Figure 3.

The histiocytic phenotype of the tumor cells is confirmed by flow cytometry, and their expression of macrophage/monocyte markers and granzyme B increases with inflammation. A: The predominant cell type in the spleen of a wild-type (WT) mouse was B cells. The majority of cells in the tail tumor of Tax⁺ mice were Mac-1 CD11b⁺ with few B220⁺ B lymphocytes or CD4⁺ or CD8⁺ T lymphocytes. The Mac-1 CD11b⁺ labeling demonstrated that the predominant neoplastic cell population in the tail tumors was macrophage/monocyte in origin. The spleen from Tax⁺ mice had increased Mac-1⁺ cells with few B and T cells. Note the majority of the splenic cells (myelopoietic cells) and the tumor neutrophils in the Tax⁺ mice were not stained by the antibody panel. B: Co-expression of granzyme B and Mac-1 in the tumor cells was increased from 12.1% in unstimulated cells (top row) to 19.9% after phorbol-myristate-acetate and ionomycin stimulation (bottom row). Co-expression demonstrates increased granzyme B in activated histiocytes, but not in B and T lymphocytes. Due to their overall low cellularity, findings are from one tumor from each genetic group. APC, allophycocyanin; FITC, fluorescein isothiocyanate; FSC, forward scatter; FSC-A, forward scatter area; PE, phosphatidylethanolamine; PE-A, phosphatidylethanolamine-area; PerCP, peridinin chlorophyll protein; SSC-A, side scatter light area.