Therapeutic efficacy of RT and R848 combination is dependent on the activity of CD8⁺ T-lymphocytes. (A) Depletion of CD20⁺ B cells does not inhibit the efficacy of 10 Gy local RT and R848 dosed weekly. P > .05 (Mann-Whitney test). **P < .01 (Mann-Whitney test). (B) Serial blood samples were taken 6, 10, and 20 days after the initiation of treatment, and the frequency of SIINFEKL-restricted CD8⁺ T cells was determined using pentamers by flow cytometry. (C) Tumor-bearing mice received 10 Gy local RT and R848 dosed weekly in addition to a CD8-depleting antibody. Experimental groups contained at least 5 mice and are representative of at least 2 independent experiments. ***P < .001 (log-rank; Mantel-Cox test).