Innate Immunity A Nobel Prize winning Topic 2011

8/3/2019 Innate Immunity A Nobel Prize winning Topic 2011

1/48

Dr.T.V.Rao. MD

INNATE IMMUNITY

NOBEL PRIZE WINNING TOPIC - 2011

DR.T.V.RAO MD 1


2/48

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 RalphSteinman 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 bodys immune system that can recognize invadingmicroorganisms as being foreign and try to destroy

them.

DR.T.V.RAO MD 2


3/48

The Nobel Prize in

Physiology or Medicine

2011 was divided, one half

jointly to Bruce A. Beutler

and Jules A. Hoffmann "fortheir 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


4/48

Infection of the humanbody by pathogenicmicroorganisms such as

bacteria, viruses,parasites or fungi triggersthe immune response. Itoccurs in a two-stepprocess: innate immunity

halts the infection, andadaptive immunitysubsequently clears it.

THE IMMUNE SYSTEM

DR.T.V.RAO MD 4


5/48

We are constantly being

exposed to infectious

agents and yet, in most

cases, we are able to resist

these infections. It is ourimmune system that

enables us to resist

infections. The immune

system is composed of twomajor 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


6/48

DR.T.V.RAO MD 6


7/48

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


8/48

What happens when the physical andchemical barriers are breached?

DR.T.V.RAO MD 8


9/48

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

InnateImmunity

DR.T.V.RAO MD 9


10/48

Leukocyte Players ofInnate Immune Responses

DR.T.V.RAO MD 10


11/48

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 theseprotective surfaces are chemical

and biological agents.

INNATE (NON-SPECIFIC) IMMUNITY

DR.T.V.RAO MD 11


12/48

The Innate Immune Systemcomposed of ?

- includes physical, chemical, and cellular barriers

- physical barriers include skin and mucusmembranes

- chemical barriers include stomach acidity,secreted anti-microbial peptides

- cellular barriers include macrophages, neutrophils

- innate immune response activation occurs withinminutes of pathogen recognition

DR.T.V.RAO MD 12


13/48

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


14/48


15/48

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 ofinfection

Components

Leukocytes & secreted factors

Blood vessels

Plasma proteins

DR.T.V.RAO MD 15


16/48

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 thatcontain anti-microbial compounds

(phagolysosome)- This may be sufficient to kill the pathogen

- If not, reactive oxygen and nitrogenspecies may need to be generated

Macrophage Microbial Killing


17/48

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


18/48

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


19/48

Neutrophils

Eosinophil's

Basophils/Mast Cells Monocytes

Macrophages

Natural Killer Cells Platelets

CELLS OF INNATE IMMUNITY

DR.T.V.RAO MD 19


20/48

DR.T.V.RAO MD 20


21/48

LEUKOCYTE TERMINOLOGY

TWO SYSTEMS

Nuclear Morphology

Mononuclear Cells

Monocytes/Macrophages

Lymphocytes

Polymorph nuclearCells

Polymorphonuclear Leukocytes, PMNLs, PMNs

Granule Morphology

Granulocytes

Neutrophils (neutral), Eosinophil's (orange), Basophils (blue)

Agranulocytes

Lymphocytes, Macrophages,DR.T.V.RAO MD 21


22/48

COMPARATIVE MORPHOLOGY OF

GRANULOCYTES

DR.T.V.RAO MD 22

L k Pl f


23/48

Leukocyte Players ofInnate Immune Responses


24/48

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 ofinfection

- stimulate production of effector molecules and cytokines

that induce innate responses and also influence

downstream adaptive immune responses

P th R iti


25/48

Most microorganisms express repeating patterns of

molecular structures termed Pathogen AssociatedMolecular Patterns (PAMPs)

Innate immune system has evolved mechanisms capable ofrecognizing 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


26/48

PHAGOCYTOSIS Phagocytosis

Definition: uptake of large particles (>0.5 mm)

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


27/48

Blood - Called monocytes (1-6%

WBC)

Tissues - Called macrophages

mature form of monocytes

normally found in tissues suchas gastrointestinal tract, lung,

liver and spleen

Functions:

Phagocytose and kills after

bactericidal mechanisms areactivated (T cells)

Produce cytokines/chemokines

(initiates inflammation)

