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Functional anatomy immune system
October 27 Lectures
151
Immunology
Graduate
10/30/2011

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Term
Leukocyte aka:
Definition
WBC
Term
Lymphocyte
Definition
type of leukocyte that has an antigen specific receptor
Term
Lymph-
Definition
clear liquid through which lymphocytes can move (from periphery to heart) lymph tissues are aggregates of lymphoid cells
Term
Lymphatic system:
Definition
thin walled vessels with valves (fluid is moved by adjacent muscles and gravity. The flow is unidirectional; periphery to the heart. Enters the pLN via the afferent lymphatics (and empties into the blood at a thoracic duct)
Term
Thoracic duct
Definition
where lymphocytes and lymph return to blood
Term
Blood
Definition
where naive lymphocytes enter lymph nodes from
Term
Lymphatics
Definition
how antigens from sites of infection reach lymph nodes
Term
Infection
Definition
starts in tissue and lymphocytes can drain out of tissues in this clear extracellular liquid and drains out to clear vessels that have valves
Term
movement of adjacent muscles
Definition
keeps movement of lymph through body, flow is from periphery back to heart. At heart the lymph joins the blood supply and circulation of blood can go back around
Term
Lymph drains to vessels by ______ by __________
Definition
nodes

afferent lymphatics
Term
afferent

efferent
Definition
1) enters

2) exits
Term
3 categories of lymphoid tissues
Definition
1) primary
2) secondary
3) teritary
Term
explain the 3 types of lymphoid tissues
Definition
1) Primary (where the b and t cells are educated/generated)
a. Bone marrow and thymus (sites of b and t cell generation)
2) Secondary
a. Collection points for circulating lymphocytes. Sites of interaction between b cells, t cells and APCs (where immune response begins)
i. Spleen (systemic infections), plays role in filtering blood
ii. Encapsulated lymph nodes (local infections) ,
iii. Peyer’s patches (small intestine)
3) Tertiary
a. MALT (mucus associated lymphoid tissue)
i. Inducible, not encapsulated (develops during inflammation) this tissue is developed in response to inflammation
Term
Primary lymphoid tissue
Definition
(where the b and t cells are educated/generated)

Bone marrow and thymus (sites of b and t cell generation)
Term
Secondary lymphoid tissue
Definition
a. Collection points for circulating lymphocytes. Sites of interaction between b cells, t cells and APCs (where immune response begins)
i. Spleen (systemic infections), plays role in filtering blood
ii. Encapsulated lymph nodes (local infections) ,
iii. Peyer’s patches (small intestine)
Term
what are the 3 parts of the secondary lymphoid tissue type
Definition
i. Spleen (systemic infections), plays role in filtering blood
ii. Encapsulated lymph nodes (local infections) ,
iii. Peyer’s patches (small intestine
Term
Teritary lymphoid tissue
Definition
includes MALT (mucus associated lymphoid tissue)

i. Inducible, not encapsulated (develops during inflammation) this tissue is developed in response to inflammation
Term
what does MALT mean
Definition
mucus associated lymphoid tissue
Term
where are primary lymphoid tissues made?
Definition
Bone marrow

b cell development takes place, get pluripotent HSC that starts out in bone marrow; and becomes common lymphoid progenitor (b cells develop level of pre b cells (undergo VDJ rearrangement in bone marrow) once they reach stage of maturation they leave and enter blood supply and go to peripheral lymph nodes of secondary lymph tissues
Term
thymus
Definition
place where T cell development occurs(positive and negative selection)
Term
characteristics of thymus
Definition
-multi-lobed nodular organ located posterior to sternum
-very large in first years of life (maximum size at puberty)
-becomes smaller during involution (degenerative process when connective tissue fibers and fat cells replace the functional (parenchyma) tissue (Hormonal control)
-some residual pieces of functional tissue remain
-evolution of thymic involution is poorly understood
Term
what type of lymphoid tissue is the thymus?
Definition
primary lymphoid tissue
Term
corticomedullary junction
Definition
Early progenitors leave bone marrow and enter thymus by these

