Our findings indicate that BMSC-derived hepcidin has a dual effect: (1) hepcidin can directly reduce the proliferation of pathogens through which mechanism it may protect hematopoietic stem and progenitor cells in the BM niche, and (2) BMSC-derived hepcidin can limit the number of infiltrating polymorphonuclear cells (PMNs) in vivo (in our peritonitis model). This evidence concerns the gene HAMP and peritonitis.