Although Pmel-1 Cd2-cre/Cx3cr1DTR/DTR CD8+ T cells do not have the function of CX3CR1 as a chemokine receptor for trafficking to the tumor via the CX3CR1/CX3CL1 axis, terminally differentiated CD8+ T cells with an active CX3CR1 promoter can still be identified using an anti-DTR antibody if residing in the tumor. The gene discussed is CX3CL1; the disease is neoplasm.