Cells and Tissues of the Immune System Flashcards
What are primary lymphoid tissues?
Primary lymphoid tissues are where white blood cells originate and develop.
Bone marrow and thymus
What tissues comprise primary lymphoid tissues?
Bone marrow and thymus
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 tissues comprise secondary lymphoid tissues?
Lymph nodes, tonsils, spleen, and lymphoid
Where do all WBCs originate?
Bone marrow
What does the common stem cell give rise to?
Lymphoid stem cells and myeloid stem cells
Which cells are derived from myeloid cells?
- Neutrophils
- Eosinophils
- Basophils/mast cells
- Monocytes/macrophages
- Other antigen-presenting cells
Which cells are derived from lymphoid cells?
- B-Cells
- T-Cells
- Natural Killer Cells
Where do all myeloid-derived cells mature?
Bone marrow
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 is MALT called when it is in the gut?
Gut-associated lymphatic tissue (GALT)
What is MALT called when it is in the airway?
Bronchus-associated lymphatic tissue (BALT)
What kind of cell is this?
Mast Cell;
Deep blue dark cytoplasmic granules
What are antigens?
Substances, tissues, or infectious organisms foreign to the body
What kind of cell is this?
Where are you likely to find it?
Monocyte; kidney shaped nucleus, lilac cytoplasm
Found in peripheral blood
What are the functions of supporting cells?
Regulate immune response and play roles in presenting antigen to lymphocytes
What does the stroma of lymphatic nodules, nodes, and spleed 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
From third branchial pouches
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
Describe the path that long-lived circulating lymphocytes move in
- Leave blood venules to enter lymphatic organs and tissues for immune surveillance
- Re-enter circulation to go to other lymphatic tissues
- Pass through walls of vasculature in high endothelial venules in lymphatic tissues and organs (postcapillary)
What kind of cell is this?
Could be a B cell or a T cell (the picture in Dr. Wolniak’s ppt is the same for both)
Identification may depend on location
- B Cells mature in the Bone marrow
- T Cells mature in the Thymus gland
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
Describe the path that short-lived circulating lymphocytes move in
One-way migration out of blood vessels to populate connective tissue of GALT and mucosa of airway
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
What is the main component of lymph nodules?
B cells
Where are lymph nodules found?
GALT, lymph nodes, and spleen
What is unique about lymph nodules involved in an immune response?
Germinal center of dividing B cells that is lighter staining
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
What is the function of lymph nodes?
Filter lymph to increase the chance of antigens encounter macrophages and lymphocytes invoking an immune response
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
What are trabeculae in lymph nodes?
Connective tissue beams the capsule sends into the medulla
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)
What is the main function of the spleen?
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
What do the PALS consist of?
Dense aggregates of T lymphocytes w/ B lymphocyte nodules scattered along the way
Which artery enters the spleen?
Where does it enter the spleen?
What does the branches of this artery branch into?
Splenic artery
At hilum
Splenic artery branches branch into trabecular arteries then central arteries within the PALS
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)
Describe what creates the open system in regard to blood flow from cords to sinuses
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 arterries that are surrounded by macrophages
Where do macrophages destroy erythrocytes and detect antigens?
Splenic cords
(where blood percolates through reticular meshwork)
Describe the path all blood cells take in an open system
- Pass throuugh walls of the splenic sinuses
- Continue into trabecular veins
- Exit spleen at hilum
- Go into splenic vein (part of hepatic portal system of veins)
- Enter the rest of the hepatic portal system
Where are all lymphocytes produced?
Bone marrow
Why can lymph nodules not be considered an organ?
Lymph nodules do not have a capsule
What is the purpose of having high endothelial venules?
To concentrate lymph to increase chance that antigen will encounter antigen-presenting cell
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)
What is a germinal center of a lymphatic nodule?
A. T-cell zone
B. The core of a newly-forming nodule
C. Highly vascular region of the nodule
D. Dividing cells in an immune response
Dividing cells in an immune response
(Germinal centers have larger dividing B-cells that react to antigen in an immune response)
What type of immunity do neutrophils participate in?
Innate
What is the major function of neutrophils in the immune system?
Ingest and kill pathogens
What kind of cells are involved in hypersensitivity and allergies?
Eosinophils
What is the major function of eosinophils?
- Kill pathogens
- Defend against parasites
How do Eosinophils combat nematode larvae?
