A novel suppressor cell develops in uterine decidua in response to fetal trophoblast-type cells.

In both murine and human pregnancy, a novel population of small lymphocytic cells with suppressive activity accumulates in the uterine decidua. In the mouse, these suppressor cells lack T cell markers, release an interleukin-2 blocking factor, are associated with cells with cytoplasmic granules, and are deficient in the decidua of mice showing increased abortion rates with loss of resistance to attack by maternal antipaternal transplantation immunity. Small granulated cells with immunosuppressive activity do not arise as a result of decidualization alone but can be induced using trophoblast-type cells and supernatants conditioned by trophoblast-type cells. Possible mechanisms of this induction and the importance of trophoblast-decidual interaction in generating localized immunosuppressive buffer zone (chemical barrier) about the implanted conceptus are discussed.