S100A9 and Sepsis: Calcium-binding proteins S100A8 and S100A9 are markedly increased during sepsis (13), and their elevated levels in circulating innateimmune phagocytes during sepsis may contribute to acute and chronic inflammation (14, 15).S100A8 and S100A9 are mainly expressed in the myeloid lineage cells (16), including monocytes and granulocytes, but notresident tissue macrophages (15) and are dominantin the systemic circulation.