Cytokines and Thelper subsets MCB 150 Pr Coscoy
Cytokines and Thelper subsets MCB 150, Pr Coscoy
I. Characteristics of Cytokines (CKs) u. CKs are small proteins (<30 k. Da) u. CKs are similar to hormones and growth factors. u. CKs control the immune system. u Cytokines include subsets called lymphokines, monokines, chemokines, etc.
Cytokine Network u. CKs are part of complex system that regulates the immune system. u. CKs are primarily produced by immune system but many other organs (liver, brain, endocrine glands) make CKs to influence immune response.
Cytokine Network
T helper and Macrophage Interaction highlighted Effector T cell Th cells control immune system through CKs.
Activation of Cells = Production of Cytokines u. Production of CKs is usually part of immune cell activation. u. Cytokines are produced in response to different stimuli (e. g antigen receptor, cytokine/chemokine receptor).
Cytokine Network on a Local Level IL-4 Re IL-4 T cell B cell IL-2 gene IL-4 gene IL-2 Receptor IL-2
II. Measuring Cytokines u. Protein amount by ELISA. Good for in vitro experiments. u. Protein amount by bioactivity assay using CK dependent cell lines. u. RNA message by PCR.
Antigen Capture ELISA for IL-2
III. Actions of Cytokines u. Autocrine acts on same cell that produced it. IL-2 for T cell activation u. Paracrine acts on nearby cells. T cell help for B cells u. Endocrine acts on cell at a distance (through bloodstream). Inflammatory cytokines.
Actions of Cytokines IL-2 for T-cell activation T-cell help for B cells Inflammatory cytokines
IV. Properties of Cytokines Pleiotropy u. Same cytokine has different effects on cells can be activating or inhibiting. u. Example: IL-10 can be inhibitory to macrophages and Th 1 cells yet activating for Th 2 cells and B cells.
Synergy Experimental Example Proliferation of CTLLs (CTLLs are cytokine dependent cell line) u. Both IL-2 or IL-4 activate CTLLs in vitro. u. Maximal proliferation obtained when both IL-2 and IL-4 added. u. Both cytokines need to be blocked in order to inhibit growth.
Properties of Cytokines Pleiotropy Redundancy Synergy Antagonism
V. Functions Of Cytokines
VI. CD 4+ T helper Subsets Th 1/Th 2 Cytokine Bias u. CD 4+ Thelper cells can be divided into subsets based on their cytokine production. u. Th 1 cells produce IL-2, IFN-g, TNF-b CKs which activate cell mediated immunity u. Th 2 cells activate IL-4, IL-6, IL-10 CKs that activate humoral immunity These Th subsets were originally identified using mouse T cell clones.
Mouse Th Subset Cytokine Th 1 Th 2 Table 12 -4 from Goldsby
Th 0 ---> Th 1 or Th 2 Original mouse experiments on Th cells (Mosmann et al (DNAX) 1986 J Immunol) Antigen specific T cells placed in culture with antigen and APCs to make T cell lines. u. Spleen cells (Th 0) add IL-12 Th 1 cells IL-2, IFN-g, TNF-b u. Spleen cells (Th 0) add IL-4 Th 2 cells IL-4, IL-6, IL-10 u (Th 0 --precursor cell that produces IL-2, IL-4, and IFN-g. )
Th 1/Th 2 Naïve Th 0 IL-12 Effector Th 1 cell IL-2, IFN-g IL-2, IL-4, IFN-g IL-4 Effector Th 2 cell IL-4, IL-6, IL-10
Th 1/Th 2 Antagonism IL-4 blocks Th 1 IL-4 IL-12 Th 1 cell IL-2, IFN-g blocks Th 2 IFN-g IL-4 Th 2 cell IL-4, IL-6, IL-10
Th 1/Th 2 Regulation T-bet is a transcription factor that is required for Th 1 specific genes such as IL-12 Rb IL-4 blocks T-bet IL-12 Th 1 cell IL-2, IFN-g Enhances T-bet Th 2 cell IL-4, IL-6, IL-10
IL-4 vs IFN-g u. T-bet (Th 1 associated) activated by IFN-g and turned off by IL-4. u. Conversely in Th 2 transcription factor GATA-3 activated by IL 4 turned off by IFN-g.
