Cytotoxicity of Endotoxin in Vitro

Summary A method to assay the eytotoxic effects of endotoxin on guinea pig macrophages in vitro is described. It employs monolayers in a serum‐free maintenance solution, and the effects of endotoxin are assessed by the proportion of cells taking tip Trypan Blue six to eight hours later. The kinetics indicate that macrophages may be affected relatively rapidly after exposure to endotoxin, but that in any population there is a small proportion of refractory cells. Large increments in the amount of endotoxin are necessary to change the proportion of affected cells. Guinea pig serum interferes with the cyto‐toxicity of endotoxins in vitro. Possible mechanisms of the endotoxin‐elicited cell injury are discussed.