S100A9 and Sepsis: In addition to these proinflammatory functions, the prolonged stimulation of cells with S100A8 and S100A9 can induce hypo-responsiveness in monocytes and macrophages similar to the well-known endotoxin tolerance and thereby subsequently trigger immune paralysis, which is the major risk factor for enhanced morbidity and mortality during sepsis and SIRS (systemic inflammatory response syndrome) [29].