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PoM > Immuno - Lymphoid Tissue > Flashcards

Immuno - Lymphoid Tissue Flashcards

1
Q

What makes up the adaptive immune system?

A

T and B cells

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2
Q

How are T and B cells named?

A

Where they are produced:
Thymus
Bone marrow

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3
Q

What are the hallmarks of adaptive immunity?

A

Specificity and memory

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4
Q

What does specificity and memory of the adaptive immune system mean?

A

This means that cells can react abasing specific antigens to produce a more effective response.
We can also form memory cells so that we can act rapidly if we ever face the same exposure again.

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5
Q

How does the adaptive immune system exhibit specificity?

A

T and B cells express T cell or B cell receptors which are specific to only one antigen. Each cell will only have 1 TCR/BCR which makes them specific to that antigen.

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6
Q

Where can a TCR/BCR encounter a specific antigen?

A

Any location within the body

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7
Q

How do we solve the problem of having a limited number of TCRs/BCRs in the body for a specific antigen?

A

Generating a specialised network of vessels and structures, known as the lymphoid tissue

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8
Q

What are primary lymphoid tissues?

A

This is where T and B cells/ NK cells are produced (lymphopoiesis)

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9
Q

What are the three main primary lymphoid organs?

A

Thymus
Bone marrow
(Foetal liver)

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10
Q

How do B cells operate?

A

B cells bind to antigens and are then helped by T helper cells producing cytokines got produce antibodies against the specific antigen - antigen elimination

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11
Q

What are CD4 T cells?

A

These are helper T cells which bind to their specific antigen to produce cytokines that will activate B cells and cytotoxic T cells which can directly kill infected cells

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12
Q

What do CD8 cells do?

A

These are cytotoxic T cells which bind to the antigen and utilise cytokines secreted from CD4 helper cells in order to directly bind to and kill cells infected by a pathogen

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13
Q

How are lymphoid organs structured to facilitate killing of pathogens with respect to white cell production?

A

Lymphopoiesis increases during inflammation or infection

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14
Q

How are lymphoid organs structured to facilitate killing of pathogens with respect to bone marrow organisation?

A

Bone marrow is organised into yellow and ret bone marrow for fat and red blood cell production respectively. There is also an established B cell repertoire formed in the Bone marrow to generate a high degree of specificity.

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15
Q

How are lymphoid organs structured to facilitate killing of pathogens with respect to white cell maturation?

A

B cells will undergo final education in the spleen (peripheral tissues) therefore allowing much more exposure of the B cells to antigens.

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16
Q

How are lymphoid organs structured to facilitate killing of pathogens with respect to vasculature?

A

Thymocytes migrate from the bone marrow where they are derived from HSC and lymphoid progenitor, and will mature in the thymus which is on top of the heart in the thoracic cavity. This is highly vascularised to allow the movement and exposure of the TCR repertoire

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17
Q

How do T cells undergo selection?

A

They undergo both positive and then negative selection

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18
Q

What occurs in positive selection?

A

Immature thymocyte will need to recognise the MHC on surrounding cells using its TCR. If unable to do so, it may not be functional therefore undergoes apoptosis

19
Q

What occurs in negative selection?

A

We need to check the affinity of the TCR to MHC antigens. If the affinity is too high, the TCR may bind to self antigens causing auto-immunity. Therefore these undergo apoptosis.

20
Q

What happens if a T cell has self antigen TCR?

A

Undergoes apoptosis

21
Q

What is one of the hypotheses for deterioration in infection prevention as we age?

A

Thymus deteriorates as we get older therefore the rate of T cell maturation decreases and we are less able to combat specific antigens

22
Q

How many T cells do we roughly have in our blood?

A

We produce 1500/µL of blood and we have about 5L of blood circulating in our body.

23
Q

What is the role of secondary lymphoid tissue?

A

Facilitates the movement of mature lymphocytes or antigens so that they can be exposed to each other. It also helps in the exposure of antigens to stimulate maturation of lymphocytes.

24
Q

What are the main secondary lymphoid tissues?

A

Spleen
Lymph nodes
Appendix
Mucosal associated lymphoid tissue

25
Q

What can secondary lymphoid tissue be in the from of?

A

Discrete organs which are encapsulated tissues e.g. lymph nodes
Or they can be regions within an organ e.g. in the spleen.

26
Q

How is the secondary lymphoid tissue system organised?

A

Highly organised to bring lymphocytes in close proximity to antigens, and is connected via the lymphatic system.

27
Q

Where are lymph nodes found?

A

All over the body

28
Q

Describe the organisation of the lymph nodes.

A

Highly organised with a constant afferent lymphatic vessel flow into and around the T/B cells areas (lymphoid follicles), with efficient efferent flow too.

29
Q

Describe the organisation of the spleen.

A

Discrete location of T and B cells with both afferent/efferent lymph connection but also an arterial/venous connection, unlike other 2LO.
There may be a discrete location - but the spleen itself is not a discrete tissue.

30
Q

What are epithelial barriers?

A

These are typically the first line defect (innate immunity) against infection through the formation of a physical barrier.

31
Q

How are epithelial barriers designed to be secondary lymphoid tissue?

A

They are connected to the extensive lymphatic network which helps drain antigens away fro the site of damage/inflammation and thus help prime local lymphoid responses

32
Q

What is gut associated lymphoid tissue?

A

Specialised lymphoid tissue found within the gut, such as Peyer’s patches

33
Q

Where are Peyer’s patches found?

A

These are found below the epithelium of the ileum in the small intestine.

34
Q

Describe the organisation of Peyer’s patches.

A

They are highly organised in terms of B and T cell follicles and form germinal centres to help with the priming of lymphocytes

35
Q

How do germinal centres form in gut associated lymphoid tissue?

A

The tissue contains a high frequency of highly activate B cells which co localise to form germline centres.

36
Q

What is the role of germinal centres?

A

Here B cells can undergo mutations thus allowing for the selection of the BCR for high affinity antibodies.

37
Q

What stimulates germinal centres to be formed?

A

Antigen rich environments

38
Q

Why do we want germinal centres in our gut?

A

Because we experienced high level of antigens in the gut from microbial products, microbiota and ingested food.

39
Q

What is the Waldeyer ring?

A

The ring of the tonsils in the nasal/oral cavity:

  • Pharyngeal
  • Tubular
  • Palatine
  • Lingual
40
Q

Why is there a high frequency of of lymphoid follies with germinal centres in the tonsils when we are younger?

A

The food we eat, the air we breathe in provide good opportunity for early maturation of the immune system through vast exposure

41
Q

Why do afferent lymphatic vessels travel all over the body?

A

Provides good opportunity for exposure to TCRs/BCRs by the antigens.

42
Q

What is the role of naive T cells?

A

Naive T cells have not encountered an antigen therefore are not specific. They circulate around the body so that if they encounter antigen they can either be retained or differentiated to help increase the number of helper T cells specific to that antigen.

43
Q

How do we transfer antigens from the site of inflammation to the secondary lymphoid tissue?

A
  1. Professional antigen presenting cells in peripheral tissue such as dendritic cells will present the antigen and migrate to the lymphatic system.
  2. Straight flow of molecules also occurs however this requires much more antigens which are then trafficked by the lymph

PoM (27 decks)

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