Oral administration of Fe-Lf leads to high levels of Lf in leukocytes in the lamina propria and Peyer’s patches, which migrate to tumors. A,B: Identification of leukocyte subsets in the lamina propria (A) and Peyer’s patches (B) that contain high levels of Lf. Representative illustrations were taken on day 43 of intestinal villus and Peyer’s patch sections, respectively, from mice in the prevention experiment fed with control and Fe-Lf diets. Sections were immunostained with FITC-conjugated (green) Abs against bovine Lf. The anti-Lf Ab-stained intestinal villus sections were further stained with Abs against markers for macrophages, NK cells, T cells, B cells and dendritic cells. Illustrated are (A) intestinal sections double-stained with an anti-Lf Ab (green), and Abs (red) against macrophages and NK cells, and (B) Peyer’s patch sections double-stained with an anti-Lf Ab (green), and Abs (red) against T cells and B cells. Magnification, x200. Arrows point to the double-stained cells. The number of double-stained cells of each leukocyte subset was counted, and the percentage of each subset was calculated and plotted as a pie chart. C: Phenotyping of Lf-laden leukocytes that infiltrate the tumors of mice fed the Fe-Lf diet. Sections of tumors on day 29 taken from mice in the prevention experiment fed the control or Fe-Lf diets. Tumor sections were immunostained with a FITC-conjugated (green) anti-Lf Ab (left panel), followed by Abs (red) against leukocyte subset markers (right panel) for T cells, macrophages, B cells, NK cells and dendritic cells, as indicated.