Innate immunity- Nobel Prize 2011

Innate immunity Nobel prize winning topic - 2011 : 

Dr.T.V.Rao. MD Innate immunity Nobel prize winning topic - 2011 Dr.T.V.Rao MD 1

2011 Nobel Prize in Physiology or Medicine: 

2011 Nobel Prize in Physiology or Medicine The 2011 Nobel Prize in Physiology or Medicine was awarded to Bruce Beutler at the Scripps Research Institute in California, Jules Hoffmann at the French National Center for Scientific Research and Ralph Steinman at The Rockefeller University in New York City. Beutler and Hoffman helped to elucidate innate immunity, the non-specific array of initial responses by the body’s immune system that can recognize invading microorganisms as being foreign and try to destroy them. Dr.T.V.Rao MD 2

The Nobel Prize in Physiology or Medicine 2011: 

The Nobel Prize in Physiology or Medicine 2011 was divided, one half jointly to Bruce A. Beutler and Jules A. Hoffmann "for their discoveries concerning the activation of innate immunity" and the other half to Ralph M. Steinman "for his discovery of the dendritic cell and its role in adaptive immunity" . The Nobel Prize in Physiology or Medicine 2011 Dr.T.V.Rao MD 3

The immune system : 

Infection of the human body by pathogenic microorganisms such as bacteria, viruses, parasites or fungi triggers the immune response. It occurs in a two-step process : innate immunity halts the infection, and adaptive immunity subsequently clears it . The immune system Dr.T.V.Rao MD 4

OVERVIEW OF THE IMMUNE SYSTEM: 

We are constantly being exposed to infectious agents and yet, in most cases, we are able to resist these infections. It is our immune system that enables us to resist infections. The immune system is composed of two major subdivisions, the innate or non-specific immune system and the adaptive or specific immune system OVERVIEW OF THE IMMUNE SYSTEM Dr.T.V.Rao MD 5

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Dr.T.V.Rao MD 6

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 Innate Immunity :definition Dr.T.V.Rao MD 7

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What happens when the physical and chemical barriers are breached? Dr.T.V.Rao MD 8

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Characteristics: rapid does not generate immunologic memory dependent upon germ line encoded receptors recognizing structures common to many pathogens Innate Immunity- First Line of Defense Innate Immunity Dr.T.V.Rao MD 9

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Leukocyte Players of Innate Immune Responses Dr.T.V.Rao MD 10

INNATE (NON-SPECIFIC) IMMUNITY : 

The elements of the innate (non-specific) immune system include anatomical barriers, secretory molecules and cellular components. Among the mechanical anatomical barriers are the skin and internal epithelial layers, the movement of the intestines and the oscillation of broncho-pulmonary cilia . Associated with these protective surfaces are chemical and biological agents. INNATE (NON-SPECIFIC) IMMUNITY Dr.T.V.Rao MD 11

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T he Innate Immune System composed of ? includes physical, chemical, and cellular barriers physical barriers include skin and mucus membranes chemical barriers include stomach acidity, secreted anti-microbial peptides cellular barriers include macrophages, neutrophils innate immune response activation occurs within minutes of pathogen recognition Dr.T.V.Rao MD 12

How Innate Immunity protects: 

How Innate Immunity protects 1 . Provides a barrier to prevent the spread of infection Mechanical (tight junctions, movement) Chemical (fatty acids, enzymes, pH, antimicrobial peptides) Microbiological (normal flora) Mucosal surfaces Nasopharyngeal, Oral, Respiratory, Intestinal tract Urogenital tract Skin (epithelial cells) Wounds, burns, insect bites Dr.T.V.Rao MD 13

How Innate Immunity eliminates pathogens: 

Identifies and eliminates pathogens Non-adaptive recognition systems Activates molecules that target the microbe and aid in it’s identification. These factors may be expressed at the surface or within cells, released from immune cells or are secreted and present within circulatory system How Innate Immunity eliminates pathogens Dr.T.V.Rao MD 14

Innate Immunity: 

Innate Immunity 3. Initiates an inflammatory response Reaction to injury or infection Trauma to tissues or cells Presence of foreign matter (self vs. non-self) Infectious agents (viruses, bacteria, fungi) Delivers effector molecules & immune cells to the site of infection Components Leukocytes & secreted factors Blood vessels Plasma proteins Dr.T.V.Rao MD 15

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Once the PRRs are activated by the PAMPs, phagocytosis is initiated Phagocytosis is active process: - Internalization of pathogen into phagosome - Acidification of phagosome Fusion of phagosome with lysosomes that contain anti-microbial compounds ( phagolysosome ) This may be sufficient to kill the pathogen If not, reactive oxygen and nitrogen species may need to be generated Macrophage Microbial Killing

Innate Immunity: 

Innate Immunity Provides signals to activate and regulate the type of adaptive immune response generated Stimulation of co-stimulatory molecules B7 family (CD80/86, PD-L, ICOSL) TNFR family (OX40L) Induction of a cytokine/chemokine response Cytokines: IL-12, IL-23, IL-4 Chemokine's: CXCR1, CXCR2, CCL20 a variety and depends on stimulus Dr.T.V.Rao MD 17

