module 05 section 01 (introduction to cytokines) Flashcards
what are cytokines?
low-molecular weight regulatory proteins or glycoproteins
what are cytokines secreted by?
leukocytes and various other cells in the body
cytokines generally act as:
local messangers of the immune system
if cytokines are secreted by lymphocytes, they’re called:
lymphokines
if cytokines are secreted by monocytes, they’re called:
monokines
what are the 4 most common classes of cytokines?
(1) interleukins (IL-1 to IL-3)
(2) tumor necrosis factor (TNF)
(3) interferon (IFN)
(4) chemokines
what are interleukins?
large group of cytokines that promote cell-to-cell interactions and the stimulation of humoral or cell-mediated immune responses
what is TNF?
- protein that’s produced cheifly by monocytes and macrophages in response to endotoxins
- mediate inflammation, induce destruction of some tumor cells and activate wbcs
what is interferon?
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
what are chemokines?
group of secreted low-molecular weight polypeptides that mediate chemotaxis for different leukocytes and regulate the adhessiveness of the leukocytes
list the three ways cytokines may exert their effects
(1) autocrine
(2) paracrine
(3) endocrine
define autocrine (in terms of cytokines)
when cytokines exert their effects by binding receptors on the same cell
define paracrine (in terms of cytokines)
when cytokines exert their effects by binding receptors on target cells nearby
define endocrine (in terms of cytokines)
when cytokines exert their effects by binding receptors on distance target cells
do cytokines exhibit high or low affinity for their receptors?
high (10^-10/1-^-12 M)
can nanomolar concentrations of cytokines mediate a biological effect?
yes
where are cytokines mainly produced?
by helper T-cells, dendritic cells and macrophages
*(but the secretion of cytokines is not limited to these cells)
what are the 5 roles of cytokines?
(1) cellular and humoral immune responses
(2) inflammation
(3) hematopoiesis
(4) cellular proliferation and differentiation
(5) wound healing
describe the role cytokines in cellular and humoral immune responses
cytokines are the messangers between the innate and adaptive immune systems
describe the role cytokines in inflammation
pro-inflammatory cytokines are produced by activated macrophages and induce an inflammatory response
describe the role cytokines in hematopoiesis
cytokine IL-7 is integral for B-cell development
describe the role cytokines in cellular proliferation and differentiation
in cell and humoral immune responses cytokines can act as cell growth regulatory factors
describe the role cytokines in wound healing
when wounded, damaged tissues elict inflammation which triggers cytokines for the healing process
describe how cytokines mediate the transition from innate to adaptive immunity (2)
- 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
what are the 4 hallmark attributes of cytokine activity?
(1) pleiotropy
(2) redundancy
(3) synergy
(4) antagonism
describe pleiotropy
provide an example
- 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
describe redundancy
provide an example
- 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
describe synergy
provide an example
- 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
describe antagonism
provide an example
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
what are the pro-inflammatory cytokines?
IL-1β, IL-6, TNF-α
what are the anti-inflammatory cytokines?
IL-10, TGF-β
what is a cytokine storm?
the release of large concentrations of inflammatory cytokines after infection or injury
why is it important that the balance of pro- and anti-inflammatory cytokines is maintained?
- prolonged inflammation can lead to complications such as tissue damage, IBD, etc.
- no inflammation = no response to infection and thus no healing
what cytokines are important for T-cell proliferation and activation? what cells are they produced by?
IL-2, IL-4 (made by T-cells)
IL-12 (made by macrophages and dendritic cells)
what cytokines are important for B-cell proliferation and differentation? what cells are they produced by?
IL-4, IL-5 (made by helper T-cells)
IL-7 (made by stromal cells)
which interferons are important? why? what cells are they produced by?
- IFNα, IFNβ (produced mainly by macrophages and dendritic cells to fight viruses)
- IFNγ (produced by NK and T-cells to enhance immune responses)
which cytokines would be present upon pathogen clearance?
anti-inflammatory cytokines (IL-10 and TGF-B)
