CORRELATION OF INCREASED LEVELS OF CLASS-I MHC H-2K(K) IN THE PLACENTA OF MURINE TRISOMY-16 CONCEPTUSES WITH STRUCTURAL ABNORMALITIES REVEALED BY MAGNETIC-RESONANCE MICROSCOPY

Murine trisomy 16 (mts16) placentas and fetuses, 17-day gestation age, were examined histologically and by magnetic resonance imaging at 9.4 T and compared with control littermate tissues. Placentas were studie d by immunohistochemical methods, at 15-days gestational age, for expr ession of the major histocompatibility complex (MHC) class I H-2K(k) c ell surface marker. Immunohistochemical studies revealed a markedly in creased expression of the MHC marker H-2K(k) on cells in the labyrinth of the placenta of mts16. There were differences between the magnetic resonance (MR) images of the trisomic and normal placentas, which may be correlated with the increased expression of H-2K(k) in the mts16 p lacental labyrinth. The decidual and labyrinthine components of the no rmal placentas showed similar high signal intensities (SI) while in tr isomic placentas a marked high SI was characteristic only of the decid ual region on proton spin density images. The MRI also revealed a smal ler cerebellum in the ts16 fetuses. The potential effects of the compr omised structure of the placental labyrinth and the overexpression of the H-2K(k) marker on the mts16 neural and placental dysgenesis are di scussed.