Cross-presentation of cell-associated antigens by dendritic cells.

There is a strict requirement for professional antigen-presenting cells (APCs) in the generation of immunity toward most viruses. Exogenous pathways of MHC class I-restricted antigen presentation play an important role in the generation of antiviral immunity, particularly in the immune surveillance of virus-infected tissues of nonhematopoietic origin, and to bypass the detrimental effects of direct virus infection on professional APCs. The mechanisms underlying generation of antiviral immunity under these circumstances are discussed.