CYTOKINES NOMENCLATURE OF CYTOKINES PROPERTIES OF CYTOKINES CYTOKINES BELONG TO FOUR FAMILIES CYTOKINES RECEPTORS CLASS I AND CLASS II CYTOKINE RECEPTORS ACTIVATION OF SIGNAL TRANSDUCTION PATHWAY BY CYTOKINE 1.Immunoglobulin superfamily receptors 2. Class I cytokine receptor family (also known as hematopoietin receptors family) Three subfamilies of the class I cytokine receptor family (hematopoietin) 3. Class II cytokine receptor family (also known as Interferon receptors family) 4. TNF receptor superfamily 5. Chemokine receptors Functional Categories of Cytokines A. Mediators of natural immunity B.Cytokines acting as mediators and regulators of adaptive immunity C. Cytokines acting as stimulators of haematopoiesis Cytokine Antagonists IMMUNE REGULATION A. Regulation by cytokines B. Regulation by regulatory T cells (Tregs) Cytokine cross-regulation Therapeutic Uses of Cytokines and their Receptors

1. ROLE OF CYTOKINES IN
IMMUNEREGULATION
PRESENTED BY: NALLA SAI PRANEET

2. CYTOKINES
The development of an effective immune response involves lymphoid cells,
inflammatory cells, and hematopoietic cells.
The complex interactions among these cells are mediated by a group of proteins
collectively designated cytokines to denote their role in cell-to-cell
communication.
Cytokines (Greek , cyto =‘cell’ & kinos =‘movement’) are low molecular weight
regulatory proteins or glycoproteins secreted by white blood cells and various
other cells in the body in response to a number of stimuli.

3. Nomenclature of cytokines
The nomenclature of cytokines is often based on their cellular sources.
• Interleukins - that act as mediators between leukocytes. The vast
majority of these are produced by T-helper cells. They are assigned as
interleukins (IL) number (e.g., IL-1, IL-2, IL-3 and so on) to maintain
a standard nomenclature.
• Lymphokines -produced by lymphocytes.
• Monokines-produced exclusively by monocytes.
• Interferons-involved in antiviral responses.
• Colony Stimulating Factors - support the growth of cells blood cell.
• Chemokines - mediate chemoattraction (chemotaxis) between cells.

4. PROPERTIES OF CYTOKINES
i) Cytokines bind to specific receptors on target cell membrane:
• All cytokines initiate their action by binding to specific membrane receptors
on target cells. Binding with receptors triggers the signal transduction
pathways that ultimately alter gene expression in the target cells.
• Cytokines and their receptors show very high affinity for each other, with
dissociation constant ranging from 10−10 to 10−12M.
• As a consequence, only very little quantities of cytokine are required to elicit
a biological effect.
• Cytokines regulate the intensity and duration of the immune response by
stimulating or inhibiting the activation, proliferation, and/or differentiation
of various cells, by regulating the secretion of other cytokines or of
antibodies, or in some cases by actually inducing programmed cell death in
the target cell.

6. (ii) Cytokine secretion is a brief, self- limited event:
• The synthesis of cytokines is transient, i.e., their synthesis is initiated by new
gene transcription as a result of cellular activation.
• Such transcriptional activation is transient as the mRNA encoding most
cytokines are unstable.
• Once synthesised, cytokines are rapidly secreted but never remain stored as
preformed molecules.

7. (iii) Cytokines show pleiotropism and redundancy synergy, antagonism and
cascade induction:
• A cytokine that induces different biological effects depending on the nature of
the target cells is said to have a pleiotropic action.
• Two or more cytokines that mediate similar functions are said to be
redundant.
• Receptors for cytokines are heterodimers (sometimes heterotrimers) that can
be grouped into families in which one subunit is common to all members of a
given family.
• Cytokine synergy occurs when the combined effect of two cytokines on
cellular activity is greater than the additive effects of the individual cytokines.
• In some cases, the effects of one cytokine inhibit or antagonize the effects of
another.
• Cascade induction occurs when the action of one cytokine on a target cell
induces that cell to produce one or more additional cytokines.

