Regulation of maternal serum and amniotic fluid cytokine profiles in the mouse: Possible roles in the onset of labour

Murine pregnancy is characterised by marked increases in serum cytokine profiles with advancing gestation, but whether these changes reflect concentrations in amniotic fluid is unknown. This study therefore profiled 23 cytokines by fluid-phase multiplex immunoassay of amniotic fluid and serum collected from naturally mated mice during mid- and late pregnancy (days 11 and 18, respectively). The marked increase in serum profile of many cytokines from days 11 to 18 was not reflected in amniotic fluid, wherein most cytokine concentrations were lower on day 18. Serum and amniotic fluid cytokine concentrations were largely inversely related, indicating separate, localised regulatory mechanisms geared towards the maintenance of pregnancy, modulation of immune effector cell function and optimisation of fetal development. We suggest that, while maternal systemic inflammatory priming prepares the mother for birth, the amniotic compartment exhibits a tightly regulated inflammatory quiescence. These findings are discussed in relation to the onset of labour, which ultimately results in the elevated cytokine amniotic levels traditionally associated with the final stages of pregnancy.