[The pyrogenic activity of native and recombinant human interleukin-1 beta]

Comparative doses (100-180 ng/kg) of highly purified human native interleukin-1 beta (nIL-1 beta) and human recombinant IL-1 beta (rIL-1 beta) intravenously injected were found to cause similar changes in body temperature in rabbits. Under these conditions, stabilization of rIL-1 beta by human serum albumin (HSA) fails to affect rIL-1 beta pyrogenic activity. nIL-1 beta, 0.05-2.0 ng, injected into the PO/AH region of the brain causes dose-dependent fever in the animals. With intrahypothalamic nIL-1 beta (versus i.v. injection), the pyrogenic activity of rIl-1 beta is much lower than that of nIL-1 beta. Moreover, pyrogenicity appears to be dependent on the type of rIL-1 beta, namely on free or stabilized by HSA. The former has about 100-fold and the latter a 25-fold lower activity than the native cytokine (in terms of a dose-pyrogenic effect relationship). The findings are discussed in the light of the existence of various interleukin IL-1 beta pools.