Fig. 4. Extravasated dextran is ingested by myeloid cells that express markers for alternatively activated macrophages, CD68 and CD206.
(A) Myeloid cells (c-fms-EGFP, green) in the tumor-stroma border that have ingested 10 kDa dextran (red) were CD68+ (yellow), a monocyte/macrophage marker, and (B) CD206+, a marker of alternatively activated (M2) macrophages (yellow). (A′) Myeloid cells that had infiltrated into the tumor mass (ACTB-ECFP, blue) had not ingested dextran, were positive for CD68, (B′) but not CD206. The orange arrowhead points to a c-fms-EGFP+ cell in the stroma that was CD68+ and had ingested dextran; green arrowheads point to c-fms+/CD68+ cells in the stroma and tumor mass that had not ingested dextran; white arrowheads point to c-fms-EGFP+ cells that were CD206−and had not ingested dextran; red arrowheads point to c-fms-EGFP+ cells that had ingested dextran and were CD206+. (C) Minimal staining was found using control IgG. Four-color overlay are shown in the first column at low magnification. The white outlined areas are shown to the right, at higher magnification, in four-color overlays and as single channels. Images are representative of five tumors. Bars, 20 μm.