Figure 1.

Depletion of the mononuclear phagocyte system increases the accumulation of exogenously injected bone marrow-derived monocytes (BMDMs) in the tumor and in other tissues. Mice were pre-treated with PBS, clodronate liposomes (CLO), anti-Gr-1 (Gr-1) or anti-Ly6G (Ly6G) antibodies 24 h before administration of 10⁶ DiD-labeled BMDMs. The total radiant efficiency was measured using macroscopic in vivo fluorescence imaging right before (pre) and directly after (post) BMDM injection as well as at 24 h and 48 h after injection. In (A), representative in vivo fluorescence images 48 h after BMDM injection are shown. The symbols represent the lungs (dashed line), the tumor (dotted circle), opposite mammary gland (asterisk), spleen (arrow) and presumed location of the liver (full line). (B–E) The fold change in BMDM accumulation immediately before (pre) and after (post) as well as at 24 and 48 h after injection of DiD-labelled BMDMs were calculated relative to control mice that were pretreated with PBS (y = 1). (F) Directly after the last in vivo measurement, the fluorescence of each individual organ was measured ex vivo and compared to the PBS pretreated control mice (y = 1). (G) Representative ex vivo fluorescence images of the tumors and dissected organs. The depletion experiments were independently conducted. This explains the variation in fluorescence between the PBS groups in G and in Figure S1D-F. The error bars represent the standard deviations (n = 6). * p < 0.05, ** p < 0.01 compared to the respective PBS control at each separate time point. Individual measurements can be found in Supplementary Figure S2.