Theme 2b Immune Cell Migration

Question 1

Define Cytokines and what are 3 ways they effect cells?

Answer 1

• Proteins that mediate the effector functions of the immune system.
• Endocrine action: released into blood to affect distant cells
• Paracrine action: released to affect nearby cells
• Autocrine action: released to bind to receptors belonging to the cell that produced the cytokine.

Question 2

List the five modes of cytokine action

Answer 2

• Synergy: When the effects of two cytokines combine to produce an effect greater than their individual sums
• Redundant: When multiple cytokines are released to activate the same target.
• Cascade: When cytokines are released to target a cell for the purpose of creating more cytokines.
• Pleiotropic: one cytokine having different targets depending on where they are released.
• Antagonistic effect: One cytokine inhibits another cytokine’s effect.

Question 3

Define Chemokines

Answer 3

a type of cytokine that directs WBC migration

Question 4

What are tertiary lymphoid organs?

Answer 4

collections of lymphocytes forming temporary structures at sites of chronic inflammation which resemble secondary lymphoid structures.

Question 5

how many times a day do lymphoid B and T cell circulate in the body?

Answer 5

1-2 times/day which increases their chances of finding an antigen as DCs present to T cells continuously (>5,000 T cells /hr)

Question 6

Extravasation
Where?
How?

Answer 6

B and T cells extravasate at high-endothelial venules (HEVs) which are specialized venous swellings in the secondary lymph organs.
high-endothelial venules express the E/L-selectin is a cell adhesion molecule expressed on naive B/T cells which will bind to E/L-selectin ligands on high endothelial venules which stops them and then allows other cell adhesion molecules to squeeze cells through the endothelial junctions.

Question 7

What are the initial steps of extravasation?

Answer 7

• Leukocyte mucin interacts with E-selectin mediate rolling
• chemokines/ chemoattractants induce change in integrins
• leukocyte integrins adhere firmly to ICAMs

Question 8

How do effector and memory T cells know travel to multiple organs and sites of infection?

Answer 8

They follow chemokine cues which are generated by innate immune responses at those areas.

Question 9

Compare Effector and Memory T cells

Answer 9

• Memory T cells are long lived and metabolically quite.
• Effector cells are short lived, usually dying out after the pathogen is cleared.