1887

Chapter 4 : Organs and Tissues of the Immune System

MyBook is a cheap paperback edition of the original book and will be sold at uniform, low price.

Preview this chapter:
Zoom in
Zoomout

Organs and Tissues of the Immune System, Page 1 of 2

| /docserver/preview/fulltext/10.1128/9781555816148/9781555812461_Chap04-1.gif /docserver/preview/fulltext/10.1128/9781555816148/9781555812461_Chap04-2.gif

Abstract:

This chapter talks about organs essential for the generation of immune cells, organs and tissues essential for the function of immune cells, anatomic factors that influence the immune response, trafficking and circulation of immune cells through the body, immune function at the mucosal surfaces of the body and immune function in the skin. The various cell types comprising the immune system and their functions are distributed throughout the body but are concentrated within the organs and tissues that support the development and function of the immune cells. In cattle and sheep, B-cell maturation takes place in a specialized lymphoid organ called the . The generative organs are those that produce hematopoietic cells involved in host defense. In most mammals, these organs are the bone marrow and the thymus. The bone marrow is the most important source of hematopoiesis-derived cells in adult mammals. Lymphocytes reside in lymphoid tissues for various periods of time, the duration depending largely on whether the lymphocytes are activated by antigen. Germinal centers are important sites for B-lymphocyte differentiation. The initial activation of B lymphocytes most likely occurs outside the germinal center. The spleen receives blood through a single splenic artery. Lymph nodes are a site for the convergence of two distinct, nonoverlapping circulatory systems. The epithelial linings of various mucosae present different types of barriers to microbial invasion. The mouth, pharynx, esophagus, urethra, and vagina all contain stratified squamous epithelium.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4

Key Concept Ranking

White Blood Cells
0.5196981
Tumor Necrosis Factor alpha
0.4483852
Major Histocompatibility Complex
0.43111706
Immune Systems
0.42829722
0.5196981
Highlighted Text: Show | Hide
Loading full text...

Full text loading...

Figures

Image of Figure 4.1
Figure 4.1

Organs and tissues of immunologic importance. In humans, the bone marrow and the thymus are the generative lymphoid organs where the various white blood cells develop and mature. The spleen, lymph nodes, tonsils, Peyer's patches, and appendix are peripheral lymphoid organs, which are highly specialized tissues designed to optimize the efficiency with which lymphocytes encounter their cognate antigens. The lymph nodes are interconnected by an elaborate network of vessels called lymphatics through which lymphocytes and antigens circulate.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.2
Figure 4.2

Cross-section of bone marrow highlighting the organization of the hematopoietic and vascular compartments of the tissue. Blood cells arise in the hematopoietic compartments, which are segregated into regions producing different types of blood cells (e.g., the erythroblastic islets where red blood cells are generated). Hematopoiesis is supported by soluble and contact-dependent factors produced by adventitial cells. When mature blood cells are generated, they migrate through the endothelium and enter the vascular sinuses, through which they leave the bone marrow. Some cell types (e.g., T lymphocytes and macrophages) enter the sinus while they are still immature. These cell types complete their maturation outside the bone marrow. Megakaryocytes can frequently be seen bordering the sinuses. From this location they continuously produce platelets, which are immediately deposited in the vascular sinus for immediate export from the marrow.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.3
Figure 4.3

Located just above the heart, the thymus is a bilobed, encapsulated organ that contains a stromal matrix (consisting of epithelial cells and dendritic cells) that supports the development of T lymphocytes. In cross-section, the thymus can be seen to consist of two layers: the outer cortex and the inner medulla. Outside the cortex is a capsule that forms the boundary of the organ. Projections of connective tissue called divide the stroma into compartments. The cortex is populated with T-lymphocyte precursors called and with nurse cells and cortical epithelial cells. The latter two cell types create an environment that promotes thymocyte development. The medulla contains thymocytes (albeit fewer than in the cortex), macrophages, and medullary epithelial cells. Numerous IDCs reside at the interface of the cortex and medulla. These cells are essential for thymocyte development. Low-power photomicrograph of a cross-section of thymus, showing the thymic cortex and medulla. High-power photomicrograph of an involuting adult thymic medulla, showing several Hassall corpuscles.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.4
Figure 4.4