(thymus divided into 2 major areas (cortex and medulla), and enter through thymus junction between those two parts.
Term
Hassall's corpuscles
Definition
important diagnostic feature, only the thymus tissue has these structures
Term
Progenitors move from bone marrow to thymus where they become ______ t cells.
Definition
immunocompetent
Term
when naïve T cells become mature, what are they? and where do they go?
Definition
CD4+ or CD8+

leave the thymus via the blood and eventually find their way to lymph nodes (where primary immune response begins), mucosa-associated lymphoid tissue, or spleen.
Term
Cortex
Definition
place of t cell positive selection, immature thymocytes. TcR: rescued from death
Term
Medulla
Definition
place of t cell Negative-selection, epithelial cells AIRE, dendritic cells, macrophages-remove apoptotic cells
Term
MHC
Definition
Thymic cortical epithelial cells expresss this
Term
Medullary epithelial cells are also called
Definition
AIRE cells
Term
positive selection of t cells
Definition
immature thymocytes are rescued from death by signal from t cell receptor and they get signals from MHC molecules which are expressed by cortical epithelial cells
Term
Cells that get survival signals then move into medulla area where they undergo _____________
Definition
negative selection
Term
Most negative selection is signaled by what cells which are in medullary area?
Definition
dendritic cells
Term
macrophages
Definition
are involved in removal of dying cells (ones that see antigen in cell fashion with too high affinity, they undergo apoptotic cell death),
Term
dendritic cells
Definition
cells can provide most of the antigens, but some antigens are not presented by these cells so epithelial cells secrete AIRE (auto immune regulator) that lets them see additional antigens that would not have otherwise been able to be recepted
Term
What are the 3 groups of the secondary lymphoid organs (sites where immune response begins?)
Definition
1) Encapsulated lymph nodes
2) Spleen
3) Peyer’s Patch (do not have a capsule)
Term
primary functions of secondary lymphoid organs
Definition
a) Promote interactions between t cells and APCs (usually dendritic cells)
b) Filter blood and lymph (spleen and lymph nodes) peyers patch is more important to immune response in gut
c) Provide survival factors for naïve b and t cells (without these survival factors, the naïve t cells will not live)
Term
development of secondary lymphoid organs
Definition
needs special type of cells, lymphoid tissue inducer cells, which responds to Lymphotoxin-alpha
Term
what types of cells respone to lymphotoxin-alpha in secondary lymphoid organs?
Definition
lymphoid tissue inducer cells
Term
organization of secondary lymphoid organs
Definition
is maintained by chemokines (in inflammation). Active process requires G protein coupled receptors
Additional reorganization occurs during inflammation (ex. Development of germinal centers)
Term
development and organization of secondary lymphoid structures requires what family members?
Definition
TNFR (tumor necrosis factor receptor)
Term
LTi
Definition
lymphoid tissue inducer
Term
LTbeta
Definition
lymphotoxin-beta
Term
LTalpha
Definition
Lymphotoxin-alpha
Term
Lymphoid tissue inducer cell comes out of the liver during what stage of life?
Definition
fetal development
Term
what does lymphoid tissue inducer do
Definition
this circulates in blood until they find stromal cells that have lymphotoxin receptor so lymphotoxin is either membrane bound or soluble
-When cells find cells that have lymphotoxin receptor, that’s where the encapsulated lymph nodes begin to develop
So Peyers patches develop (not encapsulated )
Term
When stromal cells are signaled by lymphotoxin, what happens?
Definition
they start to produce chemokines that attract immature b cells that provide more lymphotoxin
Term
If you don’t have the lymphotoxin, what happens in spleen and lymph nodes?
Definition
you will not have any uncapsulated lymph nodes on animal models and the spleen is very disorganized (it must be present to organize spleen)
Term
SLO
Definition
streptolysin
Term
In the SLO, there are 3 zones;
Definition
1) Outer Zone – antigen sampling (APC rich)
2) B cell activation zone (in resting conditions: follicle/ during inflammation it contains: germinal centers)
3) T cell activation zone (depending on which tissue you are looking at)
a. Called the Paracortex (in the lymph nodes)
b. Called the T cell areas surrounding arterioles (in the spleen)
c. Called the Interfollicular zone in (in the Peyer’s patches)
Term
What does outer zone of SLO do?
Definition
antigen sampling (APC rich)
Term
What happens in B cell activation zone of SLO?
Definition
(in resting conditions: follicle/ during inflammation it contains: germinal centers)
Term
What are the 3 types of T cell activation zones in the SLO (depending on which tissue you are looking at)
Definition
a. Called the Paracortex (in the lymph nodes)
b. Called the T cell areas surrounding arterioles (in the spleen)
c. Called the Interfollicular zone in (in the Peyer’s patches)
Term
function of peripheral lymph nodes (encapsulated)
Definition
Filter lymph and promote interactions between lymphocytes and APCs (antigen presentation); very important during local infections of peripheral tissue
Naïve t cells (ones that leave the thymus but have not yet seen the t antigen) continually circulate between the pLN via the blood and the lymphatics (survival factors) ; if they find an Ag that is specific to their receptor they will then undergo maturation and develop into an effector cell
Term
Fibrous capsule of peripheral lymph nodes
Definition
subdivided into different compartments by inward pointing trabeculae
Term
what are the 2 basic regions of the fibrous capsule of the peripheral lymph nodes?
Definition
1) Cortex: populated mainly with lymphocytes
a. B cell follicles
b. T cell areas
2) Medulla: labyrinth of lymph-draining sinuses which contain many plasma cells and macrophages which are attached to reticular fibers (function of medulla is not very well understood
Term
subcapsular sinus
Definition
this is the place where lymph enters through in the lymph node.

