Cells and Tissues of the Immune System Flashcards
What type of immunity do natrual killer cells participate in?
Innate immunity
What kind of cell is this?
Eosinophil;
Bi-lobed cells with bright pink cytoplasmic granules
Where are lymph cells most often exposed to bacteria, pathogens, and antigens?
Lymph node
What word can be used to describe the flow of lymph in reference to the body wall?
Stratified
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)
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
Describe the pathway for lymph flow through a node
- Cortical afferent lymphatics
- Subcapsular sinus
- Trabecular sinuses
- Medullary sinuses
- Efferent lymphatics exiting at hilum
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
What are primary lymphoid tissues?
Primary lymphoid tissues are where white blood cells originate and develop.
Bone marrow and thymus
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)
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
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
How do parasternal nodes drain into the intercostal lymphatics?
Upwards, not posteriorly
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 are the functions of the red pulp?
- Eliminates old/damaged RBCs
- Recycles iron
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
Where would a macrophage first encounter an antigen in a lymph node?
Subcapsular sinus
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 is a germinal center of a lymphatic nodule?
An area of dividing cells. Forms during an immune response
What are microglia?
Tissue-resident macrophages in the brain
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
What is the function of lymph nodes?
Filter lymph to increase the chance of antigens encounter macrophages and lymphocytes invoking an immune response
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 type of immunity do T-Cells participate in?
Cell-mediated immunity
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
Which cells express CD3?
T-Cells
What triggers basophils and mast cells to release histamine?
Cross linking of Fc receptors
Binding of TLRs
What is the main function of the spleen?
Filters blood in a network of vascular spaces for blood antigen surveillance by macrophages
Why can lymph nodules not be considered an organ?
Lymph nodules do not have a capsule
Describe the drainage of subcutaneous lymph vessels above the umbilicus
- Drain into axillary lymph nodes
- Go deep to form subclavian trunk
What is the main exception to stratification?
Lymph drainage of the breast
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)
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
What does the red pulp consist of?
Splenic sinuses and splenic cords
Which immune cells are stimulated by IL-5?
Eosinophils
What comprises the white pulp?
Periarterial lymphatic sheaths (PALS) surrounding central arteries
What are trabeculae in lymph nodes?
Connective tissue beams the capsule sends into the medulla
Where does lymph entering the bronchomediastinal trunk come from?
Heart, lungs, upper esophagus, and anterior intercostal lymphatics via deep parasternal nodes
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)
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
What kind of cell is this?
Where is it found?
Macrophage;
Reside in tissues
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 cytokines do macrophages produce and secrete?
TNF, IL-1, IL-12
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 is unique about high endothelial venules in lymphatic tissues and organs?
The endothelium is cuboidal instead of simple squamous
What kind of cell is this?
Plasma Cell;
Fried egg appearance, “clock face” chromatin pattern in nucleus
What are the components of lymph nodules?
Dense aggregations of mostly B cells in meshwork stroma of reticular fibers
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 kind of cells express CD3 and CD8?
Cytotoxic T-Cells
Where are aging red blood cells eliminated?
Splenic cords
Which cell types are surveillance cells?
- Macrophages
- Langerhans cells (epidermis)
- M cells (intestinal epithelium overlying lymph nodules)
- Dendritic cells (lymphatic tissues)
What kind of immunity are macrophages involved in?
Innate: cytokine production
Adaptive: antigen-presenting
What do splenic cords consist of?
A meshwork of reticular cells and fibers among dense aggregations of red blood cells and macrophages
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
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)
Where in the body are dendritic cells found?
Tissues; under skin and mucosa
What is the purpose of having high endothelial venules?
To concentrate lymph to increase chance that antigen will encounter antigen-presenting cell
Where do all myeloid-derived cells mature?
Bone marrow
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
What is MALT called when it is in the gut?
Gut-associated lymphatic tissue (GALT)
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
What do the PALS consist of?
Dense aggregates of T lymphocytes w/ B lymphocyte nodules scattered along the way