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