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What is antigen presentation? Degradation of peptides so that they can be

What is antigen presentation? Degradation of peptides so that they can be “presented” to T cells by MHC Class I or Class II molecules on the surface of APC’s. Class I MHC molecules present to T cells: Endogenous peptides- viral proteins, tumor proteins, etc.- that are processed in the

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What is antigen presentation? Degradation of peptides so that they can be

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  1. What is antigen presentation? Degradation of peptides so that they can be “presented” to T cells by MHC Class I or Class II molecules on the surface of APC’s Ch. 8b

  2. Class I MHC molecules present to T cells: Endogenous peptides- viral proteins, tumor proteins, etc.- that are processed in the cytoplasm of the cell Class II MHC molecules present to T cells: Exogenous antigens- internalized and processed by a different pathway Ch. 8b

  3. Self-MHC restriction of T cells (1970s) By TH cells p. 206 Ch. 8b

  4. By Tc (cytotoxic T) cells p. 207 Ch. 8b

  5. Role of antigen-presenting cells Antigen must be processed (p. 208) Ch. 8b

  6. What is an antigen-presenting cell (APC)? Three kinds of “professional” APCs: Dendritic cells (always express high levels of MHC Class II) Macrophages- must be activated to express high MHC Class II and B7 B cells- always express high MHC Class II but must be stimulated to express B7 Ch. 8b

  7. To review, two pathways for processing antigen In one pathway, antigens are processed and associate with Class II molecules In the other, antigens are processed through different cellular compartments and associate with Class I Various receptor and transporter proteins have been elucidated Ch. 8b

  8. Summary of the pathways p. 216 Ch. 8b

  9. These pathways produce peptide (protein) antigens What about nonpeptide antigens? Another molecule on APCs, CD1, resembles MHC Class I These molecules can present lipids and glyco- lipids like those on bacterial surfaces Not clear when, or how, this pathway is exploited Ch. 8b

  10. Recent studies of CD1 indicate that: CD1 presents lipid and glycolipid antigens derived from bacteria for specific recognition by T cells CD1 resembles MHC I and associates with beta-2-microglobulin Five genes encode human CD1 molecules May be an innate mechanism Ch. 8b

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