Immune Cells and Organs

Question 1

What is a primary lymphoid organ?

Answer 1

Organ where lymphocytes are produced by lymphopoiesis.

Question 2

What are the primary lymphoid organs?

Answer 2

Thymus and bone marrow

Question 3

What is a secondary lymphoid organ?

Answer 3

Where lymphocytes interact with antigens and each other

Question 4

Name 3 secondary lymphoid organs

Answer 4

Her Majesty the Spleen

…Lymph nodes
Mucosal associated lymphoid tissues (MALT)

Question 5

Describe the structure of the thymus

Answer 5

2 Lobes divided into lobules by septums

Question 6

What is the thymus packed with?

Answer 6

Maturing/proliferating T-lymphocytes

Question 7

What is the change in the thymus during infection?

Answer 7

No obvious changes

Question 8

How does thymic output change with age?

Answer 8

Output of NEW T cells decreases

Question 9

What is the change in the bone marrow during infection?

Answer 9

Increased white cell production

Visible change

Question 10

What are the sites of haematopoiesis in a foetus?

Answer 10

All bones, liver and spleeeeen

Question 11

What are the sites of Haematopoiesis in an adult?

Answer 11

Flat and large bones (No liver and spleen)

Question 12

What is the primary function of Lymph nodes?

Answer 12

To filter antigens present in the lymph

Question 13

How does lymph enter and leave a lymph node?

Answer 13

Through the afferent (many) leaves through the efferent (one)

Question 14

What are the cells present on the outside of a lymph node?

Answer 14

B cells in follicles

Question 15

What happens to the B cells in the nodes when an immune response is in progress?

Answer 15

They proliferate and produce antibodies in the germinal centres of the node

Question 16

Where are the T cells in a lymph node?

Answer 16

Further in from B cells, closer to the medullary sinus.

They tend to be closer to the sinuses than b cells

Question 17

What changes are seen in lymph nodes during an immune response?

Answer 17

Enlargement

Question 18

What other cells are present in the lymph nodes, and what do they do?

Answer 18

Macrophages engulf passing through pathogens

Question 19

What is a high endothelial venule?

Answer 19

Specialised area of artery with thick endothelium that causes T/B cells to leave circulation and enter lymph node.

Question 20

Does the spleen have High endothelial venules (HEVs)?

Answer 20

Nope, just lymph nodes

Question 21

What is the purpose of Her majesty the Spleen?

Answer 21

To filter antigens present in blood

Question 22

What is the spleen comprised of?

Answer 22

Red pulp: Erythrocytes present

White pulp: Lymphocytes present

Question 23

What are the 3 parts of the white pulp of the spleen, and which cells do they contain?

Answer 23

Primary follicles: B-cells
Periarterial Lymphatic Sheath (PALS): Surrounds arteries contains T-cells.
Marginal zone: Between white pulp and red

Question 24

Describe the immune system in the villi of the Gut

Answer 24

Interepithelial cells present on villi. Contains lymphatic drainage to mesenteric lymph nodes.

Question 25

What is beneath the specialised mucosal epithelium in the gut?

Answer 25

Payer's Patches - Contain large aggregates of lymphocytes/follicles which drain to mesenteric lymph nodes

Question 26

What is the function of the specialised mucosal epithelium in the gut?

Answer 26

Contains microfold cells which sample antigens in the gut to pass to the payer's patch to allow for surveillance.

Question 27

Describe the immune system in the skin

Answer 27

``` Cutaneous immune system contains intraepidermal lymphocytes that drain through epidermal lymph vessels. Epidermal langerhans (dendritic cells) capture and present antigens and migrate to lymph nodes ```

Question 28

Describe the recirculation of lymphocytes

Answer 28

Naïve lymphocytes produced in primary tissues, enter blood and circulate between blood and secondary tissues until reaction or death

Question 29

What is Extravasation of T cells?

Answer 29

The migration of naïve T-cells from blood into lymph vessels

Question 30

Describe the process of Extravasation of T-cells

Answer 30

1. Naïve T cells roll along the endothelium until they reach the HEV. 2. Selectin on the T cell binds to endothelial CD34 (weakly) 3. Chemokines on the HEV bind to receptors on T cell, causing T-cell's integrin to become high affinity binding form. 4. Intergrin binds to Intracellular adhesion molecule (ICAM) immobilising the T cell, so it can move into the tissue.

Question 31

What are clusters of differentiation?

Answer 31

Internationally recognised systematic nomenclature for cell surface markers that differentiate between haematopoietic cells

Question 32

What are lymphocytes?

Answer 32

Small cells, w/ agranular cytoplasm and large nucleus.

Question 33

Which cells are antigen presenting cells?

Answer 33

B-cells Dendrite cells Activated macrophages