Lymphocytes recirculate through the body via well-defined pathways that depend on both the maturational and activation states of the lymphocyte. Red lines indicate the route of lymphocytes through the bloodstream, solid blue lines indicate the route through the lymph, and dashed blue lines indicate the course of lymphocytes through the interstitial space. Naive lymphocytes. The recirculation of resting, naive lymphocytes occurs primarily through lymph nodes and spleen. The figure shows a representative pathway whereby lymphocytes leave the blood and enter the pelvic lymph node. After a time in the lymph node, the lymphocyte leaves the node through an efferent lymphatic and travels through the lymphatic circulation until it rejoins the blood at the thoracic duct. Memory lymphocytes. Activated or memory lymphocytes tend to prefer recirculating through barrier organs such as the gut mucosa. In the gut mucosa, the lymphocyte enters lymphoid follicles or samples antigen being transported from the intestinal lumen. The recirculation of lymphocytes also demonstrates tissue specificity. In the example shown, lymphocytes activated at the site of infection in the skin leave the site of infection to recirculate. After recirculation, the effector and memory lymphocytes preferentially home back to the skin.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.5
Figure 4.5

A cross-section of a postcapillary venule in a lymph node, showing HEV and naive lymphocytes extravasating to leave the blood and enter the node. Scanning electron micrograph of a blood vessel wall within a lymph node. Several lymphocytes are attached to the inner endothelial lining of the blood vessel in apparent transit across the vessel wall.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.6
Figure 4.6

The specificity of naive lymphocytes for the HEV of postcapillary venules is determined by the expression of specific adhesion molecules by both the lymphocyte and the HEV. Other patterns of adhesion molecules are present on the surface of memory and effector lymphocytes and on the endothelium of other tissues.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.7
Figure 4.7

Lymphoid follicles are the simplest example of organized lymphoid tissue containing lymphocytes and APCs. Photomicrograph of primary follicle. Primary follicles contain primarily a pool of recirculating B lymphocytes. FDCs are another important cell type within follicles and act as “antigen traps” by binding antigen-antibody complexes via antibody Fc receptors. Photomicrograph of germinal center. Following exposure to an antigen, a primary follicle is transformed into a secondary follicle, where intense lymphocyte proliferation takes place (gc, germinal center; m, mantle zone). Germinal centers have three areas that can sometimes be discerned by conventional light microscopy. A dark zone contains numerous densely packed large lymphocytes (centroblasts) that are actively proliferating. The germinal center also contains a basal light zone, where the lymphocytes (centrocytes) are smaller and not proliferating. An extensive network of cytoplasmic extensions from FDCs surrounds the lymphocytes of the light zone. The centrocytes in the basal light zone are being selected for high affinity for antigen. Centrocytes that survive through this period of selection proceed to the apical light zone, where they differentiate into either memory cells or plasma cells. These areas are not always seen and depend on the age and state of activation of the germinal center.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.8
Figure 4.8

Affinity maturation. During B-lymphocyte proliferation in the germinal center, centrocytes (expanded B cells that have undergone the process of somatic hypermutation) must compete with each other for a limited amount of antigen that is being displayed by FDCs in the light zone of the germinal center. Only centrocytes with the highest affinity for antigen successfully interact with FDCs and receive survival signals from them. B cells with reduced affinity for antigen die by apoptosis, and the apoptotic bodies are engulfed by tingible-body macrophages present in the germinal center. The result is that only centrocytes bearing the highest-affinity receptors for antigen survive.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.9
Figure 4.9

The spleen is divided into red pulp and white pulp. The red pulp primarily contains erythrocytes, including numerous dying red blood cells as well as macrophages that contain engulfed red blood cells. The white pulp can be subdivided into the PALS (a T-lymphocyte- rich area that also contains IDCs), follicles (containing B lymphocytes and FDCs), and the marginal zone. Blood entering through the splenic artery percolates through the vascular endothelium at the splenic sinus to enter the marginal zone. B cells stimulated by antigens migrate to the PALS to collaborate with T cells that reside in the PALS. If B-cell–T-cell collaboration is successful, activated B and T cells migrate into a primary follicle, which then becomes a secondary follicle. An external view of the entire spleen. Hematoxylin-and-eosin-stained section of spleen. Three follicles are readily evident at this low magnification as being rich in lymphocytes and essentially devoid of erythrocytes. Numerous PALSs are also apparent and assume a rather serpentine shape that follows the course of various arterioles. The red pulp comprises the areas that are rich in erythrocytes and that stain predominantly with eosin, a red dye.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.10
Figure 4.10

The lymphatics are a circulatory system that gathers lymph fluid (a plasma filtrate) from various tissues and returns that fluid to the bloodstream. Lymph enters the lymphatics at small, open-ended lymphatic capillaries and proceeds through progressively larger vessels. As the lymph makes its way through this circulatory system, it encounters various collections of organized lymphoid tissue. The most rudimentary of these are simple lymphoid follicles. At other places (usually at the junction of several lymphatics), the lymph will enter a lymph node. Eventually, the lymph reaches the largest lymphatic vessel (the thoracic duct), where it combines with the blood.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.11
Figure 4.11

