Assessment of human and mouse tumor-antigen specific CD8 + T cells by multimer staining in multiple compartments

Detection of tumor antigen-specific T cells at the tumor site and in the periphery is pivotal to study and monitor T cells directly involved in the antitumor immune response. Through their T-cell receptor (TCR), T cells recognize tumor cells presenting their antigenic peptides by major histocompatibility complex (MHC) molecules. Analyses of antigen-specific CD8⁺ and CD4⁺ T cells can be realized by flow cytometry, using fluorochrome-conjugated multiplexed peptide-MHC molecules. These peptide-MHC multimers, in conjunction with continuing advances in flow cytometry, have transformed the characterization of antigen-specific T cells. They enable the visualization, enumeration, tracking, phenotype characterization and isolation of T cells during infection, autoimmunity and cancer. They can be useful to monitor specific adaptive responses during various type of therapies. Here we detail a simple and accurate protocol of multimer staining of tumor antigen-specific CD8⁺ T cells isolated from human and mouse tumors and Peripheral Blood Mononuclear Cells (PBMCs).