Cells and Tissues of the Immune System Flashcards
What are secondary lymphoid tissues?
Secondary lymphoid tissues are where white blood cells migrate to interact and generate an effective, adaptive immune response
Lymph nodes, tonsils, spleen, lymphoid tissues (MALT, GALT, BALT)
What does the lymphatic system consist of?
- Lymph veseels
- Tissues and organs w/ high density of lymphocytes
- Lymph nodules
- Lymph nodes
- Thymus gland
- Mucosa-associated lymphatic tissue
- Bone marrow
What kind of cell is this?
Neutrophil; Multi-lobed nucleus
What kind of cell is this?
Eosinophil;
Bi-lobed cells with bright pink cytoplasmic granules
What kind of cell is this?
Basophil;
Deep blue, dark cytoplasmic granules
What kind of cell is this?
Mast Cell;
Deep blue dark cytoplasmic granules
What kind of cell is this?
Where are you likely to find it?
Monocyte; kidney shaped nucleus, lilac cytoplasm
Found in peripheral blood
What does the stroma of lymphatic nodules, nodes, and spleen consist of?
Reticular fibers (small diameter collagen fibers w/ high sugar content)
Produced by reticular cells
What does the stroma of the thymus consist of?
Branching interconnecting epithelioreticular cells
Which cell types are surveillance cells?
- Macrophages
- Langerhans cells (epidermis)
- M cells (intestinal epithelium overlying lymph nodules)
- Dendritic cells (lymphatic tissues)
What kind of cell is this?
Where is it found?
Macrophage;
Reside in tissues
What kind of cell is this?
Plasma Cell;
Fried egg appearance, “clock face” chromatin pattern in nucleus
What is unique about high endothelial venules in lymphatic tissues and organs?
The endothelium is cuboidal instead of simple squamous.
purpose of high endothelial venules: To concentrate lymph to increase chance that antigen will encounter antigen-presenting cell
What kind of cell is this?
Natural Killer Cell;
Granules produce cytotoxins to kill other molecules
Where are T lymphocytes mainly found?
Diffuse lymphatic tissue of lymphatic organs or loose connective tissue of GI, respiratory, urinary tracts
What are the components of lymph nodules?
Dense aggregations of mostly B cells in meshwork stroma of reticular fibers
found in GALT, lymph nodes, spleen
What is the main component of lymph nodules?
B cells
Why is the germinal center of dividing B cells in a lymph nodule lighter staining?
Larger cells w/ more cytoplasm and more euchromatin in the nucleus. shows that an immune response is taking place
Where do blood vessels enter and leave a lymph node?
Hilum
Where are the efferent lymphatics located in a lymph node?
Hilum
What are lymph nodes composed of?
- Connective tissue capsule
- Outer cortex w/ nodules (B cell zones)
- Inner cortex w/ diffuse T cell lymphatics
- Innermost medulla w/ T cell medullary cords
Describe the pathway for lymph flow through a node
- Cortical afferent lymphatics
- Subcapsular sinus
- Trabecular sinuses
- Medullary sinuses
- Efferent lymphatics exiting at hilum
What does the deep cortex of lymph nodes contain?
High endothelial venules (simple cuboidal epithelium)
What are the functions of the high endothelial venules in the deep cortex?
- Primary site of entry of lymphocytes from other parts of body
- High density of water channels that allow passage of fluid in lymph into bloodstream to concentrate lymph in sinuses
What is this structure?
Lymph node
What are the functions of the spleen?
- Reservoir for up to 1/3 of body’s platelets
- Destroys defective or aged RBCs (macrophages in red pulp)
- Recycling of iron
- Immune reactions to blood born antigens by T and B cells in white pulp
- Reservoir for erythrocytes (minimal in humans)
main function: Filters blood in a network of vascular spaces for blood antigen surveillance by macrophages
What comprises the spleen?
- White pulp
- Red pulp
- Dense connective tissue capsule surrounding white and red pulp
- Connective tissue trabeculae extending into pulp interior
What comprises the white pulp?
Periarterial lymphatic sheaths (PALS) surrounding central arteries
PALS = Dense aggregates of T lymphocytes w/ B lymphocyte nodules scattered along the way
What does the red pulp consist of?
Splenic sinuses and splenic cords
What do splenic cords consist of?
A meshwork of reticular cells and fibers among dense aggregations of red blood cells and macrophages
What are splenic sinuses?
Venous channels w/ very long rod-shaped endothelial cells w/ gaps between them
What allows blood cells to easily pass through walls of sinuses?
Splenic sinuses (which contain gaps between endothelial cells) are parallel to axis of sinus while incomplete loops of basal lamina are perpendicular to sinuses
Blood flow from cords to sinuses can be described as what kind of system?
Open system
(Red pulp arterioles open directly into splenic cords)
Central artereries send branches to splenic cords surrounding PALS
Sheathed capillaries of the central arteries open directly into splenic cords
What is a sheathed capillary?
Capillaries of central arteries surrounded by macrophages
Where do macrophages destroy erythrocytes and detect antigens?
Splenic cords
(where blood percolates through reticular meshwork)
What are the functions of the red pulp?