9. (v) Cytokines exert autocrine, paracrine and endocrine action:

10. Cytokines belong to four families
Falls in 4 families:
i. Hematopoietin family
ii. Interferon family
iii. Interleukin family
iv. Tumor necrosis factor family

11. Cytokine Receptors
• The cytokine receptors are trans membrane proteins with extracellular portions
that bind with cytokines and cytoplasmic portions that are responsible for
initiating intracellular signaling pathways.
• On the basis of homologies among the extracellular cytokine binding domains,
cytokine receptors are classified into five families:
(i) Immunoglobulin super family receptors
(ii) Class I cytokine receptor family (also known as haematoprotein receptor
family)
(iii) Class II cytokine receptor family (also known as the interferon receptor
family)
(iv) TNF-receptor family
(v) Chemokine receptor family

12. CLASS I AND CLASS II CYTOKINE RECEPTORS
• Many of the cytokine-binding receptors that function in the immune and hematopoietic
systems belong to the class I cytokine receptor family.
• The members of this receptor family have conserved amino acid sequence motifs in the
extracellular domain consisting of four positionally conserved cysteine residues
(CCCC) and a conserved sequence of tryptophan-serine-(any amino acid)-tryptophan-
serine (WSXWS, where X is the nonconserved amino acid).
• The class II cytokine receptors possess the conserved CCCC motifs, but lack the
WSXWS motif present in class I cytokine receptors. Initially only the three interferons,
α, β, and γ, were thought to be ligands for these receptors. However, recent work has
shown that the IL-10 receptor is also a member of this group.
• Another feature common to most of the hematopoietin (class I cytokine) and the class II
cytokine receptor families is multiple subunits, often including one subunit that binds
specific cytokine molecules and another that mediates signal transduction

13. Activation of Signal Transduction Pathway by Cytokine
• Mostly involved class I and class II receptors
• Activation of protein tyrosine kinase
• INF-γ is mostly studies example of signal transduction
•A number of cytokine receptors signal via the JAK/STAT pathway. These
include the receptors for IL-2, IL-3, IL-4, IL-6, IL-10, IL-12 and IFN-g.
• Cytokine receptor subunits are associated with JAK kinases.
1. -Binding of cytokine causes dimerization of receptors and activation of JAK
kinases.
2. -Activated JAK kinases phosphorylate receptor sites and create docking sites
for STAT molecules.
3. -After binding to the receptor (a chain), STATs are phosphorylated.
4. -They then dissociate from the receptor, dimerize and translocate to the
nucleus, where they mediate transcription of target genes.

15. 1.Immunoglobulin superfamily receptors

16. 2.Class I cytokine receptor family (also
known as hematopoietin receptors family)

17. Three subfamilies of the class I cytokine
receptor family (hematopoietin)
• GM-CSF has antagonistic effect
• GM-CSF is inhibited by IL-3
• Low affinity
• Low affinity subunit associated with
beta subunit
• Induce eosinophil proliferation and
basophil degranulation

18. • Alpha chain responsible for binding to
cytokine, other subunit for signal
transduction
• Induce synthesis of acute phase
proteins by liver hepatocytes
• Differentiation of myeloid leukemia
cell into macrophage

19. • Common gamma subunit
• Alpha for cytokine binding and beta and
gamma for signal transduction
• X- linked severe combined
immunodeficiency due to defect in gamma
chain
• Most widely studied cytokine receptor as
responsible for T cell activation
• IL-2 receptor is present in 3 forms: low,
medium, and high affinity.
• The low affinity (monomeric, IL-2Ra),
medium affinity (dimeric, IL-2Ra), and high
affinity (trimeric, IL-2Rag)

20. • Gamma subunit is constitutively
expressed
• Alpha and beta expressed after
activation by antigen
• Activated CD4+ and CD8+ cell
expresses high affinity IL-2

21. 3. Class II cytokine receptor family (also known
as Interferon receptors family)

22. 4. TNF receptor superfamily

23. 5. Chemokine receptors

24. Functional Categories of Cytokines:
Cytokines may be classified into three main functional categories based on their principal
biologic actions.
A. Mediators of natural immunity
1. TNF-α
• Tumor necrosis factor alpha is produced by activated macrophages is response to microbes,
especially the lipopolysaccharide (LPS) of Gram negative bacteria. It is an important mediator
of acute inflammation.
• It mediates the recruitment of neutrophils and macrophages to sites of infection by stimulating
endothelial cells to produce adhesion molecules and by producing chemokines which are
chemotactic cytokines.
• TNF- α also acts on the hypothalamus to produce fever and it promotes the production of acute
phase proteins.

25. 2. IL-1
• Interleukin 1 is another inflammatory cytokine produced by activated macrophages. Its effects
are similar to that of TNF-α and it also helps to activate T cells.
3. IL-10
• Interleukin 10 is produced by activated macrophages and Th2 cells.
• It is predominantly an inhibitory cytokine. It inhibits production of IFN-γ by Th1 cells, which
shifts immune responses toward a Th2 type.
• It also inhibits cytokine production by activated macrophages and the expression of class II
MHC and co-stimulatory molecules on macrophages, resulting in a dampening of immune
responses.
4. IL-12
• Interleukin 12 is produced by activated macrophages and dendritic cells.
• It stimulates the production of IFN-γ and induces the differentiation of Th cells to become Th1
cells.
• In addition, it enhances the cytolytic functions of Tc and NK cells.

