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IMMUNO > Lymphoid Tissues > Flashcards

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

How is lymph forms?

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

What cells are of the lymphoid lineage?

A

T cells, B cells and NK cells

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5
Q

Which part of the bone marrow does haematopoiesis occur on?

A

The red part

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6
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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7
Q

Which cells mature in the thymus?

A

T cells

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8
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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9
Q

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

A

Positive and negative selection

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10
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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11
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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12
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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13
Q

How does the thymus change with age?

A

Degenerates

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14
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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15
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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16
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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17
Q

What happens to the thymus during infection?

A

No change

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18
Q

What happens to the bone marrow during infection?

A

Bien marrow increased white cell production

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19
Q

What are secondary lymphoid tissues?

A

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

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20
Q

What are some secondary lymphoid tissues?

A

Spleen, peyers patches, gut, lymph nodes,tonsils

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21
Q

What are lymph nodes?

A

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

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22
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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23
Q

Through what vessel does lymph enter into the lymph nodes?

A

The afferent lymphatic vessel

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24
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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25
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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26
Q

What form the first line is defense against infection?

A

Epithelial barriers

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27
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

28
Q

Where are Peyer’s Patches Found?

A

Below the epithelium of the ilium of the small intestine

29
Q

Where are many germinal centers located?

A

The gut

30
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

31
Q

What happens in the red pulp of the spleen?

A

Red blood cells are destroyed

32
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

33
Q

What is MALT?

A

Mucosa-associated lymphoid tissues

34
Q

Which special cells do gut associated lymphoid tissues contain?

A

M cells (membrane-like) or FAE (Follicle associated Epithelial) cells

35
Q

What do FAE cells do?

A
  • 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
36
Q

What do the IgA antibodies made in the gut do?

A

They prevent microorganisms in the gut from sticking to the gut epithelium, and can also neutralize toxins and viruses

37
Q

What forms the Waldeyer ring?

A

The pharyngeal, tubular, palatine and lingual tonsils

38
Q

What are the tonsils made of?

A

Epithelial cells that are able to phagocytosis bacteria and transfer the antigenic peptides to macrophages that act as APCs

39
Q

Where are the antigen sampled from in the tonsils?

A

Directly from the external environment

40
Q

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

A

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

41
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

42
Q

Where do naive Lymphocytes go after they are produced?

A

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

43
Q

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

A

24 hours

44
Q

How to lymphocytes get inside the lymph nodes?

A

They enter via high endothelial venules

45
Q

Where are high endothelial venules found?

A

In T cell zones of the lymph nodes

46
Q

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

A

Spleen

47
Q

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

A
  1. Rolling
  2. Activation
  3. Adhesion
  4. Transendothelial migration
48
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?

A

L Selectin on T cell

49
Q

What molecules binds to L selectin?

A

CD34

50
Q

What chemokines are involved in activating LFA-1

A

Recognition of CCL21 on endothelial surface of HEV by CCR7 on T cells

51
Q

What happens when LFA1 is activated?

A

The affinity for ICAM-1 AND ICAM-2 is increased

52
Q

What does ICAM allow?

A

The migration of the lymphocytes through the blood vessel wall

53
Q

What are dendritic cells?

A

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

54
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

55
Q

How do dendritic cells display the antigens?

A

Through MCHII molecules

56
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

57
Q

What is an example of a DC?

A

Langerhans cells in epidermis

58
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

59
Q

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

A

T cells - Towards inside (further from the marginal sinus)

B cells - Towards outside (closer to the marginal sinus)

60
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

61
Q

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

A

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

So it can filter blood rapidly and in large numbers

62
Q

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

A

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

So it can filter blood rapidly and in large numbers

63
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

64
Q

What does lymph do?

A

Transports dietary lipids, drains interstitial fluid and facilitates immune responses

65
Q

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

A

Selectin binding

Integrin binding

66
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

67
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

IMMUNO (14 decks)

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