Plasma levels of soluble Fas during normal pregnancy

The Fas/Fas ligand system could reportedly help to identify a mechanism for maternal immunotolerance of the fetus in human pregnancy. However, there are few reports on soluble Fas (sFas) which is an inhibitor of apoptosis during normal pregnancy. Therefore, ascertaining plasma sFas levels during pregnancy would be of interest. The subjects studied were 10 nonpregnant healthy women and 20 healthy pregnant women in the first and third trimester with singleton gestations. The plasma sFas was measured by sandwich enzyme-linked immunosorbent assay. The mean concentration of sFas was significantly decreased in normal pregnant women in the first trimester compared to age-matched control subjects, and it did not differ significantly between normal pregnant women in the third trimester and age-matched control subjects. From these results, we presume that the decreased plasma sFas plays an important role in maternal immunotolerance in the first trimester of pregnancy.