Lymphoid Tissues Flashcards

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

What are the two primary lymphatic organs?

A

The bone marrow and thymus

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3
Q

What cells are of the lymphoid lineage?

A

T cells, B cells and NK cells

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4
Q

Which part of the bone marrow does haematopoiesis occur on?

A

The red part

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5
Q

Which cells mature in the thymus?

A

T cells

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6
Q

What is meant by thymic involution?

A

shrinking of the thymus with age, resulting in a much reduces new T cell output

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7
Q

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

A

Positive and negative selection

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8
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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9
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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10
Q

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

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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11
Q

How does the thymus change with age?

A

Degenerates

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12
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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13
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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14
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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15
Q

What happens to the thymus during infection?

A

No change

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16
Q

What happens to the bone marrow during infection?

A

Bone marrow increased white cell production

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17
Q

What are secondary lymphoid tissues?

A

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

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18
Q

What are some secondary lymphoid tissues?

A

Spleen, peyers patches, gut, lymph nodes,tonsils

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19
Q

What are lymph nodes?

A

Highly organized, encapsulated structures which are located at points of convergence of lymphatic vessels

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20
Q

What are germinal centers?

A

Anatomically restricted site where B cells undergo maturation and selection to generate high affinity antibodies

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21
Q

Through what vessel does lymph enter into the lymph nodes?

A

The afferent lymphatic vessel

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22
Q

What are the functions of the spleen?

A
  1. Store of platelets
  2. Reacts with blood borne antigen
  3. Removes defective RBCs from circulation
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23
Q

Why is the lymph nodes a discrete tissue?

A

It has no other function other than to act as a site where lymphocytes and antigen can interact

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24
Q

What form the first line is defense against infection?

A

Epithelial barriers

25
Q

What is the significance of the location of lymphoid tissues?

A

They are spread around the body so that the lymphatic sin every part of the body can reach, allowing lymphocyte and antigen interactions

26
Q

Where are Peyer’s Patches Found?

A

Below the epithelium of the ilium of the small intestine

27
Q

Where are many germinal centers located?

A

The gut

28
Q

Why is there a lot of germinal centers in the gut?

A

There are high levels of antigen coming from gut microbial, which are producing many foreign antigens which leads to high antibody production

29
Q

What happens in the red pulp of the spleen?

A

Red blood cells are destroyed

30
Q

What is a Periarteriolar lymphoid sheath?

A

An area of white pulp which surrounds the arteries running through the spleen - is highly populated with T cells

31
Q

What is MALT?

A

Mucosa-associated lymphoid tissues

32
Q

What forms the Waldeyer ring?

A

The pharyngeal, tubular, palatine and lingual tonsils

33
Q

Why is the waldeyer ring an ideal environment for the immune system to encounter antigen? d

A

Food, bacteria and things we breath in pass the oral pharyngeal section very often, therefore more antigen

34
Q

Why do lymph nodes swell during an infection?

A

The B cell follicles of the lymph nodes expand as the B cells proliferate to form germinal centers, amd the entire lymph node enlarges

35
Q

Where do naive Lymphocytes go after they are produced?

A

They enter into the blood stream and migrate to the peripheral lymphoid tissues

36
Q

How long does it take for a T cell to recirculate?

A

24 hours

37
Q

How to lymphocytes get inside the lymph nodes?

A

They enter via high endothelial venules

38
Q

Where are high endothelial venules found? d

A

In T cell zones of the lymph nodes

39
Q

Which organ is mainly associated with filtering antigen out of blood?

A

Spleen

40
Q

What are the four steps of T cells getting inside the lymph nodes?

A
  1. Rolling
  2. Activation
  3. Adhesion
  4. Transendothelial migration
41
Q

What molecule on T cells results in the rolling of the T cell before it enters the T cell zone of the lymph nodes? d

A

L Selectin on T cell

42
Q

What molecules binds to L selectin? d

A

CD34

43
Q

What does ICAM allow?

A

The migration of the lymphocytes through the blood vessel wall

44
Q

What are dendritic cells?

A

Potent, antigen presenting cells that pick up and bring antigen from sites if infection to secondary lymphoid organs

45
Q

How to dendritic cells help with the adaptive immune response?

A

They pick up antigens and present them to T cells, in order to activate the T cells

46
Q

How do dendritic cells display the antigens?

A

Through MCHII molecules

47
Q

Describe the transport of lymphocytes and antigens in the lymphatics and blood stream

A

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

48
Q

What is an example of a DC?

A

Langerhans cells in epidermis

49
Q

Describe what is meant by ‘repertoire’ in terms of lymphocytes?

A

The range of genetically distinct BCRs or TRCs present in a given host

The larger the repertoire, the more threats can be recognised

50
Q

Where in lymph nodes generally are the T cells found relative to B cells? d

A

T cells - Towards inside (further from the marginal sinus)
B cells - Towards outside (closer to the marginal sinus)

51
Q

What do the words afferent and efferent refer to respectively?

A

Afferent - the vessel the lymph enters into the lymph nodes via
Efferent - the vessel the lymph leaves the lymph nodes via

52
Q

What is it that makes the spleen so good at filtering antigens from the blood? d

A

It is highly attached to the arterial circulation via the splenic artery

So it can filter blood rapidly and in large numbers

53
Q

What is it that makes the spleen so good at filtering antigens from the blood? d

A

It is highly attached to the arterial circulation via the splenic artery

So it can filter blood rapidly and in large numbers

54
Q

How do specific T cells become activated by their specific antigen which is in a different part of the body?

A

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

55
Q

What does lymph do? d

A

Transports dietary lipids, drains interstitial fluid and facilitates immune responses

56
Q

What are the 2 steps involved in extravasation of naïve T cells into lymph nodes? d

A

Selectin binding

Integrin binding

57
Q

Define antigen presentation

A

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

58
Q

How do dendritic cells transport antigens from site of inflammation to the secondary lymphocyte tissues?

A

Once dendritic cells uptake antigen

They migrate out of the inflamed tissue

Carry antigen towards the T cells and B cells