26. 5. Type I interferons
• Type I interferons (IFN-α and IFN-β) are produced by many cell types and they function to inhibit
viral replication in cells.
• They also increase expression of class I MHC molecules on cells making them more susceptible to
killing by CTLs. Type I interferons also activate NK cells.
6. INF-γ
• Interferon gamma is an important cytokine produced by primarily by Th1 cells, although it can
also be produced by Tc and NK cells to a lesser extent.
• It activates macrophages; increases expression of MHC Class I and Class II molecules; increases
antigen presentation
7. Chemokines
• Chemokines are chemotactic cytokines produced by many kinds of leukocytes and other cell
types.
• They represent a large family of molecules that function to recruit leukocytes to sites of infection
and play a role in lymphocyte trafficking.
• Two examples are the α-chemokines which have a CXC structure (two cysteines with a
different amino acid in between) and the β-chemokines which have a CC structure (two
neighbouring cysteine).

27. 2. Cytokines acting as mediators and regulators of adaptive immunity:
1. IL-2
• Interleukin 2 is produced by Th cells, although it can also be produced by Tc cells to a lesser
extent.
• It is the major growth factor for T cells. It also promotes the growth of B cells and can activate
NK cells and monocytes.
• IL-2 acts on T cells in an autocrine fashion. Activation of T cells results in expression of IL-2R
and the production of IL-2. The IL-2 binds to the IL-R and promotes cell division.
• When the T cells are no longer being stimulated by antigen, the IL-2R will eventually decay
and the proliferative phase ends.
2. IL-4
• Interleukin 4 is produced by macrophages and Th2 cells. It stimulates the development of Th2
cells from naive Th cells and it promotes the growth of differentiated Th2 cells resulting in the
production of an antibody response.
• It also stimulates Ig class switching to the IgE isotype.

28. 3. IL-5
• Interleukin 5 is produced by Th2 cells and it functions to promote the growth and
differentiation of B cells and eosinophiles.
• It also activates mature eosinophiles.
4. TGF-β
• Transforming growth factor beta is produced by T cells and many other cell types.
• It is primarily an inhibitory cytokine. It inhibits the proliferation of T cells and the
activation of macrophages.
• It also acts on PMNs and endothelial cells to block the effects of pro-inflammatory
cytokines.

30. 3. Cytokines acting as stimulators of haematopoiesis:
Cytokines stimulating haemotopoiesis are produced by bone marrow stromal cells, leucocytes
and other cells. These include GM-CSF which promotes the differentiation of bone marrow
progenitors, M-CSF, which promotes growth and differentiation of progenitors into
monocytes and macrophages and G-CSF, which promotes production of PMNs

31. Cytokine Antagonists
 Inhibit the biological activity of
cytokines
•Bind to the cytokine receptor
•Bind to the cytokine
 Be found in the bloodstream and
extracellular fluid
 Some virus can produce cytokine-
binding protein or cytokine mimics
 Determine the intensity of the response –
IL-1Ra and sIL-2R (Biomarker for
various diseases)

32. • TH1 cells produce cytokines (IFN-γ and IL-2) that promote immune
responses against intracellular pathogens (DTH, cytotoxic T cell
responses, opsonizing Abs).
• TH2 cells produce cytokines (IL-4, IL-5, IL-6, IL-13) that promote
immune responses against extracellular pathogens (antibody responses,
eosinophilic responses, allergic reactions).
• Some cytokines are produced by both TH1 and TH2 cells. These
cytokines - GM-CSF and IL-3 - act on the bone marrow to increase
production of leukocytes - so they are needed no matter what type of
pathogen is present.

33. Cytokine by TH1 and TH2 cells

34. IV. IMMUNOREGULATION
The magnitude of an immune response is determined by the balance between antigen-driven
activation of lymphocytes and negative regulatory influences that prevent or dampen the
response. Regulatory mechanisms can act at the recognition, activation or effector phases of an
immune response.
B. Regulation by cytokines
Cytokines are positive or negative regulators. They act at many stages of the immune response,
but their activity is dependent upon the other cytokines present in the microenvironment as well
as receptor expression on effector cells. Cytokines regulate the type and extent of the immune
response generated.
Immune regulatory cytokines include TNF-α,TNF receptor superfamily including lymphotoxins,
cellular ligands e.g. CD40 and also FAS ligand i.e. CD95 stimulating apoptosis
IL1 and IL receptor superfamily too contain cytokines like IL-1α and β, IL-18, IL-33. It also
includes a series of mammalian pattern recognition molecules – Toll like receptors

