PROBLEM: In several models of abortion in rodents, the success or failure of the implanted embryos is determined by a balance between pro‐inflammatory cytokines such as tumor necrosis factor‐α (TNF‐α), interleukin‐2, interleukin‐1 (IL‐1), and γ‐interferon, and cytokines that counteract the former, such as interleukin‐10 and transforming growth factor‐β2 (TGF‐β2)‐related suppressor factor. Stress can trigger abortions in susceptible strains of mice and is thought to reflect the pathogenesis of some types of miscarriage in human pregnancy. In mice, stress increases levels of the abortogenic cytokine TNF‐α and decreases the suppressive activity of TGF‐β2‐related factor via a neurotransmitter substance P (SP)‐dependent pathway. Evidence for a role of pro‐inflammatory cytokines in SP‐mediated abortions in vivo is indirect.METHODS: Direct evidence for a role of IL‐1 and TNF‐α in stress‐triggered abortions was sought by injecting pregnant female mice with soluble receptors neutralizing TNF‐α (rhuTNFR: Fc) or IL‐1 (rmIL‐1R) beginning 1 day after implantation and prior to stress.RESULTS: The stress‐triggered abortion rate was reduced by 68% when either TNF‐α or IL‐1 antagonists were injected. The stress‐triggered decreased TGF‐β2‐like suppressive activity in the maternal uterine decidua was not restored by injection of either antagonist; indeed the soluble IL‐1 receptor significantly reduced suppressive activity in unstressed control mice, and soluble TNF‐α receptor had a lesser effect.CONCLUSIONS: Both IL‐1 and TNF‐α play a role in the pathogenesis of stress‐triggered abortions, and may induce a compensatory physiological increase in suppressive activity in normal pregnancy counteracting pro‐inflammatory cytokines.
