Cytotoxic factor in the blood and plasma of animals during leptospirosis.

Whole blood and plasma from animals in the acute stage of leptospirosis contained a toxic factor which produced a cytopathic effect on fibroblastic L cell monolayers. Firm adsorption of cytotoxic factor (CTF) to L cells occurred within 1 h. The highest titer of CTF in plasma was reached at 24 h and declined after 48 h after the inoculation of leptospires. Toxic effects were also obtained with intracerebral inoculation of mice with plasma containing CTF. Mice showed signs of motor instability and muscular spasms shortly after inoculation with CTF. Death usually occurred within 1 h.