Fig. 2. High cargo rigidity promotes phagocytic uptake.

a Phagocytic efficiency of HoxB8-ER derived macrophages challenged with IgG- and PtdS-coated DAAM particles of the indicated rigidities, quantified by flow cytometry. n = 3 replicate macrophage differentiations. hiPSC-derived macrophages (b) and murine microglia (c) were mixed with IgG- and PtdS-coated DAAM particles of the indicated rigidities, and phagocytosis monitored by video microscopy. Representative images of uptake of IgG-coated particles are shown to the left, with phagocytic index quantified on the right. Phagocytic index = number of particles phagocytosed per macrophage. In (b), n = 4 replicate macrophage differentiations, while in (c), n = 2 biological replicates (summary of 4 technical replicates/biological replicate). Scale bars in (b, c) = 30 µm. d–f DAAM particles of differential stiffness were injected into the mouse peritoneum to measure the phagocytic activity of elicited macrophages. d Schematic of macrophage elicitation and DAAM particle injection protocol (see “Methods” section). e Phagocytic efficiency (LRB⁺FITC^lo/all CD11b⁺F4/80⁺ cells) for particles of the indicated rigidities. n = 5 mice/condition. f Macrophage recruitment to the peritoneum, quantified as total F480⁺CD11b⁺ cells over all live cells in the peritoneal lavage. In (a–c) and (e, f), horizontal lines in columns denote mean values. All P values determined by two-tailed Student’s t-test. ns not significant. g–i BMDMs were challenged with Cypher5e-labeled E0771 cells expressing different levels of MRTF-A. g MRTF-A is expected to enhance phagocytosis by increasing cell stiffness. h Representative flow cytometry histogram showing Cypher5e signal in BMDMs challenged for 2 h with control E0771 cells or E0771 cells overexpressing MRTF-A. i Phagocytosis is quantified as %Cypher5e⁺ macrophages. Error bars indicate SD. n = 3 replicate macrophage differentiations. Schematics in (a–d), and (g) created with BioRender.com released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license https://creativecommons.org/licenses/by-nc-nd/4.0/deed.en.