(ĕp″ĭ-thē-lē-ŏl′ĭ-sĭn) [″ + ″ + lysis, dissolution] A specific lysin formed in blood serum of an animal into which epithelial cells of an animal of a different species were injected. The epitheliolysin destroys the cells of an animal of the same species as that from which the epithelial cells were derived.