endotoxin /en′dōtok″sin/ [Gk, endon + toxikon, poison] , a toxin contained in the cell walls of some microorganisms, especially gram-negative bacteria, that is released when the bacterium dies and is broken down in the body. Fever, chills, shock, leukopenia, and a variety of other symptoms result, depending on the particular organism and the condition of the infected person. Compare exotoxin.