A20/Luciferase cells are derived from the mouse B lymphocyte cell line A20 by stably integration of a constitutive Firefly luciferase stably expression construct. A20 cells were derived from a spontaneously arising reticulum cell sarcoma from an aging BALB/c mouse. A20 cells are highly responsive to immunomodulatory antibodies. A20/Luciferase cell line is an attractive model for use in immunotherapy drug development.