Cytokines/Chemokines 1 & 2 Flashcards
3 chemical mediators of inflammation?
1) lipid mediators
2) plasma proteins
3) cytokines & chemokines
cytokines
- cyto=cell; kine=movement
- secreted immunomodulatory proteins
- carry signals locally between cells, and thus have an immune system effect on other cells
Chemokines
- chemoattractant cytokines
- are distinct from cytokines in structure & classes of receptors recognizing them
- play critical role in efficient & target recruitment of specific immune cell populations
cytokines &Chemokines
- have diff structure & classes of receptors that recognize them
- some functions do overlap though
Chemokines and cytokines functions?
- recruit cells to site of injury/infections
- activate specific pathway for differnetiation/activation in response to injury/infection
- help macrophages/dendrites find lymph node
describe the kinetics (timing) of the inflamamtory response to microbial infection?
- inflammation, things happen in specific time zones
- controlled by specific chemokines & cytokines expressed
- see inflamm response is a regulated, choreographed dance
What controls what Chemokines and cytokines are expressed?
- the signals sent by PAMPs/DAMPs/other inflamm receptors in respond to cell stress, injury, or pathogen
- the type of activating event will determine which chemokines & cytokines are released
What are Chemokines?
1) size
2) function
- chemoattractants for specific leukocyte subsets
- very small 8-10KD
Chemokines in healthy homeostasis?
- CCL21 chemokine is heavily expressed in lymph nodes; naive T cells are attracted them
- this signal retains naive T cells in the lymph node
Chemokines in early innate immune response?
- CCL2 chemokine produced in damaged tissue (receptor= CCR2)
- recruits macrophages & neutrophils to tissue
- shows how diff chemokines recruits diff types of cells*
vascular permeability & chemokines?
- chemokines regulate vascular permeability by only attracting specific leukocytes into the tissue
- if not being signaled, then the cell will not move into the tissue
- is how make vascular permeability more tightly regulated
autoimmunity & chemokines?
- inappropriate induction of specific chemokines causes inappropriate recruitment of activated immune cells to the site of abnormal chemokines expression
how else can chemokines stimulate specific immune cells?
- in a receptor specific manner
- can lead to proliferation & activation of specific immune cells
How do chemokines act?
- through binding G-protein coupled receptors on leukocytes (very diff than how cytokines act)
- pathogens that interfere/impair GPCR can effect chemokine signaling
2 ways chemokines bind GPCR
1) tethered presentation: bind extracellular matrix of cell that produced it; is anchored to parent cell & then bind GPCR of leukocyte to activate it
2) secreted: are soluble can be secreted by parent cell, diffuse away and bind GPCR of distant leukocyte
tethered presentation of chemokines?
- chemokine receptor expressing cells can be recruited to specific sites by the tethered presentation of the recruiting chemokine to it’s parent cell
- is how can recruit leukocytes to specific tissue
different classes of chemokines?
-target different classes of immune cells & promote different types of inflammatory response
CXC chemokines? what do they target
- alpha chemokines
- have 1 AA residue separating first two conserved cysteine residues
- targeted to neutrophils than to other immune cells
number of X’s tell you?
- number of X’s (0-3) tells you how many amino acids away the two conserved cysteines are from eachother
- have structure-function relationship, CXC’s bind similar receptors & have similar functions; CXXC’s bind similar receptors & have similar functions
exception to CXC family?
- CXCL13
- this chemokine involved with lymphocyte homing, attracts B cells & makes B cell follicles
- doesn’t attract not neutrophils
CC chemokines
- Beta chemokines
- have first two conserved cysteine residues directly adjacent (no amino acids in between)
- many produced by monocytes
- not chemoattractant for neutrophils
CCL11 chemokines?
- is Eotaxin
- specifically recruits eosinophils
C chemokines
- Gamma chemokines
- lack 1st & 3rd cysteines
- tend to be chemoattractant for specific lymphocyte subsets
CXXXC chemokines?
-CX3CL1 is the only member & only example of a chemokine that’s cleaved from the cell surface
What recruits expression of specific chemokine? What happens after?
- PAMPs + DAMPs induce expression of specific chemokines
- the specific chemokines recruit immune cells & cytokines to the vicinity of injury/infection
PAMPs
- anything bacteria has that humans do not
- have unique PAMP receptor for each one, depending on which is activated, leads to different activations of cytokines
ex: flagella, proteoglycan etc
DAMPs
- receptors for anything that is chemically abnormal in the host cells
- ex: high ATP (indicate cell lysis)
do chemokines make covalent bonds with ECM of leukocytes as they are secreted?
-no; are not covalent bonds, just stuck on the leukocyte
What is the receptor for CCL2? What does CCL2 and receptor do? Where are they expressed?
- CCL2 is chemokine produced in damaged tissues & expressed on damaged epithelia’s extracellular matrix
- CCR2 is expressed on monocytes/ other leukocytes
- attracts them to site of injury/pathogen
Foam cell?
macrophage full of phagocytosed debris
Two ways CCL2 chemokine is secreted?