Role for Th 1 vs Th 2 in Immune Response u. Both subsets activated in lymph nodes (LN) immune responses to complex antigens. u. Th 1 cells leave LN to find activated endothelium tissue to activate macrophages. u. Th 2 cells can stay in LN to activate B cells.
What controls Th 1 vs Th 2? 1) Amount of antigen. Mouse experiments originally showed high dose for Th 1. 2) MHC and TCR affinity. High affinity TCR = Th 1. 3) Dendritic cell subsets during activation. APC subsets activate Th 1 or Th 2 preferentially. 4) Toll-like receptor activation.
Influence of APC Subsets on Th 1/ Th 2 Dendritic cell u. Myeloid-like dendritic cells produce abundant IL-12 and drive Th 1. u. Lymphoid-like dendritic cells produce low levels of IL-12 are permissive for Th 2.
Toll-like receptors (TLRs) Influence of APCs on Th 1/ Th 2 u. Evidence for TLR activation influencing Dendritic cell maturation. – TLR 9 binds bacterial Cp. G DNA – TLR 4 binding to bacterial heat shock proteins u. TLR activation induces APC expression of IL-12, IL-23, IL-27 Th 1
TLR vs IL-12 in Th 1/ Th 2 development u. New evidence suggests that TLR activation influencing Th 1 outcome through initiation of TLR adapter molecule My. D 88. u. May be more important than IL-12 for Th 1.
My. D 88 -/- mice fail to control acute Toxoplasma infection Survival curve shows My. D 88 is just as important as IL-12 for Th 1 response after Toxoplasma infection. Control mice ( ) My. D 88 -/- mice ( ) IL -12 p 40 -/- mice ( ) Scanga et al The Journal of Immunology, 2002, 168: 5997 -6001.
My. D 88 -/- mice default to Th 2 Role for TLR Activation in Th 1/Th 2 IFN-g A. My. D 88 -/- mice Response to Th 2 pathogen B. My. D 88 -/- mice Response to Th 1 pathogen C. WT mice Response to Th 1 pathogen IL-4 IL-5 IL-10 IL-13
Th Cytokine Bias in Disease Examples Leishmania in mice (Richard Locksley) u C 57 Bl. 6 mice have Th 1 immune response and resolve infection. u BALB/c mice produce Th 2 cytokines unable to control Leishmania lesions. Leprosy in Humans (Robert Modlin) u Tuberculoid form has Th 1 response and limits disease (healing). u Lepromatous form has Th 2 response and uncontrolled disease (leprosy).
Th Cytokine Bias in Disease: Leprosy Skin disease caused by Mycobacterium leprae Tuberculoid: has Th 1 response and limits disease (healing). Lepromatous: has Th 2 response and uncontrolled disease (leprosy).
Cytokine Bias in Leprosy RNA from skin lesions of patients
Cytokines as Ligands T Cell Ligand APC Target Receptor TNF-b or Lymphotoxin Soluble or membrane bound LT a and b Receptors
VII. Cytokine Receptors u. Expression of cytokine receptors controls the ability of a cytokine to act on a cell. u. Cell activation increases cytokine receptor expression.
Cytokine Receptor Families 5 different families of receptors based on common structural motifs. --> see book for more details
IL-2 Receptor Subfamily Shared common g subunit Only IL-2 and IL-15 have unique alpha subunit
X-Linked SCID Common g chain Deficiency u. Mutation in g chain so unable to signal through IL-2, IL-4, IL-7, IL-9, IL-15. u. No T cells abnormal thymus. u. Immunocompromised susceptible to infections. SCID Patient with severe Candida in mouth.
GM-CSF Receptor Subfamily Hematopoietin Receptors Low affinity receptors compete for common b subunit to get high affinity binding. GM-CSF Granulocyte monocyte Colony stimulating factor
GM-CSF Receptor Subfamily Hematopoietin Receptors IL-3, IL-5 GM-CSF activate common b subunit. Cytokine Receptor Signal through JAKs and STATs
Cytokine Receptor Signaling JAKs and STATs (Model of Signal) Binding of cytokine ligand brings together receptor subunits JAKs (Janus Associated Kinases) are tyrosine kinases that phosphorylate tyrosines. STAT (Signal Transducers and Activators of Transcription ) dimerize for function.
JAKs and STATs Usage by CK Receptors Overlapping and Unique JAK 1 is commonly used by CKs from completely different CKR families STAT 6 is ONLY used IL-4.
The Yin and Yang of Th 1 and Th 2 Immune Responses
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