Introduction to the Immune System, Kordofan University (1)

8/3/2019 Introduction to the Immune System, Kordofan University (1)

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The Immune System

AtifHassanKhirelsied,B.Sc.,M.Sc.,Ph.D.

Departmento B oc em stry

Faculty

of

MedicineUniversityofKordofan


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mmun ymmun y

Immune(Latin

immunus)

=to

be

free,

exempt

mmun ycan ena ura oracqu re


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Theimmune

system:

e mmunesys em sacomp exne wor o

againstinvadingpathogensandtheirtoxins


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Thepathogens

= seasecaus ngm croorgan sms

bacteria

fungi,

pro ozoa,

parasite,

prion


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eant gen

Antigenswereoriginallydefinedasnonselfmolecules

.

Inpractice,thetermantigenisusedtomeanany

moleculerecognizedbytheimmunesystem.


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eant gen

Antigenswhichinduceadaptiveimmunityarecalled

immunogens.

Allimmunogensareantigens,butsomeantigensarenot

necessarilyimmunogens

and

are

known

as

hapten.

Haptens,arenotimmunogenicunlesstheyarecovalently

linkedto

immunogenic

carriers

called

adjuvant

(usually

proteins).


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Thehapten

Asubstance

that

is

non

immunogenic

but

which

can

react

withtheproductsofaspecificimmuneresponse.Haptens

responsewhenadministeredbythemselvesbutwhichcan

whencoupledtoacarriermolecule.


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Theepitope

and

paratope of

an

antibody

A. EpitopeorAntigenicDeterminant

Thatportionofanantigenthatcombineswiththeproductsof

aspecificimmuneresponse.

. ara ope s ecomp emen arypar o ean o y a

recognizesthe

epitope


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Thepathogens

Invadingmicroorganismsenterthebodiesthrough

di erentroutesand avedi erent a itatsint e

Theorgansoftheimmunesystemarestrategically

positionedthroughoutthebody.


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immunesystem

.


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Levels of

Figure 17.7


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Theimmune

system:

Innateimmunityispresentcontinuously,itisa

e ensemec an sm a spresen rom r .

Acquiredimmunityisinducedbythepresenceof

foreignmaterialandisusuallyquitespecific


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Innate Adaptive

Non-specific Immunity Specific Immunity

Antigen-independent Antigen-dependent

Immediate response Delayed response

Not antigen-specific Antigen-specific

No immunologic memory Immunologic memory


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Thebodydefenselines


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Theelementsoftheinnate(natural)immune

systeminclude;

Anatomicalbarriers.

Secretorymolecules.

Cellularcom onents.


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NaturalresistanceisthefirstNaturalresistanceisthefirstlinesofdefencelinesofdefence

TearsSalivaant acter a

enzymesantibacterial

enzymes

SSkin preventsMucus liningstraps

dirtandmicrobesen ry

Stomachacid

lowpH

kills

goodgut

harmfulmicrobes competebad


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Thenaturalresistance

Ph sicochemicalbarrierstoinfections

System/Organ Active

component Effector

Mechanism

Skin Squamous cells; Desquamation;flushing,

GItract Columnarcells Peristalsis,lowpH,bileacid,,

Lung Trachealcilia Mucocialiary surface

Nasopharynx

ande e

Mucus,saliva,tears Flushing,lysozyme


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System/Organ Active EffectorMechanism

Circulationand

l m hoidor ans

Phagocytic

cells

Phagocytosis and

intracellularkillin

NKcellsand Directandantibody

LAK dependentcytolysis

IL2activatedcytolysis

LAK:lymphokine activatedkillercells


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Humoralinnatebarrierstoinfections

System/

Organ

Activecomponent EffectorMechanism

Serum Lactoferrinand

Transferrin

Ironbinding

Interferons Antiviralproteins

TNFalpha antiviral,phagocyteactivation

Lysozyme Peptidoglycanhydrolysis

Fibronectin Opsonizationand

phagocytosis

Complement Opsonization,enhanced

phagocytosis,inflammation


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Theinflammation

therecruitmentofphagocytic cells.

Humoralfactorsintheserumorformedatthesiteof

n ec onp ay

an

mpor an

ro e

n

n amma on.


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Thecomplement

system

Isacomplementtoantibodymediatedimmunity.

Consistsofthirtyfiveinteractingplasmaand

membraneassociated

proteins

which

contribute

to

.

Itisthemajorhumoralnonspecificdefense

mec an sm.


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Thecomplement

system

Onceactivatedcomplementcanleadtoincreased

vascular

permeability,

recruitment

of

phagocytic cells,

and l sis and o sonization of anti ens.


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Thecomplement

system


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Thecoagulation

system

contributetothenonspecificdefensesbecauseof

theirability

to

increase

vascular

permeability and

actasc emotact c agents orp agocyt c ce s.


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Thecoagulation

system

antimicrobial.Forexample,betalysin,aprotein

producedby

platelets

during

coagulation

can

lyse

manyGrampositivebacteriabyactingasacationic

.


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Thecellularcomponentsoftheinnate

mmun ty nc u e;

1. Phagocytes (monocytes,macrophages)

2. PMNCs(neutophils,

eosinophils,

basophils).

3. Natural

killer (NK)

cells.

. .


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Partoftheinflammatoryresponseistherecruitment

o neutrop i s andmacrop ages tositeso

Thesecellsarethemainlineofdefenseinthenon

specificimmunesystem.


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.

PMNsrecruitedtothesiteofinfection

p agocy ose nva ngorgan smsan em

intracellularl .

PMNscontributetocollateraltissuedamagethat

occursduringinflammation.


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unc on np agocy os s an n race u ar ngo

microorganisms.

Actas

antigen

presenting

cells,

induce

adaptive

responses.


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Naturalkiller(NK)cellsarelymphocytesthatcan

recognizeand

destroy

viral

or

cancerous

cells.

.

tobe

abnormal

(i.e.

virally

infected

or

cancerous)

causetheabnormalcelltoundergoapoptosis.


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Phagocytosis

M h


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Macrophages.


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Oxygendependentmechanismsofintracellular

killing

Reaction Enzyme

H2O2 + Cl- --> OCl- + H2O

Myeloperoxidase

- + 2 --> 2 +- + 2

+ -- - 2 2 2 2

H O --> H O + O Catalase


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Oxygenindependentmechanismsofintracellular

ng

ec or o ecu e unc on

Cationic

roteins

includin

Dama eto

microbial

membranes

cathepsin)

Lysozyme Splitsmucopeptide inbacterialcell

wall

Proteolyticand

hydrolytic

iron

Digestionof

killed

organisms

enzymes


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systeminclude:

Recognitionandremovalofantigens.

Activationofthecomplementsystem.

Recruitmentofimmunecellstositesofinfectionandinflammation..

Inductionoftheadaptivesystemwhennecessary.

Comparison between innate and adaptive immunity


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Comparison between innate and adaptive immunity.

Attribute Innate Immunit Ada tive Immunit

Response time Minutes/hours Days

Specificity Specific for molecules and

molecular patterns

Highly specific, discriminate minor

differences in molecular structures

Diversity A limited number of germline

encoded receptors

Highly diverse, very large number

of receptors arising by genetic

recom na on

Memory responses None Persistent memory

Self/nonself

discrimination

Perfect, no microbe specific

patterns in host

Very good, occasional failure of

discrimination

Soluble components Many antimicrobial peptides and

proteins

Antibodies

,

macrophages, neutrophils) NK

cells, dendritic cells

, ,

cells

Documents

Introduction to the Immune System, Kordofan University (1)