cytokines copy Flashcards
Define pleiotropism
Ability of 1 cytokine to have many functions
Define redundancy
More than 1 cytokine with the same function
Define synergism
2 cytokines acting together to enhance a biological effect
Ex. IL-4 and IL-13 promote class switching in B cells to make IgE
Define antagonism
2 cytokines oppose each other’s effects
Ex: IL-4 favors Th2 response while IFN-gamma favors Th1 response
Describe the local and systemic effects of cytokines
Autocrine: acts on same cell which secreted itParacrine: acts on nearby cellsEndocrine: goes systemic and acts on distant cells
List the cytokines involved in innate immunity
IL-1
TNF-alpha
IL-6
IL-8
Which signaling pathway does IL-1 and TNF-alpha activate?
NF-KB
Name 2 principal cellular responses to TNF-alpha
- Gene transcription: production of IL-1/TNF-alpha, inflammatory mediators and ROS
- Apoptosis: Fas/FasL death via Caspase 8
What is the main source of TNF-alpha?
activated macrophages
What other stimuli can activate the pathway stimulated by IL-1/TNF-alpha?
PAMPs like LPS or peptidoglycans stimulate the NF-KB pathway resulting in IL-1/TNF-alpha production and local inflammation
Describe the local and systemic effects of TNF-alpha.
Local: -leukocyte recruitment via increased adhesion molecule expression on endo cells-self-amplifying cascade-eicosanoid synthesis via activation of phospholipase A2 and AA pathway
Moderate systemic:-pyrogen: PG synthesis by hypothalamus-stimulate hepatocytes to make acute phase proteins-cachexia-bone marrow stimulation–> increased prod of leukocytes
Massive systemic:-hypotension via decreased myocardial contraction and decreased vascular smooth muscle tone- activation of coagulation–> thrombosisAKA toxic shock!
Name 2 differences b/t IL-1 and TNF-alpha.
- IL-1 does NOT induce apoptosis
2. IL-1 has 3 subtypes…IL-1alpha is preformed in keratinocytes
What are the principle products of the pathway stimulated by IL-1/TNF-alpha?
- IL-1/TNF-alpha…self-amplifying
- ROS…antimicrobial defense
- eicosanoids via activation of phospholipase A2
- Bcl-2…inhibitor of Caspase 8 and apoptosis
How does UV light cause inflammation in the skin?
IL-1alpha is pre-formed and active in keratinocytes–> UV light damages keratinocytes–> release of IL-1alpha–> leukocyte recruitment via increased adhesion molecules and self-amplifying cascade
How does a sunburn make you not feel well?
Massive amounts of IL-1alpha are released from keratinocytes–> systemic circulation–> pyrogen (hypothalamus), acute phase response (liver) and cachexia
Give 2 specific mechanisms of action by which glucocorticoids suppress proinflammatory effects of IL-1/TNF-alpha.
- promote synthesis of IkBalpha= inhibitor of NF-KBIkBalpha dimerizes NF-KB–> sequestering it in cytolplasm–> prevents translocation to nucleus and gene transcription
- upregulate IL-1RA–> competes w/ IL-1alpha/beta for IL-1 rececptor
Describe the 3 forms of IL-1.
IL-1alpha
IL-1beta
IL-1RA
Which form of IL-1 is active when made?
IL-1alpha
Which form of IL-1 requires enzymatic activation?
IL-1beta
Which form of IL-1 is counter regulatory?
IL-1RA
Explain how keratinocytes upregulate the innate immune system.
keratinocytes express PRR (pattern recognition receptors) like TLRs, mannose receptors, C-type lectins
These receptors recognize PAMPs (pathogen associated molecular patterns) such as LPS, bacterial peptidoglycans, bacterial DNA, viral DNA.
