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IMMUNOLOGY AND INFECTION - POM > Lymphoid Tissues > Flashcards

Lymphoid Tissues Flashcards

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1
Q

What are primary lymphoid tissues?

A

The site of lymphopoiesis, where new lymphocytes are made, the bone marrow and the thymus

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2
Q

How is lymph formed?

A

Through the draining of interstitial fluid out of the capillaries and into the lymphatic vessels

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3
Q

What are the two primary lymphatic organs?

A

The bone marrow and thymus

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4
Q

state the 2 hallmarks of the adaptive immune response, and how they are possible

A

Specificity = range of TCR and BCR
Memory = allows for rapid expansion when there is secondary re-exposure

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5
Q

what cells are involved in the adaptive immune response

A

B and T cells

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6
Q

What cells are of the lymphoid lineage?

A

T cells, B cells and NK cells

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7
Q

Which part of the bone marrow does haematopoiesis occur on?

A

The red part

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8
Q

What cells are made in the bone marrow? And which part of the bone marrow?

A

B cells in the yellow marrow in the middle

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9
Q

Which cells mature in the thymus?

A

T cells

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10
Q

What is meant by thymic involution?

A

When the thymus output massively decreases over time, and most if thymus is replaced by fat

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11
Q

What are the two selection processes which the T cells undergo?

A

Positive and negative selection

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12
Q

What is positive selection?

A

T cells with CD4 and CD8 proteins on surface will try bind MHC1 and MHC2. if it does, this is good as the correct proteins were expressed, and cell is not killed.

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13
Q

What is negative selection?

A

Keeping the cells that don’t bind and interact with self peptides
If the TCR recognizes self peptides then apoptosis is triggered

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14
Q

define non-self

A

anything recognised by the immune system as foreign

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15
Q

define self

A

anything recognized by the immune system as part of your normal molecular make-up

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16
Q

How do the T cells differentiate into T Helper Cells and T Killer cells?

A

Depending on which out of CD4 or CD8 had the strongest bond, the T cell will up regulate that one

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17
Q

How does the thymus change with age?

A

Degenerates

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18
Q

How does the number of peripheral T cells change with age?

A

Remains the same - peripheral T cells numbers are maintained by the division of mature T cells

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19
Q

Why are older people more vulnerable to new strains of pathogens?

A

Due to thymic involution, the T cell numbers are maintained by the division of mature T cells outside the central lymphoid organs, therefore you get less variety of T cells

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20
Q

How do T cells move from their site of production?

A

The thymus releases chemokines initiate the chemotaxis of T cells from the bone marrow to the thymus

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21
Q

What happens to the thymus during infection?

A

No change

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22
Q

What happens to the bone marrow during infection?

A

Bone marrow increased white cell production

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23
Q

What are secondary lymphoid tissues?

A

They are the locations where lymphocytes can interact with antigens and other lymphocytes

