Lymph nodes, dendritic cells

Cumberbatch M, Dearman RJ, Kimber I. Constitutive and inducible expression of interleukin-6 by Langerhans cells and lymph node dendritic cells. Immunology 1996 87 513-8. 

Once in the lymph node, dendritic cells may be involved in the regulation of lymphocyte traffic by secreting chemokines that can attract T lymphocytes. For example, DK-CKl is produced by dendritic cells in the T-lymphocyte-rich areas of lymph nodes and is chemotactic for naive T lymphocytes (73). IL-16 is also secreted by dendritic cells and chemotactic for T lymphocytes. Interestingly, the reverse is also true, lL-16 is secreted by T lymphocytes and chemotactic for dendritic cells suggesting a complex mechanism of crosstalk between the two cell types (74). 

The lymph node harbors a composite population of dendritic cells (DCs)—residents and emigrants—capable of selection, stimulation and elimination of effector lymphocytes. These cells trigger adaptive immunity and/or tolerance. In the human lymph node T-cell compartment, two primary subsets of DCs, compared to six in mice, have been identified monocytoid CD 1 lb CD 1 and plasmacytoid interferon (IFN)-a produc-... 

When performing cytokeratin immunostaining of SLNs, one should use a cocktail such as AE1/AE3 CAM5.2 is less desirable because of the manner in which it stains dendritic cells in the lymph node. Micrometastatic cells occur in small clusters less than 2 mm in diameter within the lymph node or subcapsular sinus, and they need to be distinguished from the dendritic appearance of the interstitial reticulum cells of the lymph node, which are also keratin positive. o Studies witfi larger numbers of patients are needed to discern if the site of lymph node micrometastasis (peripheral sinus versus parenchyma of lymph node) is clinically significant. 

In the specialized environment of secondary lymphoid tissues such as lymph nodes or spleen, dendritic cells provide the requirements for naive T-lymphocytes to become activated and to proliferate. The professional antigen-presenting cells present peptides in MHC II, express costimulatory molecules, and release cytokines into the immunological synapse, which is formed by the antigen-presenting cell and the naive T-lymphocyte. Thus, cells of innate immunity initiate and facilitate the activation of naive lymphocytes, and it is easily conceivable that their cytokines and adhesion molecules will instruct the naive T-lymphocyte during activation and differentiation to T-effector cells. 

Key Words Chemokine dendritic cell migration inflammation lymph node. 

Yoneyama H, Narumi S, Zhang Y, et al. Pivotal role of dendritic cell-derived CXCL10 in the retention of T helper cell 1 lymphocytes in secondary lymph nodes. J Exp Med 2002 195(10) 1257-1266. 

Yoneyama H, Matsuno K, Zhang Y, et al. Evidence for recruitment of plasmacytoid dendritic cell precursors to inflamed lymph nodes through high endothelial venules. Int Immunol 2004 16(7) 915-928. 

Randolph GJ. Dendritic cell migration to lymph nodes cytokines, chemokines, and lipid mediators. Semin Immunol 2001 13(5) 267-274. 

Page G, Miossec P. Paired synovium and lymph nodes from rheumatoid arthritis patients differ in dendritic cell and chemokine expression. J Pathol 2004 204(1) 28-38. 

Jang MH, Sougawa N, Tanaka T, et al. CCR7 is critically important for migration of dendritic cells in intestinal lamina propria to mesenteric lymph nodes. J Immunol 2006 176(2) 803-810. 

Reddy ST, Rehor A, Schmoekel HG (2006) In vivo targeting of dendritic cells in lymph nodes with polypropylene sulfide) nanoparticles. J Control Release 112 26-34... 

El-Ghorr, A. A. and Norval, M., A monoclonal antibody to cis-urocanic acid prevents the UV-induced changes in Langerhans cells and DTH responses in mice, although not preventing dendritic cell accumulation in lymph nodes draining the site of irradiation and contact hypersensitivity responses, J. Invest. Dermatol. 105, 264-268, 1995. 

In a biopsy of an AIDS patient s enlarged thymus (P4), the adipose involuted thymus, with persistence of many Hassall s corpuscles, was judged to be a large lymphoid follicular hyperplasia. This follicular hyperplasia was similar to that described for lymph nodes, spleen, and other lymphoid tissues at earlier stages of human immunodeficiency virus infection, before the development of acquired immune deficiency syndrome. Human immunodeficiency virus RNA and p 24 were detected in the hyperplastic germinal centers (lymphocytes and follicular dendritic infected cells) and also in many cells that may have been either lymphocytes or epithelial cells in the interfollicular areas. 

Vermaelen KY. Carro-Muino I. Lambrecht BN. Pauwels RA Specific migratory dendritic cells rapidly transport antigen from the airways to the thoracic lymph nodes. J Exp Med 2001 193 51-60. 

A lymph node consists of a cortex and an inner medulla. The cortex is composed of an outer cortex, which contains B-lymphocytes, within lymphoid follicles, and paracortical areas, which contain mainly T-lymphocytes and dendritic cells. The proliferation of B-cells occurs in central areas, called germinal centres. The medulla consists of strings of macrophages and the B-cells that secrete the antibodies (i.e. the effector cells) these are the medullary cords (Figure 17.42). Lymph carries immune cells (e.g. lymphocytes, antigen-presenting cells) and pathogens from the tissues to the lymph nodes, via the afferent lymphatics. 

The lymph node microenvironment represents a niche where CLL cells interact with different types of cells including monocyte-derived nurse-like cells (NLC), CD3+ CD4+ CD154+ T cells, mesenchymal stromal cells, dendritic cells, and endothelial cells (15). In addition to cell-cell interactions, CLL cells are also exposed to a variety of soluble factors such as antigens, cytokines, and chemokines (2). It is the combination of such signals that renders CLL cells less susceptible to chemotherapy and promotes clonal evolution and drug resistance. Thus, the role of the microenvironment needs to be carefully considered in order to develop novel and more effective therapies for CLL treatment (16). In particular, the efficacy of new drugs must be evaluated under experimental conditions that recapitulate (or at least partially mimic) the CLL microenvironment. 

Dendritic cells of skin and lymph nodes Brain microglia... 

Figure 31-1 (A) Locations of the primary and secondary tissues of the immune system. The primary lymphoid organs are the thymus, which makes T cells, and the hone marrow, which forms B cells. After moving from these organs into the blood circulation the cells reach one of the secondary lymphoid organs, which include lymph nodes, spleen, tonsils, and Peyer s patches on the small intestine. Immature dendritic cells are found in body tissues including skin and mucous membranes and respond to foreign proteins by inducing attack by T lyphocytes and antibody formation by B cells. (B) Schematic drawing of a lymph node. From Nossal.1 Courtesy of Gustav J. V. Nossal.

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