Menstrual blood-derived stromal cells (MenSCs) exhibit immunomodulatory properties, but their direct impact on innate immune populations, particularly macrophages, remains unclear. This study investigated MenSC effects on macrophage recruitment and function in mouse models of acute inflammation (thioglycollate-elicited peritonitis and *Salmonella Typhimurium* sepsis) and in vitro using human macrophages. In the thioglycollate model, MenSCs reduced macrophage recruitment and formed peritoneal aggregates. In the sepsis model, MenSCs exacerbated infection by decreasing macrophage and neutrophil recruitment and impairing bacterial clearance. In vitro, MenSCs impaired macrophage bactericidal properties, affecting bacterial killing and reactive oxygen intermediate production. These findings suggest MenSCs modulate macrophage populations, a crucial consideration for future clinical applications.

Rocío Martínez-Aguilar, Salvador Romero-Pinedo, M. José Ruiz-Magaña, Enrique G. Olivares, Carmen Ruiz-Ruiz, Ana C. Abadía-Molina