Transcript Cytokines - University of Arizona

Cytokines
and
Chemokines
Cellular interaction made simple
Leo Carr
Immunopharmacology
March 1, 2006
Cytokine Basics
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Cytokine or immunocytokine is a generic
name used to describe a diverse group of
soluble proteins and peptides which act as
humoral regulators at nano- to- picomolar
concentrations
Cytokines modulate the functional activities
of individual cells and tissues both under
normal and pathologic conditions
Cytokine Basics
• The term cytokine is used to separate this
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group of immunomodulatory proteins from
other growth factors that modulate nonimmune cells
Unfortunately, Growth factors and cytokines
both act as cellular survival factors by
preventing apoptosis - this fact adds
confusion to the understanding and naming of
cytokines
Cytokine Names
• Interleukins - produced exclusively by
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leukocytes
Lymphokines - produced by lymphocytes
Monokines - produced exclusively by
monocytes
Interferons - involved in antiviral responses
Colony Stimulating Factors - support the
growth of cells in semisolid medias
Chemokines - promote chemotaxis.
Cytokine Basics
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Cytokines behave like classical hormones
in that they act at a systemic level, affecting,
inflammation, septic shock, acute phase
reactions, wound healing, and the
neuroimmune network
Unlike hormones, cytokines are not
produced by specialized cells or in
specialized glands - they have no single
organ source (this helps clear some of the
confusion)
Cytokine Activity
• Cytokine actions may be characterized as:
–Autocrine (self modulating)
–Paracrine (modulating cells in the
immediate surroundings)
–Juxtacrine (modulating through cell
membrane signaling)
–Retrocrine (modulating to stop host
defense)
Cytokine Basics
• Defining cytokines based only on their
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producer cells or target cells is inaccurate
The historic cytokine concept of "one
producer cell -one cytokine -one target cell"
has been falsified for almost every cytokine
Cytokine Basics
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Almost all Cytokines are pleiotropic
effectors showing multiple biological
activities
Also, multiple cytokines often have
overlapping activities
A single cell frequently interacts with
multiple cytokines with seemingly identical
responses - cross-talk
Cytokine Assays
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The biological activities of cytokines can be
measured by a variety of bioassays which
may employ factor-dependent cell lines, or
antibodies (ELISA)
RT-PCR quantitation of cytokines detects
the presence of mRNA encoding specific
cytokines
Soluble - Vs - Membrane
• Many Membrane-bound cytokine forms
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have been characterized
Some cytokines may also be associated
with the extracellular matrix
Switching between soluble and membrane
bound forms of cytokines may be an
important immunoregulatory event
Cytokine Regulation
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Most Cytokines are not stored inside cells
(exceptions are, for example TGF-b and
PDGF which are stored in platelets)
The expression of most Cytokines is strictly
regulated - factors are usually produced only
by activated cells in response to an
induction signal
Expression is normally transient and can be
regulated at all levels of gene expression
Cytokine Action/Timing
• A hierarchical order of cytokine actions has
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been observed with some early cytokines
pre-activating cells so that they then can
respond to late-acting cytokines
Many cytokines induce the synthesis of
novel gene products once they have bound
to their respective receptors
Cytokine Transport
• Cytokine mediators can be transported
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quickly to remote areas of a multicellular
organism
They can address multiple target cells and
can be degraded quickly. Concentration
gradients can be used to elicit specific
responses
These capabilities far exceed the interaction
provided by cell-to-cell contacts within a
multicellular organism
Pre/Postnatal Cytokines
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Cytokines are important mediators involved
in embryogenesis and organ development
and their activities in these processes may
differ from those observed postnatally
They also play a key role in
neuroimmunological, neuroendocrinological,
and neuroregulatory processes
Cytokine - Regulation
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Cytokines are important positive or
negative regulators of mitosis,
differentiation, migration,cell survival,
apoptosis, and transformation-oncogene
Virus Effects
• Viral infectious agents exploit the cytokine
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repertoire to evade immune responses of
the host
Virus-encoded factors appear to affect the
activities of cytokines in at least four
different ways:
