Expression of cell-mediated antimicrobial immunity by mouse trophoblast monolayers

Monolayers of mouse trophoblast cells were produced after short-term culture (two to four days) of ectoplacental cone cells derived from 7.5-day-old mouse conceptuses and were then tested for phagocytic activity. Following brief intervals of coincubation with the blood stage form of Plasmodium berghei, the parasite that causes rodent malaria, cultured trophoblast cells were found to phagocytose large amounts of parasitic material. In a manner similar to that of peritoneal macrophages, trophoblast cells ingested predominantly hemozoin pigment granules, while internalization of nonparasitized red blood cells occurred infrequently. Trophoblast-mediated phagocytosis was sensitive to the inhibitory effects of cytochalasin B. The expression of this form of immunelike function by midstage trophoblastic elements may play an important role during embryogenesis by protecting the fetoplacental unit from injury by invading microorganisms or by limiting congenitally acquired infections.