Assessing in vivo presentation of exogenous antigen in the tumor microenvironment in mice

Here, we focus on tumor-associated macrophages (TAMs) in the PyMT model of breast cancer, detailing a protocol for assessing antigen presentation capabilities of immune populations of interest. We describe a stringent bone marrow chimera system to demonstrate presentation of exogenous antigen that is acquired and processed in the tumor microenvironment. We describe steps for testing antigen presentation activity of TAMs to CD8⁺ T cells in vivo and ex vivo and the requirement for the transcription factor IRF8 in this function. For complete details on the use and execution of this protocol, please refer to Nixon et al. (2022).¹.