Cellular and Humoral Response Involved in Gram-Negative Bacterial Sepsis and Septic Shock

As soon as a bacterium enters the body, it is confronted with two lines of defense: a humoral line and a cellular line. The humoral factors comprise complement, antibodies, and acute phase proteins. In the cellular line of defense, in particular the mononuclear cells (monocytes and macrophages) and the neutrophils are of great significance since these cells may recognize bacterial cell wall constituents directly or indirectly after complement and antibody bind to the bacterium and its constituents. It is now thought that continuous challenges with small amounts of bacterial constituents may be necessary to keep the immune system alert to infections. Indeed, low levels of LPS are present in healthy individuals without causing disease (Takakuwa, et al., 1994; Vogel, et al., 1990).