Useful presentation for Cytokines

2. Secreted polypeptide or low molecular weight
protein involved in cell-to-cell signaling.
 Acts in paracrine or autocrine fashion through
specific cellular receptors.
Can be produced by cells of any tissue and act on
many cells involved in immune and inflammatory
response.

4. Cytokine nomenclature
Lymfokines - produced by activated T lymphocytes direct
the immune system response by signaling between its cells
 Interleukins - presumed targets are principally
leukocytes.
Chemokines - specific class of cytokines. Mediates
chemoattraction (chemotaxis) between cells, stimulate
leukocyte movement and regulate the migration of leukocytes
from the blood to tissues.
Monokines - derived primarily from mononuclear cells such
as macrophages.

5. Cytokines: main functions
 Hematopoiesis (ex. CSFs, colony stimulating factors).
 Inflammatory reaction (ex. IL1, TNF).
 Chemotaxis (ex. IL8, MIP1- macrophage inflammatory protein 1,
BLC – B-lymphocyte chemoatractant).
 Immunostimulation (ex. IL12, IFNγ).
 Suppression (ex. IL10).
 Angiogenesis (ex. VEGFs - vacsular endothelial growth factor).
 Embryogenesis (ex. TGF-b, LT-lymphotoxin).
.

7. Type I cytokine receptor

9. γc (IL-2Rγ) Deficiency
• Common gamma chain (γc) or interleukin-2 receptor gamma (IL-2Rγ)
deficiency is transmitted in an X-linked manner. Affected males have
mutations in the IL-2Rγ chain, also known as the common gamma chain
because of its critical role as a coreceptor in IL-4, IL-7, IL-9, IL-15, and
IL-21 receptors. Multiple pathways downstream of these receptors are
essential for differentiation and growth of T cells and NK cells, hence
the abnormal immune profile and profound defect in T-cell and NK-
cellmaturation.
• Affected males typically present at 3–6 months of age, with failure to
thrive and repeated microbial and fungal infections. Infections are fatal
unless HSCT is administered. (Hematopoietic stem cell transplantation
(HSCT) involves the intravenous (IV) infusion of autologous or
allogeneic stem cells to reestablish hematopoietic function in patients
whose bone marrow or immune system is damaged or defective)

10. • Evaluation of the immune system typically reveals extremely
low to absent T and NK cells, while sparing B cells (T−B+NK−).
In vitroresponses
• to mitogens are profoundly depressed, TRECs are undetectable,
and
• the thymus appears dysplastic with absence of Hassall corpuscles
and disrupted architecture.
• γc deficiency may have an atypical presentation because of
hypomorphic mutations. Various degrees of autologous T-cell or
NK-cell levels have been reported. Importantly, patients with the
R222C mutation can present with SCID- like symptoms but have
normal numbers of T cells and NK cells, near normal responses to
mitogens, normal TREC levels, and structurally normal thymus
gland.12 Cure can be achieved by providing HSCT. Gene therapy has
recently been attempted but remains an experimental procedure.

11. • Mutations in the common gamma chain (CD132) result in an
X-linked SCID with frequent bacterial, viral, and fungal
infections with defects in antibody responses, athymia, reduced
NK cell numbers, and absent T lymphocytes (OMIM 300400)
(Noguchi et al., 1993). CD132 is a cytokine receptor chain
shared among
• multiple cytokine receptors including the those for IL-2, IL-4, IL-7,
IL-9, IL-15, IL-21, and thymic stromal lymphopoietin (Rochman,
Spolski, & Leonard, 2009).Cytokine receptors that contain the
common gamma chain (γc) recruit tyrosine kinases to
• deliver intracellular signaling.
• In particular, in all these receptors, the γc is physically and
functionally coupled to the Janus associated kinase 3 (JAK3) (105),
whose gene has been mapped to chromosome 19p12. JAK3
deficiency is inherited as an autosomal recessive trait and results in
an SCID phenotype that is indistinguishable from that of X-linked
SCID, with absence of T and NK lymphocytes (106,107), reflecting
lack of IL-7 and IL-15-mediated signaling, respectively.
Identification of the mutation allows prenatal diagnosis (108).

12. • Gamma c family cytokines generally activate three major
signaling pathways that promote cellular survival and
proliferation, the PI 3-K-Akt pathway, the Ras-MAPK
pathway, and the JAK-STAT pathway. Differences in the
expression patterns of the cytokines or their unique receptor
components, along with the activation of different STAT
proteins may account for some of the distinct effects
mediated by gc family cytokines.

13. Signaling through cytokine receptor
Phosphorylation through kinases:
 The addition of a phosphate molecule to a polar R-
group of Tyr can turn a hydrophobic portion of protein
into a polar and extreme hydrophilic portion of
molecule.
– Kinase is a type of enzyme that transfers phosphate group
(PO4) from high-energy donor molecules, such as ATP to
specific target molecules (substrates).
– The opposite, an enzyme that removes phosphate groups
from targets, is known as a phosphatase.
– Kinase enzymes that specifically phosphorylate tyrosine
amino acids are termed tyrosine kinases.

