped and isolated maturing hematopoietic cells in rat and mice bone marrows previously.26,29 The stromal “reticular cells” shared typical fibroblastic features of rough ER, microfilaments and microtubules, without phagocytosis and lysosomes described as those in the present study. On other hand, the fibroblastic “reticular cells” were also identified in HSCs niche and classified in group of BMSCs.28