immune resp & immunomechimmunomechanism

8/19/2019 Immune Resp & ImmunomechImmunomechanism

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A. Positive selection: If the thymocyte TCR engages in a low-affinity interaction with a self MHC molecules on athymic epithelial cell it is rescue! from programme! cell !eath an! continues to mature

". #ac$ of positive selection: If the thymocyte TCR !oes not engage in any interaction with pepti!e-MHCmolecule comple%es on thymic epithelial cell it will !ie in a programme! cell !eath

C. &egative selection: If the thymocyte TCR binds pepti!e-MHC comple%es on a thymic antigen presentingcell with high avinity it is in!uce! to un!ergo apoptotic cell !eath


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Immune Response '

Immunomechanism


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The line of !efence against micro(es

)Protective surface mechanism* +pithelia:

) ,$in: impenetra(le (arrier) Resp tract: surface mucous ciliary action) Maintenance of aci!ic environment stomach vagina

* Antimicro(ial su(stances pro!uce! at epithelial surface

) &on-specific tissue !efences

* Phagocytic cells an! &atural /iller cells) Macrophages) &eutrophils) &/ cells

* "loo! Proteins) Mem(er of complement system) Me!iators of inflammation

* Inflammation* &eutrophil recruitment

* Cyto$ines) Proteins that regulate an! coor!inate many of the activities of the cells of innate

immunity

) ,pecific immune responses* A!aptive immune response


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Physical and chemical barriers


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A&TI1+& R+C21&ITI2&

) Innate immunity ) A!aptive immunity

Pathogen-associate!molecular patternPAMPs recogni0e! (yT#R e%presse! inphagocytic cells

T cells ReceptorsC345 helper T cell

TCRrecogni0e!antigen

pepti!e inassociation with class II MHCmolecule

C365 cytoto%ic Tcellrecogni0e!pepti!eantigen inassociation with class I MHCmolecules

B cell

Recognized peptide antigenthroughsurface immuno lobulin


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,pecific immune responseInitiation


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C34Tcell activation an! 3ifferentiation

) Naïve CD4 T cell activated bydendritic cell

) ctivated CD4 T cell differentiate intoeffector CD4 T cells! T"#$ T"%$ T"#&$TReg

) Differentiation is initiated through an

interaction of DC and CD4' " T cells


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TH7 cells coor!inate the host

response to intracellular pathogens


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Professional antigen-presenting cells

(APCs) are distributed in dierentregions of the lymph nodes:

• Dendritic cells are found throughout thecortexin the T-cell areas

• Macrophages are found throughout thecortex

and the follicles• B cells are found mainly in the follicles


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Activation of naïve T cells requires twoindependent signals:! T"#$co-receptor %indingof M&"$peptide complextransmits the 'rst signal(arro) *!+! Activation of the T cellrequires a second signal(arro) +* to %e delivered%y the same antigen-

presenting cell!


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The principal co-stimulatory

molecules expressed on

professional antigen-presentingcells are B7 molecules, which

bind the T-cell protein, CD28.


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Bacterial ,. induces ,angerhans cellsto migrate to lymphonodus/ matureand initiating adaptive immunity

Activation of "D0 T cells required costimulatory molecules/ "D12 (B3!*4 "D15(B3!+*Activation of B cells required the help ofactivated "D0 T cells

,ymphocyte activation occur in T-celldependent 6one of lymphonodus


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Immune tolerance


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In!uction of Tolerance

) Antigen segregation

* Immuneprivile!ge site

) In!uction of tolerance

* Central tolerance) 3eletion of autoreactive lymphocytes !uring !evelopment

* Peripheral tolerance) 3eletion of autoreactive lymphocytes (y

* Apoptosis clonal !eletion* Anergy functionally in activate!

* ,upression (y a Regulatory T cells


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H2M+2,TA,I,


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Autoimmune !iseases

The normal immune system must (e a(le to!istinguish (etween self an! non-self

Autoimmune !isease is a (rea$!own oftolerance

Autoimmune !isease is a hypersensitivityreaction triggere! (y self antigens


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immune resp & immunomechimmunomechanism

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