- Eliminates old/damaged RBCs
- Recycles iron
What is the function of the white pulp?
Immune function as in lymph nodes and diffuse lymphatic tissue
Where might a macrophage first encounter antigen in a lymph node?
A. cortical nodules
B. trabecular sinus
C. efferent lymphatics
D. subcapsular sinus
E. cortical reticular fibers
Subcapsular sinus
(Lymph first enters node, macrophages send cell processes through sinus endothelium)
Which of the following cells secrete cytokines that control T-cell maturation/education?
A. Macrophages
B. Thymocytes
C. Epithelioreticular cells
D. Dendritic cells
E. Stem cells
Epithelioreticular cells
(Macrophages destroy T-cells that do not have the proper CD antigens, thymocytes are T cells)
Where in the spleen are aging red blood cells eliminated?
A. Splenic cords
B. White pulp
C. Trabeculae
D. Splenic sinuses
Splenic cords
(Splenic cords and sinuses make up red pulp, macrophages reside in splenic cords, all blood cells pass through the splenic cords and into the sinuses as the beginning of venous return, white pulp consists of periarterial lymphatic sheaths)
Which immune cells are stimulated by IL-5?
Eosinophils (through IgA)
What is the major function of basophils?
Basophils are involved in inflammation; they release histamines and other cytokines
Name some antigen presenting cells
Macrophages
Dendritic Cells
B Cells
What kind of immunity are macrophages involved in?
Innate: cytokine production
Adaptive: antigen-presenting
Which CDs do Natural Killer Cells express?
CD56, CD16
Note: CD16 is the IgG Fc receptor
What are Kupffer cells?
Tissue-resident macrophages in the liver
What are microglia?
Tissue-resident macrophages in the brain
Which cytokines do macrophages produce and secrete?
TNF, IL-1, IL-6, IL-8, IL-12 (macs are activated by IFN gamma)
Describe the structure of the thymus
Epithelioreticular cellsmake up the stroma of the thymus.Lymphoid stem cells from the bone marrow fill the spaces between the epithelioreticular cells. These will eventually become T-Cells
Shape: 2 lobes, numerous lobules that are folded, continuous arrangements of cortex and medulla parenchyma
- Trabeculae create a path for blood to enter the thymus
- Cortex (outer layer, basophillic)
- Medulla (inner, less intense staining than cortex)
- Thymic corpuscules aka Hassal’s corpuscules in the medulla
Where in the body would you find Hassal’s Corpuscules?
What are they?
What are they made out of?
Inside the medulla of the thymus
They are large pink-staining, keratinized concentric curls that secrete interleukins
They are made from Type VI epithelioreticular cells
Describe T-Cell education
Epithelioreticular cells secrete interleukins, colony stimulating factors, interferon
This induces the expression or deletion of various CD antigens on cell surfaces
Early in the cortex: T-cells are presented with self and foreign antigens by Type II and Type V epithelioreticular cells
- If the T-Cell recognizes the antigen, it lives and enters the medulla
- If the T-Cell does not recognize the antigen, it undergoes apoptosis
Later in the medulla: Another selection process occurs before the T-Cell leaves
Where would you find Type I epithelioreticular cells?
Type I epithelioreticular cells line the connective tissue components of the thymus
They compose the blood-thymus barrier that protects developing T-cells from exposure to blood antigens. They control T cell maturation/education.
Where are aging red blood cells eliminated?
Splenic cords
Describe lymph drainage into neck veins
Symmetrical if above umbilicus
Only goes to left side of neck if below umbilicus or in thoracic wall
How does deep lymph in abdominal and lower posterior body wall get into the deep path?
Via lumbar lymphatic vessels that drain into aortic lymphatics
How does deep lymph in the thoracic body wall get into the deep path?
Via intercostal lymphatics vessels into the thoracic duct
Where does lymph entering the bronchomediastinal trunk come from?
Heart, lungs, upper esophagus, and anterior intercostal lymphatics via deep parasternal nodes
What is lymphangitis?
Inflammation of lymph vessels
What is elephantiasis?
How is it produced?
Chronic blockage of lymph vessels that produces marked swelling of infected region
Produced by ova of a small tropical parasitic warm (lymphatic filiariasis - caused by wuchereria, brugia)
What is lymphadenitis?
Inflammation of lymph nodes
What is the primary route of lymphatic drainage of the breast?
Why is this the primary route?
Primary: To the axillary lymph nodes because the breast is a subcutaneous organ
What are secondary routes of lymphatic draining of the breast?
Why is this notable?
Medial lymph drains deep to parasternal nodes in mediastinum and directly through deep body wall with connections to liver through diaphragm
This is an exception the stratification rule
(also to opposite breast)
What is the main exception to stratification?
Lymph drainage of the breast
What does the ascending pathway receive lymph from?
- Superficial body wall below umbilicus
- Deep body wall of abdomen, thorax, lower extremities
- Abdominal organs via mesenteries
Describe lymph flow from the upper liver
Pierces diaphragm -> intercostal lymphatics or deep parasternal nodes -> bronchomediastinal trunk
