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POM Flashcards (Y1) > Lymphoid Tissues > Flashcards

Lymphoid Tissues Flashcards

1
Q

What is meant by a primary lymphoid organ?

A

Organs where lymphocytes are produced - Lymphopoieses

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2
Q

List 3 primary lymphoid organs

A

Thymus
Bone marrow
Foetal liver

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3
Q

What is the adaptive immune system compromised of?

A 
T cells (CD4, CD8, T regulatory cells)
B cells (B lymphocytes and plasma cells)
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4
Q

What are the hallmarks of adaptive immunity?

A

Specificity

Memory

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5
Q

What do BCR and TCR stand for respectively?

A

B cell receptors

T cell receptors

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6
Q

What do CD4 (T-helper cells) do?

A

Produce lots of cytokines which guide B cells and other T cell responses

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7
Q

What do CD8 (cytotoxic T cells) do?

A

Actively kill foreign antigen expressing cells

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8
Q

What is the primary site of haematopoiesis?

A

Bone marrow

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9
Q

What are the roles of the red and yellow bone marrows respectively?

A

Red - Produces blood cells

Yellow - Fat stores

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10
Q

What are immature T cells known as?

A

Thymocytes

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11
Q

Where do immature T cells migrate from the bone marrow to?

A

Thymus

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12
Q

Where do B cells migrate to in the immature stage for differentiation?

A

Spleen

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13
Q

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

A

The range of genetically different BCRs or TCRs in a given host.
The larger the repertoire, the more threats can be recognised.

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14
Q

What is thymic involution?

A

The shrinkage of the thymus with age → associated with a change in structure and a reduced mass

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15
Q

Where is the thymus?

A

On top of heart, above lungs in the thoracic cavity

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16
Q

What are the 3 steps in the stepwise differentiation of T cells?

A

Positive selection - can the T cell receptor signal? (Does it see the MHC receptors on the surrounding cells?)
Negative selection - does it react against our own body (if does react against self-antigens then it undergoes selective apoptosis)
Final selection and exit

17
Q

What is meant by a secondary lymphoid organ?

A

Where lymphocytes can interact with antigens and other lymphocytes to guide their activation and differentiation

18
Q

List some secondary lymphoid organs

A

Spleen
Lymph nodes
Appendix
Mucosal associated lymphoid tissue

19
Q

How are lymphoid tissues connected?

A

Via the lymphatic system and the blood

20
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 marginal sinus)

21
Q

What do the words afferent and efferent refer to respectively?

A

Afferent - Into (lymphatic vessels)

Efferent - Out of (lymphatic vessels)

22
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

23
Q

How is the spleen different to other secondary lymphoid organs?

A

Not a discrete tissue contains lymphoid compartment (white pulp) that is located within red pulp of spleen

24
Q

What are Peyer’s patches and where are they found?

A 
Specialised secondary lymphoid tissues
Found below epithelium of the ileum of the small intestine
Specialised Microfold (M) cells sample antigen directly from lumen and deliver it to antigen presenting cells
25
Q

Define a germinal centre

A

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

26
Q

Describe how lymphatic drainage occurs at gut associated lymphoid tissue

A

Intraepithelial lymphocytes enter villi
These are drained to mesenteric lymph node
The afferent lymphatic vessels at Peyer’s patches pick these up
The follicle is highly enriched with B cells and contains a high frequency of germinal centres

27
Q

Why is the intestine so enriched for these germinal centres?

A

High amount of antigen being provided in the form of microbial products from the microbiota of the intestinal wall tract

28
Q

What is the Waldeyer ring and what is it comprised of?

A

Immune tissue specialised in antigen encounter
Pharyngeal, tubular, palatine and lingual tonsils encircle the oral and nasal cavity - form the Waldeyer ring
Contains its own squamous epithelium and lymphoid follicles containing large germinal centers

29
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 via lymphatics vessels
Become activated by binding to antigens encountered in SLO
Either retained and differentiated in SLO or
Leave via efferent lymphatic vessel
Travel from SLO to site of inflammation in periphery (inflammatory signals)

30
Q

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

A

Selectin binding
Integrin binding

CCR7 and CCL21 (chemokine) interaction

31
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.

32
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 via lymphatics

33
Q

How else can the antigens be transported to the secondary lymphatic tissues?

A

Eventually, if in large enough numbers the antigens will flow into the lymphatics, as the fluid is drained from the tissues, to be trafficked through to the secondary lymphoid tissues.

34
Q

Where are lymphoid tissues particularly found?

A

At barrier surfaces, such as the lungs, gastrointestinal tract and the skin.

35
Q

What structures provide lymph nodes with physical protection?

A

Tough outer capsule

Surrounded by specialised fatty deposits

36
Q

What allows easy flow of lymphocytes in and out of lymph nodes?

A

Good lymphatic and blood vessel supply

37
Q

What is contained in the cortex and paracortex of a lymph node?

A

Cortex - B cells

Paracortex - T cells and dendritic cells, also contains high endothelial venues

38
Q

How do lymphatic vessels enter lymph nodes?

A

Enter at the outer edge between capsule and cortex

Penetrate deep within the nodes via conduits

39
Q

What is meant by Cluster of Differentiation (CD)?

A

Internally recognised standard for the systematic naming of proteins used in the phenotyping of hematopoietic cells.

POM Flashcards (Y1) (28 decks)

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