1) produced in damaged tissues & expressed on damaged epithelia’s extracellular matrix
2) by activated Foam cells (macrophages that are full of phagocytosed debris)
How is adaptive immune response activated?
-coordinated by regulating both expression of chemokines & expression of the chemokine receptors
5 steps in chemokine activation of adaptive immune response
1) CCL21 high expressed in lymph node (LN)
2) Naïve T cells express receptor for CCL21 (CCR7); move to LN from thymus
3) Activated dendritic cells carrying antigen express CCR7; run to LN cuz drawn to it’s CCL21 expression
4) Mature (activated) dendritic cells present antigen to naïve T-cells in LN
5) Activated effector T cells down-regulate CCR7 & leave LN cuz they are no longer retained in the lymph node by CCL21
-why can activated effector T cells leave lymph nodes once activated?
- their activation causes a down regulation of CCR7
- without CCR7, they can no longer “see” CCL21 in lymph node so have no reason to stay
How do activated effector T cells get to other tissues after leaving LN?
-activation causes other chemokine receptor production which draw them to damaged tisses
What are Naïve T cells?
-antigen-inexperienced T cells, have never seen antigen before
CCL21?
-chemokine expressed highly in lymph nodes that attracts naive T-cells as well as activated (antigen carrying) dendrites/macrophages
CCL21 receptor?
- CCR7
- naive T cells & ctivated (antigen carrying) dendrites/macrophages contain this receptor
When do dendrites/macrophages present CCR7 receptor?
- only after their PAMP/DAMP/ other receptors are activating signaling damage or pathogenicity
- when bind to antigen, is activated & CCR7 can be expressed on surface
Inappropriate expression of chemokines and/or receptors leads to?
- associated with specific inflammatory diseases
ex: rheumatoid arthritis, MS
Chemokine Receptor Antagonists for therapeutics?
- in current trials as therapies for chronic inflammatory & autoimmune disorders as well as lymphomas
- no break out chemokine based therapies yet though
why no “break-out” chemokine based therapies?
- chemokines participate in a wide variety of functions (from development, normal function, tissue defense & repair)
- it’s difficult to target a disease’s specific process
How are GPCR receptors for chemokines organized?
- by they action/consequence
- ex: inflammatory, homeostatic, atypical, viral
What are cytokines?
- cell derived factors
- small soluble molecules (~25KD); larger than chemokines
- can exist as monomer or multimer; can function alone or as trimer
how are cytokine actions mediated?
- via specific receptors.
- have both autocrine & paracrine actions
- have some systemic actions
Autocrine actions
- regulating self behavior
- the action is on cell the producing the cytokine
Paracrine
- regulating adjacent cells
- the action is on cells in the vicinity of the cell that is producing the cytokine
- ex:
cytokine systemic actions?
- yes, some
- effects of TNF, IL-6 & IL-1 on liver’s production of chemical mediators of inflammation (CRP etc)
What determines which cytokine is made?
- the immune & tissue cells produce cytokines in response to cell damage or the presence of pathogens
- which cytokine made depends on which receptor was bound & activated, and how much of the signal was received (PAMP, DAMP etc)
3 steps of cytokine release & effects on. macrophage?
1) Bacteria bind macrophage & triggers to cleanse cytokines& chemokines
2) vasodilation & increased vascular permeability cause redness, heat & swelling
3) inflammatory cells migrate into tissue, releasing inflammatory mediators that cause pain
cytokine structure?
- cytokines are structurally diverse (diff than chemokines)
- initially classified into interleukin families (ILs)
Cytokines receptors?
- cytokine actions mediated by Jak/Stat receptors
- NOT GPCR (chemokines use GPCR)
- cytokine receptors are activated by dimerization
Intracellular signaling pathways of cytokines & chemokines?
- they differ
- chemokines= GPCR
- cytokines= Jack/Stat
Jack/Stat overview?
1) cytokine receptor consists of 2 chains; the cytoplasmic domains bind JAK kinase
2) cytokine bind, dimerize receptor, cytoplasmic domains JAK activate eachother & phosphorylate receptor (cross-phosph)
3) Trxn factors (STAT) bind to phosphorylated receptor, are phosph. & activated by JAKs
4) phosph. STAts forom dimers, translocate unit nucleus & imitate new gene trxn
Which are easier to therapeutically target; JAK/STAT or GPCR?
- JAK/STAT
- means cytokine pathway is easier to target
What are the 3 modes of cytokine action?
1) Global
2) Local
3) Final (net) effects)
Global cytokine action?
- behavioral responses and systemic immune responses
- have literal effect on our personality/behavior
Local actions of cytokines?
-regulating differentiation of lymphocytes, antigen- presenting cells and innate immune cells
Final (net) effect actions of cytokines?
- Based on the ratio & concentrations of specific cytokines present
- tell concentration by seeing on how much signal transduction signals are coming from the receptors
- is how tailer & adapt our immune response
What are the 4 cytokines released from an activated macrophage?
