1. Cytokines and their receptors
Zhijian Cai (蔡志坚)
浙江省杭州市浙江大学紫金港校区
医学院科研楼B805
医学院免疫学研究所

2. Introduction to cytokines
Categories of CKs
Biological function of CKs
Cytokine receptor

3. Introduction to cytokines
Cytokine (CK)
Cytokines are small soluble proteins that mediate immune and inflammatory reactions and are responsible for communications between leukocytes and other cells.

4. The research of CK can help us to clarify the mechanism of immune responses at the molecular level and to understand the pathogenesis of some diseases.
Many CKs and their antagonists can be used in the treatment of many diseases (such as cancer, infection, autoimmune diseases) and to promote hemopoiesis, etc.

5. According to their source
1) Monokine
2) Lymphokine
According to their function
1) Colony stimulating factor
2) Interleukin
3) Interferon
4) Tumor necrosis factor
5) Growth factor
6) Chemokine

6. General properties of CKs
Small proteins (MW: approx KD)
Extremely potent, acting at 10-9~10-15M
The production is transient and tightly regulated
Autocrine, paracrine or endocrine
Cytokine actions: Pleiotropy, Redundancy, Synergy and Antagonism

7. Manner of action
1) Autocrine: IL Th Th
2) Paracrine : IL DC Th
3) Endocrine: IL-1, TNF-
Under certain circumstances (e.g. septic shock), large amounts of CKs (such as TNF-) are produced, they may be active distant from their site of secretion.

9. Cytokine actions 1) Pleiotropy Acts on more than one cell type (IL-4)
2) Redundancy
More than one cytokine have the same action (IL-2, IL-7,IL-15)
3) Synergy
Two or more cytokines cooperate to produce an effect that is different or greater than the combined effect of the two cytokines when functioning separately (IL-4 and IL-5)
4) Antagonism
Two or more cytokines work against each other (IL-4 and IFN-)

13. Categories of CKs CKs are classified into 6 functional categories
Interleukin (IL)
Interferon (IFN)
Tumor necrosis factor (TNF)
Colony stimulating factor (CSF)
Chemokine
Growth factor (GF)

14. Interleukin, IL Cytokines produced by leukocytes and act on leukocytes
IL-2, IL-7, IL-9, IL-15 constitute common  chain family
IL-4, IL-5, IL-6, IL-13 (Th2 type)
IL-8 (belongs to chemokine family)
IL-10 (Tr type)
IL-11 (stimulator of platelets)
IL-12 (DC, macrophages, directs Th1)

15. Interferon, IFN
IFNs are mediators of the innate immune response and Th1/CTL responses.
Groups
Type I IFN: IFN- and IFN-
The major source is leukocytes (PDC), fibroblasts
Help prevent the spread of virus to uninfected cells.
Type II IFN: IFN-
IFN- is produced by activated T cells and NK cells. Its main function is immune regulation.

16. Tumor necrosis factor, TNF
TNF was originally identified (and was so named) as a substance that can cause the necrosis of tumors in vivo.
TNF- and TNF-
TNF- is produced by LPS-stimulated mononuclear phagocytes and activated T cells. Involved in inflammation.
TNF- is also termed lymphotoxin (LT), and is produced mainly by activated T cells.

17. Colony-stimulating factors, CSF
Stimulates the differentiation and expansion of bone marrow progenitor cells.
It is assayed by its ability to stimulate the formation of cell colonies in culture.
Includes IL-3, CSF (G-CSF, M-CSF, GM-CSF), SCF, EPO, TPO, etc .

18. Chemokines (chemotactic cytokines)
Chemokines are a large family of structurally homologous CKs that stimulate movement and regulate the migration of leukocytes from the blood to tissues and within tissues.
About 50 different members.
Subfamilies: CXC, CC , C , CX3C , based on structural characteristics (cysteine residues).

19. Chemokines Subfamily Target Cells
IL CXC neutrophils
MCP CC monocyte
Lymphotactin C lymphocyte
Fractalkine CX3C lymphocyte

20. Growth factors, GF
Promote the proliferation and differentiation of cells.
Include TGF-, EGF, VEGF, FGF, NGF, PDGF, etc.

