ENDOTOXINS - A type of bacterial toxin that is not freely released by the bacteria into the bloodstream (see exotoxins). Endotoxins are complex molecules that usually make up the cell wall of bacteria. They can trigger harmful effects in the body such as lowering blood pressure, shock, and severe diarrhea. Endotoxins are often what are responsible for the elevation in white blood cell count and fever that is common with many bacterial infections.