Upon activation–> secretion of ILs, chemokines, antimicrobial peptides (beta-defensins, cathelicidins)
Keratinocytes can also be induced to express MHC II and present Ag
Give a broad definition of the following: 1. interleukins 2. interferons 3. tumor necrosis factor 4. growth factors 5. chemokines
- IL: cytokines regulating actions b/t lymphocytes and other WBCs
- IFN: glycoproteins synthesized in response to viral infection
- TNF: cytokines from MO/T cells involved in apoptosis and inflammation
- growth factors: group of cytokines which stimulate cell growth and proliferation
- chemokines: subset of cytokines which mediate chemotaxis; aid in wound healing
Which cells are responsible for IL-1 production?
IL-1alpha: keratinocytes
IL-1beta:
- MO
- dendritic cells
- T/B/NK cells
- endo cells
- fibroblasts
Describe the Jak-STAT pathway.
- binding of cytokine to receptor
- dimerization of transmembrane portions of receptor
- phosphorylation of JAK proteins
- phosphorylation of STAT proteins
- dissociation of STAT from JAK
- STAT relocates to nucleus
- act as transcription factors and induce gene expression
Which cytokines use the Jak-STAT pathway?
IL-2, -7. -9 -10, -11, -12, -15, -21, -31, GM-CSF and IFN (alpha/beta/gamma)
What are the main products of the Jak-STAT pathway?
JAK1/3= inflammation and pruritus
JAK2= hematopoiesis
What are the main differences in function b/t Th1 and Th2 cytokines?
Th1: favor cell-mediated immunity promote memory T cells MO function specific T cell responses antiviral activity B cells to produce IgG
Th2:
favor humoral immunity
B cells to produce IgE
promote eosinophil function
What is the main Th1 cytokine?
IL-2
What is the main Th2 cytokine?
IL-4;
- promotes class switching to IgE
- mast cell growth factor
- promotes Th2 polarization,
- downregulates IL-1, -6, TNF-alpha, IFN-gamma
What was IL-2 first called after it was discovered?
T-cell growth factor
List 5 effects of IL-2
- promotes T cell replication and function
- principle stimulator of IFN-gamma production
- induces Bcl-2 (anti-apoptotic factor)
- favors IgG production
- activates MO and NK cells
Which cytokine does IL-7 mimic?
IL-2
How does IL-12 regulate Th1 response?
suppresses IL-4/Th2 response, thereby favoring Th1 response
Which cytokine is important for promotion of growth and differentiation of eosinophils?
IL-5; once called eosinophil growth factor
What is the principal biological action of IL-31?
pruritus
Describe the effects of IL-6 on the innate immune response, B cells and systemic levels.
innate/systemic:
Induces hepatocytes to produce acute phase proteins
Induces pyrogens which act on hypothalamus
Produces cachexia
Adaptive response:
B cells: stimulates IgM production
promotes IL-2 production
w/ IL-5, -6 stimulates IgA production
Which cells produce IL-6?
MO mainly
also: T/B cells mast cells endo cells keratinocytes fibroblasts
Compare and contrast type I and type II interferons.
Compare:
- all have anti-viral properties (Type I > Type II)
- promote Th1 response
- strong anti-proliferative effects of certain cells (cancer)
- induce/increase expression of MHC I
Contrast:
- alpha produced by MO, beta produced by fibroblasts, gamma produced by NK cells, CD8 T cells, Th1 CD4 cells
- gamma required for MO activation
- gamma promotes Ab mediated phagocytosis
- gamma= inducer of chemokines and endo cell adhesion molecules
Which interferons are type I?
alpha and beta
Which interferons are type II?
gamma
Which cells are the major source of IFN-gamma?
Th1 cells
Describe the actions of IL-10
Debbie Downer
Inhibits IL-12 (activated MO and DCs) TNF-alpha, IFN-gamma, MHC II co-stimulation of T cells by APCs
Which cells produce IL-10
activated MO and Th2 cells
also keratinocytes
Name the Th1 cytokines
IL-2
IL-7
IL-12
IFN-gamma
Name the Th2 cytokines
IL-4 IL-5 IL-10 IL-13 IL-31