b Cellimmunity 120223050013 Phpapp01

8/18/2019 b Cellimmunity 120223050013 Phpapp01

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Copyright © 2006 by Elsevier, Inc.

IMMUNITY

• The capability to resist any organism

or toxin that tend to damage thetissues and organs.


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Immunity

Innate = ability to resist damaging organisms and toxinsskin, gastric acids, tissue neutrophils

and macrophages, complement, NK cells

Acquired = specifichumoral ----> circulating antibodies!-cell"

cellular ----> acti#ated cells$-cell mediated"


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Preprocessing of the T and Blymphocytes

• Thymus gland preprocesses the T

lymphocytes

• Lier and bone marro! preprocess

the B lymphocytes


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Lymphoid tissue


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• Millions of speci"c types oflymphocytes are stored in thelymphoid tissue.

• #ll the di$erent lymphocytes that arecapable of forming one speci"city ofantibody or T cell are called a %clone

of lymphocyte&.


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Sequence

%ormant lymphocytes

In#asion of body by foreign antigen&hagocytosis by macrophages

&resentation of antigen to lymphocytes



Antigen

An antigen is a substance that can induce

an immune response 'hen introduced into

an immunocompetent host and that can react

'ith the antibody produced from that response(



!one )arro'

&re-!

*ell

&re-$

*ell$-*ell

$+-supressor

$-helper

!-*ell &lasma *ell

Ig IgA Ig) Ig% Ig.

Interactions between T- and B-Cells



'umoral immunity and#ntibodies



(ormation of antibodies byplasma cells

• )ormant B lymphocyte

• *xposure to a speci"c antigen

•Macrophage plays role in theactiation process

• 'elper T cells also contribute in this

actiation process



• These B lymphocytes enlarge to formlymphoblast.

• (urther diferentiate into plasmablast

• The mature plasma cells+antibodyfactories, then produce gammaglobulin antibodies.



(ormation of Memory cells-

di$erence bet!een primaryand secondary response


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#irgin cellsfirst exposure to antigen

second exposure to antigen

acti#ated cellsmemory cells

Formation of Activated and Memory Cells




self-antigens

death

*entral lymphoid organ &eripheral lymphoid organ

stimulation

self-antigens

death

inacti#ation

Loss of Antigens to Self



Antibodies

antigen

binding

site

hinge region

light chain

hea#y chain

/ab fragment

/c fragment

IgA, Ig%, Ig., Ig, Ig)



IgM Antibody



#ntibodie

s• Ig- 80% total, cross placenta, opsonization

• IgM- first produced, 10-15% total, activate complement

• Ig)- not known, may help CD4 Th

• Ig#- body fluid, tears, bronchiole secretions, saliva

• Ig*- allergic reactions, histamine release



Mechanism of action of antibodies

Direct Action Complement System



Direct action of antibodies

on invading agents

1. AGGLUTINATION

2. PRECIPITATION

3. NEUTRALIZATION

4. LYSIS



Comlement System

0eries of 1 23 proteins

Acti#ated by microorganisms

4ill coat the microorganisms

&resent normally among plasma proteins

$he en5yme precursors can be acti#ated by the

so called 6classical pathway7

s


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complement

bacteria phagocyte bacteria

!( chemotaxis"( lysis #( opsoni5ation

/unctions of *omplement Acti#ation



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Antibody-Activated $%agocytosis

/c receptor bacterium

opsoni5ation


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Ig& and 'istamine (elease

Ig. receptor

histamine#esicles

binding of Ig.

to /c receptor

antigenantigen

release of histamine

b i n d i n g o

f a n t i g e n


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Thank You


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T-cells

Act o#er a short range

Interact 'ith another cell in body*an kill or signal other cell

8nly recogni5e antigen 'hen presented

on surface of target cell


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T-cells

*ytotoxic *ellskill infected cells

9elper *ells t'o types"acti#ate macrophages and !-cells

0uppressor *ellsregulate acti#ity


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$9: $92

$* ;;

B

Antibody &roduction


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M%c-molecules

)9*-I

present foreign peptides to cytotoxic cells

)9*-II

present foreign peptides to helper cells


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*$8$8I* $-*.;;0 9.;&.? $-*.;;0

$c $h

*lass I

)9*

*lass II

)9*

foreign

protein

infected

target

cell

antigen-

presenting

cell

M%c-molecules


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'eler T-cells

9elper $-*ells recogni5e foreign antigen bound to

)9*-II proteins on surface of antigen-presenting cells

9elper $-*ells stimulate macrophages and !-cells

$'o signals are required for acti#ation of 9elper $-*ells


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Activation of 'eler T-cells

$h

antigen-

presenting

cell

signal :

signal 2

acti#ation

signal 2 is chemical interleukin-:" or membrane bound molecule

*%

antigen


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Activation of 'eler T-cells

$h

antigen-

presenting

cell

signal :

signal 2

$h

Il-2 receptor

Il-2

$h $h

proliferation

*%


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Cytoto)ic T-cells

*ytotoxic $-*ells recogni5e #iral protein fragments on

surface of infected cells(

*ytotoxic $-*ells induce infected cells to kill themsel#es

!ind to infected cells

Induce cell death

&unch holes in cell membrane


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Cytoto)ic T-cells

*lass I

)9*

$c

infected

targetcell

*%+

&erforin discharge


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Natural /iller

• destroy irus-infected cells

• do not express antigen speci"creceptors

• cells !ith lo! leels of M'0 I

•

induce cells to undergo apoptosis


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TC

TC( C*+

M'C

Class I

In%ibitory

recetor

NK

Target

,o M'C

Class I

, recetor

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b Cellimmunity 120223050013 Phpapp01