Thus, while whole-body radiation is “immunosuppressive” due to triggering widespread apoptosis of immune cells via Fas, focal radiation such as that used for treatment of many types of solid tumors instead has limited immunosuppressive side effects, and may actually promote changes in the local tumor microenvironment that paradoxically enhance infiltration and activation of multiple immune cell types that may either foster, and/or suppress tumor development (de Visser et al., 2006). Here, FAS is linked to neoplasm.