14. Signaling through cytokine receptor

15. Type II cytokine receptors
Interferons (IFN)
antiviral activity.
 Secrete by cells in a response to variety of stimuli.
 Type I and type II IFN and IFN-like cytokines.
 Effects are mediated through cell receptors.
IFN activate cellular signalling pathway (gene induction or
repression).

16. Type I IFNs consist of seven classes:
IFN-, IFN-, IFN-, IFN-, IFN- IFN- and
IFN-
Type I IFNs are major components of the innate immune
system.
 Protect against viral infection.
 The expression of type I IFNs is induced by viral
challenge.
Type II IFN consist of IFN- only.
 IFN- (immune interferon) is produced by
certain activated T-cells and NK cells.
 IFN- is made in response to antigen (including
viral antigens) or mitogen stimulation of

17. Produced by macrophages, neutrophils and other
somatic cells in response to infection by viruses or bacteria.
 Inducer is double strand RNA provided by viral genom
itself.
 Receptors are expressed on most cell types.
IFN-
 IFN- is produced in activated TH1 and NK cells,
particularly in response to IL-2 and IL-12.
Binding of IFN- to its receptor increases the expression
of class I MHC on all somatic cells.
IFN- may also activate macrophages, neutrophils and
NK cells.

18. Initiation and regulation of
variety responses
antiviral
antiproliferative activity (ability
to arrest cell growth) – treatment
for cancer
 control of apoptosis
immunomodulatory (INF-
predominantly modulates
immune response, main antiviral
cytokine).
Function of IFNs:
http://www.virtualsciencefair.org/2007/sank7b2/fig1b.jpg

19.  Expression of on the surface almost of all cell types.
 High affinity receptors are located in the T- and
B-lymphocytes, NK-cells, monocytes, macrophages,
neutrophiles, fibroblasts, endotelial cells and smooth
muscle cells.
Receptor is expressed only in response to stimulus
by antigen, only in cells of lymphoid origin (NK cells,
macrophages, and some T cells).

20. IFN-R1 - 90 kDa glycoprotein (472 amino acid
residues)
Extracellular domain – 228 amino acid residues
Transmembrane domain – 24 amino acid residues
Intracellular domain – 220 amino acid residues
IFN- R2 - 62 kDa glycoprotein (315 amino acid
residues)
Extracellular domain – 226 amino acid residues
Transmembrane domain – 23 amino acid residues
Intracellular domain – 65 amino acid residues.
Ligand binds to extracellular domain of IFN-R1 only
(in absence of IFN-R1, IFN-R2 cannot bind IFN
IFN receptor has two components:
R1 and R2

21. Signal transduction is carried out through a series of
tyrosine phosphorylation events and culminates with the
activation and nuclear translocation of STAT protein and
new mRNA synthesis is induced.
• Jak proteins are brought into close after ligand-receptor
complex formation.
• Transphosphorylation between Jak1 and Jak2 proteins (Jak2
phosphorylates Jak1, Jak1 transphosphorylates Jak2).
• phosphorylation of IFN-gR1(Tyr440).
• Binding of STAT1 protein to each IFN-gR1.
• Bound STAT1 is phosphorylated by Jak.
• Dissociation of dimer from the receptor and formed dimer
translocates to the nucleus.
• Induction of transcription of many genes.

23. IFN-R1 - 530 amino acid residues (409
residues of protein are extracellular, 100
residues are intracellular.
IFN-R2 - 217 AA residues in
extracellular space, 251 AA residues in
intracellular space.
Both components bind type-IFNs
cooperatively.
 Receptor has ability to bind multiple
ligands (all subspecies of IFN- and IFN-
 and other types of IFN-type I).
Interferon ligand is boud to IFN-R1 and
than to IFN-R2 which stabilizes the
complex.

24. Tyk2 associates with IFN-R1
Jak1, STAT1 and STAT2 associate with
IFN-R2.
Jak1 transphosphorylates Tyk2 (1). Tyk2
in turn phosphorylates Jak1 and IFN-R1
(2).
Phosphorylation of IFN-R1 allows
STAT2 to bind to IFN-R2.
 STAT2 phoshorylates STAT1.
STAT1-STAT2 complex dissociates from
receptor.
Dimer STAT1-STAT2 associates with
interferon regulatory factor to form the
transcription complex.

26. Induces inflammatory reaction.
Induces antibacterial effect (activation of neutrophils, NK cells
and macrophages, increased their ability to recognize, kill,
and digest foreign materials or microbes).
Normal expression of is important in preventing the
development of cancer.
Antiviral defence (protects the cell from viral replication).