– by inhibiting the synthesis and release of
cytokines from infected cells
– by interfering with the interaction between
cytokines and their receptors
Virus Effects
• Virus-encoded factors appear to affect the
activities of cytokines in at least four
different ways:
– by inhibiting signal transmission pathways of
cytokines
– by synthesizing virus-encoded cytokines that
antagonize the effects of host cytokines
mediating antiviral processes (viroceptor and
virokines)
Cytokines In Therapy
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The many specific activities of individual
cytokines have been the basis for current
concepts of therapeutic intervention particularly, hematopoietic malfunctions and
tumor therapy
Applications involve the support of chemoand radiotherapy, bone marrow
transplantation, and general
immunostimulation - adoptive
immunotherapy
Cytokine Shape/Type
• Among the many different cytokines, the
Type I cytokines share a similar four ahelical structure and correspondingly, their
receptors also share characteristic features
that have led to their description as the
cytokine receptor superfamily, or Type I
cytokine receptors
Cytokine Shape/Type
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Despite extremely limited amino acid
sequence similarities between different Type
I cytokines - all Type I cytokines have
similar three-dimensional structures
Cytokine Type I Subgroups
• Type I cytokines can be further divided into
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either short-chain or long-chain
The short-chain cytokines include:
– IL-2, IL-3, IL-4, IL-5, IL-7, IL-9, IL-13, IL-15
– Granulocyte-macrophage colony-stimulating
factor (GM-CSF)
– Monocyte-CSF (M-CSF),
– Stem cell factor (SCF),
Cytokine Type I Subgroups
• Long-chain cytokines include:
– IL-6, IL-11
– Erythropoietin
– Thrombopoietin
– Leptin
– Leukemia inhibitory factor (LIF)
– Oncostatin M (OSM)
– Ciliary neurotrophic factor (CNTF)
– Cardiotrophin-1 (CT-1)
– Granulocyte colony-stimulating factor (G-CSF)
Cytokine Receptors
Cytokine Receptors
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The receptors for five different
immunologically important cytokines, IL-2,
IL-4, IL-7, IL-9, and IL-15, share the
common cytokine receptor g chain, gc
(CD132) p.515 in Abbas
These cytokines are all short-chain Type I
cytokines
Cytokines Receptors
IL-2
IL-2 Production
• Mature IL-2 is a peptide 133 amino acids
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long
Produced mainly by mitogen activated
CD4+T-lymphocytes
Originally called T-cell growth factor (TCGF)
Transformed T-cells and B-cells, leukemia
cells,LAK cells (Lymphokine-activated killer
cells) and NK-cells also secrete IL-2
IL-2 Actions/Modulation
• Secondary signals are required for maximal
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expression of IL-2
Resting cells do not produce IL-2
Induces cell cycle progression in resting
cells
Allows clonal expansion of activated Tlymphocytes
Growth/expansion effect is modulated by
hormones such as prolactin
IL-2 Actions/Modulation
• In vitro synthesis of IL-2 is inhibited by
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dexamethasone or CSA
Vitamin E can enhance IL-2 production
With increasing age, the antigen/mitogenstimulated synthesis of IL-2 (T-cell-mediated
immune response) decreases
IL-2 Facts
• IL-2 damages the blood-brain barrier and
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the integrity of the endothelium of brain
vessels
IL-2 does not have a saturable transport
system across the blood-brain barrier
Electrophysiological alterations may cause
neuropsychiatric side effects such as
fatigue, disorientation, and depression,
frequently observed under IL-2 therapy
IL-2 Summary
• IL-2 important actions:
– It can increase immunoglobulin synthesis and Jchain transcription
– Proliferation in B cells (with IL-4)
– potently augment the cytolytic activity of natural
killer (NK) cells
– induce the cytolytic activity of lymphokineactivated killer (LAK) cells
– Due to its effects on T-cells and B-cells IL-2 is a
central regulator of immune response
– Passes BBB
IL-4
IL-4 Production
• IL-4, like IL-2, is produced principally by
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activated CD4+ T cells
It is also produced by natural killer cells, and
by mast cells and basophils
IL-4 Actions/Modulation
• IL-4 is the major B-cell growth factor
• Vital for immunoglobulin class switch IgG to
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IgE and inhibits the synthesis of IgM and
other IgG subtypes
IL-4 induces expression of class II major
histocompatibility complex (MHC) molecules
on B cells and increases cell surface
expression of FceRII (CD23)
IL-4 Actions/Modulation
• IL-4 can inhibit responses of cells to IL-2
• IL-4 can also exert actions on:
– T-cells (proliferation)
– Macrophages
– Hematopoietic precursor cells
– Stromal cells
– Fibroblasts
– Myelomas (inhibiting IL-6 - myeloma growth factor)
IL-7
IL-7 Production
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IL-7 is not a lymphokine but instead is
produced by stromal cells