First Line of Defense -- Epithelia: 

First Line of Defense -- Epithelia Mechanical tight junctions, air/fluid flow, ciliary rejection Chemical lysozyme, pH, defensins, surfactant opsonins, TOX(ROX) Microbiological normal protective flora competition, antimicrobial colicin Inductive receptors that recognize pathogens and signal other innate and adaptive immune response Dr.T.V.Rao MD 18

Cells of Innate Immunity: 

Neutrophils Eosinophil's Basophils/Mast Cells Monocytes Macrophages Natural Killer Cells Platelets Cells of Innate Immunity Dr.T.V.Rao MD 19

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Dr.T.V.Rao MD 20

LEUKOCYTE TERMINOLOGY Two Systems: 

LEUKOCYTE TERMINOLOGY Two Systems Nuclear Morphology Mononuclear Cells Monocytes/Macrophages Lymphocytes Polymorph nuclear Cells Polymorphonuclear Leukocytes, PMNLs, PMNs Granule Morphology Granulocytes Neutrophils (neutral), Eosinophil's (orange), Basophils (blue) Agranulocytes Lymphocytes, Macrophages, Dr.T.V.Rao MD 21

COMPARATIVE MORPHOLOGY OF GRANULOCYTES: 

COMPARATIVE MORPHOLOGY OF GRANULOCYTES Dr.T.V.Rao MD 22

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Leukocyte Players of Innate Immune Responses

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Innate Immune Receptors Innate immune receptors are not clonally distributed Binding of receptors results in rapid response Innate immune receptors mediate three functions: - phagocytic receptors to stimulate pathogen uptake - chemotactic receptors that guide phagocytes to site of infection - stimulate production of effector molecules and cytokines that induce innate responses and also influence downstream adaptive immune responses

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Most microorganisms express repeating patterns of molecular structures termed Pathogen Associated Molecular Patterns (PAMPs) Innate immune system has evolved mechanisms capable of recognizing these repeating patterns termed Pattern Recognition Receptors (PRRs) Examples of Pattern Recognition Receptors: - Mannose-Binding Lectin (MBL) - Macrophage Mannose Receptor - Scavenger Receptors - Toll-like Receptors (TLRs) - Nod-like Receptors (NLRs) - RNA helicases (RIG-I, MDA-5) Pathogen Recognition

Phagocytosis: 

Phagocytosis Phagocytosis Definition: uptake of large particles (>0.5 m m) Actin-dependent, clathrin-independent High rate & efficiency of internalization Professional phagocytic cells Macrophages Neutrophils These cells have phagocytic receptors External receptors FcR, CR3, Mannose receptor Internal receptors TLRs Dr.T.V.Rao MD 26

Macrophages (MQ): 

Blood - Called monocytes (1-6% WBC) Tissues - Called macrophages mature form of monocytes normally found in tissues such as gastrointestinal tract, lung, liver and spleen Functions: Phagocytose and kills after bactericidal mechanisms are activated (T cells) Produce cytokines/chemokines (initiates inflammation) Is an antigen presenting cell (co-stim. Molecules) Macrophages (MQ) Dr.T.V.Rao MD 27

Neutrophils (PMN): 

Present in blood (55-60% of WBC) Not normally present in tissues Short lifespan - 12 hours Functions: First at the site of infection/injury Ingest and kill microbes after bactericidal mechanisms are activated (binding to pa thogen) Neutrophils (PMN) Dr.T.V.Rao MD 28

Human Neutrophil : 

Granulocytic Leukocyte Most Abundant White Blood Cell 2-6 x 10 3 cells/ μL 40 –75 % of leukocytes Very Short Lifetime t 1/2 = 6 hours 55 % of Bone Marrow Weight Devoted to Neutrophil Prod uction Human Neutrophil Dr.T.V.Rao MD 29

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Human Neutrophil Size In blood: Volume = 300 μm 3 sphere (300 fl vs. 90 fl for RBC) Diameter = 8.3 μm Dr.T.V.Rao MD 30

EOSINOPHIL EM MORPHOLOGY: 

EOSINOPHIL EM MORPHOLOGY Dr.T.V.Rao MD 31

Signal Transduction: 

Receptors recognition of pathogens chemical signals Transduction pathways G proteins, Kinases Effector activation gene induction motility, secretion adherence, phag ocytosis Signal Transduction Dr.T.V.Rao MD 32

G Protein Cycle: 

G Protein Cycle Dr.T.V.Rao MD 33

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Toll-Like Receptors (TLRs) Cellular Localization: Lysosomal localization (i.e. subcellular) of TLR-3 and TLR7-9 TLR-3 and 7-9 recognize viral/bacterial nucleic acids lysosomal expression isolates pathogen nucleic acid recognition away from potential cross-reaction with host mammalian nucleic acid motifs TNF a IFN ab

G protein-coupled receptors: 

