Tumor-induced CD11b⁺Gr-1^int iMC transfer CTL suppression if induced by GM-CSF. (A) Spleen cells of B6 mice, LoxP-Tag × Alb-Cre mice (Tg × Alb-Cre) with early primary HCC and transplanted Tag⁺ 16.113 tumors, Tg × Alb-Cre mice with early primary HCC and transplanted Tag⁺ GM-CSF-secreting 16.113 tumors (16.113-GM), and Tg × Alb-Cre mice with advanced primary HCC (but no 16.113 tumor) were double stained with antibodies against CD11b and Gr-1. One representative example per experimental group is shown. Numbers indicate the percentage of CD11b⁺Gr-1^high and CD11b⁺Gr-1^int iMC of total spleen cells. All data for CD11b⁺Gr-1^int iMC are shown in (B). (C) CD11b⁺Gr-1^int iMC from Tg × Alb-Cre mice with early primary HCC and additionally transplanted 16.113-GM tumors and LoxP-Tag × Alb-Cre mice with advanced primary HCC (but no 16.113 tumor) were transferred IV into B6 mice and immunized with pIV subcutaneously on the same day. Naive and immunized B6 mice, which did not receive CD11b⁺Gr-1^int iMC served as control. Eight to 10 days later, in vivo cytotoxicity was analyzed. One representative histogram of each experimental group is shown. All data for transferred CD11b⁺Gr-1^int iMC are shown in (D). The percentage of specific killing in vivo is indicated. Experimental groups were: no iMC (ø, n = 4), iMC from Tg × Alb-Cre with early HCC and 16.113-GM (n = 3), and iMC from Tg × Alb-Cre with advanced HCC (n = 6). Early HCC, microscopically detectable tumors; advanced HCC, macroscopically visible tumors. Bars represent mean, error bars indicate SEM. Overall significance for each graph was tested by Kruskal–Wallis 1-way analysis of variance.