Figure 7.

Pre-loading A’PB with microparticle cargo hinders tumor suppression. (A) Antibody-engineered macrophages/monocytes pre-loaded with cargo prior to treatment. (i) Schematic of in vivo marrow pre-load therapy to assess off-target effects on phagocytosis. Freshly harvested marrow cells phagocytose IgG-opsonized polystyrene microparticles for 1 h prior to tail-vein injections. (ii) Representative images of marrow cells with polystyrene microparticles, with excess particles removed by centrifugation prior to injection. (iii) Quantification of microparticles engulfed per marrow cell in a field of view (FOV). About 40% of marrow cells engulfed up to ~10 particles. (B) In vivo phagocytosis of WT B16F10 cells in A’PB marrow treatments. (i) Lung tumor burdens in control (untreated) and 2× A’PB + microparticle pre-loaded groups. Mice were treated with antibody-engineered marrow on days 4 and 6 in addition to tail-vein injections of 250 µg anti-Tyrp1 per Figure 2B through day 13. Mean and s.e.m. (n.s. not significant, Ordinary one-way ANOVA with Dunnett’s multiple comparisons, n = 5 per three groups, including 2× A’PB in Figure 5B). (ii) Projected survival curves.