it is lined by metallophilic macrophages which are critical for antigen sampling (filters lymph)
Term
Cortex area of lymph node
Definition
where b cell follicles are
Term
Deep cortex of lymph nodes
Definition
where t cell area are
Term
Hilus
Definition
a depression where vessels and ducts end up to the organs (so organs have a hilus as well as peripheral lymph nodes)
Term
TNF-alpha
Definition
required for development of FDC's
Term
FDC's
Definition
cells of the immune system found in lymph follicles of secondary lymphoid organs and tertiary lymphoid organs.[1] They are probably not of hematopoietic origin, though they look similar to true dendritic cells due to their filiform dendritic processes, but are of stromal, mesenchymal origin.
Term
FDC's aka
Definition
Follicular dendritic cells
Term
efferent lymph joins blood at the
Definition
thoracic duct
Term
modular sinus
Definition
afferent lymph enters lymph node through this
Term
efferent lymph exits through the
Definition
subscapsular space
Term
HEV's
Definition
The lymph will bring in Ag’s from periphery where they can interact with t cells. T cells enter the encapsulated lymph nodes through high endothelial venules which are small blood vessels
Term
Naïve t cells come into lymph node from blood into the HEV’s and go into t cell zone, and in the t cell zone, they will find these cells:
Definition
interdigitating dendritic cells cells (which are immature APC’s) at this point we don’t have an immune response so most dendritic cells are immature
Term
b cell follicle
Definition
has most naïve b cells but there are also follicular dendritic cells and cd4 t cells.
Term
Are Follicular dendritic cells of hematopoeitc stem cell origin?
Definition
No!

although they have a dendrite tight morphology they are not really dendritic cells. They cannot process antigen from MHC class 2 (all they can do is collect new complexes which are antigens coated with antibodies)
Term
Can FDCs process antigen from MHC class II?
Definition
NO!


