Activated macrophages restrict invasive bacterial infection in a human intestinal organoid co-culture model

Intestinal organoids provide physiologically relevant models of the epithelial barrier, but lack the immune compartment that critically shapes host responses to infection. Here, we established a human colon organoid-derived monolayer co-culture system with macrophage-like THP-1 cells positioned directly beneath the epithelial layer. The model enabled controlled apical infection with Listeria monocytogenes and Salmonella Typhimurium while preserving epithelial barrier integrity. PMA-differentiated THP-1 cells reduced intracellular L. monocytogenes burden, whereas additional activation with IFN-{gamma} and LPS resulted in a pronounced reduction of both L. monocytogenes and S. Typhimurium, accompanied by decreased infection-associated cytotoxicity. Bulk RNA sequencing revealed a distinct co-culture transcriptional signature characterized by coordinated changes in inflammatory, antimicrobial, and epithelial lineage-associated programs. These included reduced HLA-D/MHC class II-associated gene expression, altered S100A8/S100A9 expression, and changes in epithelial lineage markers indicating a shift in epithelial cellular composition and differentiation state. Together, these findings establish a versatile human organoid-macrophage platform for dissecting epithelial-immune interactions and macrophage-associated control of invasive bacterial infection.