35. B. Regulation by regulatory T cells (Tregs)
Regulatory T cells (Tregs) are a recently described populations of cells that can regulate immune
responses. They do not prevent initial T cell activation; rather, they inhibit a sustained response
and prevent chronic and potentially damaging responses. They do not have characteristics of
Th1 or Th2 cells but they can suppress both Th1 and Th2 responses.
1. Naturally occurring Tregs – The thymus gives rise to CD4+/CD25+/Foxp3+ cells that
functions as Tregs. These Tregs suppress immune responses in a cell contact dependent manner
but the mechanism of suppression has not been established.
2. Induced Tregs – In the periphery some T cells are induced to become Tregs by antigen and
either IL-10 or TGF-β. Tregs induced by IL-10 are CD4+/CD25+/Foxp3- and are referred to as
Tr1 cells. These cells suppress immune responses by secretion of IL10. Tregs induced by TGF-β
are CD4+/CD25+/Foxp3+ and are referred to as induced Tregs. These cells suppress by
secretion of TGF-β
3. CD8+ Tregs – Some CD8+ cells can also be induced by antigen and IL-10 to become a Treg
cell. These cells are CD8+/Foxp3+ and they suppress by a cell contact dependent mechanism or
by secretion of cytokines. These cells have been demonstrated in vitro but it is not known
whether they exist in vivo.

36. Cytokines profiles are cross regulated

38. Fig:- Cross regulation of TH1 and TH2 cells

39. Cytokine cross-regulation
• IFN-γ (Th-1) inhibits proliferation of Th-2
• IL-4 and IL-10 (Th-2) inhibits proliferation of Th-1 by decreasing IL-
12 production
• INF-γ (Th-1) promotes IgG2a production and decreases IgE by B cells
• IL-4 (Th-2) promotes production of IgE and IgG1 by B cells and
decreases IgG2a.

40. • Bacterial Septic Shock – Due to several Gram (-) bacteria – Stimulation of Macrophages by LPS -↑
TNF-α, IL-1β – Drop in blood pressure, fever, diarrhea, systemic blood clotting in various organs
• Bacterial Toxic Shock – Caused by superantigens (wide variety of toxins) – Activation of T cells - ↑
cytokines from T cells and activated Macrophages.
• Chagas’ disease:
Chagas’ disease is caused by the protozoan parasite Trypanosoma cruzi and is characterised by severe
immuno suppression. It has been found that in presence of T. cruzi, T cells show a dramatic reduction in
the expression of a subunit of IL-2 receptors, resulting in their inactivation of T cells with many antigens.
These, in turn, lead to immunosuppression in patients with Chagas’ disease.
• Lymphoid and myeloid cancers:
Development of some types of cancer is associated with the abnormal production of cytokines. For
example, excessive high levels of IL-6 are secreted by cardiac myxoma cells, myeloma and plasma
cytoma cells and cervical and bladder cancer cells.
Cytokine & Diseases

41. Therapeutic Uses of Cytokines and their Receptors:
From the above discussion it appeared that most cytokines are powerful
mediators of innate and adaptive immunities. Now a days, a number of cytokines
and soluble cytokine receptors have been purified and cloned. Many of such
cytokines notably, Interferons and colony-stimulating factors, such as GM-CSF
have proven to be therapeutically very useful.
Interferons:
Different types of interferons have antiviral activity and various other effects
including the capacity to induce cell differentiation, to inhibit proliferation by
some cell types, to inhibit angiogenesis and to function in various
immunoregulatory roles.

42. (i) INF-α (trade name Roferon and Intron- A) has been used for the treatment of
hepatitis C, hepatitis B and many types of cancer. Chronic myelogenous
leukemia, Kaposi’s sarcoma, non-Hodgkins lymphoma, cutaneous T-cell
lymphoma and multiple myeloma etc. respond well to treatment with IFN-α.
(ii) INF-β. In the autoimmune neurologic disease multiple sclerosis (MS), a
progressive neurologic dysfunction occurs. Treatment of that patients with IFN-β
provides longer period of remission and reduces the severity of relapses.
(iii) IFN-y has found to be effective for the treatment of a rare hereditary disease,
chronic granulomatous disease (CGD) where the patients’ phagocytic cells are
seriously impaired to kill the ingested microbes. Therapy of CGD patients with
IFN-y significantly reduces the incident of infections.

43. THANK YOU