(all they can do is collect new complexes which are antigens coated with antibodies)
Term
What type of substance do b cells make during development of lymph nodes?
Definition
lymphotoxin
Term
why is TNF-alpha important?
Definition
1) for making lymphotoxin during development of the lymph nodes

2)for organization of lymph node

3)for development of FDC’s (follicular dendritic cells
Term
Hassall's corpuscle
Definition
granular cells surrounded by epithelial cells
Term
Hilus
Definition
where the lymph vessels enter the lymph node
Term
Cortex parts:
Definition
Paracortex: (the t cell area in the encapsulated lymph nodes); where circulating lymphocytes enter the pLNs via HEV and interact with DCs (naïve t cells enterby HEV with interdigitating dendritic cells)
B- cell area= primary follicles and germinal centers (after antigen challenge). Follicular DC capture immune complexes on their surface for recognition by b cells
Term
Paracortex
Definition
a part of the cortex (the t cell area in the encapsulated lymph nodes); where circulating lymphocytes enter the pLNs via HEV and interact with DCs (naïve t cells enterby HEV with interdigitating dendritic cells)
Term
what is the b cell area composed of?
Definition
primary follicles and germinal centers (after antigen challenge). Follicular DC capture immune complexes on their surface for recognition by b cells
Term
Medulla:
Definition
labyrinth of lymph-draining sinuses which contain many plasma cells, and some macrophages and memory t cells. The function of this portion is poorly understood.
Term
The artery divides into branching arterioles which lead to:
Definition
the capillary bed and HEV (selective entry)
Term
HEV's (High endothelial venules)
Definition
venules that control selective entry into peripheral lymph nodes, and this is different from the spleen (because it is selective entry)
Term
Cells can leave the pLN via two routes:
Definition
1)Post capillary venules near the germinal centers
2)From the medulla to efferent lymph (also joins the blood supply at the thoracic duct)
Term
Naïve t cells constantly circulate between......
Definition
secondary lymphoid tissues
(peripheral encapsulated lymph node and the spleen)
Term
if naive t cells dont find the antigen what will happen?
Definition
they will keep moving from one lymph node to another depending on survival signals
Term
If there is an immune response, what happens?
Definition
the local lymph nodes will become enlarged (draining lymph node- where immune response will begin), become enlarged as response to inflammation, (infection leads to immature dendritic cell response to pick up antigen and then carrying it to local lymph node), as it moves to local node it becomes a mature dendritic cell and this activates naïve t cell and the naïve t cell leaves draining lymph node and then can go to other places of body
Infected t cells that have been activated can then go to any part of the body.
Naïve t cells begin their response in organized lymphoid tissues that contain professional APCs
Term
where do Naïve t cells begin their response ?
Definition
in organized lymphoid tissues that contain professional APCs
Term
Is lymphocyte migration an active process?
Definition
Yes!
Term
Homing receptors:
Definition
chemokines and adhesion molecules-membrane bound molecules; control access into peripheral lymph nodes across high endothelial venules, a selective process, interactions with adhesion molecules is the only way it can enter the peripheral lymph nodes (how t cells know where to go)
Term
Adhesion molecules:
Definition
(membrane bound)
-control access to pLN via HEV (selective process)
-Selectins CD62L (tethering and rolling) (form weak adhesions to t cells, so they can stick to walls of vessels)
-Integrins (activated by chemokines) firm adhesion (undergo conformation change) after firm adhesion, they can squeeze between wall and enter the lymph node
-ICAMS intercellular adhesion molecules (compartments for integrins)
Term
what are all the different adhesion molecules involved in lymphocyte migration?
Definition
-control access to pLN via HEV

1) Selectins CD62L (tethering and rolling) (form weak adhesions to t cells, so they can stick to walls of vessels)
2) Integrins (activated by chemokines) firm adhesion (undergo conformation change) after firm adhesion, they can squeeze between wall and enter the lymph node
3) ICAMS intercellular adhesion molecules (compartments for integrins)
Term
Chemokines
Definition
These are soluble and have a low MW: Chemical gradient and activate integrins; signal via g protein coupled receptors; set up chemical gradient that t cells can follow.
Term
are lymphocytes motile as they pass through the pLN?
Definition
YES they are constantly motile
Term
when lymphocytes enter by blood and then exit from pLN, they must down regulate what receptors?
Definition
regulate Sphinosine 1-phosphate (S1P) receptors via g protein coupled receptors
Term
HEV
Definition
naive and memory t cells enter the lymph nodes from the blood via these

