Changes

===Presentation Pathway===

===Presentation Pathway===

[[Image:MHC I processing.jpg|thumb|200px|left|'''MHC I presentation pathway, courtesy of B. Catchpole, 2008''']]

[[Image:MHC I processing.jpg|thumb|200px|left|'''MHC I presentation pathway, courtesy of B. Catchpole, 2008''']]

MHC I presents '''endogenous''' (intracellular) peptides. Viral proteins are broken down to peptides by the proteasome and transferred to the endoplasmic reticulum (ER) via transporters associated with antigen processing (TAP) molecules. In the ER peptides are processed with empty MHC I molecules and exported to the cell surface for presentation to the T-cell receptors of [[T_cells#Cytotoxic_CD8.2B|CD8⁺ T-cells]]. The purpose of presentation in this manner is to kill the cell to prevent viral replication. Activation of the cell with Interferon enhances expression of MHC class I molecules as part of the [[Innate Immunity to Viruses|innate immunity]] to viruses.

MHC I presents '''endogenous''' (intracellular) peptides. Viral proteins are broken down to peptides by the proteasome and transferred to the endoplasmic reticulum (ER) via transporters associated with antigen processing (TAP) molecules. In the ER peptides are processed with empty MHC I molecules and exported to the cell surface for presentation to the T-cell receptors of [[T_cells#Cytotoxic_CD8.2B|CD8⁺ T-cells]]. The purpose of presentation in this manner is to kill the cell to prevent viral replication. Activation of the cell with '''Interferon''' enhances expression of MHC class I molecules as part of the [[Innate Immunity to Viruses|innate immunity]] to viruses.

==MHC II==

==MHC II==