5. Innate Immunity III.pdf

7/28/2019 5. Innate Immunity III.pdf

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Innate Immunity (III)Soluble Molecules


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NK Cells

First line of defenseagainst: Tumor cells

Virally-infected cells Other intracellular

pathogens

Implicated in: Transplant rejection

Autoimmunity

Spontaneous abortions

Christina Trambas, Cancer Council of Tasmania,

http://www.ciml.univ-mrs.fr/fr/science/lab-eric-vivier/pour-specialistes

NK Cell

Tumor Cell


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Functions of NK

1. Direct Cytotoxicity:Target cell lysis

a. by perforines & granzymes

b. By Ab dependent cellular cytotoxicity (ADCC)


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2. NK secrete IFNs: Enhance the activation of M

Anti-viral activity

Functions of NK (II)


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Discovery of Interferons

Isaacs and Lindenmann (1957)

Found a substance that interfered with

viral replication and was therefore namedinterferon

Nagano and Kojima also independently

discovered this soluble antiviral protein


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What are Interferons?

Naturally occurring family of proteins & glycoproteineach with slightly different physiological effects

Genes (chr 9/12*) that synthesize IFN are activated

when a host cell is invaded by a virus

IFNs are secreted bycells of immune system : NK, lymphocytes

eukaryotic cells in response to viral infections,tumors


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Interferon Family

Main functions

stimulates the healthy cells which are livingneighbor an infected cell to activate genes for an

antiviral proteinblocks viral reproduction in the neighboring cell

activate macrophages and mobilize NKs


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When a tissue cell is infected by avirus, it releases interferon.Interferon will diffuse to thesurrounding cells.When it binds to receptors on thesurface of those adjacent cells, theybegin the production of a protein thatprevents the synthesis of viralproteins.

This prevents the spread of the virusthroughout the body.

General Actionof Interferons

Three types of interferons: alpha,beta and gamma.


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Type I InterferonsAlpha: produced by leukocytes

Beta: produced by fibroblasts

Largest group of interferons

Receptors: interferon cell

receptors type 1: stimulus for expression: viralinfection

different binding affinities

similar biological effects

Roles

Used to mobilize our 1st line ofdefense against invading organisms


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Anti-viraleffects of

interferona/b


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Type II Interferon (gamma)

Gamma: produced by

TH1, CTLs NK

B cells and professional antigen-presenting- cells

stimuli for Gamma production:

immune activationInflammatory state*

Bind to type 2 receptors


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Innate Immune System

First lineNatural Barriers:

I. PhysicalII. Chemical

III. Biological

Second lineComponentes:

I. Cells: NK, Phagocytes

II. Soluble molecules

III. Mechanisms


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Soluble molecules

recognition distruction

opsonization

+phagocytosis + inflammation

cellularlysis


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Soluble molecules

1. Interferons

(anti-viral proteins )2. Complement

(Membranar AttackComplex)

3. Beta lysine

(antibacterial proteins)4. Lactoperoxydase

(saliva & milk )

5. Lysosim(anti-bacterial enzyme))

1. Natural Ab (limitated

specificity)2. Pentraxines(C Reactive Protein, serumamiloid P)

3. Collectins

(MBL, pulmonar surfactants)4. Ficolines

(plasma proteins)



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Recognition Soluble Molecules

Natural Abs: Produced by some subsets of LB limited number of

specificities without overt exposure to foreign Ags Are present in plasma before the infection

Recognize common non-self molecules Pentraxines:

Recognize microbial structures Structure: pentameric proteins Members:

Short PTX: Reactive C protein, serum amyloid P Long PTX: PTX3

CRP: plasma conc low (N) 1000 fold during infection (phaseacute reactant)


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4. Ficolins:

structure : Similar to collectins

Role: recognize N-acetylglucosamin & acid

lipotheicoicG+ bacteria

Recognition Soluble Molecules

3. Collectines: Family Members: MBL (manose-binding lectin) SP-A & SP-D (pulmonar surfactants

Structure:

collagen-like tail bound to lectinic calcium-dependent (C-type)sequence

Role: recognize Man, Fru residuu

Dupa Abas at al. 2012 Elsevier/Saunders


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Soluble molecules

1. Interferons

(anti-viral proteins )2. Complement(Membranar AttackComplex)

3. Beta lysine

(antibacterial proteins)4. Lactoperoxydase

(saliva & milk )

5. Lysosim(anti-bacterial enzyme))

1. Natural Ab (limitated

specificity)2. Pentraxines(C Reactive Protein, serumamiloid P)

3. Collectins

(MBL, pulmonar surfactants)4. Ficolines

(plasma proteins)



