Secretion of platelet-activating factor acetylhydrolase by human decidual macrophages

Platelet-activating factor (PAF) metabolism in the maternal-fetal decidual interface has been investigated. Human decidua was obtained from patients at term and not in labor after cesarean section. The cells were isolated by enzymic digestion, followed by Ficoll-Paque centrifugation, or were purified further by discontinuous Percoll density gradient centrifugation. Cell populations were analyzed by flow cytometry after labeling with macrophage-specific antibodies. Twenty-seven percent of the cells obtained after enzymic digestion and Ficoll-Paque density gradient centrifugation had macrophage surface markers. The decidual cell population secreted PAF-acetylhydrolase (PAF-AH) activity. The secreted PAF-AH was the plasma-type isozyme. Synthesis and secretion was inhibited by actinomycin-D or cycloheximide. The PAF-AH activity secreted into the culture medium correlated positively with the number of macrophages. Flow cytometric purification yielded a 96% macrophage marker-positive population. The macrophages were shown to be the only cell types of decidual tissue that secreted PAF-AH. Treatment with anti-CD14 monoclonal antibody and complement specifically blocked PAF-AH secretion by collagenase-dispersed cells. It is concluded that decidual macrophages produce and secrete PAF-AH of the plasma type, and it is suggested that these cells may play an important role in PAF metabolism during parturition.