tuesday test lymphoid2 Flashcards
What kind of immunity is lymphoid tissue?
Adaptive Immunity - specific pathogen and defends against that specific pathogen, unlike a generalized like with Innate
where are B- and T-lymphocytes activated?
secondary lymphoid tissue, such as
- lymph nodes
- spleen
- tonsils (= MALT) etc.
Adaptive Immunity components?
- Antigen Presenting Cells
- Cytotoxic T-cells
- Plasma cells
- Memory cells
All of these are lymphocytes
Primary lymphoid organs? Their function?
they mature lymphocytes.
– Thymus & bone marrow
Secondary lymphoid structures? Their function?
- Lymph nodes
– Spleen
– Mucosa associated lymphoid tissues (MALT) - Tonsils
- Wall of digestive tube (i.e. gut =GALT)
- Peyer’s patches
- Wall of respiratory tubes (bronchial =BALT)
lymphocytes are activated and memory lymphocytes produced
reticular fibers job?
form walls of 3-D pockets
job of macrophages in lymphoid tissue?
eat pathogens and are APCs for lymphocyte activation.
most infectious organisms are destroyed by lymphocytes, neutrophils & Macs.
Dendritic cells job in lymphoid tissue?
super APCs; migrate in from all over body
High-endothelial venules (HEV) job?
where lymphocytes leave blood & enter lymphoid tissue
Do memory cells form in lymphoid tissue?
Most memory lymphocytes are formed, for long-term immunity
What are nodules (follicles)?
Are a dense collections of lymphocytes – a mixture of B and T cells. - vast majority is B cells
What is the difference between primary and secondary nodules?
- Primary - Accumulation of B cells resulting from antigen-driven B cell proliferation
- Secondary - Actively producing clonal B cells (plasma and memory); activated B cells, exit as a plasma cell or reside as memory cell = Germinal center
How do GC look like and where are they located? What are they?
more cytoplasm (“clock face”) than in the typical, small lymphocytes
they are located in 2° Lymphoid Nodule
Dividing B cells in GC
What is Lymphatic System?
Constitute a series of in-line filters in the system
Enclosed environment in which T and B cell encounter antigen
• Place of Plasma cell differentiation – Antibody production
How many lymph nodes are there in the body? Where?
450 Lymph Nodes
- Axilla
- Groin (inguinal )
- along major vessels of
– Neck (cervial)
– Thorax (thoracal)
– Abdomen (mesenteric)
3 structural components of a lymph node?
Outer cortex
Para cortex
Central medulla
outer cortex job?
- – Sub-capsular sinus receives lymph fluids;
- – Branches into cortical sinus;
Delivers lymph fluid to immune cells located in cortex region.
- – Nodules (GC)
• B cell rich area • Antigen can be trapped by APC
what is happening in Para cortex?
– T cell rich area (activation of cytotoxic T cells)
– circulating T & B cells enter from blood stream via HEV (High endothelial venule)
Central medulla function?
– Medullary cord • T & B cells and plasma cells
– Medullary sinuses • last lymph filter (contains macrophages)
• Converge with efferent lymph vessel
Types of cells present in the three compartments of a lymph node?
outer cortex - mostly B cells, some Th, Macrophages
Para cortex - T cells
Central medulla - T cells, B cells (activated), plasma cells, macrophages
How do lymph nodes destroy pathogens?
- Macrophages eat pathogens in sinuses → then can present Ag to T cells in pericortex.
- Other pathogens leak from sinuses into the nearby nodules and are destroyed there by NK and cytotoxic T cells
Example of MALT? what kinds? What is their job?
Tonsils
Several sets: main one is palatine tonsil (object of most infections and of tonsillectomies), adenoid tonsil and lingual tonsil.
• Tonsils sample antigens from the food we swallow and air we breathe.
they make lots of memory lymphocytes for long-term immunity
How does palatine tonsillectomy happen?
• Palatine tonsil has a capsule, and a surgeon cuts just under the capsule to remove this tonsil during tonsillectomy.
Palatine tonsil structure?
Epithelium is thrown into crypts (folds) that gather the pathogens and antigens.
- These invaders work their way into the underlying lymphoid tissue and are destroyed.
- Crypts actively invite infection, but recall that this sampling builds up lots of memory lymphocytes to improve immunity throughout life.
GALT (gut associated lymphoid tissue) organs?
Large intestine, appendix (constantly samples bacteria and antigens in the feces)
Peyer Patches - what is it? What is the function?
Aggregated Lymphoid Nodules
Form dome-like protrusions of the mucosa
- Like all GALT, they closely monitor the antigens and microbiota in gut (ileum).
- Covered by intestine’s columnar epithelium
what are the main functions of spleen?
–Largest filter of blood → important in defense against bloodborne antigens → Critical in removal of encapsulated bacteria – Hemophilus influenza, Streptococcus pneumonia
– Site of removal of senescent (old) erythrocytes → Iron recycling
– Storage of platelets
• Largest single accumulation of lymphocytes – Site of antibody production
3 distinct areas you see in the spleen?
Red pulp - RBC recycling, removed old RBC
White pulp - collection of lymphocytes (nodules of B and T cells) - they stain purple
Central arteriole - T cells wrap around, interacts with blood
What is thymus? How does it develop?
Two-lobed organ in thorax anterior to heart
– Originates from 3rd pharyngeal pouch during embryogenesis
– Derived from endoderm, so is epithelial in nature.
What is thymus? How does it develop?
Two-lobed organ in thorax anterior to heart
– Originates from 3rd pharyngeal pouch during embryogenesis
– Derived from endoderm, so is epithelial in nature.
Thymus job?
Primary lymphoid tissue, said to “produce” the T cells: killer, helper, and regulatory T cells. → no B cells → no GC, no plasma cells
First, T-cell precursors called lymphoblasts migrate from the bone marrow to the thymus. There, they divide to generate millions of T cell clones throughout life, with each clone programmed to recognize its own specific antigen.
Other thymic functions:
– Selecting which new T cell clones will survive;
– Inducing tolerance: “central immune tolerance”
How does thymus look like?
Looks like a cauliflower, divided into many incompletely separated lobules (= the florets of the cauliflower)
• Vascularized CT capsule has septae that extend inward to separate the lobules. • Each lobules has – Outer cortex (darker-basophilic) – Inner medulla (lighter) Cortex stains darker because it has more lymphocytes that are more densely packed.
What is lobule of the thymus and what does it have?
Vascularized CT capsule has septae that extend inward to separate the lobules.
• Each lobules has
– Outer cortex (darker-basophilic) - stains darker because it has more lymphocytes that are more densely packed.
– Inner medulla (lighter) - T cells maturation is completed in medulla
What are Hassall’s (Thymic) Corpuscles?
Concentrically layered groups of keratinized thymic epithelial cells (TECs) in medulla - They finish off T cells maturation
What is T cell positive and negative selections? Mediated by?
Mediated by thymic epithelial cells (TECs) in medulla.
Macrophages inspect cells in 2 ways:
- Positive selection - Have you got the right protein to now be a T cell that can get activated? - If not destroy
- Negative selection - Inspect exact form of surface protein that indicate “you are going to be active, but do you recognize the difference between self and foreign AGs?” → selects out anything autoimmune
What does Hassall’s (Thymic) Corpuscles produce? What is its function?
Produces thymic stromal lymphopoietin (TSLP) is a cytokine. TSLP is known to play an important role in the maturation of T cell populations.
Does thymus change with age?
yes, it involutes with age. more fat less cortex and medulla - about 30 yrs major change
