Cells and tissues of the immune system (original) (raw)
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Human Pathology, 1978
Tiffs article presents a view of lymphoid tissue architecture as defined by the traffic of defined lymphoid cell classes. The compartmentalization of lymphocytes is discussed in reference to specific cell-cell interactions that occur in antigen-driven immune responses. Finally, tbe distribution of normal and neoplastic lymphocytes in lmmans is defined and compared with animal model systems. Immune responses in tim vertebrates result from the efficient interaction of antigen, lymphocytes, and lymphoid accessory cells. ~ In general, accessory cells (sttch as macrophages and dendritic reticular cells) appear to be involved with uptake, processing, and presentation of antigen to lymplmcytes, z Accessory cells do not discriminate between specific antigens, whereas each lymphocyte is predetermined to interact with and respond to only one (or a few) antigenic determinants? Lymphocytes are therefore a heterogeneous population witla regard to antigen reactivity, and large numbers of lympbocytes must exist to ensure effective imlnune responses to any antigen. Ahhough lymphocytes are found as free floating cells in *Study supported by grants fronl the USPHS (AI-09072) and tile American Cancer Society (IM56, IM 114, and 878 fi'onl tile Califi)rnia DMsion of tile ACS). Dr. Butcher is the recipient of Pathology Training Grant GM-02236 from the NationalInstitutes of Health.
The conduit system of the lymph node
International Immunology, 2008
The lymphoid compartment of lymph nodes is impermeable to many molecules that are delivered via afferent lymphatic vessels. In the lymphoid compartment, fibroblast reticular cells form an interconnected network-the conduit system. This network has a structural function supporting tightly packed lymphocytes and antigen-presenting cells; however, it also has an important function as a molecular sieve, since it contains tubules that are the only entry point for fluid and allow only small molecules and particles (including antigens) to flow along the network. This size exclusion may prevent pathogens entering the blood from lymph. Dendritic cells can sample antigens from the conduit system and present them to nearby lymphocytes; this may be particularly important in initiating immune responses. The importance of larger antigen transport via macrophages or other cells is unclear. Lymphocytes and antigen-presenting dendritic cells actively move and interact along the conduit system, perhaps in response to chemokines or cytokines transported by the conduit system; these molecules may also be transported to high endothelial venules and regulate the attraction of blood leukocytes to the lymph nodes. The conduit system is also important for fluid distribution between afferent lymphatics and blood, but the mechanisms are not yet established.
Acta Histochemica, 2007
The function of lymph nodes is greatly influenced by their unique microanatomy, in which distinct subpopulations of cells are compartmentalized by a meshwork of reticular cells and fibres, specialized blood and lymphatic vessels and nerves. Using antibodies against extracellular matrix (ECM) proteins (fibronectin, collagen IV and laminin), proteoglycan (perlecan), and a fibroblastic marker (ERTR-7), the distribution and molecular organization of the system of reticular fibres was investigated by three-dimensional (3D) reconstruction methods. Fibronectin, collagen IV and laminin are restricted to reticular fibres and have a similar distribution pattern, whereas perlecan is limited to the vascular system of the lymph node. Various compartments of the lymph node, such as the B-cell follicle, paracortex (including the high endothelial venules and paracortical cord), and medulla have been reconstructed to visualize their vasculature with respect to B and T cells. Since the morphology of lymph nodes may change significantly in pathological conditions, different compartments of reactive lymph node (after low-dose Listeria monocytogenes infection), especially germinal centres, were also investigated. The data presented here should facilitate our understanding of the 3D organization of non-immune cell components of lymph nodes, which is crucial for cell adhesion, migration, activation, and differentiation in normal and pathological conditions.
Fine structure of lymph pathways in nodes from the superficial inguinal lymph centre in the pig
Journal of anatomy, 1989
In the pig lymph node most lymph passes from afferent lymphatics to trabecular sinuses in centrally located dense nodular tissue. The lining of these sinuses is continuous adjacent to the trabecula but it is interrupted by numerous gaps adjacent to the parenchyma. Where the trabeculae end, their associated sinuses are continuous with the many interstitial spaces, up to 10 microns across, in the diffuse tissue. Lymph percolates through these spaces and is directly exposed to large numbers of macrophages with elaborate cytoplasmic veils and to reticular fibres which could be involved in antigen retention. Parts of the diffuse tissue are arranged into sinuses and cords in a manner similar to the medullary tissue in other species and a subcapsular sinus is also present over the diffuse tissue. There are gaps in the lining of these sinuses through which they communicate with the interstices of the parenchyma. Lymph flows from the sinuses in the diffuse tissue into efferent lymph vessels;...