MCA-205/RFP cells are derived from the mouse fibrosarcoma cell line MCA-205 by stably integration of a constitutive RFP stably expression construct. MCA-205 cells are widely used for studying tumor-reactive T lymphocytes, the most critical requirement for adoptive immunotherapy. MCA-205/RFP cells stably express RFP, can be used for in vitro assays and in vivo imaging.