Protocol for measuring exogenous antigen presentation triggered by membranes of bone marrow-derived dendritic cell purified phagosomes

Dendritic cells are potent antigen-presenting cells that initiate T cell responses by presenting exogenous antigens associated with major histocompatibility complex (MHC) class I and MHC class II molecules. Here, we present a protocol to colorimetrically evaluate CD8+ and CD4+ T cell activation by using dendritic cell purified magnetic phagosomes previously coated with ovalbumin (OVA). We describe the procedure for recovering phagosomes through mechanical dendritic cell lysis. We also detail steps for optimal separation, fixation, and phagosomal membrane rupture to expose OVA-loaded MHC molecules to antigen-specific T cells. For complete details on the use and execution of this protocol, please refer to Cebrian et al.¹.