(lymphocytes and DC enter the pLN via these; it is an active process which requires chemokines and adhesion molecules)
Term
Diagram of initiation of immune response broken down in word form:
Definition
Local lymph nodes get bigger (TNF-alpha) --> (dendritic cells mature) --> chemokines signal --> enters through node --> local lymph nodes undergo extensive remodeling during infections --> t cells get activated --> chemokines get signaled --> PAMPS (pathogen associated molecular patterns recognized by innate immune system)
Term
Organization of secondary lymphoid tissue
Definition
Begins when there’s an infection, the immune system first recognizes the pathogen associated molecular pattern which induce inflammation. When you get inflammation, you get immature cells out in the periphery that pick up antigens and carry them to local lymph nodes. During this process, dendritic cells become mature and upregulate molecules necessary to activate naïve t cells. Naïve t cells come in to lymph node via HEV’s and they find interdigitating dendritic cells where they become effector cells. Effector cells leave via the lymph which then joins back to the blood and then they can go back to site of infection. During this process, inflammation causes the lymph node to become considerably bigger.
Term
b cells undergo positive selection in response to antigen that is collected by what?
Definition
follicular dendritic cells (FDCs)
Term
Cells that find the correct antigen become:
Definition
memory b cells and plasma cells
Term
what does an enlarged lymph node with clear germinal center indicate?
Definition
there is a local inflammatory response
Term
The Spleen:
Definition
-secondary lymphoid tissue
-has a very obvious clear capsule, but is quite different from peripheral lymph nodes
Term
primary functions of spleen
Definition
: filters blood (5% cardiac output goes straight to spleen) and recycles iron
Captures and destroys pathogens (that may be circulating in blood) and triggers adaptive immune responses
Term
what type of circulation does spleen have?
Definition
open circulation (slightly different to peripheral lymph nodes bc theres no lymphatics): discontinuous endothelial lining from artery to vein (artieries do not connect directly to vein) blood is released into red pulp area, making it discontinuous)

The blood is filtered as it crosses a fenestrated basement membrane surround the venous sinuses.
Term
diagnostic feature of spleen
Definition
red pulp ( contains large numbers CD8 T cells and plasma cells)

There are no HEV and no afferent lymphatics
Term
average spleen size/weight
Definition
About 4 inches long
Weighs 7 ounces
Term
There are 3 zones of the spleen:
Definition
1) Red pulp
a. 75%
b. Loose tissue between the venous sinuses
2) White pulp
a. B and t cell compartments
b. The t cell zone surrounds the arterioles
3) Perifollicular zone
a. 8%
b. Surrounds the b and t cell zones


The marginal zone surrouds the b cell follicles (but not the t cell zone)
Macrophages trap pathogens in the blood stream. All cells enter the white pulp via the marginal zone
Term
Red Pulp
Definition
one of 3 zones of spleen; makes up 75%, contains loose tissue between the venous sinuses
Term
White pulp
Definition
one of 3 zones of spleen
has B and t cell compartments
-has a t-cell zone that surrounds the arterioles
Term
Perifollicular zone
Definition
one of 3 zones of spleen
-make up 8%
- Surrounds the b and t cell zones
Term
The marginal zone surrouds the _______ but not the _________
Definition
b cell follicles

but not the

t cell zone
Term
Macrophages trap pathogens in the blood stream. All cells enter the white pulp via the ____________ of the spleen
Definition
marginal zone
Term
Arteries leading to spleen
Definition
-Arteries hardly anastomose at all. At the terminal end of the capillary is a blind ended structure which is surrounded by concentrically arranged macrophages. Blood cells have to pass through the sheath before reaching the lumen of the sinus.
Term
White pulp of spleen
Definition
contains discontinuous periarteriolar lymphatic t cell sheath (PALS)
The t cell regions are interrupted by the b cell follicles.
The arterioles branch and terminate at the periarteriolar macrophage sheaths
Term
what are PALS?
Definition
periarteriolar lymphatic t cell sheaths
Term
marginal zone
Definition
All lymphocytes enter the spleen via this space between the b cell and t cell area and this is where the blood is filtered by macrophages; and red pulp HEV are not required (non-selective entry)
Term
blood comes in from the trabecular artery and goes to the __________
Definition
central arterial
Term
Do arteries near spleen form anastomonses?
Definition
NO, they do not

