Abstract

The pyrogenic properties of high purified recombinant human tumor necrosis factor (rHu-TNF) were investigated in rabbits. rHu-TNF produced a clear biphasic fever reaching maximal values at 1 and 5 hr after bolus i.v. injections of 10 and 33 micrograms/kg; the initial febrile response was short-lasting, and not dose-related, but the second one was dose-related and lasted for 10 hr or more. The febrile response to rHu-TNF, unlike lipopolysaccharide, did not decrease after a single or two consecutive doses. A significant reduction in the febrile response, however, was seen after four consecutive doses starting from 7 days after the second dose; the febrile response 3 hr after rHu-TNF was much smaller, but the first peak was hardly smaller. Low anti-rHu-TNF levels were found in serum of rabbits treated repeatedly with rHu-TNF, suggesting that antibody production against rHu-TNF is not responsible for the tolerance formation although it may make some contribution. There was no cross-tolerance between rHu-TNF and lipopolysaccharide. On the other hand, the febrile response to rHu-TNF (33 micrograms/kg i.v.) was inhibited partially or completely blocked by i.v. administration of cyclooxygenase inhibitors or dexamethasone. rHu-TNF produced a marked increase in the cerebrospinal fluid prostaglandin E2 level after bolus i.v. injection. A significant level of rHu-TNF (1.6 and 6.4% of that in serum) was found in cerebrospinal fluid after bolus i.v. injection of 33 and 1000 micrograms/kg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)