Chapter 6: Antigen Recongition by T Lymphocytes

MHC Class I

all nucleated cells, peptide load in the ER

MHC Class I Intracellular Pathogens

cleared when CD8 recognizes the structural domain of the alpha-subunit of MHC class I on an infected cell

MHC Class I Intracellular Proteins

in the ER, loaded with peptides that move to the plasma membrane and present peptide to CD8 T cells

MHC Class I Load in the ER Steps

formation of peptide-loading complex, digestion of proteins by proteasome, peptide transport into ER, peptide trimming, transport of plasma membrane

TAP

transporter associated with peptide processing

ERAP

endoplasmic reticulum aminopeptidase

MHC Class II

cannot bind peptides in the ER, professional APC; begin in the secretory pathway but are not loaded until they are part of a vesicle capable of fusing with a phagolysosome

MHC Class II Extracellular Pathogens

cleared by the activation of phagocytes and B cells, antibody production when the CD4 coreceptor recognized the structural domains on both subunits of MHC class II when peptide is presented

MHC Class II Extracellular Proteins

MHC molecules are loaded with peptides from these which then move to plasma membrane and present peptide to CD4 T cells, present peptides from these on surface of APCs; macrophages, dendritic cells, B cells

MHC Class II Loading in the Late Endosomes Steps

MHC II molecules are assembled in ER, peptide-binding groove is blocked with a peptide chain (invariant chain), phagocytosis and fusion with the MHC compartment, peptide loading via HLA DM regulates exchange of CLIP for phagolysosomal peptides

MHC Class II Loading in the Late Endosomes Steps Simple

MHC Class II binds invariant chain, production of CLIP, phagolysosome fusion with MHC class II vesicle, peptide loading