Secondary lymphoid tissue dendritic cells

Dendritic cells are found in tissues in their immature form. When they contact an antigen, the cell is activated, phagocytosis occurs, and a peptide-MHC complex is formed. Once activated, the newly mature dendritic cells travel to primary and secondary lymphoid tissues. Dendritic cells are found in afferent lymph nodes only, not efferent lymph nodes, indicating that most of the migrating dendritic cells die after their arrival in lymphoid tissues (67). 

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. 

Circulating dendritic cells Langerhans cells Interdigitating dendritic cells Interstitial dendritic cells Blood, lymph Skin, mucous membrane Secondary lymphoid tissue (with T cells), thymus Gastrointestinal tract, heart, liver, lungs, kidney... 

Fig. 7.1 Phases of tissue transplant rejection. The transplanted tissue sheds antigens. These antigens undergo uptake, processing and presentation to the T cells in the secondary lymphoid tissue by APCs, which include macrophages, B cells, Langerhans cells or dendritic cells. This phase results in the production of antibodies and antigen-specific TH and Tc cells. The antibodies and effector cells then migrate to the grafted tissue where TH cells secrete cytokines and which in combination with the antibodies and Tc cells destroy the grafted tissue (see Color Insert)...

Saeki, H., Moore, A. M., Brown, M. J., and Hwang, S. T. (1999). Secondary lymphoid-tissue chemokine (SLC) and CC chemokine receptor 7 (CCR7) participate in the emigration pathway of mature dendritic cells from the skin to regional lymph nodes. J. Immunol. 162, 2472-2475. 

Chan VWF, Kothakota S, Rohan MC, Panganiban-Lustan L, Gardner JP, Wachow-icz MS, Winter JA, Williams LT. Secondary lymphoid tissue chemokine (SLC) is chemotactic for mature dendritic cells. Blood 1999 93 3610-3616. 

In addition to the role that CC chemokines play in promoting TAM infiltration, CC chemokines may also play an important role in enhancing effective immune antitumor responses. Certain CC chemokines have the ability to recruit specific Thl lymphocytes and dendritic cells that would serve as a rationale for immunotherapy in cancer. Recently, Sharma and associates have found that secondary lymphoid tissue chemokine (SLC also referred to as Exodus 2 or 6Ckine) has the ability to suppress tumor growth by recruitment of mononuclear cells (136). Intratumoral injection of recombinant SLC in syngeneic murine lung m-... 

Kirk, C. J., Hartigan-O Connor, D., Nickoloff, B. J., Chamberlain, J. S., Giedhn, M., Aukerman, L., et al. (2001). T cell-dependent antitumor immunity mediated by secondary lymphoid tissue chemokine Augmentation of dendritic cell-based immunotherapy. 

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.

The activation of the stress systems affects all tissues of the organism, and the peripheral immune system is no exception. These effects are mediated through at least tw o pathways via the HPA axis and by virtue of the innervation of lymphatic tissues by autonomic nerve fibers, especially from the sympathetic nervous system. All lymphoid tissues, primary (bone marrow and thymus) as well as secondary (spleen, lymph nodes, and gut-associated lymphoid tissue) are innervated by sympathetic nerve fibers. As discussed above, most lymphoid cells express catecholamine receptors, including B-lymphocytes, CD4- and CD 8-positive T cells, dendritic cells, monocytes, and macrophages. 

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