Col-IV is up-regulated at the implantation site and expressed by primary trophoblast cells in vitro. A–D Sections of decidua parietalis (A), n = 3, and serial sections of decidua basalis (B–D), n = 3, were stained for col-IV (A, C, D) and cytokeratin 7 (CK7). Image D) represents the box in C). Scale bars 30 μm. E Area of col-IV immunostaining in decidua basalis (DB) and decidua parietalis (DP) was quantified in ImageJ (n = 3 for each). Mean ± SD, *P < 0.001 determined using Welch's t test. F–J Confocal scanning microscopy images of decidua parietalis (F), decidua basalis (G,H) and isolated primary trophoblast cells (I,J) stained for col-IV (red), HLA-G (green) and DAPI (blue). mIgG1-FITC negative control (H) and isotype control for the anti-col-IV monoclonal antibody CIV-22, (J) show typical negative controls for immunofluorescence staining. White open arrowheads (F,G) show the expression of pericellular col-IV around individual stromal cells and white solid arrowheads show col-IV deposits around invading trophoblast cells (G). A – artery, CCC – cytotrophoblast cell column, D – decidua.