Cytokines are a broad and loose category of small proteins important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrine, paracrine and endocrine signaling as immunomodulating agents.

1. Cytokines and Chemokines

2. OBJECTIVES
General Properties
Functional Categories of Cytokines
Cytokine Receptors
Biologic Actions

3. Cytokines” are soluble protein secreted by
the cells of innate and adaptive immunity and
therefore mediate many of the functions of
these cells.
Produced in response to microbes and other antigens.
 stimulate growth and differentiation of lymphocytes
also hemopiesis.

4. Are cytokines hormones? No
• Cytokines Hormones
• Usually act locally Usually act at
distance
• Transient synthesis Continuous
synthesis
• Many cell types Specialized cells
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5. Chemical Structure
Low molecular weight proteins, <30kD
High affinity for receptors
Active in picomole amounts

6. Based on their cellular sources
 Monokines (mononuclear phagocyte)
lymphokines (lymphocytes)
Interlukins (leukocytes) (IL-1, IL-2,)
A subfamily of cytokines primarily
functions in directing migration of
cells, these are called “chemotactic
cytokines” or “chemokines”

7.  Cytokines are polypeptides
produced by the cells of innate
and adaptive immunity in
response to microbes and other
antigens as a result of cellular
activation.
 Cytokines initiate their actions
by binding to specific membrane
receptors on target cells.
The cellular responses to most
cytokines consist of gene
activation, resulting in the
expression of new functions and
sometimes the proliferation of
the target cells
What are cytokines?

8. Functional Categories of Cytokines
 Mediators and regulators of innate immunity:
Tumor necrosis factor (TNF), IL-1, IL-6, IL-
12, Type I IFNs, IL-15, IL-18,chemokines
Mediators and regulators of adptive immunity
IL-2, IL-4, IL-5, IFN-g, TGF-, LT(TNF- ),
IL-13,etc
Stimulators of hematopoiesis
granulocyte-CSF, G-CSF
macrophage-CSF，M－CSF
granulocyte-macrophage-CSF, GM-CSF)
erythropoietin, EPO
TPO
stem cell factor, SCF

9. Cytokine Receptors
 Type I cytokine receptors
 Type II cytokine receptors
 Ig superfamily
 TNF receptors
 Seven-transmembrane -helical receptors
*Classification of cytokine receptors based
on structural homologies among the
extracellular cytokine-binding domain.

10. -S-S-
-S-S-
-S-S-
C
C
C
C
C1
C3
C2
C1
C3
C2
C1
C3
C2
C1
C3
C2
G protein
Ig
superfamily
Type I
cytokine-R
Type II
cytokine-R
TNF-R Chemokine-R
IL-1 M-
CSF C-
kit
IL-2
IL-3
IL-4
IL-5
IL-6
IL-7
IL-9
IL-11
IL-12
IL-13
IL-15
OSM
GM-CSF
G-CSF
EPO
IFN-
IFN-
IFN-g
IL-10
TNF-
TNF-
CD40L
NGF
FASL
IL-8
RANTES
MIP-1
PF4
Cytokine receptor families and ligands
WSXWS
Conserved
cycteins

11. General properties of cytokines
Pleiotropism
One cytokine Can have multiple affects on different
Target Cells
Redundancy
Multiple cytokines have the same functional
actions
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12. Synergy
Two or more cytokines having greater additive
effects than one cytokine
Antagonism
One or more cytokine(s) Can inhibit the
action of the other
Cascading
–Cytokines acting sequentially
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13. 24/11/2022
General properties of cytokines
IL-4
IL-2
IL-4
IL-5
IFN-g
TNF
IFN-g
IgE
Th2 diff
Inhibition
Prolif
Increased expression
of MHC I and/or II
Macrophage
activation

15. Cytokine actions may be local and systemic
Autocrine
action
Endocrine action
circulation
act at a distance from the site of infection
Paracrine action act on a nearby cell
act on cytokine-producing cell itself

16. Action of Cytokines
Autocrine
–Affects the generating cell (self)
Paracrine
–Affects cells in the immediate vicinity
Endocrine
–Affects cells remote from the secreting cell

17. Cytokine-generating Cells
Innate immunity
–Macrophages
–Endothelial cells
–Fibroblasts
Adaptive immunity
–T lymphocytes
–Macrophages
–NK cells

18. Cytokine Network
CKs are part of complex system that regulates
the immune system.
CKs are primarily produced by immune
system but many other organs (liver, brain,
endocrine glands) make CKs to influence
immune response.

