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antigen PowerPoint Presentation

antigen

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antigen

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Presentation Transcript

  1. antigen

  2. 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

  3. Protein antigens cleaved by cathepsins

  4. Invariant Chain & MHC Class II Associate in ER Blocks cleft Sorting signal

  5. cathepsins MIIC

  6. MIIC

  7. Second peptide exchange

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

  9. 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

  10. Assembly of class I

  11. Long peptides trimmed

  12. 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

  13. molecules Autophagy - macro or micro

  14. Retrograde Cross Presentation

  15. Involvement of Retrograde Translocation ER