Figure 8. IL-12 cells (H-2^b) are capable of causing complete regression of established Cloudman S91 melanomas (H-2^d) on C57BL/6 × DBA F1 mice (H-2^b/d).

(A) H-2D^b and H-2D^d expression of B16 and Cloudman S91 melanoma cell lines exposed to 675 ng/ml of IFN-γ for 48 hours. (B) Antitumor immunity of 5 × 10⁵ IL-12 or mock cells adoptively transferred into sublethally irradiated C57BL/6 × DBA F1 H-2^b/d mice bearing subcutaneous Cloudman S91 tumors established for 21 days. All data are expressed as mean ± SEM and are representative of 2 independent experiments. *P < 0.05, Wilcoxon’s rank-sum test compared with no treatment and mock. (C) Flow cytometry plots for macrophages (CD11b⁺ F4/80^hi), dendritic cells (CD11b⁺CD11c^hi), MDSC-M (CD11b⁺Ly6C^hiLyG^lo), and MDSC-G (CD11b⁺Ly6C^Mid-hiLy6G^hi) within established Cloudman S91 melanomas on C57BL/6 × DBA F1 H-2^b/d mice 10 days following treatment with IL-12 or mock cells. All plots gated on PI^– live cells; numbers represent percentage of cells in each quadrant. (D) Data from C were quantified through a flow cytometry count and normalized to 1 gram of tumor. Data are expressed as mean ± SEM. *P < 0.05, 1-way ANOVA compared with NT and mock controls.