19. Cytokine Network

20. Chemokines
Chemoattractant Cytokines
Small (8-10kd) secreted heparin-
binding
Promote recruitment and activation of
leukocytes
Can be divided into subclasses by
virtue of structural properties

21. Chemokine Function
Recruitment of inflammatory cells to
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

22. Chemokine Function

23. Chemokine Function
• Chemokines promote chemotaxis in the
direction of highest concentration

24. Chemokine/Cytokine Interaction
• Allergic reaction

25. Break

27. NK cells secret cytokine, mainly IFN-g—to activate
macrophage to destroy phagocytosed microbes.
 Tumor necrosis factor (TNF)
 IL-1
 IL-12
 Type I IFNs
 IL-15
 IL-18
Mononuclear phagocytes are the principal source of
cytokines of innate immunity
As a result of cellular activation:

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Tumor Necrosis Factor
- Mediate acute inflammation to G-ve and
other microbes.
- Produced by activated MNCs, NK, Ag
stimulated T cells and mast cells.
- MQ produced it in influence of LPS

29. TNF
Low quantities
(plasma conc.<10-9M)
Moderate
quantities
High quantities
(plasma conc.10-7M)
Local inflammation
Systemic effects Septic shock
Leukocyte
Activation
Adhesion
molecule
Endothelial cell
IL-1,
chemokines
Fever
Low output
Hypoglycemia
Thrombus

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Type I IFN (IFN and IFN)
• Source:
–IFN a: mononuclear phagocytes , Nk cells,
Ag stimulated cells.
– IFNb: Many cells (ex. Fibroblasts)
• Stimulus: viral infection, Ag activated T cells

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Type I cytokines (IFN and IFN)
• Actions:
– Bind to the same receptor, induce similar biological
effects
– Protect against viral infections
– Promote cell-mediated immunity against intracellular
pathogens
» Inhibit viral replication (enzymes interfering with
transcription of viral RNA,DNA):
» Paracrine: IFN secreted protects neighbouring cells
» Autocrine: inhibits viral replication in the infected
cell
– Increase MHC Class I cell surface expression (CTL killing)
– Th1 (promotes expression IL-12R)
– Anti proliferative effect

32. type I IFN inhibits viral replication
virus
Viral replication
Induction of
“antiviral state”
IFN-
Induction of enzymes that
block viral replication
Potent
stimulus
nucleus nucleus
Virus infected cells Nearby uninfected cell

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Major biological activities of IL-12
• Induction of cytokine secretion
– Induces production of large amounts of IFN-g from
resting and activated T cells and NK cells
– Induces the production in low amounts of:
• TNF, IL-2, GMCSF, IL-8
• IL-10 (negative feedback regulating its own
production as IL-10 inhibits IL-12 synthesis)

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Major biological activities of IL-12
• Induction of cytokine secretion
– Induces production of large amounts of IFN-g from
resting and activated T cells and NK cells
– Induces the production in low amounts of:
• TNF, IL-2, GMCSF, IL-8
• IL-10 (negative feedback regulating its own
production as IL-10 inhibits IL-12 synthesis)

35. Macrophage
Microbes
Activation
Dendritic
cell
Antigen
presentation
CD40 CD40L
Naïve
CD4+
T cell
IL-12
TH1
cell
NK
cell
IFN-g
Macrophage activation;
killing of phagocytosed microbes
CD8+ T cell
Killing of infected cell
Increased cytolytic activity
NK
cell

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IL-1
• Source:
– Activated macrophages (neutrophils, EC, some epithelial
cells)
• Structure
– a and b forms, bind to same receptors, same biologic
activities
• Function:
– mediator of host inflammatory response to infections and
inflammatory reactions (similar as TNF except no apoptosis
and no septic shock induced)
• Receptors: members of Ig family . Type I on almost all cell
type; Type II on B cells, does not induce response to IL-1:
Decoy inhibiting IL-1 binding to type I receptor

