Isolation, purification and characteristics of mononuclear phagocytes from human placentas.

Methods for the isolation of mononuclear phagocytes from human placentas by digestion with collagenase or with trypsin are described. Mononuclear phagocytes were approximately 35% of the cells obtained. Preparations were enriched for mononuclear phagocytes by sequential density gradient centrifugation over Ficoll-Hypaque and Percoll, adherence to plastic and removal of contaminating trophoblastic cells with brief trypsin exposure. Monolayers obtained by these methods were greater than 85% mononuclear phagocytes. These cells were predominantly of fetal origin; most were mature macrophages but up to 20% appeared to be recently derived from blood monocytes as determined by ultrastructural peroxidase cytochemistry.