M1 – Immunology CYTOKINES AND CHEMOKINES March 26, 2009 Ronald B M1 – Immunology CYTOKINES AND CHEMOKINES March 26, 2009 Ronald B. Smeltz, Ph.D. rbsmeltz@vcu.edu

Learning Objectives 1. Define the term cytokine 2. Recognize and understand the difference between a cytokine and chemokine 3. Discuss the mode-of-action for cytokines 4. Know the functions of TGF-, TNF, and IFN- 5. Contrast the roles of IL-12 and IL-10 in inflammation 6. Predict the consequence of mutations in the common c receptor

Cytokines and cytokine receptors: Basic concepts A. Definitions: A cytokine is a protein made by a cell, that when it binds to a cytokine receptor it exerts a biological effect. Example: IFN- (gamma interferon) Cytokines cause naïve T cells to differentiate into effector cells with specialized effector functions (Th1, Th2, Th17, Treg) A lymphokine is a cytokine produced by a lymphocyte. An interleukin (IL) is a generic term used for many lymphokines: IL-2

Cytokines and cytokine receptors: Basic concepts 2. A chemokine is a special type of cytokine, known as a chemoattractant cytokine CXCL8: recruits neutrophils from blood into tissues Most cytokines are beneficial and act locally However, cytokines can also have negative effects on the host: dysregulated cytokine production can cause tissue damage systemic cytokine production can cause death

Cytokines and cytokine receptors: Basic concepts B. How do cytokines work? Secretion Binding to cytokine receptor Activation of Jak-Stat pathway Biological effect 1. Cytokines can be secreted in the following manner: autocrine production: when the cell that secretes the cytokine is also the target cell paracrine production: when the cytokine binds to a receptor that is expressed on a neighboring cell

Autocrine production

Paracrine production

Cytokines and cytokine receptors: Basic concepts 2. Cytokines bind to receptors with different structures:

Cytokines and cytokine receptors: Basic concepts 3. After a cytokine binds to a cytokine receptor, the JAK-STAT pathway is activated and leads to increased transcription of genes. STAT: Signal Transducers and Activators of Transcription

II. Categories of cytokines important for the immune system A. COMMON GAMMA CHAIN CYTOKINES (c) IL-2 , IL-7, IL-15 Cytokine Biological effects IL-2 T cell growth IL-7 T cell survival IL-15 T cell survival, memory T cells NK cell development

II. Categories of cytokines important for the immune system Common gamma chain (c) cytokine receptor All common gamma chain cytokines use the common c receptor  X-linked severe combined immunodeficiency syndrome(X-SCID) 1. mutation in c 2. severe deficiency in T cells and NK cells, defective B cell responses (B cells cannot class switch properly)

II. Categories of cytokines important for the immune system B. PRO-INFLAMMATORY CYTOKINES: IL-12 family, interferons, TNF family 1. IL-12 family  IL-12, IL-23, IL-27  Products of macrophages and dendritic cells  Effects of IL-12: 1. Stimulates secretion of IFN- 2. Induces the differentiation of T cells into IFN--producing Th1 cells 3. Immunity to intracellular pathogens (M. tuberculosis)

II. Categories of cytokines important for the immune system IL-12 receptor: Patients with IL-12 or IL-12R1 deficiencies are highly susceptible to Salmonella and Mycobacterial infections How could a mutation in a cytokine receptor be more severe than a mutation in the cytokine that binds to that receptor?

II. Categories of cytokines important for the immune system Interferons IFN-, IFN-, IFN- Originally called interferons because they interfered with viral replication. Double-stranded RNA is a potent inducer of IFN-. There are two types of interferons: Type I interferons: IFN-: produced by leukocytes, dendritic cells IFN-: produced by fibroblasts

Effects of Type I interferons

II. Categories of cytokines important for the immune system b. Type II interferons IFN- (gamma interferon) Produced by Th1 cells and NK cells  Effects of IFN-: activates macrophages increased killing of intracellular pathogens c. increased expression of MHC molecules d. increased antigen presentation e. promotes antibody class switching

II. Categories of cytokines important for the immune system Hereditary IFN-R-deficiency severe infections, death from intracellular bacterial infections

II. Categories of cytokines important for the immune system 3. Tumor Necrosis Factor (TNF) family  TNF-, TNF- (lymphotoxin ), lymphotoxin , Fas-L, CD40 ligand Cytokine Biological effects TNF-a Activates neutrophils, macrophages TNF-b (lymphotoxin-a) Cytotoxicity lymphotoxin-b Lymph node development Fas-L Apoptosis

II. Categories of cytokines important for the immune system Effects of TNF- production: Local TNF- stimulates IL-12 production, IL-12 induces IFN- production, IFN- activates macrophages, stimulates further TNF- production, containment of infection Excessive local TNF- autoimmune disease (rheumatoid arthritis) Systemic TNF- septic shock

II. Categories of cytokines important for the immune system TNF receptor: Mutations in Fas can cause defects in apoptosis (ie. ALPS) Mutations in CD40L can lead to hyper IgM syndrome. Why?

II. Categories of cytokines important for the immune system C. ANTI-INFLAMMATORY CYTOKINES  Transforming growth factor  (TGF-, IL-10  Effects of TGF- 1. Inhibits T cell proliferation 2. Inhibits inflammation 3. Regulatory T cells (Treg) can express TGF-  Effects of IL-10: Suppresses IL-12 production by macrophages Inhibits T cell proliferation

III. Chemokine and chemokine receptors Chemokines are chemoattractant cytokines. They are chemoattractant because they act as chemical signals to attract and recruit leukocytes from the blood into various tissues and organs. How to recognize a chemokine “L” = chemokine ligand i. CXCL would be a chemokine “R” = chemokine receptor i. CXCR would be a chemokine receptor

III. Chemokine and chemokine receptors Chemokine receptors are a class of 7-transmembrane, G-protein-coupled receptors How do cytokine and chemokine receptors differ?

III. Chemokine and chemokine receptors Important functions of chemokines: 1. Recruitment of lymphocytes into lymphoid tissues 2. Recruitment of cells from bone marrow to combat infection 3. Recruitment of cells into inflammatory sites Chemokines are selective for the cells they recruit: 1. CXCL8: neutrophils 2. CCL2: monocytes 3. CCL11 eosinophils 4. CXCL13: B cells 5. XCL1: T cells

IV. Chemokines and chemokine receptors of clinical relevance 1. CXCL4 CXCL4-heparin complexes cause autoimmune heparin-induced thrombocytopenia 2. CXCR4 and CCR5 HIV uses these receptors to infect cells 3. DARC (Duffy antigen receptor for chemokines) Plasmodium (causative agent of malaria) uses DARC to infect cells 4. CXCL8 glomerulonephritis 5. CCL2 and CCL5 Recruit macrophages into atherosclerotic plaques