Antigen
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antigen. T Cell Antigen Specificity - a:b. Antigen determinant = epitope - Part of antigen that binds antigen receptor T cells with a:b TCR are specific for denatured or fragmented (peptides) forms of protein antigens which are linear determinants

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Antigen

antigen


T cell antigen specificity a b

T Cell Antigen Specificity - a:b

  • Antigen determinant = epitope - Part of antigen that binds antigen receptor

  • T cells with a:b TCR are specific for denatured or fragmented (peptides) forms of protein antigens which are linear determinants

  • Antibodies specific for TCR or MHC inhibit T cell responses, but those specific for intact antigens rarely inhibit

  • CD4+ T cells usually recognize exogenous antigens, while CD8+ T cells usually recognize endogenous antigens

  • This dichotomy is NOT mutually exclusive


Antigen

Protein antigens

cleaved by

cathepsins


Antigen

Invariant Chain & MHC Class II

Associate in ER

Blocks cleft

Sorting signal


Antigen

cathepsins

MIIC


Antigen

MIIC


Antigen

Second peptide

exchange


Antigen

Treatment of presenting cells with brefeldin A may or may not interfere with antigen processing


Mechanism of antigen processing

Mechanism of Antigen Processing

  • Lysosomotropic agents usually do not inhibit killing of target cells

  • Viral proteins are synthesized by target cells

    Target cells incubated with UV irradiated virus are not killed

    Target cells incubated with intact viral proteins are not killed

  • Brefeldin A blocks target cell killing


Antigen

Assembly of class I


Antigen

Long peptides

trimmed


Important concepts

Important Concepts

  • Antigen processing for both pathways is an integral part of synthesis and assembly of MHC class I & class II molecules

  • The two antigen processing pathways are not completely separated

  • Intracellular transport inside antigen-presenting cells allows antigens to access both pathways


Antigen

molecules

Autophagy - macro or micro


Antigen

Retrograde

Cross Presentation


Antigen

Involvement

of Retrograde

Translocation

ER


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