Structure of a lymph node. The diagram is divided into three sectors, each displaying a different level of detail. The left sector demonstrates the arrangement of the three layers of each node. The outermost layer, the cortex (shown in blue in the left sector), contains mostly B cells and FDCs in primary lymphoid follicles. The middle layer, the paracortex (shown in yellow in the left sector), is enriched for T cells and IDCs. The innermost layer, the medulla (shown in red in the left sector), is enriched for antibody-secreting plasma cells. The middle sector of the figure shows the cellular detail and architecture of the node. Lymph that contains foreign antigens enters the nodes via the afferent lymphatics and is deposited beneath the capsule. The lymph percolates through the node to interact with T cells in the paracortex and with B cells in the cortex. Lymph exits the node through the single efferent lymphatic. The right sector displays the blood vasculature of the node. Each node is fed by a single lymphatic artery, which branches out to a number of arterioles. Each arteriole ends in a postcapillary venule that then empties into a lymphatic vein. Lymphocytes extravasate at the postcapillary venules to enter a lymph node. Photomicrograph of lymph node cortex, showing the cortical sinus immediately underneath the lymph node capsule. Cortical sinusoids originate from the cortical sinus and penetrate the lymph node parenchyma. Low-power photomicrograph of a naive lymph node, immunostained for IgM. IgM-positive cells are colored brown. IgM-negative cells are counterstained blue. The photomicrograph shows the segregation of T- and B-cell zones, as B lymphocytes (brown cells) are located in primary follicles toward the periphery of the lymph node. Some IgM staining is also seen in the medulla, a site where plasma cells can often be found.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.12
Figure 4.12

Antigen sampling in the skin is carried out by APCs known as Langerhans cells. Langerhans cells reside in the epidermal layer, where they serve in antigen capture. After antigen uptake, the Langerhans cells leave the skin, migrate to the draining lymph node, home to the node's paracortex, and display antigen to T cells. The skin also contains many different types of lymphocytes, some of which reside in the epidermis and others in the dermis.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.13
Figure 4.13

Antigen sampling across the intestinal barrier occurs at so-called inductive sites by specialized antigen-transporting cells known as M cells. M cells have a unique morphology in that their basolateral membrane contains a large pocket, which is occupied by lymphocytes and macrophages. The M cell continuously transcytoses antigen from the intestinal lumen to the immune cells residing in the basolateral pocket. Lymphocytes or macrophages that encounter antigen in this manner leave the M cell and travel to the underlying lymphoid follicles.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 4.14
Figure 4.14

A Peyer's patch is visible macroscopically as a small bulge in the side of the small intestine. Photo by John Warner. Antigens transported across the intestinal epithelium by M cells will be delivered to large aggregates of lymphoid follicles known as Peyer's patches. Each Peyer's patch contains approximately 30 to 40 lymphoid follicles.

Citation: Bogen S. 2004. Organs and Tissues of the Immune System, p 67-84. In Pier G, Lyczak J, Wetzler L (ed), Immunology, Infection, and Immunity. ASM Press, Washington, DC. doi: 10.1128/9781555816148.ch4
Permissions and Reprints Request Permissions
Download as Powerpoint

References

/content/book/10.1128/9781555816148.chap4
1. Askin, D. F.,, and S. Young. 2001. The thymus gland. Neonatal Netw. 20:713.
2. Fabbri, M.,, E. Bianchi,, L. Fumagalli,, and R. Pardi. 1999. Regulation of lymphocyte traffic by adhesion molecules. Inflamm. Res. 48:239246.
3. Fu, Y.-X.,, and D. D. Chaplin. 1999. Development and maturation of secondary lymphoid tissues. Annu. Rev. Immunol. 17: 399433.
4. Guy-Grand, D.,, and P. Vassalli. 2002. Gut intraepithelial lymphocyte development. Curr. Opin. Immunol. 14:255259.
5. Kucharzik, T.,, N. Lugering,, K. Rautenberg,, A. Lugering,, M. A. Schmidt,, R. Stoll,, and W. Domschke. 2000. Role of M cells in intestinal barrier function. Ann. N. Y. Acad. Sci. 915: 171183.
6. Kupper, T. S. 2000. T cells, immunosurveillance, and cutaneous immunity. J. Dermatol. Sci. 24(Suppl. 1):S41S54.
7. Loy, A. L.,, and C. C. Goodnow. 2002. Novel approaches for identifying genes regulating lymphocyte development and function. Curr. Opin. Immunol. 14:260265.
8. McHeyzer-Williams, L. J.,, D. J. Driver,, and M. G. McHeyzer- Williams. 2001. Germinal center reaction. Curr. Opin. Hematol. 8:5259.
9. Moser, B.,, and P. Loetscher. 2001. Lymphocyte traffic control by chemokines. Nat. Immunol. 2:123128.

This is a required field
Please enter a valid email address
Please check the format of the address you have entered.
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error