Eosinohphils attach to the surface of migratory nematode larvae by binding IgE and IgG antibiodies
This triggers antibody-dependent cell-mediated cytotoxicity (ADCC)
Which immune cells are stimulated by IL-5?
Eosinophils
What is the major function of basophils?
Basophils are involved in inflammation; they release histamines and other cytokines
Which cell types release histamine?
Basophils (in the blood)
Mast cells (in tissues)
Describe the important features of basophils and mast cells
- They have receptors for the Fc portion of IgE -> Anaphylaxis
- They have toll-like receptors (TLRs) on their surface -> innate immunity
- Both release histamine and other cytokines
What triggers basophils and mast cells to release histamine?
Cross linking of Fc receptors
Binding of TLRs
Describe the major funciton of monocytes
Monocytes circulate in peripheral blood
They migrate to tissues to differentiate to macrophages
Describe the major funcitons of macrophages
- Phagocytosis
- Production and release of 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
Where in the body are dendritic cells found?
Tissues; under skin and mucosa
Describe the major functions of dendritic cells
- Ingest pathogens
- Migrate to lymph nodes to present antigens to helper T-cells
- Main inducer of the T-Cell and primary antibody response
Which antigens do B-cells express?
CD19, CD20
Describe the major functions of B-Cells
- Present antigens to T-cells
- Part of adaptive immunity
- Differentiate to plasma cells
Describe the major functions of plasma cells
Humoral immunity (anti-body based)
- Produce and secrete antibodies
Which cells express CD19 and CD20?
B-Cells
Which antigens do T-Cells express?
CD3
Helper cells express CD4
Cytotoxic cells express CD8
What are the major functions of T-Cells?
- Recognize protein antigens bound to MHC
- Activated T-Cells kill virus-infected cells, tumor cells, foreign cells (organ rejection)
(70% of circulating lymphocytes are T-Cells)
What type of immunity do T-Cells participate in?
Cell-mediated immunity
Which cells express CD3?
T-Cells
Which antigens do Natural Killer Cells express?
CD56, CD16
Note: CD16 is the IgG Fc receptor
What are the major functions of natural killer cells?
- Mediate the killing of virus-infected cells and tumor cells
- They have a receptor for MHC1, which all human cells have
- Natural Killer cells will kill anything that doesn’t have MHC1
(Note: NK cells do not have receptors for specific antigens)
What type of immunity do natrual killer cells participate in?
Innate immunity
Which cells express CD56 and CD16?
Natural Killer Cells
Which cells are “professional antigen-presenting cells?”
Macrophages
Where in the body would you find macrophages?
Blood or tissues
What are alveolar macrophages?
Tissue-resident macrophages in the lungs
What are Kupffer cells?
Tissue-resident macrophages in the liver
What are microglia?
Tissue-resident macrophages in the brain
What are red pulp macrophages?
Tissue-resident macrophages in the spleen
What are tingible body macrophages?
Tissue-resident macrophages in the germinal centers of lymph nodules
What are antigen-presenting cells? Why are they important?
- Macrophages, dendritic cells, B-Cells
- They link innate and adaptive immunity
- They express TLRs to bind PAMPs
- They present antigens by…
- Engulfing pathogens
- Digesting proteins of pathogens
- Expressing the peptides of the pathogens in MHC II
Which cytokines do macrophages produce and secrete?
TNF, IL-1, IL-12
What is the significance of MHC II?
MHC II is expressed on the cell surface of antigen-presenting cells.
Antigen-presenting cells engulf pathogens, digest their proteins, and then express their peptides in MHC II so that they can present them to T-Cells
What kind of cells express CD3 and CD4?
Helper T-Cells
What kind of cells express CD3 and CD8?
Cytotoxic T-Cells
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 intesnse 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 stimulatinf 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 undergos apoptosis
Later in the medulla: Another selection process occurs before the T-Cell leaves
Where would you find Type I epithelioretcular 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
What is the blood-thymus barrier?
What is its function?
The blood-thymus barrier is made from Type I epithelioreticular cells
It protects developing T-Cells from exposure to blood antigens
Where would a macrophage first encounter an antigen in a lymph node?
Subcapsular sinus
Which cells secrete cytokines that control T-cell maturation and education?
Epithelioreticular cells
Where are aging red blood cells eliminated?
Splenic cords
What is a germinal center of a lymphatic nodule?
