Identification of Fetal Inflammatory Cells in Eosinophilic/T-cell Chorionic Vasculitis Using Fluorescent In Situ Hybridization.

Eosinophilic/T-cell chorionic vasculitis (ETCV) is an inflammatory lesion of placental fetal vessels. In contrast to acute chorionic vasculitis, inflammation in ETCV is seen in chorionic vessel walls opposite the amnionic surface. It is not known whether inflammation in ETCV consists of maternal cells from the intervillous space or fetal cells migrating from the vessel. We used fluorescent in situ hybridization (FISH) to differentiate fetal versus maternal cells in ETCV. Placentas with ETCV, previously identified for a published study, were used. Infant sex in each case was identified using the electronic medical record. For male infants, 3-μm sections were cut from archived tissue blocks from placentas involving ETCV and stained with fluorescent X- and Y-chromosome centromeric probes. A consecutive hematoxylin/eosin-stained section was used for correlation. FISH analysis was performed on 400 interphase nuclei at the site of ETCV to determine the proportion of XX, XY, X, and Y cells. Of 31 ETCV cases, 20 were female and 10 were male (1 sex not recorded). Six of 10 cases with male infants had recuts with visible ETCV. In these 6 cases the average percentages (ranges) of XY cells, X-only cells, and Y-only cells in the region of inflammation were 81 (70-90), 11 (6-17), and 8 (2-14), respectively. There was a 2:1 female:male infant ratio in ETCV. Similar to acute chorionic vasculitis, the inflammation in ETCV is of fetal origin. It is still unknown, however, whether the stimulus for ETCV is of fetal or maternal origin.