Ex vivo live macrophage engineering strategies in immunotherapy.

Immune cell-based therapies have transformed immuno-oncology by converting living cells into therapeutic agents able to recognize, infiltrate, and eliminate diseased tissues. While T cell, NK cell, and dendritic cell platforms have delivered meaningful clinical advances, in solid tumors and chronically inflamed tissues, poor trafficking and retention, and functional suppression within hostile microenvironments, often constrain their efficacy. Macrophages provide a complementary therapeutic platform because they are abundant tissue-resident sentinels, professional phagocytes, and key coordinators of local inflammation and adaptive immunity. However, successful macrophage immunotherapy requires solving two central in vivo determinants: preserving a therapeutically favorable functional state despite suppressive cues, and achieving robust, disease-selective localization and engagement. These determinants map onto two defining macrophage properties (i.e., plasticity and homing), which serve as central engineering levers. Here, we review recent strategies that (1) reprogram and stabilize engineered macrophage phenotypes within the disease environment, and (2) enhance targeting, retention, and contact-dependent functions through engineered recognition modules. We further highlight emerging combinatorial designs that integrate phenotype maintenance with improved tissue targeting and discuss design considerations to translate both genetic and non-genetic macrophage engineering approaches into effective therapy in complex disease microenvironments.