Cell-mediated immunity in pregnant women.

Phytohemagglutinin-induced lymphocyte transformation (PHA-T) was depressed in pregnant women, as compared with that in nonpregnant women. Pregnancy serum had a suppressive action on PHA-T which was enhanced with the advance in pregnancy. Hydrocortisone, progesterone, alpha-fetoprotein and trophoblast-specific antigen, were demonstrated as immune suppressive factors. From these results, it was concluded that cell-mediated immunity might be reduced in pregnant women and that this reduction might be one of the causes for the maintenance of pregnancy.