Lecture 15

Question 1

What is leukocyte homing?

Answer 1

Leukocyte moves out of the blood and into a tissue or site of infection

Question 2

What is lymphocyte recirculation?

Answer 2

When lymphocytes cycle through blood, lymph nodes (stay for a bit), exit via lymphatic system, then back to blood

Question 3

How do lymphocytes enter and exit the spleen?

Answer 3

Blood vessel, blood vessel

Question 4

How do lymphocytes enter and exit the lymph node?

Answer 4

Enter: HEV OR afferent lymph vessel
Exit: efferent lymph vessel

Question 5

How do lymphocytes enter and exit PP’s and ILF’s?

Answer 5

Enter: HEV
Exit: efferent lymph vessel

Question 6

What do lymphocytes need to be able to home in the lymph node, PP or ILF?

Answer 6

• leukocytes express chemokine receptors and adhesion molecules
• HEVs express chemokines and adhesion molecules, integrins and stable arrest
  (SECRET HANDSHAKE)

Question 7

What are selectins? How do they get the T/B cell into the lymph node/PP/ILF?

Answer 7

• A CAM (adhesion molecules) that bind to the carbohydrates of glycoproteins (make the T cell stick to the HEV!)
• theyre now sticky— and roll along the HEV wall by sticking to a bunch of selectins

Question 8

What is an integrin? What is cool about them?

Answer 8

A protein that binds to ligand, they can go from inactive to active (flopped over to standing up straight)

Question 9

What is inside out and outside in signalling in integrins?

Answer 9

Inside out: activates ligand-binding mode (basically the stuff inside the cell like talin and kindling binds to the inside part of the protein, then the pp part can bind to stuff)
Outside in: ligand binding (OUTSIDE causes cellular responses (IN) (like proliferation for example)

Question 10

What are Selectins? What do they bind to?

Answer 10

Proteins that bind to [fucosylated carbs] sialylated Lewisx and mucins

Question 11

What is stable arrest?

Answer 11

LFA-1 binds to |CAM-1, gets stuck to the HEV, (then needs to get “told which direction to move”

Question 12

What is diapedesis/extravasation?

Answer 12

Lymphocytes squeeze between the endothelial cells of the HEV and into the lymph node

Question 13

Why are DCs recruited to the T cell zone of the lymph node?

Answer 13

DCs express CCR7

Question 14

How do DCs enter the lymph nodes? Other lymphatic vessels?

Answer 14

Afferent lymphatic vessel, blood

Question 15

What receptor does CCL19 and CCL21 bind to?

Answer 15

CCR7 (on the T cels)

Question 16

How long does a T cell spend crawling through the FRC looking for antigen presenting DCs?

Answer 16

about 24 hours

Question 17

What chemokine mediates the migration of B cells into the follicle? What receptor does the B cell have to bind to the chemokine?

Answer 17

CXCL13, CXCL51

Question 18

What are the three motivating factors for the B cell to go from the paracortex into the follicle

Answer 18

1. needs more BAFF signalling
2. Only the FO DC can present antigen to the B cell
3. The B cell needs to provide the follicular dendritic cell with a survival signal

Question 19

Are there HEVs in the spleen?

Answer 19

no

Question 20

How do T/B cells move through the spleen (start at the blood vessel and move from there)

Answer 20

T/B cells enter the red pulp, then white pulp
- B cell moves into the follicle and this is mediated by CXCL13 (produced by FO DCs)