11 Lymphoid tissues

Question 1

Where are lymphocytes produced?

Answer 1

Primary lymphoid organs

Question 2

What is lymphopoieses?

Answer 2

Production of lymphocytes

Question 3

Name 3 primary lymphoid organs

Answer 3

• Thymus
• Bone marrow
• Foetal liver

Question 4

Name 3 lymphocytes

Answer 4

• B cells
• T cells
• NK cells

Question 5

The adaptive immune response is comprised of

Answer 5

B cells and T cells

Question 6

Two characteristics of the adaptive immune response

Answer 6

• Specificity: vast range of unique T cell and B cell receptors
• Memory: rapid expansion in response to secondary encounter

Question 7

What is the primary site of haematopoiesis?

Answer 7

Bone marrow (non foetal)

Question 8

Where is the B cell ‘repertoire’ generated?

Answer 8

Bone marrow

Question 9

Where does final maturation occur?

Answer 9

Periphery (e.g. spleen)

Question 10

Define repertoire

Answer 10

The range of genetically distinct BCRs or TCRs present in a given host (larger repertoire = more threats recognised)

Question 11

What is positive selection of T cells?

Answer 11

• Can the T cell receptor signal

- Can the T cell receptor receive signals

Question 12

What is negative selection of T cells?

Answer 12

-Does the cell react against our own body

Question 13

Immature T cells enter the thymus from the bone marrow as

Answer 13

double negative T cells

Question 14

Process of selection

Answer 14

• Enter as double negative
• Positive selection (double positive)
• Negative selection (single positive) or apoptosis

Question 15

As age increases, thymus function?

Answer 15

Decreases

- Gets smaller, T cell production decreases

Question 16

Where do lymphocytes interact with antigens and other lymphocytes?

Answer 16

Secondary lymphoid organs

Question 17

Name 5 secondary lymphoid organs

Answer 17

• Spleen
• Mucosal associated
• Appendix
• Lymph nodes
• Lymphoid tissue

Question 18

Where are lymphoid tissues found?

Answer 18

• Distributed around the body

- Interconnected via lymphatic system + blood

Question 19

Examples of discrete organs?

Answer 19

• Lymph nodes

- Adenoids

Question 20

Examples of distinct regions?

Answer 20

• Within a tissue

- Spleen

Question 21

Afferent lymphatic vessels

Answer 21

Flowing into the lymph nodes

Question 22

Efferent lymphatic vesseks

Answer 22

Flowing out of the lymph nodes

Question 23

Key signals in lymphoid tissue

Answer 23

• Fibroreticular cells (CCL19, CCL21, IL-7)

- Follicular dendritic cells (CXCL13, BAFF, immune complexes)

Question 24

B cells are compartmentalised in

Answer 24

B cell follicles

Question 25

What is the first line of defence against infection?

Answer 25

Epithelial barriers - Physical barrier - Extensive lymphatic network

Question 26

What are Peyer's patches?

Answer 26

- Specialised secondary lymphoid tisses | - Found below the epithelium of the ileum of the small intestine

Question 27

What is thymic involution?

Answer 27

Shrinking of thymus with age (associated with change in structure and reduced mass)

Question 28

What is a germinal centre?

Answer 28

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

Question 29

What is Waldeyer's ring?

Answer 29

Ring of lymphoid tissues surrounding oral and nasal cavity (pharynx)

Question 30

2 to 3 litres of lymph returned to blood each day (via superior vena cava)

Answer 30

The lymph is a rapid flow fluid draining lots of tissue of antigens

Question 31

The lymph nodes

Answer 31

- Site to which lymphatic fluid is drained | - Source of antigens

Question 32

Each naïve T cell recirculates once every

Answer 32

24 hours

Question 33

Why do T cells have to return to the secondary lymphoid tissues

Answer 33

To receive its survival signal, otherwise if the cell was stuck somewhere, it would die

Question 34

What happens when a blood vessel is running parallel to lymphatic vessels or high endothelial venules?

Answer 34

T cells migrate across blood vessels to high endothelial venules and then into the lymph node

Question 35

What happens if a T cell encounters a dendritic cell presenting an antigen?

Answer 35

Activation --> Antigen recognition

Question 36

Extravasation of T cells into lymph nodes

Answer 36

Similar to neutrophil extravasation | Entering endothelium

Question 37

What does the protein L selectin (CD62L) allow?

Answer 37

Engagement with CD34 on endothelial cells of the high endothelial venule

Question 38

Engagement with CD34 allows?

Answer 38

Initial binding and rolling along the endothelium

Question 39

What does LFA-1 do?

Answer 39

Binds ICAM on the lymphocyte endothelial vessels allowing them to migrate across the endothelium

Question 40

What happens to ICAM during inflammation?

Answer 40

It is upregulated to encourage T cells to migrate into those lymph nodes

Question 41

What is antigen presentation?

Answer 41

Display of peptides in the MHC I or II proteins such that the T cell receptor can attempt to bind them

Question 42

Role of dendritic cells

Answer 42

- Professional APCs - Range of migratory and tissue resident variety - Migrate out of the site of inflammation

Question 43

Dendritic cell migration

Answer 43

- Via afferent lymph into lymph nodes | - To interact with T cells

Question 44

What does CD stand for?

Answer 44

Cluster of differentiation

Question 45

What CD do T cells uniquely express?

Answer 45

CD3

Question 46

What CD do B cells uniquely express?

Answer 46

CD19