organs of the immune system Flashcards
where are lymphoid cells first produced in the fetus
- yolk sac
- fetal omentum
- liver
in older fetuses and adults lymphoid cells are produced
-in bone marrow
what type of organ is bone marrow
- hematopoietic organ
- it gives rise to all blood cells
what two types of lympoid organs are there
- primary lymphoid organs
- secondary lymphoid organs
what makes up the primary lymphoid organs
- bone marrow
- thymus
- bursa of fabricius in birds
what makes up the secondary lymphoid organs
- spleen
- lymph nodes
- non-encapsulated lymphoid tissue
- peter’s patches
Primary lymphoid organs:
organs that regulate the development of lymphocytes
Where do t lymphocytes develop and mature
t cells develop in bone marrow and mature in the thymus
What is different about the t and b lymphocytes development and maturation differ
b cell development and maturation depends on the animal species
where do B lymohocytes develop/mature in birds
-Bursa of Fabricius
where do B lymohocytes develop/mature in primates and rodents
-bone marrow
where do B lymohocytes develop/mature in rabbits, dogs, ruminants and pigs
intestinal lymphoid tissue
where is the thymus located?
the thymus is located in the thoracic cavity in front and below the heart
what does it mean when the thymus undergoes involution
-The thymus starts large in newborns but regresses to invisible in adult animals
what is the structure of the thymus
-covered by connective tissue capsule and consists of lobules
what is contained in the cortex of they thymus
thymocytes (lymphocytes)
what is contained in the medulla of the thymus
- only a few lymphocytes
- no lymphatic vessels leave the thymus
what is the primary function of the thymus
-the maturation of T lymphocytes
where do T lymphocytes learn to recognize self antigens
thymus
how myst t lymphocytes bond to self antigens
They must not respond/bond strongly to self antigens
what happens to thymocytes with receptors that bind strongly to self antigens
they are destroyed through apoptosis
apoptosis during the antigen selection is what kind of selection
negative selection
what happens to thymocytes that cannot bind any MHC 2 molecules
they are also removed
What happens to thymocytes that recognize MHC 2/Ag complexes with moderate affinity
-they are allowed to live and is known as positive selection
What happens to the positively selected cells in the thymus
-the positively selected cells leave the thymus as mature T lymphocytes and populate the secondary lymphoid organs
what regulates the maturation process in the thymus
- a mixture of cytokines and thymic hormones
which cytokines and thymic hormones are used in the maturation of t cells in the thymus
- thymosin
- thymopoietins
- thymulin
- thymostimulins
where is the bursa of fabricius found
- only in birds
- round sac located just before the cloaca
how is the bursa of fabricius and thymus similar in regards to the animals age
they both undergo involution
what is the interior structure of the burs of fabricius
-epithelium embeds the lymphocytes and lines a hollow sac connected to the cloaca by a duct
What are the follicles in the bursa fo fabricius
fold made of epithelium that extend into the sac
each follicle in the bursa of fabricius has 2 zones called
the cortex and medulla
the cortex of the bursa of fabricius containes
- lymphocytes
- plasma cells
- macrophages
what is the function of the bursa of fabricius
-maturation of B lymphocytes
what kind of selection takes place inside the bursa of fabricius
-negative and positive selection of B lymphocytes
what differentiation takes place in the bursa of fabricius
differentiation of antibody-forming cells (b-Lymphocytes)
what are the secondary lymphoid organs divided into
- encapsulated organs
- non-encapsulated tissue
what are examples of encapsulated secondary lymphoid organs
- lymph nodes
- splee
what are examples of non encapsulated secondary lymphoid tissue
-mucosal lymphoid aggregates
when do secondary lymphoid organs develop and how long do the persist
- develop late in fetal life
- persist in adult life
how do secondary lymphoid organs react to antigenic stimulation
Enlarge
how is the immune system impaired when a secondary lymphoid organ is removed surgicaly
-this does not impair immune capabiltiy
how do DC interact with the secondary lymphoid organs
-The secondary lymphoid organs contain DC which trap and process antigens, and later present these antigens to lymphocytes to initiate an immune response
Lymph nodes act as
filters of lymph to trap antigens
what is the shape of the lymph nodes
- round/bean shaped
- encapsulated organ
how is the interior of the lymph nodes divided
- outer:cortex
- between the cortex and medulla: paracortex
- Inner: medulla
where are B lymphocytes found in the lymph nodes
- in the cortex
- in germinal centers surrounded by capsules
where are T cells and DC found in lymph nodes
-mainly in the paracortex
what is contained in the medulla of the lymph node
-the medullar contains many different types of cells
what is the dirrection of the afferent lymph flow.
flow of lymph from local tissue into the lymph node
Lymphocytes, DCs and Antigens are carried in the ______ lymph flow (to/from) the lymph node
- Afferent
- to the lymph node
Lymph enter the lymph node through
the subscapsular sinus
what happens to the lymph oafter it enters the lymph node via the subscapular sinus
-it percolates through the lymph node to the medullary sinus
Where does lymph exit the lymph node
-through the efferent lymphatic vessels
do lymph nodes have blood supply?
yes lymph nodes have arterial and venous blood supply
what is the principle function of Lymph nodes
-is to facilitate the interaction between dendritic cells and antigen sensitive T and B lymphocytes
what is the spleen
- a large encapsulated organ found in almost all vertebrate animals
- structured by a network of connective tissue trabeculae
what two types of tissue makes up the spleen
- Red pulp
- White pulp
What is Red pulp tissue in the spleen
it is tissue that does blood filtering and RBC storage
what is the white tissue in the spleen
- where immune induction occurs
- rich in lymphocytes
what does the spleen filter the blood for
the spleen filters blood for
- blood-borne antigens
- cellular debris
- aged blood cells
what does the spleen store
- RBC
- Platelets
- recycles iron
what type of lymphoid organ is the peyers patch and where is it located?
- it is a non encapsulated lymphoid tissue
- located in the wall of the small intestines
where is the peyers patch found in ruminants pigs dogs and rabbits
in the ileum
what type of lymphoid organ is the peyers patch found in ruminants pigs dogs and rabbits
it is a primary lymphoid organ for B cell development
what is in the peyers patch
-it contains densely packed lymphoid follicles containing only B lymphocytes
Peyers patches are covered by an _________ layer containing specialized cells called ________ which have characteristic membrane ruffles
- epithelial layer
- M cells
does the peyers patch undergo involution
yes
what other lymphoid organ has a similar function to the peyers patch
-Bursa of Fabricius
where is the peyers patch located in rabbits and rodents
-located in the ileum and jejunum at random intervals
what is different about the peyers patch in the rodents and rabbits
-in these species the PP develops 2-4 weeks after birth and do not undergo involution
T/F non-encapsulated lymphoid aggregates do not make up a large portion of the total lymphoid tissue
false
where is most of the non-encapsulated lymphoid tissue found
in the intestinal mucosal
MALT
Mucosal-associated lymphoid tissue
what 4 groups of tissues make up MALT
- GALT
- BALT
- NALT
- CALT
GALT:
Gastrointestinal associated lymphoid tissue
BALT:
Bronchial associated lymphoid tissue
NALT:
Nasal associated lymphoid tissue
CALT:
conjunctiva associated lymphoid tissue
which of the 4 tissues that makes up the MALT is the best know
GALT
Why is the GALT important
-it is the induction site and effector site of the intestinal immune response
