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

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

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.

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.

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

General properties of CKs Small proteins (MW: approx. 8-30 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

Manner of action 1) Autocrine: IL-2 Th Th 2) Paracrine : IL-12 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.

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-)

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)

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)

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.

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.

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 .

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).

Chemokines Subfamily Target Cells IL-8 CXC neutrophils MCP-1 CC monocyte Lymphotactin C lymphocyte Fractalkine CX3C lymphocyte

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

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

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

The functions of Th1 and Th2 cells.

Functions Of Cytokines

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.

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

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.

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

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

Features of Cytokines Whose Receptors Share γc CK 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

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.

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

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