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24
Q

State 5 secondary lymphoid tissues

A

Spleen, peyers patches, gut, lymph nodes,tonsils

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25
What are lymph nodes?
Highly organized, encapsulated structures which are located at points of convergence of lymphatic vessels
26
What are germinal centers?
Anatomically restricted site where B cells undergo maturation and selection to generate high affinity antibodies
27
Through what vessel does lymph enter into the lymph nodes?
The afferent lymphatic vessel
28
What are the functions of the spleen? - 3
1. Store of platelets 2. Reacts with blood borne antigen 3. Removes defective RBCs from circulation
29
Why is the lymph nodes a discrete tissue?
It has no other function other than to act as a site where lymphocytes and antigen can interact
30
What form the first line is defense against infection?
Epithelial barriers
31
What is the significance of the location of lymphoid tissues?
They are spread around the body so that the lymphatic can reach every part of the body, allowing lymphocyte and antigen interactions
32
Where are Peyer’s Patches Found?
Below the epithelium of the ilium of the small intestine
33
Where are many germinal centers located?
The gut
34
does the lymph nodes have distinct T and B cell zones, where are they found?
Yes T cell area B cells = Germinal centre
35
Why is there a lot of germinal centers in the gut?
There are high levels of antigen coming from gut microbial, which are producing many foreign antigens which leads to high antibody production
36
what are secondary lymphoid organs connected to
circulation and lymphatics
37
does the spleen have distinct T and B cell zones
Yes
38
What happens in the red pulp of the spleen?
Red blood cells are destroyed
39
What is a Periarteriolar lymphoid sheath?
An area of white pulp which surrounds the arteries running through the spleen - is highly populated with T cells
40
What is MALT?
Mucosa-associated lymphoid tissues
41
Which special cells do gut associated lymphoid tissues contain? - 2
M cells (membrane-like) or FAE (Follicle associated Epithelial) cells
42
What do FAE cells do? - 3
- take up small amount of gut antigen - pass onto APCs - B lymphocytes react, making type IgA antibodies which are secreted directly into the gut lumen
43
What do the IgA antibodies made in the gut do?
They prevent microorganisms in the gut from sticking to the gut epithelium, and can also neutralize toxins and viruses
44
What forms the Waldeyer ring?
The pharyngeal, tubular, palatine and lingual tonsils
45
What are the tonsils made of?
Epithelial cells that are able to phagocytosis bacteria and transfer the antigenic peptides to macrophages that act as APCs
46
Where are the antigen sampled from in the tonsils?
Directly from the external environment
47
Why is the waldeyer ring an ideal environment for the immune system to encounter antigen?
Food, bacteria and things we breath in pass the oral pharyngeal section very often, therefore more antigen exposure here
48
Why do lymph nodes swell during an infection?
The B cell follicles of the lymph nodes expand as the B cells proliferate to form germinal centers, and the entire lymph node enlarges
49
Where do naive Lymphocytes go after they are produced?
They enter into the blood stream and migrate to the peripheral lymphoid tissues
50
How long does it take for a T cell to recirculate?
24 hours
51
How to lymphocytes get inside the lymph nodes?
They enter via high endothelial venules
52
Where are high endothelial venules found?
In T cell zones of the lymph nodes
53
Which organ is mainly associated with filtering antigen out of blood?
Spleen
54
What are the four steps of T cells getting inside the lymph nodes?
1. Rolling 2. Activation 3. Adhesion 4. Transendothelial migration
55
What molecule on T cells results in the rolling of the T cell before it enters the T cell zone of the lymph nodes?
L Selectin on T cell
56
What molecules binds to L selectin?
CD34
57
What chemokines are involved in activating LFA-1
Recognition of CCL21 on endothelial surface of HEV by CCR7 on T cells
58
What happens when LFA1 is activated?
The affinity for ICAM-1 AND ICAM-2 is increased
59
What does ICAM allow?
The migration of the lymphocytes through the blood vessel wall
60
What are dendritic cells?
Potent, antigen presenting cells that pick up and bring antigen from sites if infection to secondary lymphoid organs
61
How to dendritic cells help with the adaptive immune response?
They pick up antigens and present them to T cells, in order to activate the T cells
62
How do dendritic cells display the antigens?
Through MCHII molecules
63
Describe the transport of lymphocytes and antigens in the lymphatics and blood stream
Free antigen and antigen bearing DC’s travel from the site of infection through afferent lymphatic vessels into the draining lymph nodes Activate lymphocytes then undergo period of proliferation and differentiation- once mature then leave through efferent vessels
64
What is an example of a DC?
Langerhans cells in epidermis
65
Describe what is meant by 'repertoire' in terms of lymphocytes?
The range of **genetically distinct** BCRs or TRCs present in a given host The larger the repertoire, the more threats can be recognised
66
Where in lymph nodes generally are the T cells found relative to B cells?
T cells - Towards inside (further from the marginal sinus) | B cells - Towards outside (closer to the marginal sinus)
67
What do the words afferent and efferent refer to respectively?
Afferent - the vessel the lymph enters into the lymph nodes via Efferent - the vessel the lymph leaves the lymph nodes via
68
What is it that makes the spleen so good at filtering antigens from the blood?
It is **highly attached** to the arterial circulation via the **splenic artery** So it can filter blood rapidly and in **large numbers**
69
What is it that makes the spleen so good at filtering antigens from the blood?
It is **highly attached** to the arterial circulation via the **splenic artery** So it can filter blood rapidly and in **large numbers**
70
How do specific T cells become activated by their specific antigen which is in a different part of the body?
Each naive T cell recirculates once every 24 hours They enter Lymph nodes with antigens (lymphatic vessels) Become activated by binding to antigens from lymphatic vessels Leave via efferent lymphatic vessel Travel from peripheral tissue and inflammation occurs The lymphatic vessels enter the lymph node via the afferent lymphatic vessels
71
What does lymph do?
Transports dietary lipids, drains interstitial fluid and facilitates immune responses
72
What are the 2 steps involved in extravasation of naïve T cells into lymph nodes?
Selectin binding Integrin binding
73
Define antigen presentation
The display of peptides in the major histocompatibility complex (MHC) I or II proteins such that the T cell receptor can attempt to bind them
74
How do dendritic cells transport antigens from site of inflammation to the secondary lymphocyte tissues?
Once dendritic cells uptake antigen They migrate out of the inflamed tissue Carry antigen towards the T cells and B cells
75
define non-self
anything recognised by the immune system as foreign
76
does the spleen have distinct T and B cell zones
Yes

IMMUNOLOGY AND INFECTION - POM (14 decks)

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