1) IL-1B
2) TNF-a
4) IL-6
5) IL-12
IL-1B local effects? (x4)
1) activates vascular endothelium
2) activates lymphocytes
3) local tissue destruction
4) increases access of effector cells
IL-1B systemic effects? (x2)
1) fever
2) production of IL-6
TNF-a local effects? (x3)
1) activates vascular endothelium
2) increases vascular permeability, which allows increased IgG entry, increase cells into tissue, increased fluid drainage into lymph nodes
3) activates complement
TNF-a systemic effects? (x2)
1) fever
2) mobilization of metabolites
3) shock
IL-6 local effects? (x2)
1) lymphocyte activation
2) increased antibody production
IL-6-a systemic effects? (x2)
1) fever
2) induces acute-phase protein production
IL-12 local effects? (X2)
1) activates NK cells
2) induces differentiation of CD4 T cells into TH1 cells
cytokines & programmed sickness behavior?
-Cytokines shape a coordinated inflammatory response that includes programmed “sickness behavior”
what is sickness behavior? what causes it?
- anorexa, lethargy, slow-wave sleep, decreased social behavior, decreased reproductive behavior
- due to IL-1B, IL-6, TNF-a acting on brain as a result of a pathogen binding a macrophage
why is sickness behavior a good thing evolutionarily? From a biology standpoint?
1) are weak, don’t want to be around others who can kill you
- isolate self until healed; protecting own gene pool
2) it promotes conservation of resources w/ generation of toxic env for the invading pathogen
Why sickness behavior include anorexia?
-if don’t eat, blood isn’t full of metabolites for the pathogen, make pathogen work harder for materials
Fever importance?
- fever means you’re hot, means metabolism is faster
& require more energy to do the same work
-increased protein denaturation/lifespan
-hopefully both cause death of pathogen
side effects of certain cytokine inhibitors?
-certain inhibitors can cause depression and other symptoms cuz are blocking the healthy actions of cytokines on the brain
IL-1, IL-6, and TNF-a act on what tissues during sickness behavior?
1) liver
2) bone marrow epithelium
3) hypothalamus
4) fat/muscle
5) dendrtic cells
What determines the final effector function of antigen-activated T cells?
-Cytokines produced by antigen-presenting cells
(dendrites, macrophages, B cells)
-all are the same CD4 T cells; depending on PAMP/DAMp determines pathway/end result
TGF beta (alone) effect on CD4 T cell?
- made in high levels in brain, ovaries, testes
- makes Treg cells
- Treg cells cause increased production of TGF-B as well as IL-10 ( anti-inflamm cytokine)
IL-10
-anti-inflamm cytokine produced by T reg cell
TGF-Beta + IL-6?
- IL-6 made by innate cells, TGF-B in brain, ovaries, testes
- makes CD4 T cell–> TH-17
- TH-17 makes IL-6 & IL-17 which both activate more neutrophils
- indicates in early part of immunity
IL-12+ IFN-gamma effect on CD4 T-cell?
- turns it into TH 1 cell
- TH1 cell releases: IL-2 & IFN-gamma
- increases T cell proliferation, IFN-super killers, ROS species
IL-4 cytokine effect on CD4 T cell?
- makes CD4 into TH2 cells
- produce IL-4 & IL-5 cytokines
- both help make antibodies & fight parasites
IL-4 & IL-5
-help make antibodies & fight parasites
How does body determine stage & pathogen specific immune responses?
- cytokines produced vary by the severity and type of infection/tissue damage
- this help to determine severity- and pathogen- specific immune responses
cytokines & innate immune response? good or bad?
- Cytokine expression can amplify innate immune responses
- if amplifies locally this is good; but if causes a systemic amplification is bad & can lead to septic shock
How does sepsis happen?
-when the inflamm response is worse than the pathogen
Explain how an over response of immune system could happen in response to a hand infection to gram - bacteria?
1) macrophages activated in liver & spleen to secret TNF-Alpha into bloodstream
2) systemic edema occurs
3) decreased blood volume causes collapse of blood vessels
4) disseminated intravascular coagulation leading to wasting & multiple organ failure
5) death
What does systemic edema cause?
1) decreased blood volume
2) hyperpoteinemia
3) neutropenia
4) neutrophilia
Explain how a correct response of immune system could happen in response to a hand infection to gram - bacteria?
1) macrophages activated to secrete TNF-alpha locally in tissue
2) increase: release of plasma protein into tissue. phagocyte & lymphocyte migration into tissue
3) phagocytosis of bacteria; local vessel occlusion, plasma + cells drain to lymph node
4) removal of infection w/ adaptive immunity
therapies to block cytokines?
- yes
- have anti-TNF therapies to treat Rheumatoid arthritis & Psoriasis
- but are not first line of defense
why are anti-TNF not our first line therapies for all chronic inflammatory diseases?
- TNF is required for normal pathogen defense
- w/o TNF you are immunodeficient so on these anti-TNF meds your risk for infection is huge
issues with anti-TNF therapies and the brain?
- TNF promotes proliferation of myelinating cells & remyelination during demyelinating diseases (MS)
- Anti-TNF therapies associated w/ increased demyelination & nerve damage in individuals with diagnosed (and previously undiagnosed) CNS diseases
