Immunity Assignment 8-9

1) Describe the five ways in which dendritic cells process and present antigens.

Dendritic cells carry antigens from sites of infection to secondary lymphoid tissues

Dendritic cells are adept and versatile at processing pathogen antigens

Maturation of dendritic cells is associated with changes in form and function.

· Uptake of antigens by phagocytosis or macropinocytosis delivers antigens to endocytic vesicles for presentation by MHC class II molecules to CD4 T cells (first two panels).

· Viral infection of the dendritic cell delivers peptides processed in the cytosol to the endoplasmic reticulum for presentation by MHC class I molecules to CD8 T cells (third panel).

· Viral particles taken up by the ‘class II’ pathways of phagocytosis and macropinocytosis can be delivered to the cytosol for processing and presentation to CD8 T cells by MHC

· class I (fourth panel). The mechanism of this cross-presentation is poorly understood. Lastly, antigens taken up by one dendritic cell can be delivered to a second dendritic cell for presentation by MHC class I molecules to CD8 T cells (fifth panel).

2) Describe how centrocytes that have undergone somatic hypermutation resulting in better antigen binding are selected for survival while those that have worse binding are removed.