Assays to Detect Cross-Dressing by Dendritic Cells In Vivo and In Vitro

Abstract

The presentation of peptides derived from exogenous antigens on major histocompatibility complex (MHC) class I molecules of antigen-presenting cells (APCs), termed cross-presentation, is crucial for the activation of cytotoxic T-lymphocytes during cell-mediated immune response. Typically, the APCs acquire exogenous antigens by (i) endocytosis of soluble antigens present in their external milieu, or (ii) through phagocytosis of dying/dead cancer cells or infected cells, followed by intracellular processing, before presentation by MHC I on the surface, or (iii) uptake of heat shock protein–peptide complexes generated in the antigen donor cells (3). In a fourth new mechanism, preformed peptide–MHC complexes can be directly transferred from the surface of antigen donor cells (i.e., cancer cells or infected cells) to that of APCs, without the need of further processing, in a process referred to as cross-dressing. Recently, the importance of cross-dressing in dendritic cell-mediated antitumor immunity and antiviral immunity has been demonstrated. Here, we describe a protocol to study cross-dressing of dendritic cells with tumor antigens.