Cell Migration

Question 1

What are the three types of selectins?

Answer 1

E-selectin, P-selectin, L-selectin

Question 2

Where is E-selectin expressed and what is its function?

Answer 2

Expressed on activated endothelial cells; mediates rolling of leukocytes.

Question 3

Where is P-selectin found and what does it do?

Answer 3

Found on endothelial cells and platelets; initiates leukocyte rolling.

Question 4

What cells express L-selectin?

Answer 4

Naive T cells, B cells, and neutrophils.

Question 5

What is the role of L-selectin in lymphocyte trafficking?

Answer 5

Mediates homing to lymph nodes via high endothelial venules (HEVs).

Question 6

What do selectins bind to?

Answer 6

Selectins bind to specific carbohydrate ligands like sialyl Lewis X on leukocytes.

Question 7

What are chemokines?

Answer 7

Chemotactic cytokines that direct the migration of immune cells.

Question 8

What is chemotaxis?

Answer 8

The movement of leukocytes toward the source of chemokines follows the concentration gradient

Question 9

What are the major families of chemokines?

Answer 9

CC, CXC, C, and CX3C based on cysteine patterns.

Question 10

Which chemokines attract neutrophils?

Answer 10

CXC chemokines with ELR motifs, e.g., CXCL8 (IL-8).

Question 11

Which cells produce chemokines?

Answer 11

Leukocytes, endothelial cells, epithelial cells, fibroblasts.

Question 12

What induces chemokine production?

Answer 12

Microbial recognition and inflammatory cytokines like TNF, IL-1, and IL-17.

Question 13

What type of receptors are chemokine receptors?

Answer 13

G-protein-coupled receptors (GPCRs).

Question 14

What is the DRYLAIV motif?

Answer 14

A sequence in chemokine receptors essential for G protein signaling.

Question 15

What happens when chemokine receptors are activated?

Answer 15

Trigger actin polymerization and integrin activation for cell movement.

Question 16

Which chemokine receptors are HIV coreceptors?

Answer 16

CCR5 and CXCR4.

Question 17

What are atypical chemokine receptors (ACKRs)?

Answer 17

Receptors that regulate or scavenge chemokines without activating G-protein signaling.

Question 18

Where is ACKR1 found?

Answer 18

On erythrocytes and postcapillary venule endothelium.

Question 19

What are integrins?

Answer 19

Adhesion molecules on leukocytes that mediate firm adhesion.

Question 20

What triggers integrin activation?

Answer 20

Signals from chemokine receptors.

Question 21

What are examples of integrins?

Answer 21

LFA-1 (CD11a/CD18) and VLA-4 (α4β1).

Question 22

What do integrins bind to?

Answer 22

ICAM-1 and VCAM-1 on endothelial cells.

Question 23

What is the role of integrins in leukocyte trafficking?

Answer 23

Enable firm adhesion of leukocytes to endothelium before migration.

Question 24

Where are ICAM-1 and VCAM-1 found?

Answer 24

On activated endothelial cells.

Question 25

What is the function of ICAM-1?

Answer 25

Ligand for LFA-1 on leukocytes.

Question 26

What is the function of VCAM-1?

Answer 26

Ligand for VLA-4 on lymphocytes and monocytes.

Question 27

What are the four steps of leukocyte extravasation?

Answer 27

Rolling, activation, adhesion, and transmigration.

Question 28

Which molecules mediate rolling?

Answer 28

Selectins and their ligands.

Question 29

Which molecules are responsible for activation?

Answer 29

Chemokines and chemokine receptors.

Question 30

Which molecules are responsible for adhesion?

Answer 30

Integrins and their ligands.

Question 31

Where does transmigration occur?

Answer 31

Between endothelial cells into tissue, guided by chemokines.

Question 32

What is the first step of leukocyte recruitment?

Answer 32

Selectin-mediated rolling on endothelium

Question 33

Which selectins are involved in leukocyte rolling?

Answer 33

E-selectin and P-selectin

Question 34

What induces E-selectin expression on endothelial cells?

Answer 34

Cytokines TNF and IL-1

Question 35

What induces P-selectin expression on endothelial cells?

Answer 35

Histamine from mast cells and thrombin

Question 36

What is margination?

Answer 36

The process where leukocytes move to the periphery of blood flow near the endothelium

Question 37

Why do leukocytes roll along the endothelium?

Answer 37

Due to low-affinity interactions between selectins and their ligands

Question 38

What is the second step of leukocyte recruitment?

Answer 38

Chemokine-mediated activation of integrins

Question 39

What happens during chemokine-mediated activation?

Answer 39

Chemokines bind to leukocyte receptors, increasing integrin affinity

Question 40

What is the third step of leukocyte recruitment?

Answer 40

Stable integrin-mediated arrest on endothelium

Question 41

Which integrins are involved in firm adhesion?

Answer 41

LFA-1, MAC-1, and VLA-4

Question 42

What are the ligands for leukocyte integrins?

Answer 42

ICAM-1 for LFA-1 and MAC-1, VCAM-1 for VLA-4

Question 43

How do integrins achieve high-affinity binding?

Answer 43

Via conformational change triggered by chemokine signaling

Question 44

What is the fourth step of leukocyte recruitment?

Answer 44

Transmigration (diapedesis)

Question 45

What is paracellular transmigration?

Answer 45

Leukocytes move between endothelial cells

Question 46

What molecule facilitates transmigration?

Answer 46

CD31 (PECAM-1)

Question 47

What complex must be disrupted for transmigration to occur?

Answer 47

VE-cadherin adherens junction complex

Question 48

What does VE-cadherin do?

Answer 48

Maintains adherens junctions between endothelial cells

Question 49

What is the role of ICAM-1?

Answer 49

Ligand for LFA-1 and MAC-1 integrins on leukocytes

Question 50

What is the role of VCAM-1?

Answer 50

Ligand for VLA-4 integrin on leukocytes

Question 51

How does blood flow change during inflammation?

Answer 51

Blood vessels dilate and flow slows, promoting leukocyte margination

Question 52

What is the function of chemokines in leukocyte recruitment?

Answer 52

They activate leukocyte integrins for firm adhesion

Question 53

Where are selectins expressed?

Answer 53

On endothelial cells during inflammation

Question 54

Where are integrins expressed?

Answer 54

On leukocytes

Question 55

What is transcellular migration?

Answer 55

Rare process where leukocytes pass through endothelial cells