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Complement (C) Definition

Definition:Group of 30 different heat labile

proteins, component of normal plasma exist normally in an inactive form

(zymogen).When activated, they can enhance

aspects of innate immunity & some ofthe biological effects of Abs their activity was said to complement

antibacterial activity of antibodies


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C Protein Sources

Nomenclature: are designated by letter C followed by a

number (C1-C9) fragments obtained by cleavege a/b** Factors: B, D, P, H, I

Source:Hepatocytes

Tissue macrophagesEpithelial cells of the GIBlood monocytes


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The effector functions ofcomplement can be activated

through 3 major pathways

The Classical Pathway

Lectin Pathway

The Alternative Pathway


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Innate Immune Activation ofComplement Pathway:

2 modes of initiation


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Alternative Pathway of

Complement Activation

Triggered by

LPS Cell Walls of some bacteria andyeasts

Cobra venom

C f Al i


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Proteins structure Conc (g/dL) function

C3 Heterodimer : 180kDa: terminal C: thiolesther domainTED2S

: terminal N: bound C5

1000-1200 Non-enzymatic Activated

C3a: stimulate inflammation

C3b: opsonin; component of

C3 convertase

Factor B

(zymogen)

Monomer: 93 kDA1 chain AA

200 Bb=Ser protease: active form

of C3 & C5 convertase

Factor D

(active

protease

Monomer 25 kDA 1-2 Plasmal Ser-protease

Cleavage factor B

FactorP

/properdin

Monomers 56KDa

(max 4 subunits)

25 Stabilize C3 convertase

(C3bBb)

Components of AlternativePathway of Complement



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Alternative Pathway ofComplement Activation



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Final Stages of C cascade

Abas at al. 2012 Elsevier/Saunders


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3 Main Consequences ofComplement Activation

Opsonization of Pathogens: C3b

Acute Inflammation: C3a, C5a

Killing of Pathogens: pore formation


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Functions of C system (a)



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Functions of C system (b)


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Functions of C system (b)



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Regulation of Complement

Activation Regulators of Complement Activation

Decay Accelerating Factor, Membrane

Cofactor 1, Complement Receptor 1, C1Inhibitor etc.

Inhibit formation of C3 convertase Breakdown and inactivate C3 and C5

convertase Inhibit formation of MAC


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Regulation of Complement Activation

Regulatory Protein placed on the surface of host cellprevent/dissociate formation of Bb complexDecay Accelerating Factor/ Complement Receptor 1,

Membrane Cofactor 1



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Inhibition ofactivation of C

Plasma Factors:

H Factor: bound C3b & C3bBb complex

Catalyze the activity of Ifactor

I Factor (inhibitory): proteasecleavage bound C3b inactivC3b

Dupa Thao Doan 2008; LWW


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The end


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Interferon Family

Interferons are a family of related

Lymphocytes secrete gamma () interferon, but

most other WBCs secrete alpha () interferon Fibroblasts secrete beta () interferon

Interferons also activate macrophages andmobilize NKs

FDA-approved alpha IFN is used: As an antiviral drug against hepatitis C virus

To treat genital warts caused by the herpes virus

4 I t f (IFN)


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Interferon molecules leave the infected cell

and enter neighboring cells

Interferon stimulates the neighboring cells to

activate genes for PKR (an antiviral protein) PKR nonspecifically blocks viral reproduction in the

neighboring cell

4 a. Interferon (IFN)


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The exact mechanism of type I interferons are not

fully understood, but this is an idea of what

happens: Alpha and beta bind to heterodimeric receptor on cell surface. Alpha receptor is made up of at least 2 polypeptide chains:

IFNa-R1 and IFNa-R2

IFNa-R1 is involved in signal transduction

IFNa-R2 is the ligand-binding chain that also plays a role in

signal transduction Ligation induces oligomerisation and initiation of the signal

transduction pathway

This results in phosphorylation of signal transductors andactivators of transcription proteins, which translocate to the

nucleous as a trimeric complex, ISGF-3. ISGF-3 activates transcription of interferon stimulated genes,

with many biological effects.


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Interferon Gamma Receptor

Composed of two ligand binding IFNg-R1 chainsassociated with two signal transducing IFNg-R2chains

The IFNg-R2 chain is generally the limiting factorin IFNg responsiveness, as the IFNg-R1 chain isusually in excess.

The IFNg-R1 intracellular domain contains binding

spots for the Jak 1, latent cytosolic factor, signaltransducer and activator of transcription (Stat1)

IFNg only associates with IFNg-R2 when the IFNg-R1 chain is present.

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5. Innate Immunity III.pdf