OBJECTIVE: According to a novel mechanism for fetal evasion from maternal immune attack via the engagement and down-regulation of the maternal natural killer cell receptor NKG2D by soluble MHC class I chain-related proteins (sMIC) A and B derived from placenta, we aimed to measure whether the sMICA/B level altered during pregnancy. DESIGN AND SETTING: Healthy women undergoing routine antepartum examination at Kee-Lung Chang Gung Memorial Hospital from December 2006 to December 2007 were prospectively registered for this study. SAMPLES: We collected 337 serum specimens and 10 amniotic fluid samples from 300 normal pregnant women for sMICA/B analysis. METHODS: Capture ELISA procedures were used to determine sMICA/B concentration in serum and amniotic fluid specimens. MAIN OUTCOME MEASURES: We hypothesized that the sMICA/B level would increase in proportion to the gestational age to protect the fetus from maternal immune rejection in the normal pregnancy. Results. The serum sMICA/B level rose gradually with the progression of gestation and decreased after the second trimester, with the lowest level appearing before delivery. In addition, we found that levels of soluble MICA/B were extremely low in amniotic fluid. CONCLUSIONS: We suggest that, as delivery approaches, the reduced production of soluble MICA/B by the aged placenta may be playing a role in parturition. Furthermore, we suggest that the effect of soluble MICA/B on natural killer cells of pregnant women is limited to the maternal placental surface, but not transferred through the placenta into the amniotic cavity.
OBJECTIVE: According to a novel mechanism for fetal evasion from maternal immune attack via the engagement and down-regulation of the maternal natural killer cell receptor NKG2D by soluble MHC class I chain-related proteins (sMIC) A and B derived from placenta, we aimed to measure whether the sMICA/B level altered during pregnancy. DESIGN AND SETTING: Healthy women undergoing routine antepartum examination at Kee-Lung Chang Gung Memorial Hospital from December 2006 to December 2007 were prospectively registered for this study. SAMPLES: We collected 337 serum specimens and 10 amniotic fluid samples from 300 normal pregnant women for sMICA/B analysis. METHODS: Capture ELISA procedures were used to determine sMICA/B concentration in serum and amniotic fluid specimens. MAIN OUTCOME MEASURES: We hypothesized that the sMICA/B level would increase in proportion to the gestational age to protect the fetus from maternal immune rejection in the normal pregnancy. Results. The serum sMICA/B level rose gradually with the progression of gestation and decreased after the second trimester, with the lowest level appearing before delivery. In addition, we found that levels of soluble MICA/B were extremely low in amniotic fluid. CONCLUSIONS: We suggest that, as delivery approaches, the reduced production of soluble MICA/B by the aged placenta may be playing a role in parturition. Furthermore, we suggest that the effect of soluble MICA/B on natural killer cells of pregnant women is limited to the maternal placental surface, but not transferred through the placenta into the amniotic cavity.