Tubuloreticular inclusions in placental chorionic villi of rhesus monkeys after maternal treatment with interferon

Tubuloreticular inclusions were observed in placental chorionic villi of rhesus monkeys after pregnant female monkeys were injected intramuscularly with recombinant leukocyte A interferon (25 X 10(6) units/kg). They were identified in endothelial cells, fibroblasts, and Hofbauer cells of the chorionic villi, providing evidence that interferon crossed at least part of the maternal-fetal partition. Induction of tubuloreticular inclusions in these cells by exogenous interferon has not been previously reported. Tightly packed regular tubular arrangements appeared in endothelial and Hofbauer cells and loosely organized tubular arrays in fibroblasts. The maximum dimension of the tubuloreticular inclusions measured 3 micron and the diameter of the tubules was 20 nm. The tubuloreticular inclusions were continuous with, and surrounded by, smooth endoplasmic reticulum that was often connected to rough endoplasmic reticulum. The tubuloreticular inclusions were not detected in placental chorionic villi from monkeys not treated with interferon or from interferon-treated monkeys 30 days after cessation of treatment. These results indicate that the formation of tubuloreticular inclusions in rhesus monkey placentas was a transient response associated with elevated serum levels of interferon.