Is an antigen presenting cell

(co-stim. Molecules)

MACROPHAGES

(MQ)

DR.T.V.RAO MD 27


28/48

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 pathogen)

NEUTROPHILS

(PMN)

DR.T.V.RAO MD 28


29/48

Granulocytic Leukocyte

Most Abundant White Blood Cell

2-6 x 103 cells/L

4075 % ofleukocytes

Very Short Lifetime

t1/2 = 6 hours

55 % of Bone Marrow Weight

Devoted to Neutrophil Production

HUMAN NEUTROPHIL

DR.T.V.RAO MD 29


30/48

Human Neutrophil Size In blood:

Volume = 300 m3 sphere (300 fl vs. 90 fl for RBC)

Diameter = 8.3 m

DR.T.V.RAO MD 30

EOSINOPHIL


31/48

EOSINOPHIL

EM MORPHOLOGY

DR.T.V.RAO MD 31


32/48

Receptors

recognition ofpathogens

chemical signals

Transduction pathways

G proteins, Kinases

Effector activation

gene induction

motility, secretion

adherence,phagocytosis

SIGNAL TRANSDUCTION

DR.T.V.RAO MD 32


33/48

G PROTEIN CYCLE

DR.T.V.RAO MD 33

Toll Like Receptors (TLRs)


34/48

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

TNFa

IFNab


35/48

G PROTEIN-COUPLED RECEPTORS

Largest receptor family appx ~1000 types

Bind proteins, peptides, absorb light

Highly homologous in structure

Gab protein exchange factors

G protein splitters ==> Ga-GTP & Gb

Primary transducers are Ga-GTP & Gb

Activate membrane phospholipases and cyclases


36/48

GTPa b

GTP

a b GDP

GDP

a b a

GDP

b

GTP GDP

P

L

C

INTERNALIZED

GDP

a

P110

PIP2 PIP3

Receptor - G protein

CouplingR

R

RR

R

L

L

L

L

LL

L

L

L

L

L

L

L

a

DR.T.V.RAO MD 36


37/48

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


38/48

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

Activated macrophages secrete proteins that drive


39/48

Activated macrophages secrete proteins that driveinnate 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 TNFa,

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


40/48

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

O2-, H2O2 & Myeloperoxidase

Nitrogen-derived products

NO (nitrogen oxide)

Produced by inducible NO synthase (iNOS) enzyme

Enzyme is induced by cytokines (LT, TNFb)

DR.T.V.RAO MD 40


41/48

NADPH OXIDASEMitochondrial-independentrespiratory burst

P47phox & p67phoxnormally resides in the

cytoplasma.

P47phox becomeshyperhposphorylatedfollowing phagocytosis andbinds to p67phox.

These components moveto the membrane and bindthe NADPH complexresulting in an active

complex.DR.T.V.RAO MD 41


42/48

ENZYME REACTIONS OF

RESPIRATORY BURST

Respiratory BurstNADPH NADP+ Superoxide

+ dismutase

2 O2 2 O-

H2O2

Myeloperoxidase

Enzyme which is stored in primary granules of PMN & MQ and uses the products of the

respiratory burst.

H2O2 + C1-

Chloramines

DR.T.V.RAO MD 42

Clinical symptoms of inflammation:


43/48

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, increasesleukocyte 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)


44/48

CHEMOKINE'S

Infection induces the

release of various

chemokine's

Theses substances bindspecific and sometimes

shared receptors to

recruit various types of

immune cells to the site

of infection


45/48

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 goodstimulators of adaptive T cell responses

Once they are activated by pathogens and activation of

their PRRs, they secrete cytokines to initiateinflammation and then they migrate to lymph nodes andmature

As mature DCs they are excellent APCs for T cellstimulation

DR.T.V.RAO MD 45


46/48

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 immunereactions to cancer. Their insights also inform

efforts to damp down the immune system when

it becomes too zealous, which can lead toexcessive inflammation and autoimmunity.

DR.T.V.RAO MD 46


47/48

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


48/48

Programme created by Dr.T.V.Rao MD

for Medical and Paramedical students in

the Developing World

Email

[email protected]

Documents

Innate Immunity A Nobel Prize winning Topic 2011