Describe cross presentation of antigen in which dendritic cells are able to capture and ingest a virus infected or tumor cell and present the antigen to naive CD8 T cells via the class I MHC pathway
The ability of antigen-presenting cells to acquire extracellular antigens by phagocytosis and present processed material by means of class I MHC molecules to Tcyt cells is termed as cross-priming or cross-presentation. Cross-priming is a defence against pathogens such as viruses, bacteria, tissue grafts and tumours.
Dendritic cells are potent stimulators of T-cell responses and can induce CD8+ CTLs by phagocytosis of dead tumor or virus-infected cells.
Classically, the MHC class I pathway provides for the presentation of endogenous cellular antigens. For example, in virally infected cells, viral protein expressed in the cytosol is subject to proteosomal proteolysis, and the resulting peptides are translocated via transporters associated with antigen processing (TAP transporters) into the endoplasmic reticulum lumen and loaded onto MHC class I molecules. Although this process remains true for infected dendritic cells, non infected dendritic cells can also take up, process, and present viral antigens to CD8+ T cells through a process called cross-presentation. Soluble exogenous antigens can also be cross presented to CD8+ T cells.