Cytokines

Question 1

What are interleukines? (IL)

Answer 1

cytokines that are produced by leukocytes and act on leukocytes

Question 2

What are chemokines? What do they do?

Answer 2

another group of molecules important in communication of leukocytes

• recruit and activate leukocytes
• regulation of leukocyte migration during homeostasis and inflammation
• selectively regulate adhesion process, chemotaxis, and activation of various populations and subpopulations of leukocytes

Question 3

What is Chemotaxis?

Answer 3

a phenomenon in which cells move from an area of low chemical signal to an area of high chemical signal

Question 4

What are the properties of cytokines?

Answer 4

• bind to their receptors on target cells thus initiate activating or suppressive signals
• have high affinity for their receptors. Low concentrations are enough to initiate cytokine signalling

Question 5

What is autocrine signalling?

Answer 5

a substance produced by a cell binds to a receptor located on the same cell that produced it and activates the cell.

Question 6

What is paracrine signalling?

Answer 6

a substance binds to a receptor found on a cell in the proximity of the producer cell

Question 7

What is endocrine signalling?

Answer 7

a substance binds to a receptor found on a cell located in a distant part of the body.

Question 8

Cytokines are able to perform what kinds of signalling?

Answer 8

• autocrine
• paracrine
• endocrine

Question 9

What actions do cytokines have?

Answer 9

• pleiotropic action
• redundancy
• synergistic action
• antagonistic action
• cascade action

Question 10

What is pleiotropic action of cytokines?

Answer 10

a given cytokine has different biological effects on different target cells

Question 11

What is the redundancy of cytokines?

Answer 11

two or more cytokines exert the same biological effect on the same cells

Question 12

What is the synergistic action of cytokines?

Answer 12

the effect of two cytokines on a particular cell is greater than the additive effect of individual cytokines

Question 13

What is the antagonistic action of cytokines?

Answer 13

action of one cytokine inhibits the effect of another cytokine

Question 14

What is the Cascade action of cytokines?

Answer 14

action of a cytokine leads to induction of one or more cytokines which in turn induce production of other cytokines

Question 15

Cytokines act in an antigen-nonspecific manner. What does this mean?

Answer 15

cytokines will bind to any cell that expresses a cytokine receptor

Question 16

What are the biological functions of cytokines?

Answer 16

• development of cellular and humoral immunity
• induction of inflammatory responses
• regulation of intensity and duration of immune response
• regulation of hematopoeisis
• regulation of proliferation and differentiation of cells
• wound healing

Question 17

What cytokines are involved in innate immunity? What is their generalized function?

Answer 17

• Interleukin 1 (IL-1) - inflammation
• Tumor necrosis factor-a (TNF-a) - inflammation
• Interleukin 12 (IL-12) - influences adaptive immunity
• Interleukin 6 (IL-6) - influences adaptive immunity
• Interferon a (IFN-a) - antiviral state
• Interferon B (IFN-B) - antiviral state

Question 18

What cytokines are involved in adaptive immunity? What is their generalized function?

Answer 18

• Interleukin 2 (IL-2) - T and B cell proliferation, NK activation and proliferation
• Transforming growth factor B (TGF-B) - inhibits proliferation of certain cells
• Interferon y (IFN-y) - activates macrophages and increases MHC expression and antigen presentation

Question 19

What are the different groups of proteins that cytokines belong to?

Answer 19

• hematopoeitins
• interferons
• chemokines
• tumor necrosis factor family (TNF)

Question 20

What are the four protein families that cytokine receptors belong to?

Answer 20

• Immunoglobulin superfamily receptors
• Class I cytokine receptors (hematopoietin)
• Class II cytokine receptors (interferon)
• TNF receptors

Question 21

How many subunits are required for cytokine binding? How many subunits are required for signal transduction?

Answer 21

Binding - one

Signalling - one

Question 22

What is the minimum number of subunits a cytokine receptor can have?

Answer 22

2

Question 23

What is a common feature of subfamilies of class I cytokine receptors?

Answer 23

possession of an identical signalling subunit but different binding subunit

Question 24

What are the subfamilies of class I cytokine receptors and what is their common subunit(s)?

Answer 24

• GM-CSF receptor subfamily (common B subunit)
• IL-6 receptor subfamily (common gp130 subunit)
• • IL-2 receptor subfamily (common y subunit)

Question 25

Tue or false? Possession of a common signalling subunit may explain why redundancy or antagonism is possible.

Answer 25

True

Question 26

What are the actions of IL-3, IL-5, and GM-CSF?

Answer 26

• affect hematopoietic cells
• activate monocytes
• differentiation of megakariocytes
• induce proliferation of neutrophils
• induce degranulation of basophils to release histamine

Question 27

What does possession of a single signalling subunit allow?

Answer 27

• elicitation of an identical signal by all involved cytokines

Question 28

Why could posession of a common signalling subunit lead to antagonism?

Answer 28

• leads to antagonism because there is competition for the common subunit