Published online before print 25 June 2003. DOI 10.1095/biolreprod.103.017574

Dendritic cells (DCs) in the pregnant human uterine mucosa have been poorly characterized, although they are likely to reg-ulate immune responses to both placental trophoblast cells and uterine infections. In this study an HLA-DR1, CD11c1 lin2 (CD32, CD192, CD562, CD142) population has been identified by three-color flow cytometry. The cell isolates were prepared either by collagenase digestion or mechanically from first-tri-mester decidual tissue. The decidual DCs comprised;1.7 % of CD451 cells in the isolates and had the phenotype of immature myeloid DCs. No CD1a1 Langerhans cells or CD1231 plasma-cytoid DCs were detected. The decidual DCs were DC-SIGN2, DEC-2051, CD401. Two subsets could be distinguished on the basis of relative expression of HLA-DR, which also differed in expression of DC-activation markers. The DCs were identified in situ by immunohistology by DEC-205 staining. Cells with den-dritic processes were found scattered through both the decidua basalis (in which trophoblast cells are infiltrating) and the de-cidua parietalis. They were also visible in endothelial-lined spac-es. This is the first study to identify and describe the phenotype and distribution of human decidual DCs. decidua; immunology; implantation; pregnancy; uteru