Second, bacteria produce toxins, which have diverse pathologic effects. The tox- ins may be endotoxins, which are components of bacte- rial cell walls, or exotoxins, which are secreted by the bacteria. The endotoxin of gram-negative bacteria, also called lipopolysaccharide (LPS), has been mentioned in Chapter 4 as a potent activator of macrophages, den- dritic cells, and endothelial cells. Many exotoxins are cytotoxic, and others cause disease by various mecha- nisms. For instance, diphtheria toxin shuts down pro- tein synthesis in infected cells, cholera toxin interferes with ion and water transport, tetanus toxin inhibits neuromuscular transmission, and anthrax toxin dis- rupts several critical biochemical signaling pathways in infected cells. Other exotoxins interfere with normal cellular functions without killing cells, and yet other exotoxins stimulate the production of cytokines that cause disease.