Macrophages interact with but do not engulf or remove senescent cells. (A) Schematic representation of senescence induction in murine and human primary and transformed cells. (B) Senescence was induced in actin-GFP mouse embryonic fibroblasts (MEFs) by either passaging stress until the Hayflick limit was reached by γ-irradiation or by treatment with palbociclib. Senescent MEFs were co-cultured with BMDMs, isolated from tdTomato⁺ mice, in a ratio of 10 BMDMs to 1 senescent cell and imaged over 48 h. In each image group, the same field of view was shown across time. Data are representative of three independent experiments; scale bars indicate 100 µm. (C) Quantification of green fluorescent area signal of senescent cells in co-culture with different ratios of BMDMs as indicated. Data are representative of three independent experiments. All values are means ± SEM. Statistically significant differences were determined by two-way ANOVA with Bonferroni correction. (D) Senescent NHLF (upper panel) or senescent human pancreatic epithelial cancer cells (Panc1; lower panel) stained with green Cytolight dye and co-cultured with human MDMs (unstained). Images were taken over 24 h. In each image group, the same field of view was shown across time. Data are representative of three independent experiments; scale bars indicate 200 µm.