this means that the same vessel does not branch and rejoin so they have these sort of large areas/sinuses at the end which have macrophages which are important to filter blood.
Term
Once t cells leave marginal zone, where do they go?
Definition
lymphocyte sheath
Term
explain the sinuses
Definition
interconnecting mesh, with bulb-like extensions and blind ends
Term
Describe The veins
Definition
they are remarkable for their numerous anastomoses (reconnections between streams that previously branched out).
Term
are there many anastomoses in red pulp in venous blood supply?
Definition
YES!
Term
Red Pulp is divided into 2 zones
Definition
1) Filtering Zone
a. Loose reticular tissue rich in partially sheathed capillaries and venous sinuses surrounded by circular bands of basement membrane. The arterial blood arrives into cords of red pulp and passes into venous sinuses, where it is forced through the slits formed by the stress fibers and endothelial cells. (Red blood cells cannot pass through these sinuses).
2) Non-filtering areas: no capillaries
Term
Filtering zone of red pulp
Definition
a. Loose reticular tissue rich in partially sheathed capillaries and venous sinuses surrounded by circular bands of basement membrane. The arterial blood arrives into cords of red pulp and passes into venous sinuses, where it is forced through the slits formed by the stress fibers and endothelial cells. (Red blood cells cannot pass through these sinuses).
Term
Non-filtering areas
Definition
this zone of red pulp has no capillaries
Term
The conduit system
Definition
-a tubular network in spleen and lymph nodes; bundles of collagen fibers surrounded by stromal cells
-small molecules (delivers chemokines and peptides/antigens into lymph node) (not carried by dendritic cells; they are soluble antigens)
-some cells can also enter during inflammation
Term
reticular fibroblasts
Definition
what part of the conduit system of the spleen is in white pulp supplies (supplies the blood)
Term
type I collagen fibers
Definition
this material makes up part of the conduit system in pLN that is surrounded by basement membrane and reticular fibroblasts (supplies the lymph)
Term
what are the 2types of mucus-associated lymphoid tissues (MALTs) :
Definition
Gut associated lymphoid tissue (GALT) or the Peyer’s Patches
Term
where are Peyer's patches found?
Definition
small intestine
Term
Where are single lymphoid follicles that actually make up inducible tertiary lymphoid tissue found?
Definition
large intestine
Term
is the peyers patch attached to lymphatics?
Definition
no

