Brain interleukin-1 is involved in generation of the serum suppressive factor induced by restraint stress in mice

Our previous work showed that a factor (a protein with a high molecular weight) in serum was induced by restraint stress in mice and rats, and suppressed lymphocyte proliferation induced by concanavalin A. It was also found that the generation of the serum suppressive factor was under the control of the central nervous system. The present work was designed to investigate the role of interleukin-1 (IL-1) in the brain in the serum suppressive factor. IL-1 receptor antagonist (IL-1ra) was injected intracerebroventricularly in mice and the generation of the serum suppressive factor was found to be significantly decreased in a dose-dependent manner. When the dose of IL-1ra reached 5 micrograms, the generation of the suppressive factor was almost totally abolished. Intracerebroventricular injection of IL-1 beta (1.0 pg) enhanced the generation of the suppressive factor. Taken together, these results indicate the involvement of IL-1 in the brain in mediating generation of the suppressive factor.