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

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GTP   GTP    GDP GDP     GDP  GTP GDP PLC  INTERNALIZED GDP  P110  PIP2 PIP3 Receptor - G protein Coupling R R R R R L L L L L L L L L L L L L   Dr.T.V.Rao MD 36

GPCR OF INNATE IMMUNITY: 

GPCR OF INNATE IMMUNITY Dr.T.V.Rao MD 37 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

Killing Mechanisms: 

Killing Mechanisms Phagosome - membrane bounded vesicle that becomes acidified Lysozome - granules that contain products that damage or kill pathogens Enzymes Lysozyme - dissolves cell walls of some bacteria Acid hydrolases - digests bacteria Proteins Lactoferrin - binds Fe ++ needed for bacterial growth Vitamin B12-binding protein Peptides Defensins and cationic proteins - direct antimicrobials Dr.T.V.Rao MD 38

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Activated macrophages secrete proteins that drive innate response Cytokines - induce response by binding to specific receptors - can function in autocrine or paracrine manner - cytokines (and their receptors) are clustered according to structural similarities - critical cytokines secreted by macrophages following activation include TNF a , IL-1, IL-6, IL-12 to stimulate inflammation and phagocytosis/killing Chemokines - diverse family of chemotactic cytokines, induce directed chemotaxis of cells all related in amino acid structure - certain chemokines induce cell activation in addition to cell recruitment - promiscuous in receptor usage, each can bind more than one receptor - likewise, receptors are promiscuous

Killing Mechanisms - cont.: 

Killing Mechanisms - cont . Respiratory Burst Activated following phagocytosis Stimulated by PRR Requires increased oxygen consumption Produces substances that are directly toxic to the bacteria Oxygen-derived products O 2 - , H 2 O 2 & Myeloperoxidase Nitrogen-derived products NO (nitrogen oxide) Produced by inducible NO synthase (iNOS) enzyme Enzyme is induced by cytokines (LT, TNF b ) Dr.T.V.Rao MD 40

NADPH Oxidase : 

NADPH Oxidase Mitochondrial-independent respiratory burst P47phox & p67phox normally resides in the cytoplasma. P47phox becomes hyperhposphorylated following phagocytosis and binds to p67phox. These components move to the membrane and bind the NADPH complex resulting in an active complex . Dr.T.V.Rao MD 41

Enzyme Reactions of Respiratory Burst: 

Enzyme Reactions of Respiratory Burst Respiratory Burst NADPH NADP+ Superoxide + dismutase 2 O 2 2 O - H 2 O 2 Myeloperoxidase Enzyme which is stored in primary granules of PMN & MQ and uses the products of the respiratory burst. H 2 O 2 + C1 - Chloramines Dr.T.V.Rao MD 42

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Clinical symptoms of inflammation: pain, redness, heat, swelling 1. Increased vascular diameter , increased blood flow (heat, redness) 2. Activation of vascular endothelium to express adhesion molecules, increases leukocyte binding 3. PMNs are first cell type recruited to site, followed later by monocytes 4. Increased vascular permeability results in local swelling and pain Microvascular coagulation helps prevent pathogen spread into bloodstream (physical barrier)

Chemokine's: 

Chemokine's Infection induces the release of various chemokine's Theses substances bind specific and sometimes shared receptors to recruit various types of immune cells to the site of infection

Dendritic Cells: 

Dendritic Cells DCs link innate and adaptive immunity DCs are immature as they circulate waiting to encounter pathogens At this point, they are highly phagocytic, but not good stimulators of adaptive T cell responses Once they are activated by pathogens and activation of their PRRs, they secrete cytokines to initiate inflammation and then they migrate to lymph nodes and mature As mature DCs they are excellent APCs for T cell stimulation Dr.T.V.Rao MD 45

The current knowledge helps for newer vaccine trends : 

The current knowledge helps for newer vaccine trends The detailed understanding of the immune system provided by the new Nobel laureates has given other researchers the ability to improve vaccines and to attempt to stimulate immune reactions to cancer. Their insights also inform efforts to damp down the immune system when it becomes too zealous, which can lead to excessive inflammation and autoimmunity. Dr.T.V.Rao MD 46

For further information . . .: 

For further information . . . Immunology Project Resources – Understanding Autoimmune Disease http://www.niaid.nih.gov/publications/autoimmune/work.htm Antibody descriptions [IgG, IgM, IgA] http://sprojects.mmi.mcgill.ca/immunology/Ig_text.htm Immunology Hyperlinked History & Molecular Movies http://www.bio.davidson.edu/courses/Immunology/Bio307.html Nature Magazine & Immunology http://www.nature.com/nature/view/030102.html NCBI Genome http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1589796 NCBI Genome Base http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1589796 Immune System Animation Links through Anatomy & Physiology Groups http://science.nhmccd.edu/biol/ap2int.htm Pier,G . , Lyczak,J ., Wetzler,L ; Immunology, Infection, and Immunity ; American Society for Microbiology Press,2004,p.12.

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Dr.T.V.Rao MD 48 P rogramme created by Dr.T.V.Rao MD for Medical and Paramedical students in the Developing World Email doctortvrao@gmail.com