In Vivo Suppression of Uterine Lymphocytes During Early Human Pregnancy

Abstract
Lymphocytes were collected from the uterus in the 1st trimester before legal abortion. There was a significant suppression of both T [thymus-derived] and B [bone marrow-derived] cells from uterine blood as compared to those simultaneously collected from a peripheral cubital vein. Apparently an immunosuppressive factor is present in the retroplacental, maternal circulation. An in vivo function of a soluble immunosuppressive factor produced by the pregnant uterus was demonstrated.