MCA-205/iRFP cells are derived from the mouse fibrosarcoma cell line MCA-205 by stably integration of a constitutive miRFP670 stably expression construct. MCA-205 cells are widely used for studying tumor-reactive T lymphocytes, the most critical requirement for adoptive immunotherapy. MCA-205/iRFP cells stably express miRFP670, can be used for in vitro assays and in vivo imaging.