IMMUNOLOGY

Detailed explanation-1: -Cross-presentation is of particular importance, because it permits the presentation of exogenous antigens, which are normally presented by MHC II on the surface of dendritic cells, to also be presented through the MHC I pathway.

Detailed explanation-2: -During infections, cross-presentation is essential for the initiation of cytotoxic CD8+ T cell responses when DCs are not directly infected. The DC subsets involved differ depending on the site of infection and the inflammatory environment.

Detailed explanation-3: -Cross-presentation of cell-associated antigens by MHC class I in dendritic cell subsets. Dendritic cells (DCs) have the unique ability to pick up dead cells carrying antigens in tissue and migrate to the lymph nodes where they can cross-present cell-associated antigens by MHC class I to CD8+ T cells.

Detailed explanation-4: -Cross-presentation is the only pathway by which the immune system can detect and respond to viral infections or mutations that exclusively occur in parenchymal cells rather than in bone marrow-derived antigen-presenting cells (APCs).