CD8 T cells are absolutely required for the survival benefit of combined surgery and IMQ treatment. BALB/c mice bearing AB1-HA tumors were left untreated or partially (75%) surgically debulked (dotted line) of tumor, then treated with immunotherapy (IMQ; 50 μg i.t. q1dx6 on day of surgery; shaded box) and anti-CD4 (GK1.5) or anti-CD8 (YTS.169) specific antibodies (arrows) administered from day 17 (1 day pre-surgery), given every second day for a total of three doses. The initial dose was given intravenously (i.v.), followed by two i.p. injections of 150 μg. A) Survival curves of treatment groups as indicated. Number of survivors/total number of animals in parentheses. ***p =0.0004 comparing 75% debulk + IMQ + anti-CD8 to 75% debulk + IMQ, **p = 0.0014 comparing debulk alone to debulk + IMQ; log-rank test B) Tumor growth curves of treatment groups as indicated (survivors with complete tumour regression not included).