you don’t get lymph from a capsule bc there is no capsule;
Term
Peyer’s patch
Definition
-different to encapsulated lymph node
-its not attached to lymphatics
-actually faces in toward the lumen of the small intestine
-there are specialized cells so it has a dome structure (specialized cells, apex of dome brings antigens in from the intestine)
-) these cells actually have a folded surface on them and they can pass antigens all the way through
-At the bottom there are pockets with dendritic cells in them and these dendritic cells pick of Ag’s and bring them to b and t cell areas and sometimes they will end up in afferent lymphatics and then mesenteric lymph nodes (largest lymph nodes ; serve the intestine)
Term
how do T cells enter and exit?
Definition
enter via HEV and leave via afferent lymphatics (go to mesenteric lymph nodes)
Term
Antigens and microorganisms are transported by what?
Definition
by M cells (microfolds on their luminal surface to DC which are located in the dome.
Term
most immature DCs remain where?
Definition
in the sub epithelial dome
Term
Upon maturation the DC move where?
Definition
into interfollicular t cell areas, b cell zone, and draining lymphatics
Term
what is the function of the Peyers patch?
Definition
specialized site that takes up bacteria and produces immune response
Term
Mucosal associated lymphoid tissues (MALT)
Definition
organized collections of lymphocytes (separate t and b cell zones)
-development is induced/maintained by inflammation (TNFalpha)
-Lymphotoxin is not required (even if animal doesn’t have lymphotoxin and wont have encapsulated lymph nodes however,they can still produce MALT)
-predominantly antigen-experienced t cells
-has 3 sub-types
Term
What are the types of teriary lymphoid tissues?
Definition
1) Mucosal associated lymphoid tissues (MALT)
2) Gut associated lymphoid tissues (GALT) (type of MALT)
3) Nasal associatied lymphoid tissues (NALT) (type of MALT)
4) Bronchus associated lymphoid tissue (BALT) (type of MALT)
Term
Gut associated lymphoid tissues (GALT)
Definition
Isolated lymphoid follicles in the large intestine (type of tertiary lymphoid tissue and type of MALT)
Term
Nasal associated lymphoid tissues (NALT)
Definition
type of tertiary lymphoid tissue in respiratory tract (type of MALT)
Term
Bronchus associated lymphoid tissue (BALT)-
Definition
type of teriatry lymphoid tissue of(respiratory tract) in children (and not very obvious in adults) (type of MALT)
Term
lymphoid neogenesis
Definition
when tertiary lymphoid tissues form at sites of chronic inflammation
Term
what are the characteristics of tertiary lymphoid tissues?
Definition
-not capsulated
-form at sites of chronic inflammation through a process referred to as lymphoid neogenesis
-organized b cell compartments, which contain germinal centers
- t cell compartments in which contain antigen-presenting cells
High endothelial venules through which lymphocytes can enter from blood
Term
Tonsils
Definition
part of MALT’s of upper respiratory tract (filter against disease)
Term
Palatine tonsils
Definition
ovoid masses of lymphoid tissue situated on either side of the throat
Term
Pharyngeal tonsils (adenoids):
Definition
part of nasopharynx
Term
Lingual tonsils:
Definition
at the back of the tongue (act as a filter against disease organisms); often becomes site of infection (tonsilitis) and becomes enlarged.
Term
Thymus:
1) Diagnostic features
2) Germinal centers?
3) Circulation
4) Stroma
5) Migrating cells
6) Functions
Definition
primary lymphoid tissue
Diagnostic features: poorly developed capsule, has Hassall’s corpuscles
Germinal centers: none
Circulation: HEV; blood efferent lymphatics
Stroma: epithelial reticular cells; few fibers
Migrating cells:lymphocytes
Functions:produces t cells. Not exposed to blood or lymph-borne antigens. No afferent lymph vessels
Term
Spleen:
1) Diagnostic features
2) Germinal centers?
3) Circulation
4) Stroma
5) Migrating cells
6) Functions
Definition
for primary immune response
Diagnostic features: well developed capsule; red pulp
Germinal centers: present
Circulation: efferent lymphatics; red pulp
Stroma: reticular cells and fibers
Migrating cells: all white blood cells
Functions: systemic infections; filters soluble antigen from blood; phagocytosis; production of antibodies; sequestration of blood cells, reprocessing hemoglobin
Term
Lymph Node:
1) Diagnostic features
2) Germinal centers?
3) Circulation
4) Stroma
5) Migrating cells
6) Functions
Definition
Diagnostic features: Well developed capsule
Germinal centers: Present
Circulation: afferent and efferent lymphatics; HEV: blood
Stroma: Reticular cells and fibers
Migrating cells: Lymphocytes, plasma cells, macrophages/DC
Functions: Local infections; filters soluble antigen from lymph (rather than the blood); phagocytosis; production of antibodies; clonal expansion of b cells
Term
MALT (mucous associated lymphoid tissue)
1) Diagnostic features
2) Germinal centers?
3) Circulation
4) Stroma
5) Migrating cells
6) Functions
Definition
Diagnostic features: No capsule (except in tonsils)
Germinal centers: present
Circulation: efferent lymphatics; HEV
Stroma: Reticular cells and fibers
Migrating cells: Lymphocytes; plasma cells
Functions: Protect mucosal tissues (induced during inflammation); production of antibodies to; produce lymphocytes found in lamina propria
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