Figure 6

Expression of Tnfrh1 is restricted to a discrete sub-population of cells near the fetal-maternal boundary. A, low-magnification image of 10.5 dpc placenta subjected to ISH with the Tnfrh1-antisense probe, showing a band of Tnfrh1-positive cells near the fetal-maternal junction. Signal in other areas is not higher than that seen with the sense control probe (not shown). Fe=fetal side of placenta, Ma=maternal side. B, the same section stained with hematoxylin-eosin (HE) to show cellular morphology. The arrows indicate trophoblast giant cells at the fetal-maternal boundary. The in situ image has been superimposed on the HE image, revealing Tnfrh1-positive cells restricted to the zone immediately under the trophoblast giant cells. C, superimposed ISH and HE images obtained from a placenta at 12.5 dpc, showing a distribution of Tnfrh1-positive cells similar to that at the earlier stage. Trophoblast giant cells are indicated by arrows. D, high-magnification field of another section at 12.5 dpc, which was first subjected to ISH and then lightly counterstained with periodic acid Schiff (PAS). The ISH reaction product persists under these conditions, revealing Tnfrh1-positive cells in close proximity to trophoblast giant cells.