Effect of length of gestation on maternal cellular immunity to human trophoblast antigens.

Maternal lymphocyte reactivity to human trophoblast antigens was studied in placentas of gestational ages 8 to 14 weeks and 32 to 34 weeks, respectively. Significant trophoblast lysis became apparent after 24 hours' incubation in the latter case compared with a time lag of 72 hours in the terminated gestations. Maternal cellular immunity, therefore, was not detected during the first 3 1/2 months of pregnancy, but was detectable by the time of parturition. The possible significance is discussed with respect to the antigenic stimulus and survival of the fetal allograft.