An area of dividing cells. Forms during an immune response
Name the components of the lymphatic system
- Tissues w/ significant populations of lymphocytes (B cells, T cells, plasma-secreting antibodies): spleen, tonsils, thymus, appendix, lymph nodes, lymph nodules
- Circulating lymphocytes
- Lymphatic vessels
What are the functions of the lymphatic system?
- Recycle fluid from body tissues
- Re-circulate proteins that escape from blood capillaries
- Absorb emulsified fat from lacteals in intestinal villi
- Defense mechanism for the body
Describe the general path of lymph drainage
- Starts blindly in lymph capillaries
- Go through jugular, subclavian, or bronchomediastinal trunk
- Ends up in blood of large of veins at root of neck
Most lymph encounters lymph node(s) along the path
Why are lymph capillaries more permeable than blood capillaries?
Lymph capillaries are made from endothelial cells that have no basal lamina and that have gaps between them
What is the basic function of a macrophage?
Engulf and present antigen for the immune response
What is the main function of T-cells?
Participate in cell-mediated immunity (become killer cells)
What do B cells differentiate into?
- Plasma cells for humoral immunity (antibody production)
- Memory cells that can produce stronger antibody immune response w/ subsequent exposure to the same antigen
Where are lymph cells most often exposed to bacteria, pathogens, and antigens?
Lymph node
What do intercostal lymphatics drain into?
Where are intercostal lymphatics located?
Intercostal lymphatics drain into thoracic duct
Intercostal lymphatics are in deep thoracic wall
Describe lymph drainage into neck veins
Symmetrical if above umbilicus
Only goes to left side of neck if below umbilicus or in thoracic wall
Describe the drainage of subcutaneous lymph vessels above the umbilicus
- Drain into axillary lymph nodes
- Go deep to form subclavian trunk
Describe drainage of subcutaneous lymph vessels below the umbilicus
- Drain into superficial inguinal lymph nodes
- Pierce deep body wall the deep inguinal nodes
- Deep path to veins on left side of neck
Describe the path for deep flow towards the veins of the neck
- Aortic lymphatics (plexus of lymphatic vessels) carry lymph cranially through abdomen
- Aortic lymphatics converge on cysterna chyli below diaphragn
- Cisterna chyli continues as thoracic duct
- Thoracic duct goes from diaphragm to junction of left internal jugular and subclavian veins
Lymph from what sources flows into the deep path?
- Subcutaneous lymph below umbilicus
- Deep lymph in lower extremities to deep inguinal nodes
- Deep lymph in abdominal and posterior body wall
- Deep lymph in thoracic body wall
- Lymph from pelvic and abdominal viscera
What is the exception to lymph below the umbilicus flowing into the deep path?
Lymph from lateral foot and calf drains w/ greater saphenous vein into nodes and vessels in popliteal fossa
Joins path of deep lymph flow along femoral vessels to deep inguinal nodes of femoral canal
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
What do the lower esophagus and posterior mediastinum drain into?
Thoracic duct
Where does lymph from pelvic and abdominal viscera converge?
Aortic lymphatics and/or cisterna chyli
How are the abdominal and thoracic lymph drainage related?
Abdominal and thoracic lymph drainage connect w/ each other
How does lymph in the upper liver connect with intercostal lymphatics and deep parasternal nodes?
Pierces diaphragm
Which lymphatic trunks empty into the same venous junction on both sides?
- Subclavian trunks
- Jugular trunks
- Bronchomediastinal trunks
Where does lymph entering the subclavian trunk come from?
Axillary lymph nodes draining upper limbs and superficial lymph above umbilicus
Where does lymph entering the jugular trunk come from?
Head and neck
Where does lymph entering the bronchomediastinal trunk come from?
Heart, lungs, upper esophagus, and anterior intercostal lymphatics via deep parasternal nodes
How do parasternal nodes drain into the intercostal lymphatics?
Upwards, not posteriorly
Describe the mechanisms of lymph flow
- Little smooth muscle in lymph vessel wals
- Valves keep flow in one direction
- Lymph movement results from milking action from organ movement and skeletal muscle contraction
- Negative intrathoracic pressure helps direct lymph towards thorax
What is lymphogenous metastasis?
Spread of cancer via lymphatic system
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
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 word can be used to describe the flow of lymph in reference to the body wall?
Stratified
What is the structure of axillary nodes?
Five major groups forming a triangular cone pointing towards the neck
Apical and central nodes form core of triangle and are surrounded by anterior (pectoral), lateral, and posterior (subcapsular) nodes
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
