module 05 section 01 (introduction to cytokines)

Question 1

what are cytokines?

Answer 1

low-molecular weight regulatory proteins or glycoproteins

Question 2

what are cytokines secreted by?

Answer 2

leukocytes and various other cells in the body

Question 3

cytokines generally act as:

Answer 3

local messangers of the immune system

Question 4

if cytokines are secreted by lymphocytes, they’re called:

Answer 4

lymphokines

Question 5

if cytokines are secreted by monocytes, they’re called:

Answer 5

monokines

Question 6

what are the 4 most common classes of cytokines?

Answer 6

(1) interleukins (IL-1 to IL-3)
(2) tumor necrosis factor (TNF)
(3) interferon (IFN)
(4) chemokines

Question 7

what are interleukins?

Answer 7

large group of cytokines that promote cell-to-cell interactions and the stimulation of humoral or cell-mediated immune responses

Question 8

what is TNF?

Answer 8

• protein that’s produced cheifly by monocytes and macrophages in response to endotoxins
• mediate inflammation, induce destruction of some tumor cells and activate wbcs

Question 9

what is interferon?

Answer 9

group of glycoprotein cytokines produced and secreted by certain cells that induce an antiviral state in other cells and also help regulate the immune response

Question 10

what are chemokines?

Answer 10

group of secreted low-molecular weight polypeptides that mediate chemotaxis for different leukocytes and regulate the adhessiveness of the leukocytes

Question 11

list the three ways cytokines may exert their effects

Answer 11

(1) autocrine
(2) paracrine
(3) endocrine

Question 12

define autocrine (in terms of cytokines)

Answer 12

when cytokines exert their effects by binding receptors on the same cell

Question 13

define paracrine (in terms of cytokines)

Answer 13

when cytokines exert their effects by binding receptors on target cells nearby

Question 14

define endocrine (in terms of cytokines)

Answer 14

when cytokines exert their effects by binding receptors on distance target cells

Question 15

do cytokines exhibit high or low affinity for their receptors?

Answer 15

high (10^-10/1-^-12 M)

Question 16

can nanomolar concentrations of cytokines mediate a biological effect?

Answer 16

yes

Question 17

where are cytokines mainly produced?

Answer 17

by helper T-cells, dendritic cells and macrophages

*(but the secretion of cytokines is not limited to these cells)

Question 18

what are the 5 roles of cytokines?

Answer 18

(1) cellular and humoral immune responses
(2) inflammation
(3) hematopoiesis
(4) cellular proliferation and differentiation
(5) wound healing

Question 19

describe the role cytokines in cellular and humoral immune responses

Answer 19

cytokines are the messangers between the innate and adaptive immune systems

Question 20

describe the role cytokines in inflammation

Answer 20

pro-inflammatory cytokines are produced by activated macrophages and induce an inflammatory response

Question 21

describe the role cytokines in hematopoiesis

Answer 21

cytokine IL-7 is integral for B-cell development

Question 22

describe the role cytokines in cellular proliferation and differentiation

Answer 22

in cell and humoral immune responses cytokines can act as cell growth regulatory factors

Question 23

describe the role cytokines in wound healing

Answer 23

when wounded, damaged tissues elict inflammation which triggers cytokines for the healing process

Question 24

describe how cytokines mediate the transition from innate to adaptive immunity (2)

Answer 24

• T-cell derived cytokines play a role in limiting the innate response and promote the initiation of the antigen-specific adaptive response
• cytokines mediate the magnitude and nature of the immune response by influencing the growth and differentation of lymocytes and other cells

Question 25

what are the 4 hallmark attributes of cytokine activity?

Answer 25

(1) pleiotropy
(2) redundancy
(3) synergy
(4) antagonism

Question 26

describe pleiotropy

provide an example

Answer 26

• a single cytokine can produce multiple effects by acting on a single cell type or on multiple cell types
• e.g. IL-4 stimulates multiple effects in B-cells and the proliferation of thymocytes and mast cells

Question 27

describe redundancy

provide an example

Answer 27

• cytokines can target the same cell and elict the same effect
• e.g. IL-2, IL-4 and IL-5 can stimulate B-cells to undergo proliferation
• important because if one of them is downregulated, the others can continue to exert the effects and maintain the immune response

Question 28

describe synergy

provide an example

Answer 28

• some cytokines can act synergistically - their combined effect is greater than the added effect of each of them seperately
• e.g. IL-4 and IL-5 together can more effectively stimjlate B-cells to induce class switching to IGE relative to any one cytokine acting alone

Question 29

describe antagonism

provide an example

Answer 29

cytokines can act on other cytokines to impact their effects 
-e.g. IL-4 and IFN-y can be secreted by a helper T-cell - IL-4 normally functions to induce B-cell class switching, but IFN-y can act to block or antagonize the effects of IL-4

Question 30

what are the pro-inflammatory cytokines?

Answer 30

IL-1β, IL-6, TNF-α

Question 31

what are the anti-inflammatory cytokines?

Answer 31

IL-10, TGF-β

Question 32

what is a cytokine storm?

Answer 32

the release of large concentrations of inflammatory cytokines after infection or injury

Question 33

why is it important that the balance of pro- and anti-inflammatory cytokines is maintained?

Answer 33

• prolonged inflammation can lead to complications such as tissue damage, IBD, etc.
• no inflammation = no response to infection and thus no healing

Question 34

what cytokines are important for T-cell proliferation and activation? what cells are they produced by?

Answer 34

IL-2, IL-4 (made by T-cells)

IL-12 (made by macrophages and dendritic cells)

Question 35

what cytokines are important for B-cell proliferation and differentation? what cells are they produced by?

Answer 35

IL-4, IL-5 (made by helper T-cells)

IL-7 (made by stromal cells)

Question 36

which interferons are important? why? what cells are they produced by?

Answer 36

• IFNα, IFNβ (produced mainly by macrophages and dendritic cells to fight viruses)
• IFNγ (produced by NK and T-cells to enhance immune responses)

Question 37

which cytokines would be present upon pathogen clearance?

Answer 37

anti-inflammatory cytokines (IL-10 and TGF-B)