Adoptive transfer of Tag-specific TCR splenocytes following sub-lethal irradiation results in T cell infiltration of solid tumors. Representative frozen sections of tumors from 16 week old Rip1-Tag2 pancreas were analyzed by immunohistochemistry for CD4, CD8 and CD11c. The transgenic mice were treated as follows: (A-C) untreated, (D-F) TCR splenocytes, (G-I) 600R, and (J-L) 600R + TCR splenocytes. Extensive CD4+ T cell infiltration (A, D, G, J) is observed only in mice receiving both sub-lethal irradiation and adoptively transferred TCR splenocytes (J). When analyzed for infiltration by CD8+ T cells (B, E, H, K), again only tumors from mice treated with the combination therapy showed significant infiltration (K). Dendritic cells, as detected by the antibody to CD11c (C, F, I, L), were observed in all tumors, but mice receiving both 600R (I) and the combination therapy have a greater degree of CD11c+ cell infiltrate (L).