IL-7 is secreted constitutively into bone
marrow stroma, and thymic cells
Murine and human keratinocytes have been
shown also to express and secrete IL-7
IL-7 Actions/Modulation
• Its major role is to enhance thymocyte
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growth, survival, and differentiation
It also has some activity for the growth of
mature T- cells
Although important for growth of murine preB cells, it is now clear that human B cells
can develop in the absence of IL-7
IL-7 Actions/Modulation
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IL-7 stimulates the proliferation of pre-B
and pro-B-cells without affecting their
differentiation
IL-7 can replace murine bone marrow
stromal cells in supporting the extended
growth of both pre-B-cells and pro-B-cells
It does not act on mature B-cells
IL-9
IL-9 Production
• IL-9 was originally described as a murine T-
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cell growth factor. Human and murine IL-9
are 126 amino acids long
IL-9 is produced by activated T-cells and
supports the growth of T-helper (Th) clones
but not CD8+ cytolytic clones
In contrast to IL-2, its production is much
more delayed, suggesting late/secondary
signaling
IL-9 Production
• IL-9 can be isolated from culture of mitogen-
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or antigen-stimulated T helper cells
In primary lymphocyte cultures it is
produced predominantly by cells expressing
CD4
The synthesis of IL-9 can be induced by
calcium ionophores (Ionomycin)
IL-9 Actions/Modulation
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IL-9 stimulates the proliferation of a number
of T helper cell clones in the absence of
antigens or antigen-presenting cells
It does not promote the proliferation of
freshly isolated T-cells or cytolytic T-cells
The activity as a growth factor seems
restricted to a distinct subpopulation of cells
or to a particular late activation state
IL-15
IL-15 Production
• IL-15 is the most recently identified Type I
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cytokine
Although IL-15 messenger RNA (mRNA) is
produced by a range of non-lymphocytic cell
types, it is difficult to detect IL-15 protein
production
IL-15 Actions/Modulation
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IL-15 receptors are widely expressed, and
it is becoming more clear that IL-15 plays a
major role related to NK cell development
and cytolytic activity
Type I Cytokines
• IL-2, IL-4, IL-7, IL-9, and IL-15 collectively
exhibit overlapping roles related to T cells,
NK cells, B cells, and mast cells, and
together would be expected to play vital
roles in normal development and function of
these cells
Break
Chemokines
• Chemoattractant Cytokines
• Small (8-10kd) secreted heparin-binding
• Promote recruitment and activation of
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leukocytes
Can be divided into subclasses by virtue of
structural properties
Chemokine Subclasses
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Most chemokines have 4 cysteine residues which
form disulphide bonds
CC class – The first two cysteines are adjacent
(example: MCP-1, RANTES)
CXC class- The first two cysteines are not
adjacent (example: IL-8)
C class – Only has 2 cysteines not 4 (example:
Lymphotactin)
CX3C class – Has 3 amino acids between the first
two cysteines and a different N-terminal
Chemokine Subclasses
Chemokine Function
Chemokine Function
• Recruitment of inflammatory cells to
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infection
Provide immune homeostasis
Important in host defense against bacteria,
parasitic and viral infection
Role in wound healing
Role in hematopoesis and angiogenesis
under study
Chemokine Function
• Chemokines promote chemotaxis in the
direction of highest concentration
Chemokine Effects
• Chemokines promote shape change in cells
• Polymerization and breakdown of actin
• Breakdown of lamellipodia (cell anchoring
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arms/legs)
Upregulate integrins causing cell adhesion
in vascular endothelium
Promote cell diapedesis
Chemokine Effects
Chemokine Signaling
7 transmembrane g-coupled signaling on 3rd loop
Chemokine Receptors
• Specific receptors bind specific chemokine
– CXCR1 binds IL-8
• There are also shared receptors
– CCR1 binds MIP-1a,RANTES, MCP-2 and MCP3
• Promiscuous receptors bind any class
• Viral encoded receptors
– Encoded by cytomegalovirus- CMV U28 binds CC
chemokines
Chemokine Receptors
Chemokines in Disease
• MIP-1, and RANTES were discovered to be
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HIV suppressor factors
CCR2 Ko mice and MCP-1 Ko show reduced
atherosclerotic lesions
Chemokines in Transplantation
• Many chemokines are expressed in
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transplantation (RANTES, MIP-1, IP-10)
CXCR3 Ko mice show reduced graft rejection
Antibodies to CXCR3 ligands imiprove graft
survival
Chemokines in Transplantation
• Chemokine receptors are differentially
expressed on effector T-cells
Chemokine/Cytokine Interaction
• Allergic reaction
Chemokine/Cytokine Interaction
• Dermatitis
Therapeutic Trials
Questions?