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Chemokines
Stimulate leukocytes movement and regulate
their migration from blood to tissue.
- Sources : MQ, Endothelial cell , T Cells,
Fibroblast & platelets.
- Regulate traffic of lymphocytes and leukocytes
through peripheral lymphoid.
- Organ development(angiogenesis

38. inflammation
Blood
Secondary
lymphoid
organs
Primary
lymphoid
organs
Tissue
directing migration of leukocytes
Chemokines
Physiologic traffic of lymphocytes through the organs
(1) inflammatory stimuli
(2) Constitutively produced in lymphoid
organs
to inflammatory
sites
Cellular sources

39. 24/11/2022
Major biological activities of IL-12
• Induction of cytokine secretion
– Induces production of large amounts of IFN-g from
resting and activated T cells and NK cells
– Induces the production in low amounts of:
• TNF, IL-2, GMCSF, IL-8
• IL-10 (negative feedback regulating its own
production as IL-10 inhibits IL-12 synthesis)

40. 24/11/2022
Interleukine-10(IL-10)
Sources :MQ, TH2 .
- Homeostatic control of innate immunity&
adaptive one.
- Inhibit production of IL-12 & TNF.
- Inhibit expression of MHC11 & co stimulatory
molecules.
- Stimulate prolifrate human B cell in culture

41.  Cytokine of adaptive immunity are produced mainly by T
lymphocytes in response to specific recognition of protein Ags.
The function of T helper cells is mediated by cytokines

42. 24/11/2022
Interferon IFN-g
• Source: CD4+ Th1 cells, CTL, NK
• Function:
–In association with TNF IFN-g is the
major macrophage-activating
cytokine
• Stimulate MHC Class I and II molecules
and costimulators on APCs.

43. 24/11/2022
IFN-g functions
• On B cells acts on isotype switching :promotes
Ig2a (Fcg receptors binding on phagocytes),
inhibits IL-4 induced class switch to IgE and
IgG1
• Promotes indirectly Th1 differentiation: activates
mononuclear phagocytes to produce IL-12,
inhibits proliferation of Th2 cells
• Activate neutrophils and stimulates cytolytic
activity of NK cells

44. Leukocyte recruitment (inflammation)
Neutrophil activation (killing of phagocytosed microbes)
IFN-g: A principal macrophage-activating cytokine

45. 24/11/2022
IL-4 (18kD)
• Source: CD4+ Th2 cells, CD4+ NK1.1+ T cells, mast
cells, basophils
• Action:
– B cells
– B cell growth factor
– Isotype switch to IgE
– Increase MHC ClassII and FceRII
– Thymocytes, T cells
– Th2 differentiation, proliferation
– Macrophages
– MHC ClassII expression, phagocytic activity
– Mast cells proliferation

46. IL-2 Production
• 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

47. IL-2 Actions/Modulation
• Resting cells do not produce IL-2
• Induces cell cycle progression in resting
cells
• Allows clonal expansion of activated T-
lymphocytes
• Growth/expansion effect is modulated by
hormones such as prolactin

48. IL-2 Summary
• IL-2 important actions:
–It can increase immunoglobulin synthesis and J-
chain transcription
–Proliferation in B cells (with IL-4)
–potently augment the cytolytic activity of natural
killer (NK) cells
– induce the cytolytic activity of lymphokine-activated
killer (LAK) cells
–Due to its effects on T-cells and B-cells IL-2 is a
central regulator of immune response
–Passes BBB

49. 24/11/2022
Transforming Growth Factor beta(TGFβ)
Sources: T cells, MQ & other cells
- Inhibit proliferation and activation of
lymphocytes and leukocytes.
- Stimulate production of IgA in mucosal
immunity.
- Synthesis of collagen, cellular receptor for
matrix protein ( Repair mechanism).

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Hematopoietic Cytokines

51. 24/11/2022
Cytokines stimulate hemopoiesis
- Stem cell factor (c-kt): produced by bone
marrow stormal cells.
- IL-7: Fibroblast, BM S cells , induced
maturation of B & T cells.
- IL-3:T cell, target immature progenitors of all
cells.
- M-CSF, GM-CSF, G-CSF: MQ, Endothelial cells,
BM cells.

52. Pluripotent
stem cells

53. Cytokine Assays
• 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

54. Questions?

55. THANK
YOU