21. Biologic functions of CKs (1)
Anti-bacteria: IL-1, TNF, IL-6, IL-8 and IL-12
Anti-virus: type I,II IFN
Mediation and regulation of adaptive immunity:
*Stimulating the proliferation of lymphocytes:
IL-2, IL-7, IL-15.
*Stimulating the development of lymphocytes:
IL-12, IFN-, IL-4.
*Enhancing the activity of effector cells:
IFN-, IL-2,IL-6.
*Inhibiting immune response: TGF-, IL-10

22. Cytokine secretion and biological activities of Th1 and Th2 subsets
Type 1
Type 2
Cell-mediated
Immune response
(intracellular
organisms)
Humoral
response
(parasites, extracellularmicrobes)
T cell
IL-2
IFN-γ
TNF
IL-4
IL-5
IL-10

23. The functions of Th1 and Th2 cells.

25. Functions
Of Cytokines

26. Biologic actions of CKs (2)
Stimulation of hemopoiesis
SCF → stem cells
CSF → granulocytes and monocytes
IL-4 and GM-CSF → dendritic cells
EPO → erythrocytes
IL-11 and TPO →platelets
IL-7, IL-15 → formation of Tm
Apoptosis, killing target cell
TNF-α,FasL
Angiogenesis
IL-8, VEGF, etc.

28. Cytokine receptors 1. Five families Immunoglobulin superfamily
Class I cytokine receptor family
Class II cytokine receptor family
TNF receptor family
Chemokine receptor family

30. Note: The receptor contains a distinct set of 4 spaced cysteines in their extracellular domains and a conserved sequence motif (WSXWS) located near the external membrane surface.

31. 2. Multi-subunit receptor and common receptor subunit
one for cytokine binding
another for cytokine signaling
Common receptor subunit
There is same receptor subunit for cytokine signaling among the different cytokine receptors. e.g. IL-2R

32. IL-4, 7,9,15
IL-11, LIF
IL-5, GM-CSF

36. Features of Cytokines Whose Receptors Share γcCK
Major Source
Size
Actions
Chromo.
Location(h/m)
Genomic
Org
IL-2
Activated T cells (Th1 cells)
h153aa/20aa
m169aa/20aa
15.5 kDa
T-cell growth factor, B-cell growth, Ig production, J-chain expression, Induce LAK activity, Induce tumor infiltrating lymphocyte activity, Augment NK activity, Critical role in antigen-induced cell death (AICD), Stimulate macrophage/monocyte antitumor effects
4q26-
27/3 4
exons
IL-4
Activated T
cells (Th2 Cells), CD4+NK1.1+ NKT
h153/24 aa
m140 aa/20
Aa 18 kDa
B-cell proliferation, Ig class switch—IgG1, IgE production, Augment MHC II, Fcε receptors, IL-4Rα and IL-2Rβ expression, Th2 cell differentiation, Antitumor effects
5q31.1/11
IL-7
Stromal cells
H177aa/25aa
m154aa/25aa
17–25 kDa
Thymocyte growth, T-cell growth, Pre-B cell growth in mice but not humans, Survival and growth of peripheral T cells
8q12-
13/3 6
IL-9
Activated helper T cells
h144aa/18aa
m144aa/18aa
14 kDa
Th-helper clones, Erythroid progenitors, B cells Mast cells, Fetal thymocytes
5q31-
35/13 5
IL-15
Monocytes
and many
Cells outside the immune system
h162aa/48aa
m162aa/48aa
14–15 kDa
Mast-cell growth, NK-cell development and activity, T-cell proliferation
4q67-27 9
IL-21
Activated
CD4+ T cells
TFH cells
NKT cells
Th17 cells
h162aa/31aa
m146aa/24aa
Co mitogen for T-cell proliferation, Inhibits B-cell proliferation to anti-IgM + IL-4, Augments B-cell proliferation to anti-CD40, Conflicting reports related to NK cells, Cooperates with IL-7 and IL-15 to expand CD8 cells, Antitumor effects, Drives terminal B-cell differentiation to plasma cells, Proapoptotic for B and NK cells

37. In 1993, it was reported that the γ chain was defective in patients with X-linked severe combined immunodeficiency (XSCID; the disease is formally designated as SCIDX1)
Absent or profoundly diminished numbers of T cells and mitogen responses.
2. Absence of NK cells
3. Normal numbers of B cells, but defective B-cell responses.
4. IgM can be normal, but greatly diminished immunoglobulins of other classes.
SCID Patient with severe Candida in mouth.

39. Contains 3-6 cysteine-rich domains
Contains 3-6 cysteine-rich domains. Each domain is made up of approximate 40 amino acid residues.

40. GTP-binding protein coupled receptor superfamily or seven predicated transmembrane domain receptor superfamily.