Antigen PresentationFundamentals I for Dentistry & Optometry

Textbook:Medical Microbiology, 6th Edition, Murray

Chapter 11

Jim Collawn, MCLM 350jcollawn@uab.edu

934-1002

Study Objectives1. Compare and contrast class I and class II

MHC-restricted responses with regard toA. source of antigensB. antigen processing requirementsC. role of chaperonesD. types of T cell involved

2. Discuss the invariant chain’s role in the demarcation between class I and class II MHC-restricted responses.

3. Discuss HLA-DM’s possible role in antigen processing.

Humoral and Cell-

mediated Immune

Responses

Major Players in T cell Responses

T lymphocyte and Macrophage (right)

Types of T cells1. Cytotoxic T cells (CTLs)

A. Kill virally infected cellsB. Kill cells containing cytosolic

bacteriaC. Kill tumor cells

2. Inflammatory T cells (TH1)A. Activate macrophages to kill intracellular bacteria

3. Helper T cells (TH2)A. Activate B cells to make antibody

Schematic Diagrams of MHC class I and class II Molecules

MHC class I (top view)

Major Histocompatibility Complex

HLA-DR1 (blue) and HLA-A2

MHC class I

MHC class II

Anchor Residues for MHC class I peptides

Conformation of Peptides Bound to MHC class I

Solvent-accessible Area of H-2Kb

Anchor Residues for MHC class II peptides

Antigen Processing is Necessary for Helper T cell Activation

Antigen-presenting Cells(MHC Class II-positive cells)

HLA-DR, HLA-DP, HLA-DQ

Target Cells(MHC Class I-positive cells)

HLA-A, HLA-B, HLA-C

All nucleated cells

Degradation of Intracellular Proteins

Transporter associated with Antigen Processing

Generation of Peptide-class I MHC Complexes

Demarcation between MHC

class I and class II

Processing Pathways

Cytosolic and Endocytic Pathways for Antigen Processing

Assembly of MHC class II Molecules

Study Objectives1. Compare and contrast class I and class II

MHC-restrictedresponses with regard to

A. source of antigensB. antigen processing requirementsC. role of chaperonesD. types of T cell involved

2. Discuss the invariant chain’s role in the demarcation between class I and class II MHC-restricted responses.

3. Discuss HLA-DM’s possible role in antigen processing.

Sample Questions• The MHC class II molecule

– is associated with ß-2 microglobulin.– binds peptide antigens from the endogenous pathway.– is associated with the invariant chain.– is expressed on all cell types.

•  • Exogenous antigens

– are taken up by cells through endocytosis or phagocytosis.– are bound to MHC class I molecules.– are processed by the proteasome.– become associated with MHC class I molecules in the endoplasmic

reticulum.•  

Sample Questions• HLA-DR

– presents antigens to cytotoxic T cells.– is a chaperone that facilitates CLIP removal and peptide binding.– is an MHC class II molecule.– binds to endogenous antigens.

•  • The proteolytic activity necessary for the generation of MHC class II-

associated peptides is provided by– the proteasome.– the lysosome.– furin.– the endoplasmic reticulum.