Table 1.

Summary of immune cells in the tumor microenvironment.

Innate immune cells	Interaction with radiation therapy	References
Dendritic cells	• Batf3-dependent DCs induced by RT promote anti-tumor immune responses by activating CD8 + T cells • DCs upregulate MHC-I after RT, promoting efficient tumor antigen presentation for better anti-tumor immune responses • RT enhances tumor antigen presenting capacity of infiltrating DC through type I IFN production	(5, 6) (6–8) (9)
Macrophages	• RT induces TGF-ß and IL-4 leading to production of alternatively activated/M2 macrophages which inhibit anti-tumor immune responses • Macrophages promote matrix remodeling, vasculogenesis which support tumor regrowth post-RT • Inhibiting macrophages via CSF-1R, Axl, Cd11b results in better anti-tumor responses post-RT	(4, 10–13) (14, 15) (4, 16–18)
NK cells	• RT enhances cytotoxic activity of NK cells against various solid tumors including pancreatic cancer and sarcoma	(19–21)

Innate and adaptive immunity play many roles in the context of tumor biology. Key functions of each of the immune cells is listed.