Interleukin 1 (IL-1), IL-6 and tumour necrosis factor alpha (TNF-α) are expressed in the mouse uterus on days 1–3 of pregnancy. Cytokine production is temporally associated with the post-mating intrauterine acute inflammatory response. In this study, IL-1, IL-6 and TNF-α were detected in the uterus of pregnant mice from day 3 to day 9, using northern blotting, bioassays and immunocytochemistry. IL-1 bioactivity increased from a low concentration on day 3 to a peak between days 4 and 5 and decreased to low concentrations on days 7 and 8. Blastocyst implantation occurs late on day 4. IL-6 bioactivity was high from day 3 to day 9 and activity was maximal on days 5 and 6. TNF-α bioactivity increased from its lowest concentration on day 3 to a peak on day 8. Although changes in bioactivity concentrations occurred at different times from changes in mRNA concentrations, the changes were approximately parallel. Translation of mRNA into an immunologically detectable product was confirmed using immunocytochemistry with polyclonal anti-cytokine antibodies. We conclude that the cytokines IL-1, IL-6 and TNF-α are produced in the uterus during the periimplantation period of pregnancy in mice. Changes in cytokine concentrations suggested the existence of some form of regulated expression.
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