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Innate Immunity

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Innate Immunity Know Differences and Provide Examples Chapter 3 * * Innate Immunity Skin and Epithelial Barriers * Antimicrobial peptide – psoriasin -Activity against Gram (-) E. coli Connection Between Innate and Adaptive Immunity 1 1 INFLAMMATION * PRRs – Pattern 2 Recognition * Receptors on 0 5 – Tissue Repair 3 HOST CELLS 4 PAMPs – 5 Pathogen- Associated Activation Molecular 6 Patterns on MICROBES Inflammation 4 Steps in Cell Recruitment from Blood Vessels Tissue damage Acute • 1) Release of Vasoactive and chemotactic Mediators histamine, serotonin, etc. • 2) Action on Blood Vessels ↑ cell adhesion molecules (CAMs) • 3) Vasodilation : ↑diameter of capillaries, ↑blood flow • 4) Increased Vascular Permeability : ↑ leakiness from blood vessels ↑ recruitment of cells and fluid edema • 5) Extravasation of Phagocytes – recruitment of leukocytes Chemotaxis (chemokines; C3a/C5a, N-formyl peptides) • 6) Phagocyte activation – chemokine and cytokine production CAMs – cell adhesion molecules • 6) Tissue Repair – fibrin (clotting) and fibroblasts Soluble Molecules and Membrane- Associated Receptors • 1) Antimicrobial Peptides – defensins, interferons Blood vessel – Defensins – α-Defensins, β-Defensins 2 4 5 endothelial cells • Cationic (+) peptides (29-35 aa) • Antibacterial and anti-fungal 3 • Disrupt microbial membranes and synthesis of RNA, DNA, and proteins • Produced among others by neutrophils and epithelial 1 1 1 cells ( paneth cells ) 0 – Interferons (Type I) -IFN-α and IFN-β Inflammatory • Block viral replication (RNA viruses) Mediators 2 Soluble Molecules and Membrane- Associated Receptors S 2) Acute Phase Response Proteins S – C Reactive Proteins (CRP), Mannose Binding S Protein (MBP), etc S • Increased in blood after tissue injury M • Synthesized by liver and macrophages • Phagocytosis IL-1β, IL-6, TNF-α Liver • CRP – binds polysaccharides and phosphorylcholine on M microbial membranes ↑ phagocytosis and complement activation • MBL - binds mannose residues on molecules found on S – soluble, M – membrane microbial membranes Activates complement Nucleotide-binding oligomerization domain Soluble Molecules and Membrane- Pattern-Recognition Receptors Associated Receptors - Receptors of the innate immune system NOD – Nucleotide-Binding Oligomerization - Recognize unique antigens (motifs) in micro- Domain organisms ( Danger Signals!!!) - Cytosolic receptors - These antigens are absent in the host (non- - Two types: NOD1 and NOD2 self) - Recognize products derived from peptidoglycan degradation. - Both Gram (+) and (-) Soluble Molecules and Membrane- Interact with Associated Receptors Ligand 1 TLRs – Toll-Like Receptors - 11 found in humans and 13 in mice - Structure: Exterior – Leucine-rich repeats; Interior – TIR (Toll-IL-1 Receptor) domain - Can form (HETERO or HOMO) DIMERS affect their binding specificity Interact with - Membrane and cytoplasmic localization Adaptor 2 Proteins 3 TLR-1 – Tri acyl lipopeptides ( Mycobacterium ) TLR-2 - Lipoarabinomannan), Lipoproteins, Peptidoglycans, and Fungi zymosan TLR-3 – dsRNA TLR-4 (MD2, CD14) - LPS TLR-5 - Flagellin TLR-6 – Dia cyl lipopeptides ( Mycobacterium ) TLR-2/6, TLR-1/2 - Lipoproteins TLR-7 - ssRNA TLR-8 – ssRNA TLR-9 – unmethylated CpG DNA Location : Outer membrane: TLR-1,2,4,5,6. Surface of endosomes: TLR-3,7,8,9. Pathways : 1) Nuclear factor-κB (NF-κB) and mitogen- activated protein kinase (MAPK) p38 and JNK, and 2) NF- κB and interferon regulatory factor-3 and 7 (IRF-3, IRF-7) 1) MyD88 inflammatory cytokines & type I IFN genes 2) TRIF inflammatory cytokines & type I IFN genes Biological Cell Types of Innate Immunity PAMP PRR Consequence of Interaction Microbial cell wall Complement Opsonization; components components Complement activation Mannose- Mannose-binding Opsonization; containing protein Complement carbohydrates activation Polyanions Scavenger receptors Phagocytosis Lipoproteins of TLR-1, 6 (Toll-like Macrophage Myocobacterium receptor) recruitment & activation; Secretion of inflammatory cytokines 4 Neutrophils • Phagocytosis • Express PRRs on surface (TLRs, Complement, Antibodies, etc) 1 2 3 • Oxidative and Non-oxidative Killing • Oxidative: ROS (reactive oxygen species) and RNS (reactive nitrogen species) triggered by NADPH Phagosome Oxidase ( phox ) • Respiratory Burst ↑ oxygen uptake 5 6 • Non-oxidative Killing – lysozyme, acidic 4 cathepsins, proteases, defensins, etc Activated Macrophages NK Cells • TLRs, Cytokines, etc – ↑ phagocytic activity • Protect against viral infections – ↑ killing activity • Produce cytokines: IFN-γ and TNF-α – ↑ MHC-II expression • These cytokines activate Macrophages, – ↑ cytokine production and differentiation of Th cells (Th1) – ↑ APR proteins and complement synthesis – ↑ iNOS (inducible nitric oxide synthase) • L-arginine + O 2 + NADPH NO + L-citruline + NADP 1 Dendritic Cells • Immature Antigen Mature 2 • Interact with both Th and Tc cells (Cross- P 3 presentation) 4 5 • Activation TLRs leads to ↑ MHC-II and co-stimulatory molecules 6 • Produce cytokines: type I IFNs and IL-12, 7 P TNF-α, IL-6. IRAK - IL-1R-associated kinase TRAF6 - tumor necrosis factor receptor • Killing by oxygen-dependent mechanisms associated factor 6 TAK1 - Transforming growth factor β- activated kinase 5 TLR Pathways IKK –IĸB Kinase 1 P • Two major pathways: IRF 3/7 and NF-kB IkB-P 3 MAP – mitogen activated protein • IRF 3/7 activation can result in the 2 production of type I interferons • NF-kB activation results in production of type I interferons and pro-inflammatory cytokines • Most TLRs signal through MyD88, except TLR3. TLR4 signals through both!!! NF-kB – IL-12, IL-1β, IL-6, TNF-α/ ↑ Tc cells ( MyD88 ) MAPK – Type I IFNs/ / ↑ Tc cells ( TRIF ) 1 2 3 4 The End!!! 6.
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