Innate Immunity definition

INNATE IMMUNITY Signal Transduction Effector Mechanisms Innate Immunity:definition • no need for prolonged induction • no clonal expansion of Ag specificity • act quickly – immediate direct response 0-4 hrs – rapid induced 4-96 hrs • failure ==> adaptive immune response • dependence on germ line encoded receptors • high discrimination of host and pathogen First Line of Defense -- Epithelia • Mechanical – tight junctions, air/fluid flow, ciliary rejection • Chemical – lysozyme, pH, defensins, surfactant opsonins, TOX(ROX) • Microbiolgical – normal protective flora competition, antimicrobial colicin • Inductive – receptors that recognize pathogens and signal other innate and adaptive immune response Cells of Innate Immunity • • • • • • • Neutrophils Eosinophils Basophils/Mast Cells Monocytes Macrophages Natural Killer Cells Platelets LEUKOCYTE TERMINOLOGY Two Systems • Nuclear Morphology – Mononuclear Cells • Monocytes/Macrophages • Lymphocytes – Polymorphonuclear Cells • Polymorphonuclear Leukocytes, PMNLs, PMNs • Granule Morphlogy – Granulocytes • Neutrophils (neutral), Eosinophils (orange), Basophils (blue) – Agranulocytes • Lymphocytes, Macrophages, COMPARATIVE MORPHOLOGY OF GRANULOCYTES Human Neutrophil • Granulocytic Leukocyte • Most Abundant White Blood Cell – 2-6 x 103 cells/μL – 40 –75 % of leukocytes • Very Short Lifetime – t1/2 = 6 hours • 55 % of Bone Marrow Weight Devoted to Neutrophil Production Human Neutrophil Size •In Peripheral Blood Smear: – 12 – 15 µm diameter Human Neutrophil Size • In blood: • Volume = 300 μm3 sphere (300 fl vs. 90 fl for RBC) • Diameter = 8.3 μm NEUTROPHIL EM MORPHOLOGY EOSINOPHIL EM MORPHOLOGY BASOPHIL/MAST CELL EM MORPHOLOGY Signal Transduction • Receptors – recognition of pathogens – chemical signals • Transduction pathways – G proteins, Kinases • Effector activation – gene induction – motility, secretion – adherence, phagocytosis Three Types of Receptors ACh receptor Chemotaxis receptor Growth factor receptor G protein-coupled receptors • • • • • • • Largest receptor family appx ~1000 types Bind proteins, peptides, absorb light Highly homologous in structure G protein exchange factors G protein splitters ==> G-GTP & G Primary transducers are G-GTP & G Activate membrane phospholipases and cyclases FPR mutations affecting ligand binding rendered in CPK HII - L78A HIII - D106A(N), L109A HIV - T157A HV - R201A, I204A, R205A HVI - W254A, Y257A HVII - F291A FPR and G Protein: Functional Interaction G Protein Cycle L L L Receptor - G protein Coupling L L L L L L R R  GDP R      GDP  L L GTP L L R  GDP    GDP P L C  GTP R   PIP2 PIP3 P110 GTP GDP INTERNALIZED GPCR OF INNATE IMMUNITY • Peptide receptors – fMLF receptor-- chemotaxis toward bacteria – Complement receptors C5a, C3a -- chemotaxis toward sites of complement activation • Lipid receptors – Leukotriene (LTB4), Eiosanoid (LPXA4), PAF, PG • Chemokine receptors – CXC (IL-8), CC (MCP), CXXXC(Fractalkine) » nomenclature from amino terminal cysteines » IL-8, MCP induce extravasation of neuts, M » Fractalkine - monocyte /endothelial adhesion Enzyme Associated Receptors • Growth factor-like receptors – Cytokine receptors • Adherence/Phagocytosis receptors – Integrins – Selectins – FcR • Pattern/Pathogen recognition receptors – – – – – Mannose/Glucan receptors LPS receptor Scavenger Complement Toll receptors Enzyme-associated Receptors Mechanism of TK Receptors Primary Transduction by TK Receptors Mechanisms of Cytokine Receptors Primary Transducers of Cytokine Pathways • Non-receptor protein tyrosine kinases – Janus Kinase (JAK) family Primary Transducers of Pattern Recognition Receptor Pathways • Non-receptor protein tyrosine kinases – Src family; Fc-mediated Phagocytosis » Igene familyTyrActivation Motif phosphorylation (YXXL) » p72SykSyk kinase – MyD88; IL-1R-like Toll receptors » Serine threonine Immunity Kinase – P130cas; FocalAdhesionKinase;vinculin, talin; integrin-mediated Adhesin Mechanism Phagocytosis FcR-mediated Phagocytosis Three types of FcR • FcRI(CD64) – monocytes, M. IF-stim neutrophils – high affinity binds monomeric IgG • FcRII (CD32) A&B forms – low affinity binds to multimeric IgG – A - phagocytic and NK cells – B - B/T cells • FcRIII (CD16) – monocytes, M, neutrophils – GPI anchored Garcia-Garcia et al JLB 72:1092,2002 FcR-mediated Phagocytosis early events • Receptors clustered by geometry of binding • ITAMs phosphorylated by Src Y kinases • Small fraction of active Src kinases associated w/cytoplasmic domains • Fgr,Fyn, Hck, Lyn,Yes, Src • Pi ITAM dock SH2 domain of Syk(Y-Kin) • Syk maybe need for actin cup formation Syk Downstream Signaling Calcium? PKC-S/|T Kinases - 11types ? PLA  AA release (Ca dep/ind) PLC Ca++ release PLD Activ PKC via DAG PI-3K PIP2, PIP3 PHs(Vavs)  Pseudopod extension ERK S/T Knse; MAPK1(aka) (nucl. transcription factor activation) PKC@PM w/Raf1 SMGsCDC42, Rac, Rho? 50 GEFs(Vav w/PHs) WASPs/Arps PAK LIMK Cofilin Midterm Questions • 1. Choose a receptor that mediates directed motility. Trace the events that may lead to formation of pseudopods that extend in the appropriate directions. Make sure that you cover the SMGs and how they participate and what regulates their participation. Describe key points of evidence? Do innate immune cells differ from B & T cells in this function? • 2. Compare and contrast inflammatory and apoptotic phagocytosis. Name names, identify key regulatory points, be clear about SMG participation