The systemic inflammatory response reflects the non-specific clinical expression of a profound activation of the body?s immune responsive elements. Immune activation and immune suppression coexist in the blood of patients with severe sepsis. It is their interaction and the resultant host parenchymal responses that ultimately define the course of sepsis. Importantly, neither profound immune activation (pro-inflammatory) or immune suppression (anti-inflammatory) characterize the dominant process. Rather, there is a combined low grade pro-inflammatory state associated with an immune hyporesponsiveness that defines the usual immunologic state of the patient with severe sepsis.